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Health & Management / Rabbits and their Relatives: Disease Investigation and Management / List of hyperlinked Techniques & Protocols:

Imaging in Lagomorph Diagnosis and Treatment:

Radiographic views of the rabbit skull. Click here for full page view with caption Radiograph showing congenital incisor malocclusion. Click here for full page view with caption Rabbit skull. Click here for full page view with caption Radiograph Stage 4 dental disease. Click here for full page view with caption Radiograph rabbit with ingested lead pellet. Click here for full page view with caption Radiograph rabbit with ingested lead pellet. Click here for full page view with caption Lateral radiograph acute gastrointestinal obstruction. Click here for full page view with caption Lateral radiograph spine. No contrast. Click here for full page view with caption Lateral spine. Myelography. Click here for full page view with caption Vertrodorsal radiograph spine. No contrast. Click here for full page view with caption Ventrodorsal spine - myelography. Click here for full page view with caption  Endoscopic examination of a rabbit's ear. Click here for full page view with caption Click here for full page view with caption. Nasal foreign body and rigid endoscope Endoscopic examination of a rabbit's ear. Click here for full page view with caption Rabbit skeleton. Click here for full page view with caption

Introduction and General Information

As in other species, imaging techniques are a useful diagnostic adjunct to physical examination, for detection of internal foreign bodies, confirmation of diagnosis, determination of the site of lesions, detection of pregnancy etc. Commonly, radiography and ultrasonography are used together, as complementary imaging techniques. (B339.1.w1, B604.3.w3, J29.10.w1)

Radiography, ultrasonography and endoscopy also play a role in treatment, for example radiographic confirmation of correct placement of implants, and ultrasonographic or endoscopic guidance for biopsy.

Published Guidelines linked in Wildpro
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Radiography

Radiography is useful for determining the size, shape and position of organs and lesions both within the body and in relation to one another. (J29.10.w1)

Restraint and positioning
  • Proper restraint and correct positioning are essential for adequate radiographs allowing proper diagnostic interpretation. (B542.1.w1, B601.5.w5, B602.37.w37)
  • It is essential that the patient is immobile while the radiograph is taken. (J29.10.w1)
  • Generally, chemical immobilisation is required. (B339.1.w1, B601.5.w5, B602.37.w37, B604.3.w3, J29.10.w1, J72.49.w1)
    • Safe, accurate positioning of the patient is facilitated. (B542.1.w1)
    • Motion artefacts are reduced. (B542.1.w1)
    • Personnel can remain well away from the area during radiography. (B339.1.w1)
  • It may be possible to obtain lateral and ventrodorsal views using manual restraint. (B602.37.w37)
    • However, it may be difficult to produce good positioning with the limbs drawn well away from the body. 
    • Additionally, there is a risk of an unsedated rabbit suddenly jumping up and off the table.
    • Use of "trancing", followed by gentle placement of the rabbit in lateral recumbency and restraint by use of a long sandbag over the neck, may allow a lateral radiograph to be taken. (J513.6.w) 
      • Note: "trancing", also known as tonic immobility, is a fear response. Not all rabbits respond to trancing (B600.3.w3, J15.29.w2) and the period of time for which the immobile state is invoked is variable. (J15.29.w2) However, use of this may be preferable to inducing anaesthesia for a short, non-painful procedure. (B600.3.w3)
  • Endotracheal intubation is preferable if a lengthy sequence of radiographs is to be taken. (B602.37.w37)
  • For wild lagomorphs, radiography should be carried out with the animal under general anaesthesia. (J213.9.w4)
  • For details of appropriate chemical restraint, see: Treatment and Care - Anaesthesia and Chemical Restraint
  • Required positioning can be achieved in the anaesthetised rabbit using sandbags, radiolucent tape and foam wedges. (B542.1.w1) sandbags and limb ties may be used. (J72.49.w1)
    • Thorax:
      • Lateral view - place the rabbit in right lateral recumbency on the cassette. Extend the pelvic limbs using a sandbag or tape. Extent the thoracic limbs fully and tape them to the cassette in an extended position, using radiolucent tape. Gently extend the neck. (B542.1.w1)
      • Dorsoventral view - place the rabbit on the cassette in ventral recumbency. Extend the thoracic limbs cranially and secure them with tape close to either side of the head, to minimise superimposition of the scapulae and associated musculature  on the cranial thorax. Extend the pelvic limbs caudally and secure with a sandbag. Position the ears to minimise their superimposition on the thoracic cavity. (B542.1.w1)
    • Abdomen:
      • Lateral view - place the rabbit in right lateral recumbency on the cassette. Extend the pelvic limbs caudally and the thoracic limbs cranially, holding them in place with sandbags or radiolucent tape. (B542.1.w1)
      • Ventrodorsal view - Place the rabbit in dorsal recumbency on the cassette. Gently extend the thoracic limbs cranially and the pelvic limbs caudally, securing them e.g. with tape. (B542.1.w1)
    • Head:
      • Lateral view - place the rabbit in right lateral recumbency with its head on the cassette. Place a foam wedge under the rostal part of the head to bring the sagittal plane of the head parallel with the table; if necessary, use radiolucent tape to maintain the head position. Keep the rabbit's body in a straight lateral posture and have the legs positioned symmetrically. (B542.1.w1)
      • Dorsoventral view - Place the rabbit in ventral recumbency, mandible resting on the casette. Extend the thoracic limbs cranially and laterally at about a 45-degree angle to the long axis of the body. (B542.1.w1)
Views
  • Standard practice is to take two views, 90 degrees apart, of the part of the animal which is of interest, generally a lateral and a dorsoventral or ventrodorsal view. (B601.5.w5, B602.37.w37, B604.3.w3)
    • Taking both right and left lateral views can improve assessment of unilateral lesions. (J29.10.w1)
  • Thorax:
    • Exposing the radiograph when the patient is at maximum inspiration (natural, if this point can be seen, or by use of positive pressure ventilation in an intubated rabbit), enhances evaluation of the lung fields. (B542.1.w1, J29.10.w1)
    • Standard views are lateral plus dorsoventral. (B339.1.w1)
    • For the lateral view, centre the x-ray beam on the caudal border of the scapulae (thoracic limbs extended forwards), with the field of the x-ray beam including both the caudal neck and the cranial abdomen. (B542.1.w1)
    • Maximum information is obtained by taking both left and right lateral views. (J29.10.w1)
    • For the dorsoventral view, centre the x-ray beam on the middle of the thoracic spine, in the midline, with the field of the x-ray beam including the caudal neck and the cranial abdomen. (B542.1.w1)
  • Abdomen: 
    • Lateral and ventrodorsal views are usually taken; sometimes a dorsoventral view is taken in addition to the lateral view. (B339.1.w1, J29.10.w1)
    • For the lateral view, centre the x-ray beam in the mid-abdomen, with the field of the x-ray beam extending to include the caudal thorax and the whole of the pelvis. (B542.1.w1)
    • For the ventrodorsal view, centre the x-ray beam on the middle portion of the lumbar spine, in the midline, with the field of the x-ray beam including the caudal thorax and the whole of the pelvis. (B542.1.w1)
    • Expose when the rabbit is at end expiration. (B542.1.w1)
  • Head
    • For separate views of the dental arcades, oblique views are needed. (B601.5.w5, B602.37.w37, B601.5.w5)
    • For the lateral view, centre the x-ray beam just rostral and ventral to the eye, with the field of the beam extending to the cervical region. (B542.1.w1)
    • For the dorsoventral view, centre the x-ray beam on the midline directly between the eyes; a for the lateral view, the field of the beam should include the cervical vertebrae. (B542.1.w1)
    • A rostrocaudal view of the head is useful for visualising the frontal sinuses or the temporomandibular joints. (B601.5.w5)
    • Note: Right and left oblique views (which separate the dental arcades), in addition to lateral and ventrodorsal views, provide optimum information; all four views can be obtained on a single small x-ray plate. (V.w125)
  • Limbs:
    • Mediolateral views plus dorsopalmar (for the front legs) or dorsoplantar (for the hind legs) views. (B339.1.w1, B604.3.w3)
Equipment

