Perineal urethrotomy for removal of cystic calculi in a gelding.

A 10-year-old 575-kg ~horoughbred gelding was admitted to the equine hospital because of a 4-month history of intermittent hematuria. Brownish-red urine was noticed after the horse was ridden. The history suggested that the urine discoloration might be related to exercise-induced myositis and associated myoglobinuria. Intravenous fluid therapy, nonsteroidal anti-inflammatory agents, and reduction of the grain diet did not alter the clinical signs. Muscle enzymes were not measured. Further examination of the urine examined at the farm revealed a pH of 8.5, and the urine contained calcium carbonate crystals. Examination per rectum indicated a 6 X 2.5 X 4-cm mass within the bladder lumen. Although the mass was moveable, it was believed to be adherent to the bladder wall mucosa. Differential diagnosis included calculus formation, dystrophic calcification of the bladder mucosa. or neo~lasia. Physical examination at this clinic revealed an alert horse in good body condition. The horse's rectal temperature was 38 C, pulse rate was 36 beatdmin, and respiratory rate was 18 breathdmin. Transrectal ultrasonography of the bladder by use of a 5.0-MHz linear transducer confirmed the location of the mineralized mass (Fig 1). The differential diagnosis for neoplasia was not ruled out. Percutaneous ultrasonographic appearance of the kidneys was normal. The CBC, hemoglobin content, platelet count, serum electrolyte concentrations, BUN concentration, creatinine concentration. and serum biochemical values were all within referenke ranges. Results of urinalysis were indicative of hematuria (30 to 40 R B ~ ~ O O X field). No bacteria were isolated from urine by aerobic culture. A tentative diagnosis of hematuria secondary to a cystic calculus was made. Options for treatment included subischial urethrotomy, laparocystotomy, pararectal cystotomy and electrohydraulic 1ithotripsy.l-lo Subischial urethrotomy was selected because it is easily performed, does not require general anesthesia, and complications are minimal.1.4.8-10 Large cystic calculi can be fragmented manually with whelping forceps or a lithotrite, and urethral calculi may be removed through the same approach. Some of the disadvantages of this technique, as compared with laparocystotomy, are in-