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Risk of recurrent urethral obstruction in cats

Seitz MA, Burkitt-Creedon JM, Drobatz KJ. Evaluation for association between indwelling urethral catheter placement and risk of recurrent urethral obstruction in cats. J Am Vet Med Assoc. 2018 Jun 15;252(12):1509-1520.

Lower urinary obstruction is a common occurrence in male cats that may be life threatening if not treated properly and promptly. Obstruction of the urethra may occur as a result of crystals or stones, mucous plugs, and inflammation from FIC or other conditions, among other causes. Regardless of the cause, placement of a urethral catheter is the standard of care for lower urinary obstruction, as it allows the blockage to be resolved and maintains a patent lumen for urine to drain. The usual protocol involves placement of an indwelling catheter until urine production and metabolic condition have normalized, followed by removal of the catheter and discharge of the patient.

This protocol results in an excellent rate of survival to discharge, especially if animals are metabolically stable on admission. However, re-obstruction rates can be quite high with 15 to 46% of cats re-blocking, often in the first week. One downside to this protocol is the significant cost incurred by clients due to the need for hospitalization, medical therapy, and catheter care. As a result of this, alternative protocols have been developed. Some, not involving any catheterization, have resulted in a significantly lower chance of survival than standard of care. One often practiced “alternative” protocol is placement of a urinary catheter to relieve obstruction and drain the bladder, followed by immediate removal and out-patient therapy. This results in lower client costs, but the prognosis for cats treated in this fashion is not known.

The purpose of this study was to determine if cats receiving the standard of care had a greater 30 day risk of re-obstruction than cats receiving one-time catheterization and outpatient care. The study was designed as a prospective observational study on cats presenting to a private practice over a 1.5 year period.

Male cats greater than 1 year of age with no recent history of urinary tract surgery, urethral or bladder tear, lower urinary neoplasia, urolithiasis, neurologic disease as the cause for UO, trauma, or existing perineal urethrostomy were enrolled. Cats were excluded if their catheter was removed in <12h after placement (for the standard of care group), or if they died of non-urinary issues or were lost to follow up within 30 days post obstruction.  Group assignment was based on owner decision on treatment plan.

163 cats presented to the hospital for urinary obstruction during the study period, of which 91 were enrolled in and completed the study. 46 cats were treated with in-patient therapy and 41 out-patient. No significant differences in age, difficulty of catheterization, urinalysis, results, or other factors were seen between the populations. Only the number of years in practice of treating veterinarians differed (3y for inpatient vs 4y for outpatient).

The incidence of recurrent obstruction within 30 days was 11% for the in-patient group and 31% for the out-patient group, a statistically significant difference. Of the cats who re-obstructed, 95% of the blockages occurred within the first week, with a median of 2.2 days to re-blockage.

Non of the initial patient or veterinarian related factors (ie urinalysis findings, metabolic compromise, difficulty of de-obstruction, duration of catheterization, etc) had any relation not the risk of re-obstruction. However, color of the urine at the time of de-catheterization was significantly correlated with the risk for re-obstruction, with cats with a red urine more likely to re-block.

The overall risk of reobstruction in this study was lower than that reported in previous studies. This may be coincidental, or may be linked to the use of standardized protocols or the exclusion of some of the “sicker” cats presenting.

There were several drawbacks to this study. Among them included the exclusion of many cats with more significant disease(such as bladder stones or urinary tract rupture). While their inclusion in the outpatient group would not have been reasonable, their exclusion may give a more favorable appearance to the data in general. Though treatment plans were standardized, a significant amount of variation inevitably existed between individuals (such as the use of antimicrobials and anti-inflammatories).

The authors concluded that there is an almost 3-fold difference in the risk of urethral obstruction for cats treated with an outpatient when compared to an inpatient protocol. The use of current standard of care therapy including indwelling catheter placement and maintenance of this catheter until urine appearance is grossly normal should be encouraged whenever possible due to decreased risks of re-obstruction in the short term. (MRK)

See also:

Eisenberg BW, Waldrop JE, Allen SE, et al. Evaluation of risk factors associated with recurrent obstruction in cats treated medically for urethral obstruction. J Am Vet Med Assoc 2013;243:1140–1146