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Complications after treatment of urethral obstruction:
1. Post obstructive diuresis
Post obstructive diuresis (POD) is observed in 46 – 74% of cats within 12 hours of relief of urethral obstruction and urine production up to 14 ml/kg/h has been documented (9, 10). Cats with metabolic acidosis have a higher risk of POD and there is a correlation between the severity of POD after 4 hours and venous blood
pH. POD needs to be addressed by adequate  uid therapy particularly initially when patients are severely compromised and do not compensate for  uid loss by food intake and drinking. After 48 hours, 80 to 100%
of cats have urine production of > than 2 ml/kg/h, but the amount of urine produced exceeded the amount of intravenous  uids in only 37% of cats. At later time points it therefore appears that intravenous  uid therapy could be the driving force for the increased urine production. One way to avoid excessive  uid therapy is to decrease the rate of intravenous  uids and see whether the urine output drops accordingly. If so,  uid therapy can be tapered continuously. If urine production is higher than  uid rate, the iv  uids need to be increased and reduction of the  uid rate should be attempted later.
2. Bacterial urinary tract infection
Prophylactic antimicrobial therapy for the prevention
of UTI in catheterized animals is never indicated. One third of cats with an indwelling urinary catheter for 48 hours develop signi cant bacteriuria (11). Only cats with signi cant bacteriuria should be treated with antimicrobial agents. Unless there is evidence of pyelonephritis or septicemia, antibiotics should be administered after removal of the indwelling catheter. At the time the catheter is removed, a urine sample is again sent for culture and sensitivity testing.
3. Trauma to the urethra with formation of strictures
An uncommon complication of urethral catheterization is trauma to the urethra causing a urethral tear. With a catheter in place to limit the contact of the injured tissue and prevent leakage of urine in the periurethral tissue, tears can heal spontaneously.
4. Repeated urethral obstructions
Repeated urethral obstructions are seen in 17 – 58%
of cats. These can be caused by debris in the bladder that move into the urethra causing a new urethral plug, by spasm of the urethra due to urethritis, urethral injury and stricture formation, and a urethral calculus. The fact that a urinary catheter can be passed does not exclude the presence of a urethral calculus. Documentation
of the site and extent of urethral strictures or urethral neoplasia are best accomplished by positive contrast urethrography. Two studies have revealed a lower
risk of recurrent urethral obstruction with the use
An Urban Experience
of smaller catheters, indwelling catheters for more than 26 hours, and the use of prazosin compared to phenoxybenzamine.
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