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

Imaging in Ferret Diagnosis and Treatment:

 

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. (B631.19.w19, 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.
  • It is essential that the patient is immobile while the radiograph is taken. (J29.10.w1)
  • Usually, positioning used is similar to that used for cats and dogs. (J29.10.w1)
  • Generally, chemical immobilisation is required. (J15.24.w5, J29.10.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)
  • Endotracheal intubation is preferable if a lengthy sequence of radiographs is to be taken. (B602.37.w37)
  • For details of appropriate chemical restraint, see: Treatment and Care - Anaesthesia and Chemical Restraint
  • Required positioning can be achieved in the anaesthetised ferret using sandbags, radiolucent tape and foam wedges. (J15.24.w5, B542.1.w1)
    • Thorax:
      • Lateral view - place the patient 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 patient 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 ferret 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 ferret 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 ferret 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 ferret's body in a straight lateral posture and have the legs positioned symmetrically. (B542.1.w1)
      • Dorsoventral view - Place the ferret 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. (B602.37.w37)
    • Taking both right and left lateral views can improve assessment of unilateral lesions. (J29.10.w1)
  • Thorax:
    • Standard views are lateral plus ventrodorsal; maximum information is obtained by taking both left lateral and right lateral views in addition to the ventrodorsal view. (J29.10.w1)
    • 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 ferret), enhances evaluation of the lung fields. (J29.10.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)
    • The field must include the thoracic inlet cranially and the last rib caudally if the entire lung field is to be covered. (J15.24.w5)
    • 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: 
    • Radiographs may provide information on the liver, gastrointestinal tract, spleen, kidneys and urogenital tract.
    • Lateral and ventrodorsal views are usually taken. (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) Centre the beam between the last rib and the wing of the ileum, with the ferret's legs extended caudally. (J15.24.w5)
    • 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 ferret is at end expiration. (B542.1.w1)
  • Head
    • For the skull, standard views are lateral and dorsoventral; sometimes a rostrocaudal view is taken also. (BJ29.10.w1)
      • The dorsoventral view allows the tympanic bullae to be seen. (J29.10.w1)
      • Oblique views may be used for examination of particular areas. (J29.10.w1)
      • The rostrocaudal view is useful for imaging the frontal sinuses and the temporomandibular joint. (B631.19.w19)
    • 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)
    • Note: Right and left oblique views (which separate the dental arcades) allow the dental arcades to be viewed separately. (B631.19.w19)
    • For assessment of periodontal disease, including confirming the true length of the tooth root, bisecting angle radiographs are useful. For this view, the X-ray beam is positioned at 90 degrees to the axis of the tooth being examined and 90 degrees to the radiographic film, avoiding distortion and allowing the alveolar socket to be assessed properly. (B631.19.w19)
  • Limbs:
    • Mediolateral views plus dorsopalmar (for the front legs) or dorsoplantar (for the hind legs) views. (B339.1.w1)
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. (J29.10.w1, J34.23.w2, B631.19.w19)
    • The higher end of the kVp is used where bone is thick or superimposed (e.g. radiography of the skull). (J29.10.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, allowing magnification (which is particularly useful with smaller patients). (B631.19.w19, J34.23.w2)
    • For enlarged radiographs, the focal-film distance is reduced to 80 cm with a focal size of 0 - 15 mm. (J29.10.w1)

Film and cassettes

  • Generally no grid is needed for these small animals. (B602.37.w37)
  • Non-screen dental film is available in small sizes, ideal for dental, including intra-oral, views, and for imaging the distal limbs. (B631.19.w19, J29.10.w1)
  • Non-screen mammography film is useful for enhancement of both soft tissue and distal limb detail. (B631.19.w19, J29.10.w1); single-intensifying screen cassettes and single-emulsion mammography film is also useful. (B602.37.w37)
  • Human dental radiographic units combined with non-screen dental film can produce fine-detailed imaging. However, the exposure time may be relatively long (e.g. 0.3 s) requiring chemical restraint of the patient to avoid image blurring. (B631.19.w19)

