Methods: Consented patients who undergo urogenital surgery and fail their post-operative voiding trial will be randomized to either extended release nitrofurantoin 100mg or an identical appearing placebo capsule to be taken daily while performing CISC and for three subsequent days after stopping CISC. Catheterized urine specimens will be sent for culture and sensitivity when women report symptoms consistent with cystitis. Symptomatic UTI will be defined using strict culture-based definitions. We anticipate that the study will end within 6 weeks of starting CISC.