One of the most common complications after pelvic floor surgery is an urinary tract infection (UTI), with an estimated risk of 10-64%. Antibiotics as prophylaxis may reduce the prevalence of UTI’s by 50%, but microbial resistance is a large disadvantage, necessitating the search for other prophylactic options.
Cranberry products have been used before to reduce the incidence of UTI’s. Cranberries contain A-type proanthocyanidins (PACs), which interfere with the attachment of fimbriae of the E. Coli bacteria to uroepithelial cells and thereby prevent the bacteria to ascend to the bladder. Recent research found a 50% reduction (approximately 40% to 20%) in the rate of UTI’s with the use of cranberry capsules after elective gynecologic surgery suggesting that cranberry capsules may serve as a good prophylaxis for UTI’s peri-operatively.1
The aim of this study was to assess whether peri-operative cranberry prophylaxis reduces the risk of clinical overt UTI after elective pelvic floor surgery with indwelling catheter postoperatively compared with placebo.

We conducted a single center randomized, double blind, placebo controlled trial. All women, planned for pelvic organ prolapse or incontinence surgery were informed about the trial. Women were randomized for cranberry prophylaxis with a cranberry product containing 36 mg of Proanthocyanidin (PAC-A) twice daily, or identical placebo capsules. Treatment started the evening before surgery and study medication was used for 6 weeks. 
Primary endpoint was incidence of clinical diagnosis of UTI within 6 weeks after surgery, defined as clinical diagnosis and treatment of UTI by the medical doctor blinded for investigation arm. Secondary endpoints were proven UTI by microbiological  urine culture, type of bacteria growing in the urine culture and safety endpoints like allergic reactions. In our power analysis we calculated a sample size of 100 women in each arm, as we expected the rate of UTI to drop from 40% to 20% and expected a 10% drop-out. Per protocol analysis was performed.

Between October 2016 and September 2018 210 women were included in this trial, of which 204 participants completed the study. These women, 102 in each arm, were included for primary analysis. Baseline characteristics were similar in both arms for age, postmenopausal status, body mass index (BMI), ethnicity and delivery in history. In the placebo group more women experienced a UTI in the past year (table 1). Most performed surgeries were anterior repair, posterior repair, sacrospinous ligament fixation (SSF), separately or in combination. Significantly more SSFs were performed in the control group: 60,8% versus 44,1% in the intervention group (p=0,02). Peri-operative complications were similar in both groups, 0 in the cranberry group and 2,7% in the placebo group (p=0,08). Postoperative urinary retention was also not significantly different (11,8% versus 10,8% respectively, p=0,83).
There was no significant difference in primary endpoint, the clinical diagnosis of UTI between the cranberry arm  (n=13, 12,7%) and the placebo arm (n=21, 20,6%; p=0,13). No significant difference was found in growth in urine cultures, respectively 8,8% and 13,7% (p=0,27). Compliance to treatment protocol was high (88,2% and 82,4% respectively) and not significantly different between both arms. There were no differences in reported serious adverse events, nor in side effects, respectively 8,8% and 7,8% (p=0,90). Reported side effects were mostly gastrointestinal. In the cranberry group one women experienced allergic reaction of the skin.

The incidence of UTI was 12,7% in de cranberry arm and 20,6% in the placebo arm, this was not a significant difference. This might be explained by underpowerment of the trial, due to lower prevalence of UTI in this trial than anticipated.

This trial shows no beneficial effect of cranberry prophylaxis in women undergoing pelvic floor surgery, although such effect cannot be ruled out in settings with a higher prevalence of UTI’s.

Foxman B, Cronenwett AEW, Spino C, et al. Cranberry juice capsules and urinary tract infection after surgery: results of a randomized trial. Am J Obstet Gynecol 2015;213:194.e1-8.