Contrast media

  • Contrast 
  • 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)
Thoracic cavity
For assessment of the heart, lungs and mediastinum.
  • Ferrets have a rapid respiratory rate, therefore short exposure times are preferred. (B631.19.w19)
  • Heart
    • This is placed further caudally than in the dog or cat. (B631.19.w19, J15.24.w5) The apex is to the left of the midline. (J15.24.w5)
    • The relatively narrow thoracic cavity means that the heart may look large and globe-shaped even when normal. (B631.19.w19)
    • To evaluate the size of the heart, measure the long axis and the short axis on a right lateral view, and measure the distance from the start of the fifth to the end of the eighth thoracic vertebrae, all in centimetres. Long axis (cm) plus short axis (cm) divided by T5-T8 length. This should be 1.35 (+/- SD 0.07) for males, 1.34 (+/- 0.06) for females. 
    • Cardiac enlargement may occur with: (B631.19.w19)
    • The heart may appear elevated from the sternum due to (normal) fat deposition in the pericardial ligament; this must be distinguished from pneumothorax. (B631.19.w19, J15.24.w5)
  • Lungs
  • Calcification of soft tissues (lungs, major thoracic blood vessels, also kidneys) may be incidental or indicate calcium/vitamin D3 oversupplementation. (B631.19.w19)
  • Oesophagus
    • In normal ferrets this is not easily visible. (B631.19.w19)
    • Megaoesophagus in Ferrets may be seen on plain lateral views. Contast studies make visualisation easier.
      • Barium sulphate, 10-15 mg/kg given orally; this may be mixed with a palatable food such as a meat-mased enteric suport formula, or e.g. strawberry-flavoured barium sulphate may be accepted. (B631.19.w19, B631.28.w28)
      • Radiographs with barium may show an enlarged cervical and thoracic oesophagus which may be as large as 2 cm in diameter. (B631.28.w28)
        • Note: Anaesthesia can cause dilatation of the oesophagus; this should be taken into consideration. (B627.11.w11)
      • The condition of the mucosa can also be assessed. (B627.11.w11)
    • Barium sulphate paste may be used to assess strictures and motility of the oesophagus. (B631.19.w19)
    • Fluoroscopy may also be useful in assessing the oesophagus. (B627.11.w11)
Abdominal cavity
This is elongated in shape. retroperitoneal fat deposits help to delineate the organs clearly. (B631.19.w19)
  • The liver
  • The spleen
  • The stomach
    • On a dorsoventral view the stomach should be visible on the left, with its cranial border at the level of T13; on the lateral view, it should be just caudal to the dorsal part of the liver shadow. No gas should be visible, except a small gas cap may be seen in the fundus if a ferret has been starved prior to anaesthesia. The pylorus should be just right of midling on the dorsoventral view and the pyloric opening points craniodorsally. (B631.19.w19)
    • Large quantities of gas are abnormal. (B631.19.w19) See:
  • The intestines
    • The duodenal loop descends on the right side, close to the body wall before curving cranially in the mid-abdomen, while the jejunum is found further ventrally and in the mid-abdomen; on a lateral view it is caudal and ventral to the stomach and should contain ingesta and small gas bubbles. The ileum and large intestine are not easily visible (the descending colon and rectum are most easily seen) unless abnormal (e.g. filled with gas due to obstruction).
    • Complete obstruction or radiodense foreign bodies may be visible on plain radiographs. (J29.10.w1)