Radiography unit and settings

  • Because of their rapid respiratory rate, short exposure times (less than 1/60th of a second) are needed. (B604.3.w3)
  • A radiographic machine capable of producing 40 - 70 kV, 300 mA and exposure times of 0.008 - 0.16 s (i.e. down to 1/120 s) is recommended. (B601.5.w5, J29.10.w1, J34.23.w2)
    • For thoracic and abdominal radiographs, kVp 45 - 60, 2 - 6 mAs and a 1/30 to 1/120th second exposure time is suggested. (B604.3.w3)
    • The higher end of the kVp is used where bone is thick or superimposed (e.g. radiography of the skull). (J29.10.w1)
    • A range of 40 - 100 kV, 5.0 - 7.5 mAs and rapid exposure times (down to 0.017 of a second and faster) is suggested. (B542.1.w1)
  • A tube stand allowing 90 degree rotation for horizontal beam radiography is useful. (B602.37.w37)
  • Equipment which allows alteration of the focal-film distance is useful. (J34.23.w2)
    • Usually the focal-film distance used in about 90 cm. (B604.3.w3)
    • For enlarged radiographs, the focal-film distance is reduced to 80 cm with a focal size of 0 - 15 mm. (J29.10.w1)
  • Human dental radiograph machines can be useful for fine detail views of the head and distal limbs. However, these machines, which usually have a fixed voltage and amperage, may require longer exposure times (0.1 - 3.0 s) so that chemical restraint is essential. (B601.5.w5)
  • Preferably use a beam-limiting device. (B604.3.w3)

Film and cassettes

  • Rabbits have low soft tissue density; it is useful if contrast can be enhanced. (B604.3.w3)
  • Generally no grid is needed for these small animals. (B601.5.w5, B602.37.w37)
    • A grid is necessary for larger rabbit breeds where the body thickness is likely to exceed 10 cm. (B601.5.w5, B602.37.w37)
  • Fast, high-resolution, high detail rare earth intensifying screens should be used. (B604.3.w3)
  • For imaging the distal limbs as well as for dental imaging, non-screen dental film is useful. (B601.5.w5)
    • These films are available in small sizes, ideal for intra-oral views. (B601.5.w5, J29.10.w1)
  • Non-screen mammography film is useful for enhancement of both soft tissue and distal limb detail. (B601.5.w5, J29.10.w1); single-intensifying screen cassettes and single-emulsion mammography film is also useful. (B602.37.w37)

