Microscopically, a monotonous proliferation of neoplastic lymphocytes infiltrates the interstitium. The lower urinary tract comprises ureters, urinary bladder and the urethra. All have in common that the inner most lining is the urothelium, a transitional stratified epithelium. Most ailments of the system arise from primary obstructions or from inflammation. Urolithiasis designates the presence of calculi or uroliths in the urinary passages.
Minerals predominate in plugs.
Several factors are important in precipitating disease and in predisposing to calculus formation. Predisposing factors are a preceding infection, reduced water intake, diet-induced changes of urine pH and inborn errors of metabolism. This obstructive disease of the urethra occurs quite often in male, intact cats. Urethral obstruction induces post-renal azotemia, dysuria and hematuria. Secondary bacterial infection causes severe hemorrhagic, transmural cystitis.