Feline urological syndrome (FUS) ‐ theory and practice

Feline urological syndrome (FUS, urolithiasis, feline urethral obstruction, ‘blocked cat’) is the most important condition of the lower urinary tract of the cat, both because of its frequency of occurrence and the immediately serious nature of some facets of the clinical condition. It is also an enigmatic disease on which much clinical and research effort has been expended, but about which much remains to be understood. Problems include those of definition, of aetiology and of pathogenesis, and each are of practical as well as theoretical importance. The first, in the absence of a single diagnostic criterion, is clearly essential as a basis for clinical management. Considerable efforts have been made to define a single cause or aetiology but have not proved helpful and it is now clear that the development of FUS may be related to a number of factors. Understanding of the pathogenesis of FUS remains patchy, for while the metabolic consequences of urethral obstruction are relatively well understood, little is known of the earlier, pre‐clinical stages of the disease where the role of struvite crystals and the colloid matrix of the obstructing material remains unclear. These aspects, and their relevance in the management of clinical FUS will be discussed.