Contrast media

  • Liquid barium sulphate, 10 - 15 mL by mouth or via an orogastric tube can be useful for an upper GIT contrast study. (B602.37.w37)
    • This is useful for demonstrating a gastric hairball (B604.3.w3) which is often present in cases of gastric stasis.
  • Iohexol (Omnipaque) can be used instead if there is a suspicion of gastrointestinal perforation. (B602.37.w37)
  • For excretory urogram:
    • Iothalamate sodium or meglumine at 2 mL/kg intravenously. (B602.37.w37)
    • Meglumine can also be administered into the bladder via a urinary catheter for cystography; if the bladder is distended until it is palpably turgid, filing defects etc. are visible. (B602.37.w37)
  • Iodine-based contrast medium for myelography and urinary contrast studies. (B601.5.w5, P3.2005a.w1)
Radiographic Interpretation
"The most important requirements for radiographic interpretation are a firm appreciation of normal anatomy and an awareness of the patterns of radiographic change in response to disease processes." (J34.23.w2)
  • Interpretation follows the same principles as for other species. (B602.37.w37)
  • Note any changes in the size, shape, number, location, margins and opacity of body parts on each view. (B602.37.w37)
  • Interpret in conjunction with the known anatomy and variations, (B602.37.w37) and in the light of clinical signs. (J29.10.w1)
  • Experience is needed for accurate interpretation. (B604.3.w3)
Thoracic cavity
For assessment of the heart, lungs and mediastinum.
  • On lateral view, "The thorax is short cranio-caudally and the heart lies well forward and in an upright position. The diaphragm is long and sloping. The trachea runs dorsally almost parallel with the thoracic vertebrae and its cartilage rings are usually well mineralized." The cairina is at about the 4th or 5th intercostal space. The aorta is generally not visible; the caudal vena cava may be visible. (J8.22.w1)
  • On the ventro-dorsal or dorso-ventral view, the cardiac silhouette is approximately triangular and relatively large. Much of the dorsal diaphragmatic lung field is covered by the liver density. The aortic arch may be visible (overlying the left side of the hear. The scapulae may overlie the caudal lung fields. J8.22.w1)
  • Rabbits have a small thoracic cavity relative to their body size. Radiographically, this means that the heart appears abnormally large and occupies most of the cranioventral part of the thoracic cavity. Additionally, the front legs are superimposed on the cranial thorax, obscuring detail. It can be difficult to interpret thoracic radiographs. (B339.1.w1, B601.5.w5, B601.7.w7, J34.23.w2)
  • The heart, trachea, aorta, vena cava and caudal lung lobes should be visible. (J513.6.w5)
  • Major blood vessels (e.g. aorta, subclavian arteries) may have increased density in: (B601.5.w5, J513.6.w5)
  • The heart may be displaced caudally with thymic neoplasia; the thymus will also be visible as a precardiac shadow. (B601.5.w5)
  • The lungs are small, particularly the cranial lobes. (B601.7.w7)
  • Radiographic abnormalities include: (B601.5.w5)
    • Consolidation of one or more lobes due to chronic infection or abscess. (B601.5.w5)
      • Note: indistinct radiographic contours may be due to subcutaneous and pericardial fat rather than lung consolidation. (J34.23.w2)
    • Parenchymal masses such as metastases from neoplasia elsewhere in the body (e.g. Endometrial Adenocarcinoma and other Uterine Neoplasia in Lagomorphs). (B601.5.w5, B601.7.w7, J29.10.w1, J513.6.w5)
    • Pleural effusion - caudal lung border rounded, pleural space widened on dorsoventral view. (B601.5.w5, B601.7.w7)
    • Empyema - on lateral views, ventrally in the thorax, homogenous increased density obscuring the cardiac silhouette. Trachea in a normal position. On dorso-ventral views, homogenous increased density and cardiac shadow obscured, with the trachea displaced to one side in unilateral cases while in bilateral cases fluid density was visible between the lung lobes (collapsed) and the thoracic wall. With large amounts of pus, the diaphragm wa displaced caudally and the ribs were spread wider than usual. (J8.22.w1)
    • Possibly air alveolograms and air bronchograms in early lung infection. (B601.5.w5)
Abdominal cavity
  • The abdominal cavity is relatively large. (B601.5.w5)
  • Large amounts of retroperitoneal and abdominal fat may displace the abdominal contents ventrally. (J34.23.w2)
  • The liver, kidneys, stomach, intestines and bladder should be visible; the spleen is not visible. (J513.6.w5)
  • Large amounts of gas in the GIT indicates reduced motility. (J513.6.w5)
  • The liver is in the cranial abdomen, flattened, cranial to the stomach, and is normally under the caudal ribcage. (B339.1.w1, B601.5.w5, J8.23.w1)
  • The stomach
    • Normally lies mainly within the costal arch. (J8.23.w1)
    • Should always contain food and may have a small gas cap (normal). (B601.5.w5)
      • Appears as mottled soft-tissue density plus gas. (J8.23.w1)
      • Ventro-dorsal view: antrum, on the right, is considerably cranial to the fundus which is on the left. (J8.23.w1)
    • Large amounts of gas are abnormal. (B601.5.w5) The stomach may contain only fluid and gas, or be empty, with intestinal impaction. (J8.23.w1)
    • With gastric stasis, the stomach may be full of gas and ingesta/trichobezoars and is large; it may project caudal to the margin of the ribcage. (B339.1.w1, B600.10.w10, B601.5.w5, B602.16.w16, J8.23.w1, J60.8.2)
      • The typical trichobezoar is a soft tissue density, ill-defined with a rim of gas outlining it. J34.23.w2
    • May contain visible lead in rabbits with Lead Poisoning. (J29.10.w1)
  • The small intestines
    • These are displaced dorsally and to the left in the abdomen by the caecum. (J34.23.w2)
    • Segments of small bowel containing gas may be distinguished from large bowel by their curvilinear radioluscent configuration. (J8.23.w1)
    • These may be full of gas for example with Mucoid Enteropathy. (B600.10.w10)
    • If the stomach and small intestines, but not the large intestines, are severely distended, obstruction should be suspected. (J34.23.w2)
    • Complete obstruction or radiodense foreign bodies may be visible on plain radiographs. (J29.10.w1)
    • Contrast studies may show partial obstructions, lesions, and the position of the small intestines. (J29.10.w1)
  • The large intestines and caecum take up a large percentage of the abdomen; the contents are of mottled radiographic density. (B339.1.w1, B601.5.w5, J8.23.w1, J29.10.w1)
  • The caecum
    • Is ventral and mainly on the right side of the abdomen. (B339.1.w1, B601.5.w5)
    • It is generally large and fluid-filled. (B604.3.w3); it should always be filled with ingesta. (B339.1.w1, B601.5.w5)
    • Small amounts of gas may be present in the normal caecum. (B339.1.w1, B601.5.w5)
    • Excessive gas and fluid suggests colic and ileus. (B601.5.w5) Some sections of intestines may be distended with gas and others filled with ingesta. (J8.23.w1)
    • The large bowel may be empty and distended with gas in gastric impaction (while the stomach contains large amounts of dense material). (J8.23.w10
    • With Mucoid Enteropathy in Rabbits the whole caecum and large intestines may be full of fluid and gas. (B601.5.w5)
    • With Mucoid Enteropathy in Rabbits, typically the small intestines are full of gas, the stomach is full, the colon is grossly distended with mucus and the contents of the caucum are dense and dehydrated. (J513.6.w5)
    • With Caecal Impaction a sausage-shaped mass is visible in the ventral abdomen (B600.10.w10); the colon is relatively empty and the small intestines are often mildly or moderately distended with gas. (J34.23.w2)
  • The descending colon and rectum contain faecal pellets. (B601.5.w5, J8.23.w1) these are generally but not always visible. (J8.23.w1)
  • The kidneys are generally easy to see outlined by the retroperitoneal (sublumbar) fat pads.
    • A 1982 study noted that the left kidney was usually visible on both lateral and ventro-dorsal views, while the right kidney was only seen in about half of 27 normal rabbits, and was more easily seen in the lateral view. (J8.23.w1)
    • The right kidney is at about T13/L1 with the left kidney more caudal, about L3 - L5. (J8.23.w1)
    • Each kidney should measure about 1.8 (range 1.4 - 2.2) times the length of the second lumbar vertebra. (B601.5.w5); 1.25 -1.75 times he length of the second lumbar vertebra. (J8.23.w1)
    • Common abnormal findings are renal and/or ureteral calculi (Urolithiasis in Lagomorphs). (B601.5.w5)
    • Note: the kidneys are often pushed ventrally by the large retroperitoneal (sublumbar) fat pads in pet rabbits. (B339.1.w1)
  • The bladder normally contains calcium carbonate crystals which assist in visualisation of the bladder as a radiodense structure on plain radiographs. (B339.1.w1, B601.5.w5)
    • The bladder itself is not generally visible, but the urine within it is generally visible as a homogenous soft tissue density, ventral to the colon in the caudal abdomen. (J8.23.w1)
    • Excessive amounts of calcium sludge results in an intense bladder outline. (B601.5.w5)
    • Uroliths in rabbits are usually composed mainly of calcium and are radiodense; therefore large uroliths (calculi) may be clearly visible on a plain radiograph (Urolithiasis in Lagomorphs). (B601.5.w5, J29.10.w1, J34.24.w3, J513.6.w1)
    • There may be radio-opaque urolith "sand" in the dependent part of the bladder; in an extreme case the whole bladder may be distended and radio-opaque, and may displace other abdominal organs cranially. (J4.217.w4)
    • Note: it is important that the radiograph covers the whole pelvis if urethral calculi are to be detected. (J513.6.w1)
  • The uterus may be enlarged associated with pregnancy, neoplasia (particularly adenocarcinoma - Uterine Neoplasia in Rabbits), Endometrial Hyperplasia - Uterine Polyps in Rabbits or pyometra (Uterine Infection in Lagomorphs). (J8.23.w1)
    • "Multiple large locular masses" in the caudoventral abdomen, with craniodorsal displacement of the intestines, may be seen with pyometra. These can be very large and take up a large part of the abdomen. (J8.23.w1)
    • Mummified fetuses (both intra- and extra-uterus) have been detected radiographically as fetal skeletal remnants, sometimes in abnormal configurations, in the caudo-ventral abdomen. (J8.23.w1, J495.32.w5)
    • Fetal malpresentation may also be seen (e.g. transverse presentation). (J8.23.w1)
  • The abdominal aorta and iliac arteries may be visible if calcified (Soft Tissue Mineralization - Kidney Calcification in Rabbits). (J29.10.w1)
  • In parous does, the nipples can be seen - on ventro-dorsal views these appear as small circular densities superimposed over the abdominal contents, while in lateral views they are seen along the ventral body wall. (J8.23.w1)
  • Abdominal abscesses may be visible on radiography and may have diffuse calcification; occasionally a calcified abscess may be visible radiographically (circumscribed calcified mass) but not causing any clinical signs. (J8.23.w1)
  • Free fluid in the distended abdomen may be visible radiographically and should be sampled by abdominocentesis (Abdominocentesis and Diagnostic Peritoneal Lavage in Rabbits). Transudate is present with heart failure (cardiomegally also seen). (J8.23.w1)
  • Contrast medium:
    • Gastro-intestinal
      • An air gastrogram may be useful to highlight trichobezoars. (B339.1.w1)
      • 10 - 15 mL of positive contrast medium (barium sulphate) given by orogastric or nasogastric tube, may be used to outline the gastric contents (B601.5.w5) and may be useful in detection of gastro-intestinal foreign body, although the presence of gas, and recirculation of barium by caecotrophy, may make interpretation problematic. (B602.16.w16)
        • Take films at time zero and then every 20 minutes. (B339.1.w1)
      • One study found that with a liquid marker, 32% reached the caecum within an hour and 80% reached it within 12 hours. 
    • Urinary
      • Negative contrast (5 - 8 mL/kg air injected into the bladder through a 3.0 - 3.5 French urinary catheter). can be used to outline the lining of the bladder. (B601.5.w5)
        • Use of carbon dioxide rather than air removes the risk of an iatrogenic air embolism. (B542.1.w1)
      • Adding 2.0 - 3.0 mL of an iodine-based contrast medium allows double-contrast radiographs. (B601.5.w5)
        • Double-contrast studies are particularly useful in rabbits with large amounts of radiopaque material in the bladder. (B542.1.w1)
        • Note: if, at the end of the study, the bladder is prominently distended, use the catheter to withdraw urine and contrast media. (B542.1.w1)
      • An excretory urogram (Intravenous pyelography) can be carried out by injection of 1- 2 mL/kg iodine-based contrast medium intravenously, for evaluation of renal function in rabbits with renal calculi. (B339.1.w1, B601.5.w5, B602.18.w18, J513.6.w1)
Head
  • Normal rabbits with a wild-type head have a relatively elongated skull, six cheek teeth in the upper arcade and five in the lower  arcade, four main incisors (two maxillary and two mandibular) and two peg teeth behind the main maxillary incisors. 
    • There are no canines and there is a considerable diastema (gap) between the incisors and the cheek teeth. (B601.5.w5)
    • At rest, the cheek teeth should not be in contact; there should be a zig-zag occlusal surface on each dental arcade. (B601.5.w5)
    • The lower incisors should meet with the groove between the main upper incisors and the peg teeth. (B601.5.w5)
  • Brachycephalic rabbits are commonly seen. (B601.5.w5)
  • Mandibular prognaithism is commonly seen. (B601.5.w5)
    • Overall skull length is reduced and length of the maxillary diastema is reduced, while mandibular length is normal. (B614.13.w13)
  • The rabbit has quite large rostral nasal passages, in which are fine trabeculae which may be visible on a lateral radiograph. (B601.5.w5)
    • To view the nasal passages on a dorsoventral view, use small dental non-screen film placed inside the mouth. (B601.5.w5)
  • On lateral view, "The cranial cavity is not clearly delineated. The frontal sinuses are small and the frontal bones overlying them are often slightly roughened. The nasal bone forms a marked spicular prominence." (J8.22.w1)
  • On ventro-dorsal view, "The cranial cavity is small and its margins are indistinct. The zygomatic arches are flat and have prominent bony projections at their rostral ends." (J8.22.w1)
  • Radiography is an essential tool in the assessment of rabbit dental disease. (B601.18.w18)
  • Assess: (B601.18.w18)
    • Length of the supragingival crown in the incisors and the cheek teeth.
    • Positions of the apices of the teeth.
    • Occlusal surfaces of the cheek teeth.
    • Condition of alveolar bone.
    • Whether the palatine shelf and the dorsal border of the mandible slightly converge rostrally (normal).
  • Abnormalities which may be visible include: (B601.5.w5, B601.18.w18, J8.22.w1, J29.10.w1, J513.6.w6)
    • Malocclusion of the incisors;
    • Abscess formation with bone lysis, and proliferation of new bone around the abscess;
    • Periodontal disease;
    • Lysis of alveolar bone;
    • Ankylosis - blurring of the boundaries between the alveolus and the tooth.
    • Dental arcades (cheek teeth) touching one another at rest;
    • Palatine shelf and the dorsal border of the mandible parallel (due to excessive length of the cheek tooth crowns forcing the mandible away from the maxilla).
    • Elongation of tooth roots;
      • In the maxilla, tooth roots may extend into the nasal passages and the orbit.
      • In the mandible, tooth roots may distort the ventral surface of the mandible.
    • "Wave mouth" - occlusal surface between the dental arcades irregular and uneven.
    • Cheek teeth grossly irregular;
    • Pathological fractures of the mandible.
      • Fractures generally occur in the thin caudal section of the mandubular ramus. (J513.6.w6)
  • Assessment of the bony structures of the middle ears:
    • A dorsoventral view is most informative; it is important to have accurate alignment. (B600.12.w12, B601.5.w5)
    • The bullae are well developed, with relatively thicker bone than in cats and dogs, and are easily distinguished particularly in ventro-dorsal views. (J8.22.w1)
    • Bone sclerosis and loss of fine trabecular bone structure may be seen. (B601.5.w5, J29.10.w1)
    • With a unilateral disease process, the bone of one tympanic bulla may be obviously thickened and proliferative compared to the normal bulla on the other side. (J513.6.w6)
    • Note: radiographic changes in the bullae are not always easily correlated with clinical signs. (J513.6.w6)
  • Other abnormalities which may be seen include traumatic jaw injuries and skull neoplasia. (B601.5.w5, B601.18.w18)
  • Contrast studies are useful for assessment of the nasolacrimal duct in Dacrocystitis in Rabbits
    • Iodine-based contrast medium, 0.5 - 1.0 mL (B339.1.w1) is injected into the punctum lacrimale - the single nasolacrimal ostium which is deep in the craniomedial portion of the lower conjunctival sac. (B528.14.w14, B600.11.w11, B601.5.w5, J34.24.w3)
      • Take films (lateral or oblique lateral) immediately after injecting the contrast medium. (B339.1.w1)
      • With blockage of the duct, the contrast material remains in the portion of the duct, often dilated, caudal to the blockage, and does not pass through to the nasal cavity. 
      • A dilute preparation (e.g. sodium/meglumine iothalamate, Conray 280) is cheap and easy to inject into the duct.
      • A concentrated solution is harder to inject but provides a clearer image, and for a longer period of time.
      • A good image of the duct is harder to achieve if the duct is normal since it passes through to the nose where it may be inhaled into the nasal passages, resulting in superimposition on the radiographic film.

