Although many diseases of the urinary and genital systems are similar in many aspects in all mammals, there are features and
presentations which are unique to certain species. Ferrets and rabbits each have specific disease presentations, and the understanding
of these disorders is essential in recognizing normal and abnormal, and treating these pets. Although diagnostic evaluation
is similar, etiologies, interpretation of laboratory results, and therapeutic strategies may vary substantially. A thorough
understanding will lead to the most rapid, effective treatment plan.
General principles
Anatomy
Similar to that of other mammals. Kidneys are usually radiographically evident in the retroperitoneal space in both species,
surrounded by fat. Rabbit kidneys may be radiographically located more ventrally than usual due to the presence of retroperitoneal
fat. The bladder is cranial to the pelvic inlet and easily palpable when full.
Evaluation
When azotemia is present, determine whether prerenal, renal, or postrenal. Assess chronicity and duration of renal disease.
Physical examination
Assess hydration, renal discomfort, kidney size and shape, presence of other abdominal masses, and urinary obstruction.
Urinalysis
Essential in evaluation of the urinary system – polyuria, hematuria, casts, proteinuria, crystalluria, or isosthenuria accompanying
dehydration all are indicators of urinary disease. Normal urine pH values in carnivores are acidic, and are alkaline in herbivores.
Microcytic, hypochromic, nonregenerative anemia, hyperphosphatemia, hypocalcemia, and metabolic acidosis often accompany chronic
renal failure.
Radiography
Radiographs are ideal for detection of calculi (bladder, renal, urethral, or ureteral) or calciuria, as well as prostatic
or uterine enlargement. Excretory urography (IVP-Intravenous pyelography) is useful to detect obstruction and hydronephrosis,
and to evaluate renal perfusion. Contrast cystography can be used as in other species for evaluation of the bladder and urethra.
Both sexes of rabbits can be easily catheterized; male ferrets, however, are extremely difficult to catheterize and always
require sedation. There is a j-shaped os penis, which is exteriorized by placing pressure on the base of the penis, and the
urethral opening is not quite at the distalmost aspect of the penis. Female ferrets are extremely difficult to catheterize.
Ultrasound
An excellent diagnostic tool for evaluating the renal system as well as other organs. Also enables aspirates of masses or
fluid-filled structures, and can be used to guide renal biopsies. (Note: due to the small patient size, there can be increased
risk of injury to the renal vessels in small patients.)
Nuclear scintigraphy
Can be used to determine glomerular filtration rate (GFR) in mammals, and can assess each kidney individually. This is the
most accurate assessment of renal function. Although not yet described for ferrets or rabbits, this is an emerging technique
in veterinary medicine which enables assessment of GFR in each kidney individually with no patient risk other than anesthesia.
(Note: the author has performed GFR scans in ferrets and in rabbits, although there are no published normal values for comparison.)
Renal or bladder biopsy is performed as in other species.
