The presence of calculi (urolith) in the urinary system is termed as urolithiasis, and the disease is characterized by distension of bladder and partial or complete absence of urine passage.
Etiology: Precipitation of urinary solutes and its deposition around the nidus results in calculi formation in the urinary tract. Mostly the inorganic salts are precipitated. Nidus is formed by casts, bacteria, leukocytes, degenerated or desquamated cells, and mucoproteins. Change in the pH, dehydration, lack of water and metabolic defects help in precipitation of the solutes over the nidus. Mucopolysaccharides serve as cementing agent and help in enlargement of calculi.
Urolith formation is common in castrated animals. Ingestion of fodder crops high in phosphates also helps in calculi formation. This may be the reason why ruminants in some areas like paddy growing areas are more prone to urolithiasis. The problem is also common in hilly areas with high mineral contents of feed, fodder and water. Males because of longer urethra and presence of curve due to sigmoid flexure are more commonly affected than females. In males, calculi commonly occur in urethra while in females these are seen in urinary bladder.
The pH of urine affects composition of calculi. In alkaline urine, carbonate and phosphates of calcium, magnesium and ammonium are the major constituents of calculi while oxalates, urates and xanthines are mainly present in animals with acidic urine. Bacterial infection also alters the composition of calculi. Deficiency of vitamin A, presence of infection in urinary tract, concentration of salts, deficiency of green fodder, excess use of sulfonamides and estrogenic hormone are the major predisposing factors for calculi formation.
Pathogenesis: The calculi block the urinary passage either partially or completely resulting in retention of urine and distention of bladder, leading to uremia and toxaemia. The distended bladder ruptures after 24-48 h and urine accumulates in the pelvic cavity.
Clinical signs: Urolithiasis is characterized by complete cessation of urination or partial flow of urine and continuous dribbling of urine. The animal shows signs of severe abdominal pain, uneasiness, stiff gait, kicking at the belly. Repeated twitching of penis in male animals and frequent attempts to urinate are commonly noticed. Urine mixed with few drops of blood may be passed with grunting. The abdomen is distended and on rectal palpation, full urinary bladder may be felt. Bladder or urethra ruptures releasing urine into pelvic cavity if corrective measures are not taken for continuance of urine flow.
Diagnosis: Clinical examination of the patient, symptoms and rectal palpation can help in tentative diagnosis of urolithiasis. It can be confirmed by passing catheter through urethral opening. Radiological examination reveals presence of calculi in the urinary passage. On microscopic examination of urine, presence of excessive crystals and cells is indicative of the disease. Blood urea nitrogen and serum / plasma creatinine level are highly elevated.
The disease should be differentiated from pyelonephritis and cystitis. In these cases, urinary bladder is not full of urine and radiological examination also helps in the differentiation.
Treatment: Calculi can be removed by the surgical treatment. Calculi present in the upper portion of urethra can be pushed into bladder with the help of a catheter. Use of protein-free extract of mammalian pancreas @ 5-10 ml intramuscularly for 2-3 days and muscle relaxants like amino-promazine also helps in these cases. Urinary antiseptics like 4-5 g of hexamine and antibiotics like streptomycin, nitrofurantoin, norfloxacin or cephalosporines should be administered for 5 to 7 days. Some of the ayurvedic preparations like cystone powder or tablets are of value in dissolution of the small calculi.