      (B600.11.w11)

    • An oblique lateral view allows assessment of both nasolacrimal ducts, avoiding superimposition. (B601.5.w5)
Axial and appendicular skeleton
  • The skeleton is relatively delicate (6 - 7% of total body mass). Rabbits have a hamate process and a hooked suprahamate process on the scapula; they also possess small clavicles. (B339.1.w1)
  • Radiography is essential in the investigation of paresis or paralysis. (B600.12.w12, J513.6.w6)
  • Radiography of the spine allows detection of fractures, luxations or subluxations and spondylosis, as well as spinal abnormalities such as scoliosis or hemivertebrae. (B600.12.w12, B601.5.w5, B601.11.w11, B602.20.w20, J15.28.w1, J245.24.w1, J513.6.w6)
  • Radiography allows assessment of skeletal mineralisation and detection of osteopaenia and osteosclerosis. (B600.12.w12)
  • Radiographic assessment of the limbs is useful in the diagnosis and assessment of: (B601.5.w5, J29.10.w1, J513.6.w6)
  • Myelography
    • This is extremely valuable for the detection of Intervertebral Disc Disease in Rabbits, spinal abscesses and spinal tumours. (B601.5.w5, N12.38.w1)
    • Myelography is usually performed via the L5 - L6 or L6 - L7 intervertebral space, but can also be performed via the cisterna magna. (J29.16.w7, P3.2005a.w1)
    • If contrast is injected at the lumbar site:
      • 0.4 mL of iodine-based contrast medium, injected via a 23 G, 30 mm (1 1/4 inch) needle (for an average 2.5 kg rabbit) generally will provide contrast from T2 to L7 and demonstrate lumbar spinal lesions within a few minutes. (P3.2005a.w1)
      • This site is generally preferred for myelography, since most lesions are in the lumbar area. (J29.16.w7)
      • 1.0 - 3.0 mL (depending on the rabbit's size) iohexol (300 mg iodine per mL, Omnipaque, GE Healthcare, Buckinghamshire, UK) can be injected. (J29.16.w7)
    • If contrast is injected at the atlanto-occipital junction (cisterna magna): (J29.16.w7)
      • Inject contrast agent (e.g. 1.0 - 3.0 mL (depending on the rabbit's size) iohexol (300 mg iodine per mL, Omnipaque, GE Healthcare, Buckinghamshire, UK), then withdraw the needle. 
      • Place the rabbit in lateral recumbency with its head elevated above its body; this allows gravity to assist movement of contrast agent caudally. 
      • Periodically turn the rabbit over onto the other side so that the contrast agent is not in contact with one side rather than the other for too long.
      • Take lateral and dorso-ventral radiographs as the contrast medium moves caudally.
      • Note: compared with lumbar injection of contrast, a longer time is needed for the medium to reach the lumbar area where lesions are most commonly found, and the contrast medium will be diluted more, which may give poorer imaging. 

