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Disorders of the lower urinary tract are common in cats. Optimal patient care depends on an accurate diagnostic assessment of clinical information and thoughtful analysis of the trade offs between the benefits and risks of further testing and treatment. Systematic approaches to data collection can minimize diagnostic uncertainty and maximize diagnostic efficiency.

Crystalluria results from oversaturation of urine with crystallogenic substances. However, oversaturation may occur as a result of in vivo and in vitro events. Therefore, care must be used not to overinterpret the significance of crystalluria. Evaluation of urine crystals may aid in (1) detection of disorders predisposing cats to urolith or matrix-crystalline urethral plug formation; (2) estimation of the mineral composition of uroliths or urethral plugs; and (3) evaluation of the effectiveness of medical protocols initiated to dissolve or prevent urolithiasis.

Congenital urinary tract disorders of young cats may result from heritable (genetic) or acquired disease processes that affect differentiation and growth of the developing urinary tract, or from similar disease processes that eventually affect the structure or function of the mature urinary system. Although congenital diseases of the feline lower urinary tract are uncommon, clinical signs associated with these anomalies may be indistinguishable from those of other acquired causes of lower urinary tract disease. Early detection and proper management of congenital disorders may result in restoration of urinary bladder and urethral function and/ or progressive urinary tract dysfunction.

Many forms of therapy currently used for empiric treatment of feline low.er urinary tract diseases represent significant predisposing factors for fungal infection (i.e., prolonged antibiotic and/ or glucocorticoid therapy, aciduria, and indwelling transurethral catheters). Therapy of fungal urinary tract infection should be based on the eat's clinical history, physical examination, and laboratory findings. Amelioration of risk factors has been associated with spontaneous resolution of funguria. For other patients, alkalinization and administration of antifungal chemotherapy are needed to control disease.

Lower urinary tract disorders of male and female cats may be caused by a variety of fundamentally different causes. The term Feline urologic syndromeshould be abandoned and substituted with descriptive etiopathogenic terms whenever possible. If the underlying cause cannot be identified, the term Idiopathic lower urinary tract diseaseis recommended.

A variety of different types of uroliths occur in cats, of which calcium oxalate and magnesium ammonium phosphate are the most common. Treatment and prevention are most likely to be successful if associated risk factors are identified and eliminated or controlled.

Feline urethral plugs commonly are composed of large quantities of matrix mixed with minerals (especially struvite). However, some urethral plugs are composed primarily of matrix, some consist of sloughed tissue, blood, and/ or inflammatory reactants, and a few are composed primarily of aggregates of crystalline minerals. The formation of matrix-crystalline urethral plugs may be analogous to the preparation of fruit jello.

Understanding the biologic behavior of diseases is crucial to determine when to treat and when not to intervene. Under normal circumstances, the body is equipped to defend against invasion and to repair itself once disease has been mitigated. In fact, if given the opportunity to resolve its own dilemmas, the body can develop life-long natural protection to repeat invasion by some diseases. This article discusses the natural course of several common urinary tract diseases in cats.