    • Radiolucent gastrointestinal foreign bodies often presented with distended intestines and gas in the stomach. (B232.7.w7, B602.3.1.w3A, B627.11.w11, B631.19.w19)
    • Contrast studies may show partial obstructions, lesions, and the position of the small intestines. (J29.10.w1) 
    • A contrast (barium) study will show any blockages caused by a radiolucent foreign body. (B232.19.w19, B602.3.1.w3A, B628.11.w11, B631.25.w25)
    • It may be possible to detect intestinal thickening, focal e.g. with Lymphoma in Ferrets or Proliferative Bowel Disease in Ferrets or more diffuse e.g. with Inflammatory Bowel Disease in Ferrets or Eosinophilic Gastroenteritis in Ferrets(B631.19.w19)
  • The kidneys are generally easy to see outlined by the retroperitoneal (sublumbar) fat pads. (B631.19.w19)
  • The bladder  
    • Urolithiasis in Lagomorphs and Ferrets is common, particularly in male ferrets, in which urinary obstruction may occur when uroliths get lodged behind the os penis. (B631.19.w19)
    • Usually these are easily seen radiographically because they are usually struvite (magnesium ammonium phosphate), although small uroliths at the os penis may not be easily visible. (B631.19.w19)
  • The uterus
    • Pyometra in Ferrets may be seen. (B631.19.w19)
    • Fetuses may be detected in the last third of pregnancy, when skeletal ossification has started. (B631.19.w19)
  • Os penis this is J-shaped and can be seen radiographically in male ferrets. (B631.19.w19)
  • Contrast studies:
    • Gastro-intestinal: Before a contrast study the ferret should be faster for 3-4 hours, reducing the contents of the intestinal tract. Longer periods of fasting have been used but risk hypoglycaemia, particularly in ferrets with Insulinoma in Ferrets. (B631.19.w19)
    • 10-15 mL/kg liquid barium sulphate may be given orally (Oral Medication and Syringe Feeding of Ferrets) or by stomach tube. Strawberry-flavoured barium, or barium mixed with a palatable liquid meat-based food may improve palatability. (B631.19.w19)
      • Take views at 5, 10, 20, 40, 60, 120 and 150 minutes. (B631.19.w19)
      • Expect almost immediate emptying of the stomach, with a total time for passage through the GIT of 75 +/-45 minutes in a conscious ferret, but up to 130 +/-40 minutes in a ferret sedated with ketamine plus diazepam. (B631.19.w19)
      • If there is concern about a possible rupture or perforation of the GIT, use a radio-opaque iodine-based product such as iohexol, diluted 1:1 with tap water and given at 10-15 mL/kg. (B602.37.w37, B631.19.w19)
    • Urinary
      • Positive contrast studies can be used but uretheral catheterisation can be challenging, even in the anaesthetised ferret. (B631.19.w19)
      • If catheterisation can be achieved, iothalamate meglumine and be injected and used for contrast; if the bladder is expanded until turgid, this allows filling defects or abnormal bladder location to be detected. (B602.37.w37)
      • An intravenous pyelogram can be used to assess kidney size, position and perfusion (and, after a delay, the bladder), highlight renal and ureteral calculi and show cystic changes and neoplasia. A non-ionic iodine containing medium such as iohexol is used at 720 mg/kg given intravenously e.g. into the cephalic vein (B631.19.w19) (or iothalamate sodium or iothalamate meglumine, Conray, Mallinckrodt Medical, St Louis, USA, at 2 mL/kg). (B602.37.w37)
        • Non-ionic iodine is preferred, to avoid osmotic diuresis.
        • The ferret should be properly hydrated before the contrast medium is given.