      (J29.16.w7)

    • Note: 
      • Rabbits often appear weak and slightly sore in the hours immediately after myelography, probably due to the spinal manipulation associated with the procedure. Analgesics should be given to rabbits undergoing myelography. (J29.16.w7)
      • Seizures can occur post-myelography. Control with diazepam and provide supportive care. (J29.16.w7) See: Epilepsy and Convulsions in Bears and Lagomorphs
      • Paralysis can occu post-myelography; in a reprted case, resolution of the condition occurred within two days. (J29.16.w7)
Other uses of radiography

Radiography is also used for:

  • Checking correct placement of a nasogastric tube or oesophagostomy tube. (B601.2.w2, J29.15.w2)
  • Confirming adequate alignment of fractures after reduction and placement of implants, and monitoring fracture repair. (B601.17.w17, B606.10.w10, P112.1993.w1)
Records
  • For wild lagomorphs, keep records of the species, age, weight, region examined, radiographic techniques used and radiograph quality; this will assist in developing the best techniques for future examinations. (J213.9.w4)
Associated techniques linked from Wildpro

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Ultrasonography

This is particularly useful for the investigation of cardiac disease. (J34.23.w2)

Positioning and restraint

  • This may be carried out in the conscious patient, with manual restraint, or under chemical restraint. (B339.1.w1)
  • In the conscious rabbit, a standing position may be best tolerated. (B601.5.w5)
  • If right lateral recumbency is required for standard views e.g. of the heart and kidneys, sedation may be needed. (B601.5.w5)

Equipment

  • A sector probe transducer is preferred because of its smaller footprint. (B601.5.w5)
    • This is very important for imaging the heart through the small spaces between the ribs. (B601.5.w5)
  • Usually a 5 - 7.5 MHz transducer frequency is needed; for structures such as the eye, 10 MHz may be preferable. (B601.5.w5)
  • Note: for echocardiography, a machine with an update rate/frame rate sufficintly fast to cope with the rabbit's rapid heart rate is needed. (B543.15.w15)
  • Equipment for shaving the rabbit.
    • Minimise the area shaved. (J29.10.w1)
  • Ultrasound coupling gel. (B601.5.w5, J29.10.w1)
  • A stand-off for visualising structures less than 3-5 cm from the body surface.
    • Commercially produced stand-offs are constructed to avoid attenuation, distortion and resolution artefacts. (B601.5.w5)
  • Video recording and/or printing, so images can be retained. (B601.5.w5)
  • A table or bench with an area cut out, allowing access of the probe to the dependant side of the animal, is useful. (B339.1.w1)

Modes

  • B-Mode (brightness mode) provides a two-dimensional real-time image; this is the mode used most commonly. (B543.1.w1)
  • M-Mode (motion mode) employs a single ultrasound beam in a fixed position, recording how the dimensions of the section being imaged change with time. This is the mode used in echocradiography for assessing cardiac contractility. (B543.1.w1)
  • Doppler is useful for cardiac assessment, including assessment of direction of blood flow (pulsed wave Doppler) and measurement of ejection volumes (continuous-wave Doppler).
    • A Doppler ultrasound transducer can also be useful in indirect blood pressure measurement - see Treatment and Care - Anaesthesia and Chemical Restraint (Anaesthetic Monitoring)
Interpretation
Thoracic cavity
  • The rabbit's heart has a bicuspid not tricuspid right atrioventricular valve. (B601.5.w5)
  • Echocardiography can be carried out and used to assess cardiac function. (B601.5.w5)
    • It is important to consider the effects of different anaesthetic agents on myocardial contractility. (B601.5.w5)
  • Cardiomyopathy can be detected. (B601.5.w5, J29.10.w1)
  • Bacterial endocarditis, myocardial fibrosis, atherosclerosis and thrombi associated with this condition may be detected. (B601.5.w5)
  • A ventricular septal defect has been diagnosed by ultrasonography in a rabbit with chronic dyspnoea. (J29.10.w1)
  • Other organs which may be imaged include the cranial mediastinum and the thymus, even in adult rabbits. (B601.5.w5)
    • Cranial mediastinal masses can be visualised, but it is difficult to biopsy or aspirate samples from this area due to its position relative to the heart. (B601.7.w7)
  • Pulmonary and pleural masses can be detected, and biopsies or aspirates obtained under ultrasonographic guidance. (B601.7.w7)
  • Ultrasonography can be used in investigation of pleural effusion. (B601.7.w7)

Cardiac function values reported include: 

Data from 11 Dutch Belted rabbits (weight 2.32 +/- 0.36 kg, mean age seven months, two males and nine females) sedated with 1 mg/kg diazepam intravenously. (J495.49.w1)

  • Right ventricular wall thickness: 1.63 +/- 0.56 mm
  • Interventricular septum: 3.95 +/- 0.47 mm
  • Left ventricular wall 4.24 +/- 0.64 mm
  • Right ventricular chamber diameter: 7.00 +/- 2.09 mm
  • Left ventricular chamber diameter: 5.41 +/- 2.30 mm
  • Total cardiac dimensions: 24.55 +/- 2.30 mm
  • Left ventricular end diastolic dimension: 1.17 +/- 0.19
  • Left ventricular end systolic dimension: 0.70 +/- 0.09
  • Fractional shortening: 39.50 +/- 5.39
  • Left ventricular ejection time: 0.08 +/- 0.01 s
  • Velocity of circumferential fibre shortening: 4.74 +/- 0.45
  • Ejection fraction: 76.17 +/- 5.81
  • Left ventricular free wall thickness diastolic: 0.31 +/- 0.08
  • Intraventricular septum thickness diastolic: 0.25 +/- 0.05
  • Left atrial dimension systolic: 0.17 +/- 0.41
  • Aortic root dimension diastolic: 0.67 +/- 0.10
  • Left atrial-to-aortic-root ratio: 1.38 +/- 0.32
  • Right atrial dimension systolic: 0.61 +/- 0.08
  • Aortic root dimension diastolic 0.69 +/- 0.10
  • Right atrial-to-aortic-root ratio:0.88 +/- 0.17
  • E-pont septal separation 0.05 +/- 0.05
  • DE excursion, slope velocity: 0.55 +/- 0.08
  • E-to-F slope: 70.17 +/- 31.82
  • Right ventricular outflow tract velocity: 0.83 +/- 0.10
  • Left ventricular outflow tract velocity: 0.65 +/- 0.14

Data from 10 male New Zealand white rabbits (2.5 - 3.0 kg) under isoflurane or halothane anaesthesia; values given as mean +/- SEM: (J83.31.w)

  • Interval between cardiac cycles: isoflurane 0.21 +/- 0.005; halothane 0.22 =/- 0.001
  • Velocity of heart rate corrected circumferential fibre shortening: isoflurane 1.16 +/- 0.07; halothane 1.37 +/- 0.06 (significant difference p < 0.01)
  • Left ventricular end-systolic wall stress: isoflurane 88.3 +/- 1.8; halothane 65.7 +/- 3.8 (significant difference p < 0.01)
  • Left ventricular ejection time: isoflurane 0.39 +/- 0.01 s; halothane 0.42 +/- 0.02
  • Maximum of the first derivative of the ventricular pressure (dp/dtmax) isoflurane 6655 +/- 314; halothane 2850 +/- 271
  • Mean arterial pressure: isoflurane 89 +/- 5.2 mmHg; halothane 93.3 +/- 6.5 mmHg
  • Note: myocardial contractility was better preserved by use of isoflurane rather than halothane anaesthesia. 

Data from 52 young adult male New Zealand white rabbits (weight 2.2 - 3.2 kg, mean 2.59 kg) anaesthetised with ketamine and medetomidine; values given as range and mean +/- SD: (J13.67.w3)

