Congenital Defects
David C. Van Metre
Most severe congenital defects of the urinary tract of ruminants manifest at an early age, although occasionally defects remain clinically occult until adulthood and some are incidental findings at necropsy or slaughter.
Congenital defects of the urinary system should be considered in the differential diagnoses for a young animal with renal disease or abnormal urination. However, tubular necrosis caused by severe volume depletion, nephrotoxins, and infectious diseases are much more common. If a congenital defect of the urinary tract is identified, a careful examination of other body systems should be performed; 73% of lambs with urogenital defects were found to have one or more defects in other organ systems.1Renal Defects
Common renal defects in cattle include fused kidney, polycystic kidney, unilateral renal agenesis, and renal oxalosis.2 A single report exists of ectopic fused kidneys and hermaphroditism in a cross-bred calf.3 In sheep, common defects include renal lobulation, fused kidney, hydronephrosis and hydroureter, polycystic kidney, and unilateral or bilateral renal agenesis.1,2 Unilateral renal agenesis and polycystic disease involving the liver, pancreas, and kidney have been reported in goats.2,4 A retroperitoneal, perirenal pseudocyst (a fluid sac lacking an epithelial layer) was described in a ram with acute abdominal pain.5 Pseudocysts typically develop as outpocketings of the renal capsule and can develop as a result of renal trauma, urinary tract obstruction, or vascular or lymphatic anomalies.
Renal oxalosis is a metabolic disease that is suspected to have an inherited basis6; a severe form has been reported in Beefmaster calves.7 Affected calves show weakness, lethargy, and anorexia within days to several weeks of age.
Dehydration, diarrhea, and alopecia may develop. Evidence of renal failure is found on serum chemistry analysis. An inherited abnormality of glycine or glyoxalate metabolism may generate high levels of endogenous oxalate, which readily complexes with calcium. Subsequently, calcium oxalate crystals accumulate in the renal tubules, obstructing tubular outflow. Exposure to oxalate- containing plants and ethylene glycol must be ruled out in all cases of renal oxalosis.Ectopic Ureter
Ectopic ureter is a rare congenital defect in which one or both ureters terminate in an abnormal location. An ectopic ureter may terminate in the urethra, vagina, or cervix or caudal to the bladder trigone in females. In males, the ectopic ureter usually terminates in the urethra, vas deferens, or seminal vesicles. Urinary incontinence is the most common presenting complaint for affected animals.8 Urine dribbling results in scalding of the perineum and medial surfaces of the hindlimbs in heifers, and scalding in males is usually located on the prepuce and ventral abdomen. Occasional episodes of normal micturition may be seen. UTI, polycystic kidney(s), and hydronephrosis may exist concurrent to ectopic ureter(s). Diagnosis and treatment of this condition in ruminants are similar to horses (see the previous section in this chapter). The use of affected animals for breeding should be discouraged.
Neoplasia
David C. Van Metre
Other than those associated with ingestion of bracken fern, primary neoplasms of the urinary tract of ruminants are rare. In a North American abbatoir survey, primary tumors of the bladder were detected in 0.05% of more than 21,000 cattle examined, with cases of papillomas, adenomas, and transitional cell carcinomas identified in the sample population.1 Tumors of the genitalia, typically fibropapillomas and squamous cell carcinomas, may impinge upon urine egress from the urethra. Urinary tract involvement may be seen in occasional cases of lymphosarcoma in ruminants.3