      (B631.19.w19)

Head
  • Radiography of the head is commonly used in assessment of dental disease, also in investigation of masses. (B631.19.w19)
    • The dental formula in the adult ferret is I 3/3, C1/1, P3/3, M1/2. (B631.19.w19)
    • A bisecting angle radiograph (as described above) is useful in assessing periodontal disease (Periodontal Disease in Rabbits and Ferrets). (B631.19.w19)
    • Tumours which may be seen (Neoplasia in Ferrets) include osteomas, visible as increased irregularly shaped  areas growing from the surface of the normal bone of the skull or mandible, and gingival squamous cell carcinoms seen as radioluscent areas as they invade the underlying bone. (B631.19.w19)
Axial and appendicular skeleton
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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)
    • Sedation or anaesthesia is often preferable to physical restraint, which may be stressful. (B543.15.w15)
  • Ferrets may tolerate ultrasonography better if held standing or upright (front end off the table); this provides good access to the liver, kidneys and bladder for ultrasonography. (B631.19.w19)
    • Sedation or anaesthesia may be required if the ferret is to lie in lateral recumbency on a table. (B631.19.w19)

Equipment

  • A sector probe is recommended, because of its smaller footprint. (B631.19.w19)
    • This is particularly important when imaging the heart, due to the small spaces between the ribs. (B631.19.w19)
  • Usually, a 5.0 - 7.5 MHz transducer frequency is used; for looking at the eye, a 10 MHz transducer may be useful. (B631.19.w19)
  • Note: for echocardiography, a machine with an update rate/frame rate sufficiently fast to cope with the rapid heart rate is needed. (B543.15.w15)
  • Equipment for shaving the ferret.
    • Minimise the area shaved. (J29.10.w1)
  • Ultrasound coupling gel. (B631.19.w19, J29.10.w1)
    • This should be applied a few minutes before imaging begins, allowing it to penetrate the top layers of the skin. (B631.19.w19)
  • A stand-off is useful for visualising structures less than 3-5 cm from the body surface. (B631.19.w19)
  • A table or bench with an area cut out, allowing access of the probe to the dependant side of the animal, is useful. (B631.19.w19; 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, B631.19.w19)
  • 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, (B631.19.w19))
  • Doppler is useful for cardiac assessment, including assessment of direction of blood flow (pulsed wave Doppler) and measurement of ejection volumes (continuous-wave Doppler). (B631.19.w19)
    • 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
  • In two studies under different anaesthetic regimes, left ventricular internal diameter was greater under isoflurane than with ketamine plus diazepam anaesthesia, while isoflurane produced smaller left ventricular width (in both systole and diastole), left atrial appendage diameter and aorta than ketamine plus diazepam. (B631.19.w19)
  • For measurement of volume flow, the pulmonary artery is prefered to the aorta in ferrets, because it is difficult to get the correct alignment with the aortic outflow tract. (B631.19.w19)
  • A small amount of mitral valve and pulmonary valve regurgitation may be detected in the normal ferret. (B631.19.w19)
  • Cardiomyopathy can be detected. (J29.10.w1)
    • Dilated Cardiomyopathy in Ferrets 
      • Left and/or right ventricular dilatation. (B631.19.w19)
      • Left: increased end-diastolic and end-systoli dimensions, also increased left atrium dimensions and usually reduced ventricular outflow velocities. (B631.19.w19)
      • Reduced fractional shortening. (B543.15.w15, B631.19.w19)
    • Hypertrophic Cardiomyopathy in Ferrets
      • Left ventricular wall thickening, reduced left ventricular systolic and diastolic dimensions. (B631.19.w19)
      • Sometimes left atrial enlargement. (B631.19.w19)
      • Sometimes thickening of the interventricular septum. (B631.19.w19)
      • Turbulence of the left ventricular outflow, due to mitral regurgitation and dynamic obstruction. (B631.19.w19)
  • Valvular Heart Disease
    • Valves thickened, often with increased left ventricular diastolic dimensions but in the early stages normal systolic dimensions and normal fractional shortening.(B631.19.w19)
    • Turbulent flow and regurgitation (although aortic regurgitation is a common incidental finding in the normal ferret. (B631.19.w19)
  • With Heartworm Infection in Bears and Ferrets (with a note on Lagomorphs) ultrasonography may reveal
    • Double-lined structures within the pulmonary artery, right atrium or right ventricle (i.e. heartworms);
    • Enlargement of the right atrium and right ventricle;
    • Tricuspid valve regurgitation;
    • Right-sided enlargement (due to pulmonary hypertension);
    • Tricuspid or pulmonic regurgitation jets (due to pulmonary hypertension)