  • Intraventricular septum thickness (diastole): 1.43 - 3.10 mm, mean 2.03 +/- 0.37 mm.
  • Intraventricular septum thickness (systole): 2.17 - 4.03 mm, mean 3.05 +/- 0.45 mm.
  • Left ventricular internal diameter (diastole): 11.87 - 19.06 mm, mean 14.37 +/- 1.49 mm.
  • Left ventricular internal diameter (systole): 7.83 - 13.53 mm, mean 10.05 +/- 1.22 mm
  • Left ventricular free wall (diastole): 1.60 - 2.80 mm, mean 2.16 +/- 0.25 mm.
  • Left ventricular free wall (systole): 2.43 - 4.55 mm, mean 3.48 +/- 0.55 mm.
  • Fractional shortening: 22.60 - 36.83%, mean 30.13 +/- 2.98%
  • Ejection fraction: 49.07 - 70.0%, mean 61.29 +/- 4.66%.
  • Aortic diameter: 6.73 - 9.80 mm, mean 8.25 +/- 0.76 mm.
  • Left atrial appendage diameter: 7.53 - 12.0 mm, mean 9.66 +/- 1.14 mm
  • Left atrial appendage to aortic diameter ratio: 0.94 - 1.54; mean 1.17 +/- 0/14
  • Mitral valve E-point-to-septal separation interval: 1.20 - 2.33 mm, mean 1.71 +/- 0.29 mm
  • Doppler heart rate: 115 - 234 bpm, mean 155 +/- 29 bpm
  • Maximal aortic outflow velocity: 0.56 - 1.06 m/s, mean 0.85 +/- 0.11 m/s (data from 35 rabbits)
  • Maximal pulmonary artery outflow velocity: 0.34 - 0.84 mm/d, mean 0.59 +/- 0.10 mm/s
  • Maximal mitral E-wave velocity: 0.41 - 0.83 m/s (0.59 +/- 0.10 m/s (data from 35 rabbits)
  • Maximal mitral A-wave velocity: 0.19 - 0.44 m/s, mean 0.28 +/- 0.07 m/s (data from 35 rabbits)
  • Maximal mitral E-wave velocity: Maximal mitral A-wave velocity (peak E-to-peak-A wave velocity ratio): 1.35 - 3.55, mean 2.19 +/- 0.46 (data from 35 rabbits)
Abdominal cavity
  • Percutaneous ultrasound via the flank allows visualisation of the kidneys and ovaries while a ventral abdominal approach is used for the liver, bladder and uterus. (J29.10.w1)
    • Ultrasonography may be hindered by the large caecum and colon. (J29.10.w1)
    • The bladder can be used as an acoustic window although transmission of the ultrasound beam may be reduced by calcium carbonate crystals in the urine (causing a "snow storm" effect). (B601.5.w5)
  • The liver 
    • This can be imaged just caudal to the xiphoid cartilage. (B601.5.w5)
    • An increase in echogenicity is seen with diseases such as hepatic lipdosis. (B601.5.w5)
    • The gall bladder can be seen, as can hepatic vessels. (B601.5.w5)
    • The hepatic biliary tree may be dilated in rabbits with Hepatic Coccidiosis in Lagomorphs. (B543.15.w15)
  • The urinary tract
    • The kidneys and bladder can be visualised. 
    • Structure of the kidneys is similar to that of the cat, except the kidneys are unipapillate. (B601.5.w5)
    • Abnormalities such as irregular kidney outline, distortion of the medulla and cortex and disruption of the renal papilla can be imaged. (B601.5.w5)
    • Kidneys which are smaller than normal and have an irregular surface may indicated chronic Encephalitozoonosis in Lagomorphs. (B601.5.w5)
    • Discrete uroliths and an associated acoustic shadowing can be detected, as can bladder wall thickening. (B543.15.w15)
  • The reproductive tract
    • Ultrasound can be used for pregnancy diagnosis and to diagnose and distinguish between Uterine Neoplasia in Rabbits, pyometra (Uterine Infection in Lagomorphs) and haemorrhage due to Endometrial Venous Aneurisms in Rabbits. (B601.5.w5, B543.15.w15, J29.10.w1)
      • Pyometra: large, fluid-filled uterus. (B601.9.w9, B602.18.w18, J213.5.w1)
      • Uterine neoplasia: uterine mass or masses; often multiple and affecting both horns. (B601.9.w9, B602.18.w18, J27.64.w4, J34.24.w3, J213.5.w1, J213.7.w1)
    • Fetuses can be assessed to see if they are alive or dead. (B543.15.w15, J29.10.w1)
    • The ovaries can be assessed for size and presence of cysts. (B543.15.w15)
    • The contents of the scrotum of 28 New Zealand white rabbits was evaluated using a 5 MHz linear array transducer, with the rabbits in dorsal recumbency. For the examination, a rubber pad, 0.8 cm thick and with a central hole 0.5 cm diameter was placed between the testis and the rabbit's body, ultrasound coupling gel was applied to the scrotum, and a rubber sac containing 250-300 mL tap water was placed over the scrotum as a stand-off. (J503.X.w1)
      • The dimensions of the testes were measured (right testis average 3.2 +/- 0.08 cm (mean +/- SEM) long, 1.1 +/- 0.03 cm wide; left testis mean 3.3 +/- 0.09 cm long, 1.1 +/- 0.03 cm wide). (J503.X.w1)
      • The testicular parenchyma was described as "homogenous and moderately echoic" while the cauda of the epididymis seen in sagittal plane images was "a homogenous, less echoic structure localised next to the testicular parenchyma" and the caput epididymis was "smaller than the cauda, homogenous and less echoic compared with the testicular parenchyma" but could only be visualised in eight rabbits (28.6%). (J503.X.w1)
      • Abnormalities which could be detected included biopsy needle scars (hyperechoic, from 3-4 days to day 14 after biopsy), while in a testis undergoing necrosis, reduction in testicular volume and variation in echogenicity were noted. (J503.X.w1)
Head
  • The eye can be examined (10 mHz probe) in the assessment of ocular conditions such as ocular abscesses, lymphoma and uveitis associated with lens rupture caused by Encephalitozoonosis in Lagomorphs. (B601.5.w5)
  • In rabbits with exophthalmos, retrobulbar masses may be identified ultrasonographically, distinguishing between abscess and neoplasia. (B543.15.w15, J29.10.w1)
Other uses of ultrasonography
  • Guidance for biopsy of internal organs such as the liver, kidney and uterus. (B533.142.w142, B543.3.w3, B543.15.w15, B601.9.w9, J29.9.w1, J29.10.w1, J281.173.w1)
Associated techniques linked from Wildpro

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Endoscopy

A rigid endoscope can be used for most of the following; a flexible endoscope is generally used for bronchoscopy. (B602.36.w36, J513.2.w2, J513.8.w1)
  • Before starting any endoscopic procedure, ensure that the endoscope and associated instruments and equipment are working correctly and that the endoscope has been cleaned and sterilised properly. (J513.8.w1)
  • Before starting any procedure using a flexible endoscope, the view thought the endoscope should be checked, confirming the plane of flexion and that the notch in the dorsal edge of the tip, which provides the oerpator with orientation, is visible. (J513.8.w1)
  • Endoscopy should be carried out with the animal anaesthetised; this protects both the animal and the equipment. (J513.7.w2)
Oral examination

Particularly examination of the cheek teeth.

  • Fasting the rabbit for one to four hours before examination minimises the chance of food being present in the mouth.
  • The rabbit should be sedated or anaesthetised. 
  • Gaseous anaesthesia can be maintained using a small cone over the nares.
  • A self-retaining mouth gag to keep the mouth open, and cheek spreaders, improve access.
  • Using an endoscope with a 30 degree view allows excellent visualisation of each arcade in turn with the endoscope pointed directly into the oral cavity.
  • Examine the lingual, buccal and occlusal surface of each tooth.
  • Check the gingiva for lesions, particularly on and around the tongue, and on the cheeks opposite the upper cheek teeth.
  • Repeat the examination following dental work, to confirm appropriate tooth surfaces.
  • The pharyngeal tonsils can be seen as the scope passes over the caudal aspect of the tongue.

(B602.36.w36, J513.2.w2, P6.3.w1)

Aural examination (otoscopy)

Particularly in individuals with torticollis.

  • Have the rabbit help in sternal recumbency, head supported and ear held erect by an assistant. (B602.36.w36)
  • Gently insert the endoscope into the external ear canal; the aural sulcus (blind-ending diverticulum off the vertical ear canal) will be seen. Continuing, the canal deviates medially to become the horizontal canal and ends at the tympanic membrane, which is oval. (B602.36.w36)
  • Using a rigid endoscope with 30 degree view (2.7 mm diameter,18 cm long rigid rod-lens Hopkins telescope Karl Storz Veterinary Endoscopy America Ltd.), it is important to remain aware of the difference between "straight ahead" with the end of the endoscope and the "straight ahead view, or iatrogenic damage to the mucosa of the ear canal may occur. 
  • In the normal ear canal, the mucosa should be uniformly bright pink, without any haemorrhage, debris or discharge. 
    • Epithelial lesions and exudate may be found. (B602.36.w36)
  • If necessary, the canal can be flushed and cleaned to facilitate examination. (P6.3.w1)
  • The tympanic membrane should be clear and glistening.
    • Abnormal findings include membrane opacity, material (e.g. pus) accumulating behind the membrane, and any evidence the membrane is not patent.

(B602.36.w36, J513.2.w2, P6.3.w1)

Transurethral endoscopy and vaginoscopy in does
  • Dorsal, ventral or lateral recumbency of the anaesthetised rabbit can be used as preferred by the operator.
  • Particularly useful as a diagnostic aid in does with haematuria.
  • Infuse warmed sterile physiological saline through the infusion port to create an optical cavity.
    • Make sure there is an egress route for the saline and allow saline out by this route as the bladder fills; regularly palpate the bladder to chek it is not becoming overfilled.
  • Vaginoscopy is useful in the diagnosis of diseases of the caudal reproductive tract.
    • Rotate the endoscope through 180 degrees for complete evaluation.
    • In a large individual with uterine pathology, it may be possible to enter the uterine horns; this is not usually possible in a non-breeding female with a normal reproductive tract. (J513.7.w2)
    • The vaginal body should be pink with prominent mucosa. (J513.7.w2)
      The cervices have a prominent rosette appearance and should normally be tightly closed; if there is uterine hamorrhage, a blood clot may be visible at the cervix. (J513.7.w2)
    • The normal uterus is white to pale pink, and smooth. (J513.7.w2)
  • The opening to the urethra can be identified on the cranial ventral aspect of the vaginal vestibulum.
  • The normal urethra is smooth, pale and even in colour and texture. (J513.7.w2)
  • The normal bladder appears smooth and white to pale pink in colour, and the bladder wall is thin. (J513.7.w2)
  • Abnormalities include "nodules, ulcerations, irregular mucosal surfaces and accumulations of mucus, blood and debris."  (J513.7.w2)
  • It is important to distinguish between tiny haemorrhages due to the tip of the endoscope brushing against the wall of the bladder, and mucosal lesions. (J513.7.w2)
  • Cystoscopy can be used in assessment of urolithiasis.
    • It is easy to identify large uroliths; smaller cystals may be flee-floating but may adhere to the mucosa of the bladder.
    • With saline insufflation, a "snow globe" effect may occur, preventing visualisation; preventing saline outflow for a short while may allow debris to settle, improving visibility. (J513.7.w2)
  • Sometimes cystoscopy can be used for retrieving uroliths from the neck of the bladder.
  • Samples can be collected for cytology, culture and histopathology. (J513.7.w2)
    • Care is required not to perforate the bladder wall or other thin structures, or to cause haemorrhage. (J513.7.w2)
    • The thicker wall generally present in an abnormal bladder can usually be sampled safely. (J513.7.w2)

(B602.36.w36, J513.2.w2, J513.7.w2)

Gastrointestinal examination
  • Oesophagus
    • An endoscope can be inserted through the mouth as for oral or tracheal examination and the scope extended down the oesophagus.
    • With air insufflation, gross lesions and foreign bodies can be seen.
    • With water irrigation, mucosal detail can be visualised better.
    • Note: while a flexible endoscope can be advanced into the stomach, this contains ingesta even after a 24-hour fast, therefore gastroscopy is not very useful.
  • Rectum and colon
    • An enema is needed before the scope is introduced.
    • The rectum and colon can then be examined.

(P6.3.w1)

Laparoscopy
  • Anaesthetise the rabbit, intubate it and provide respiratory support (since the abdominal cavity will be filled with air, putting pressure on the diaphragm).
  • A left flank approach is useful for visualisation of "the liver, stomach, jejunum, spleen, cecum, sacculus rotundus, ampulla coli, ascending colon, and left kidney" while a right flank approach is used for "the liver, duodenum, pancreas, cecum, and right kidney." (B602.36.w36)
    • The left flank is useful for the left liver lobes and spleen; the right sided approach is useful for most other structures. (P6.3.w1)
  • Note that kidneys, ovaries and uteri may be masked by fat. (B602.36.w36)
    • In obese rabbits, all organs may be covered with fat. (P6.3.w1)
  • Use a Veress pneumoperitoneum needle and carbon dioxide to inflate the abdomen to a pressure of 8 - 12 mmHg. Remove the Veress needle once pre-inflation has been performed. (B602.36.w36)
  • Following aseptic preparation of the skin, make a small skin incision then advance haemostats or a trochar and cannula through into the abdominal cavity. (P6.3.w1)
    • Keep the length of the incision in the muscles (or linea alba if a midline approach is used) to a minimum in order to reduce leakage of gas around the outside of the telescope. (B602.36.w36)
  • Insert the telescope (sheathed) and attach an insufflator to a port on the sheath, adjusting the pressure setting as required to maintain the pleuroperitoneum at the desired pressure. (B602.36.w36)
  • Examine the organs.
  • Biopsies and microbiological samples can be taken under endoscopic guidance.
    • Liver, spleen and pancreas biopsies can be taken easily.
    • For a kidney biopsy, the perirenal fat must first be incised.
    • Biopsies of the intestinal wall should be avoided, due to the risk of intestinal perforation followed by peritonitis; biopsies may be taken of grossly proliferative lesions.

(B602.36.w36, P6.3.w1)

Respiratory evaluation
Rhinoscopy
  • Place the anaesthetised, intubated rabbit in sternal recumbency, head held down. (B602.36.w36)
  • Flush the nares with sterile saline to remove debris and mucus.
  • Use a 2.7 mm or 1.2 mm rigid endoscope. (J513.4.w3)
  • Use the endoscope with an examination sheath to protect the telescope if size allows this; take great care if using the telescope unprotected.
  • Have an assistant support the head.
  • Gently advance the endoscope into one nostril and past the alar fold to the nasal meatus. It is possible to move deeper and see the dorsal and ventral nasal conchae, and even, deeper still, the cranial part of the ethmoid labyrinth.
  • Note: the nasal membranes are very vascular; care is needed to avoid traumatising the membranes, or haemorrhage can occur.
  • Visibility can be increased by use of saline irrigation.
  • Biopsies can be taken; haemorrhage following this procedure is minor.
  • Samples of exudate can be collected.

(B602.36.w36, J513.4.w3)