    (B150.w4, B602.6.I.w6a, B626, B631.26.w26, J213.2.w6)

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)
  • The liver: 
    • The normal liver has six lobes, deeply divided from one another and a gall bladder which empties via a common duct with the pancreas into the small intestine. (B631.19.w19)
    • Hepatomegaly may indicate e.g. neoplasia, right-sided heart failure, or mycobacterial infection. (B631.19.w19)
      • Neoplasms (Neoplasia in Ferrets) include biliary cystadenoma, cholangiosarcoma and hepatocellular sarcoma as well as juvenile lymphoblastic leukaemia (Lymphoma in Ferrets). Hepatocellular tumours tend to be anechoic while those of the biliary tree tend to by hyperechoic with linear features and hypoechoic cysts. (B631.19.w19)
    • Hepatic lipidosis may be indicated by a homogenously increased echogenicity. (B543.15.w15)
    • Multiple irregular cysts may be found in the liver as well as the kidneys in with true Polycystic Kidney Syndrome in Rabbits and Ferrets. (B631.19.w19)
  • The spleen: 
    • Splenomegaly is not necessarily a sign of disease, but abnormalities may be detected in the splenic parenchyma. (B543.15.w15, B631.19.w19)
    • Haemangiosarcomas (Neoplasia in Ferrets) are seen with anechoic blood-filled cysts as in dogs. (B631.19.w19)
    • Lymphoma in Ferrets may be seen as increased echogenicity, slightly grainy, with small (usually <5 mm) hypoechoic areas, contrasting with the normal parenchyma. (B631.19.w19)
  • The gastrointestinal tract
  • The urinary tract
    • The kidneys and bladder can be visualised.
    • Normal kidneys are no larger than 3 x  3 cm. (B631.19.w19)
    • Solitary renal cysts may be detected also (rare) multiple irregular cysts in Polycystic Kidney Syndrome in Rabbits and Ferrets. (B631.19.w19)
    • Hydronephrosis in Ferrets can be detected. (B631.19.w19)
    • In the bladder, discrete uroliths and an associated acoustic shadowing can be detected, as can bladder wall thickening. (B543.15.w15)
      • Diffuse bladder wall thickening may be noted in ferrets with Bacterial Cystitis in Ferrets; focally thickened and irregular areas may indicate neoplasia (Neoplasia in Ferrets); neoplasms are usually found at the neck of the bladder and on the dorsal surface. (B631.19.w19)
    • In males, care is required to differentiate between the os penis and calculi in the urethra. (B543.15.w15)
    • Males have a bilobed prostate at the neck of the urinary bladder. This can be grossly enlarged and cystic with prostatic hyperplasia (Prostatic Cysts in Ferrets) usually associated with adrenal gland disease (Adrenocortical Neoplasia in Ferrets). (B543.15.w15, B631.19.w19)
    • Prostatic neoplasia is rare but does occur. (B631.19.w19)
    • Cystic changes in the proximal urethra and the dorsal wall of the bladder can occur associated with adrenal disease (Adrenocortical Neoplasia in Ferrets); these can cause urinary obstruction by pressure on the bladder outflow. (B631.19.w19)
  • Adrenals: adrenomegaly can be detected (Adrenocortical Neoplasia in Ferrets). (B543.15.w15)
    • There is some variation in normal adrenal size with sex of the ferret (larger in males) and with ferret size (larger in larger individuals). Ultrasonographically, the normal left adrenal measures 5 - 10.5 x 3 - 4.8  x 2 - 3.8 mm and the right adrenal 7.5 - 12.7 x 2.9 - 5.1 x 2.2 - 4.1 mm (length x breadth x depth). (B631.19.w19)
    • Nodules may be visualised within the adrenal. Increased echogenicity and focally increased adrenal width or thickness may be detectable before any obvious general change in size, but some tumours are not detected ultrasonographically. (B631.19.w19)
    • Malignant/non-resectable tumours lack periglandular fat between the adrenal and the caudal vena cava or aorta or liver, or the aorta or caudal vena cava  are seen to be compressed by the tumour. (B631.19.w19)
  • Pancreas:  
    • Sometimes insulinomas may be detectable, if relatively large; they are usually seen in the descending limb of the pancreas, alongside the duodenal loop. (B631.19.w19)
  • The reproductive tract:  
    • The normal non-gravid uterus has a diameter of just 1.1 - 2.5 mm. (B631.19.w19)
    • Ultrasonographically, it is possible to detect pregnancy, Pyometra in Ferrets and neoplastic changes (Neoplasia in Ferrets). In ferrets which have previously been spayed and have later developed adrenal gland disease (Adrenocortical Neoplasia in Ferrets), ultrasonography may demonstrate hypertrophy of the uterine stump. (B631.19.w19)
    • Pregnancy can be diagnosed and the stage of gestation can be estimated. (B627.8.w8)
      • By day 12, two or more 3 - 5 mm dark (anechoic) fluid spots are visible; as gestation progresses, these become larger. (B627.8.w8)
  • Mesenteric lymph node
    • The single large mesenteric lymph node is found embedded in fat at the root of the mesentery, at the junction of the cranial and caudal mesenteric arteries; it is more ventrally placed and more mobile than the adrenal glands. (B631.19.w19)
Head
  • In individuals with exophthalmos, retrobulbar masses may be identified ultrasonographically, distinguishing between abscess and neoplasia. (B543.15.w15, J29.10.w1)
  • For ultrasonography of the eye, the patient must be anaeshetised and local anaesthetic applied to the cornea, before ultrasound gel is applied in a thick layer as a stand-off; imaging is challenging. (B631.19.w19)
  • A 10 MHz transducer is needed and usually B-mode images are used. The anterior chamber has a depth of 1.31 +/- 0.16 mm (SD), lens thickness is 3.42 +/- 0.15 mm, the vitreous chamber is 2.26 +/- 0.11 mm in dept and the axial length is 7 mm +/- 0.24 mm. (B631.19.w19)
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, J29.10.w1)
Records
  • It is useful if images can be recorded electronically or printed out, to build up a library of images, to monitor progress and to show to the owner. (B631.19.w19)
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Endoscopy