Bronchoscopy

  • Endoscopy can be used for evaluation of the respiratory tract. (J13.68.w1, J513.4.w3, J513.8.w1)
  • Flexible endoscopes are usually used. (J513.8.w1)
    • With a flexible endoscope of external diameter less than 3 mm, most of the lobar bronchi can be reached; short length scopes (e.g. 33 cm) are easier to manoeuvre. (J513.8.w1)
  • A rigid endoscope (2.7 mm) can be used for assessment of the respiratory tract down to the level of the bifurcation and it may me possible to see the primary and secondary bronchi. (J513.4.w3)
  • Pre-oxygenate rabbits with respiratory embarrassment before inducing anaesthesia. J513.8.w1
  • Give glycopyrrolate to reduce respiratory secretions. (J513.8.w1)
  • Anaesthetise the rabbit to protect the endoscope, minimise patient stress, suppress coughing and laryngospasm and minimise the risk of trauma. (J513.8.w1) (J513.8.w1)
    • Injectable anaesthesia is recommended, with oxygenation via a small facemask (nosecone) placed over the nares. Alternatively, the rabbit may be sedated by injectable agents with anaesthesia maintained using oxygen and inhalant anaesthesia via a nosecone. (J513.8.w1)
    • Use an anaesthetic protocol which minimises cardiorespiratory depression. 
  • Place the rabbit in sternal recumbency and elevate the jaw on e.g. a rolled towel; make sure the larynx is not occluded. (J513.8.w1)
  • Use a gag (incisor dilator) and pouch dilators to ensure the mouth is kept open. (J513.8.w1)
  • If there is any indication the anaesthetic is becoming too light (gagging, swallowing, increased respiratory rate), remove the endoscope. (J513.8.w1)
  • Apply a small amount of sterile water-based lubricant to the distal 2 - 3 cm of the endoscope before insertion. (J513.8.w1)
  • While an assistant pulls the tongue forward gently using a piece of gauze, advance the endoscope to the larynx and use the tip of the endoscope to gently disengage the epiglottis from the soft palate. (J513.8.w1)
  • Advancement of the endoscope, rotation of the endoscope (by wrist movements) and flexion of the endoscope tip are used in combination to move the endoscope into the airway segment of interest. (J513.8.w1)
  • Prominent bilateral arytenoid cartilages are visible ventral to the entrance to the larynx. (J513.8.w1)
  • The pharyngeal area has a pronouced mucosal vascular pattern, and submucosal vessels are also easily visible in the trachea. (J513.8.w1)
  • The trachea appears hyperaemic due to the bright colour of the smooth muscle surrounding it; the dorsal ligament is much paler. (J513.4.w3)
  • Ventrally in the trachea, "C"-shaped tracheal cartilages should be visible; dorsally is the tracheal membrane. (J513.8.w1)
  • At the cairina there is a sharp bifurcattion into the left and right primary bronchi. (J513.8.w1)
  • Openings to the distal airways should be round to elliptical, and the airways should be smooth. (J513.8.w1)
  • In New Zealand white rabbits (2.75 - 4.25 kg) sedated with ketamine and xylazine and anaesthetised with isoflurane, a 3.8 mm endoscope enabled visualisation of the larynx and associated structures, trachea, principle bronchi and divisions into the primary lobar bronchi, while a flexible 2.5 mm endoscope, all lobar bronchi could be entered. (J13.68.w1)
    • Mucosal hyperaemia was noted to the level of the carina, after which the epithelium was pale pink and the bronchial vasculature was visible. Airways had a mild glistening appearance and no mucus accumulation was seen. (J13.68.w1)
  • Bronchioalveolar lavage (BAL) can be carried out in the caudal lung lobes for investigation of diffuse disease, otherwise in the area of interest.
    • Following initial bronchoscopy, remove the bronchoscope, flush the instrument channel with sterile saline and wipe the external sheath of the endoscope with sterile gauze sponge soaked in sterile saline. (J513.8.w1)
    • Replace the endoscope in the airway to the desired point, keeping the endoscope as central as possible to minimise contamination. (J513.8.w1)
    • Gently wedge the end of the endoscope against the smallest bronchus possible. (J513.8.w1)
    • Via the instrument channel, instill 3 mL of warm sterile saline, then 2 mL of air to clear the channel. (J513.8.w1)
    • after a minimal amount of time, apply manual suction to the instrument channel using a 12 mL syringe, to remove the fluid. (J513.8.w1) 
      • Expect to retrieve 40 - 60% of the instilled fluid. (J513.8.w1)
      • Froth in the recovered fluid indicates surfactant present. (J513.8.w1)
    • Repeat the lavage at the same site if desired, to increase recovery of fluid. (J513.8.w1)
    • Repeat in at least one other site (a different airway segment or lobe) to improve the chance of disease detection. (J513.8.w1)
    • Evaluate the recovered fluid by cytology and culture. (J513.8.w1)
  • Bronchial brushing can be performed; this should be carried out after BAL (to reduce the risk of blood contaminating the lavage fluid).
    • Extend the brush past the tip of the endoscope. (J513.8.w1) 
      • Do not flex the tip of the bronchoscope while the brush is extended, as the fibres of the scope may be damaged. (J513.8.w1)
    • Move the brush gently backwards and forwards across the endobronchial surface to dislonge cells/tissue. (J513.8.w1)
    • Retrieve the brush and roll it onto a microscope slide for a cellular preparation or insert it into a small amout of saline to dislodge tissue from the brush for cytology. (J513.8.w1)
  • Biopsy of nodules/lesions should be carried out last. (J513.8.w1) 
    • Do not flex the tip of the bronchoscope while the biopsy forceps are extended, as the fibres of the scope may be damaged. (J513.8.w1)
    • Tracheal or bronchial wall lesions are difficult to grasp and sample. (J513.8.w1)
    • The best site for sampling bronchial tissues is at a non-cartilaginous bifurcation point; at these sites the forceps can be placed either side of the airway opening. (J513.8.w1)
  • Following BAL or biopsy, preferably intubate the rabbit and supply oxygen; as a minimum continue oxygen supplementation via facemask or in a chamber until the rabbit is fully recovered from the anaesthetic. (J513.8.w1)
  • Note:
    • There is a risk of coughing if the airway is irritated by high-pressure oxygen. (J513.8.w1)
    • There is a risk of transferring infection from one site to another, previously uninfected site. (J513.8.w1)

Thoracoscopy

  • Thoracoscopy allows direct visualisation of the lungs without full thoracotomy.
  • The anaesthetised rabbit should be intubated and intermittent positive pressure ventilation used.
  • Aseptically prepare the required side of the thorax.
  • Make a skin incision 1 - 3 cm caudal to the intended intercostal entry site.
  • Insert blunt haemostats, or a trochar and cannula, and advance subcutaneously to the intercostal space between ribs 7 to 8 or 8 to 9.
  • Insert the haemostats or trochar and cannula through the intercostal space.
    • The lung will collapse unless there are extensive adhesions.
  • Insert the endoscope through the trochar.
  • Examine the pleural membranes, lung and heart as required.
  • Biospies can be taken of masses seen using other imaging techniques (radiography, ultrasonography or CT scan).
  • Once the endoscope is removed, evacuate as much air as possible from the thorax.
  • Hold the lungs at maximum insiration and remove the trochar.
  • Allow the skin to return to its normal position; air rarely re-enters the thorax after this.
  • Observe the rabbit closely.
    • If signs indicate a worsening pneumothorax, use fine-needle aspiration to remove air.
    • Very rarely, a chest drain may be needed.

(J513.4.w3, P6.3.w1)

Other uses of endoscopy

A rigid or semi-rigid endoscope can be used for guidance of endotracheal intubation. (B602.36.w36)

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Computed Tomography (CT)

This involves use of a rotating X-ray beam, with computer analysis producing a cross-sectional image slice of the individual, showing the internal structure. (B544.3.w3, B601.5.w5, J29.10.w1)
  • Anaesthesia is needed, since it is important for the patient to remain completely still.
  • CT provides better differentiation between soft tissue and fluid than does conventional radiography.
  • CT allows an area to be imaged without superimposition of adjacent tissues.
  • Disadvantages of CT include:
    • Expense.
    • Higher dose of radiation than with conventional radiography.
  • CT is particularly useful for assessment of a variety of diseases affecting the head, including advanced dental disease, neoplasia, infection of nasal sinuses and turbinates, middle ear sclerosis etc.

(B601.5.w5, B601.7.w7, J29.10.w1)

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Magnetic Resonance Imaging (MRI)

This involves use of a strong magnetic field to align proton magnetic dipoles along an axis, with computer generation of images following measurement of signals from excited protons. It is particularly useful for assessment of soft tissue structures, bone marrow and neurological imaging of the brain. Two different image sets (T1-weighted and T-2 weighted) are commonly used. (B544.3.w3, B601.5.w5, J29.10.w1)
  • General anaesthesia or deep sedation is needed, since it is essential for the patient to remain completely still in order for a clear image to be obtained.
  • MRI provides greater spatial resolution and soft tissue contrast than CT.
  • MRI can be used for musculoskeletal imaging, including articular imaging.
  • It can be used for imaging of brain lesions, and has been used experimentally for imaging of pyelonephritis, spinal abscesses, bacterial sinusitis and sinovitis in rabbits.
  • It is also useful for imaging of e.g. soft tissue masses in the thorax.

(B601.5.w5, B601.7.w7, J29.10.w1)

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Authors & Referees

Authors Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Frances Harcourt-Brown BVSc FRCVS (V.w140)

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