  • 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)
  • Endoscopy should be carried out with the animal anaesthetised; this protects both the animal and the equipment. (J513.7.w2)
  • Rigid endoscopy with air insufflation can be used to visualise most of the abdominal organs. (J213.7.w5) 
Respiratory examination
  • Endoscopy can be very useful for examining inside the lumen of the upper respiratory tract. (J213.7.w5) 
Gastrointestinal examination
  • Endoscopy can be used to examine the oesophagus, and may show ulcers, erosion or reddening of the mucosa. (B627.11.w11)
  • Endoscopy can be used to examine the stomach, including the pylorus, and the colon. (B631.25.w25, J213.7.w5)
  • A 5mm flexible fiberoptic bronchoscope has been used for examination of the ferret stomach and is useful in evaluation of gastric ulceration (Gastric Ulceration in Lagomorphs and Ferrets), and foridentification (and sometimes removal) of foreign bodies (B627.19.w19)
  • Endoscopy can be used to examine the stomach, with a 3 mm fibre optic endoscope. (B232.7.w7)
    • This can help with viewing the ulcer and assist with taking a biopsy. (P132.7.w1)
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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, B631.19.w19, 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 assessing bony changes such as those associated with neoplasms and with osteomyelitis.

(B631.19.w19, B631.30.w30, J29.10.w1, J213.7.w5)

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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 is useful for imaging of soft tissue structures, including tumours and enlarged organs..

(B631.19.w19, B631.30.w30, J29.10.w1, J213.7.w5)

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Authors & Referees

Authors Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Tiffany Blackett (V.w44)

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