If you don't remember your password, you can reset it by entering your email address and clicking the Reset Password button. You will then receive an email that contains a secure link for resetting your password
If the address matches a valid account an email will be sent to __email__ with instructions for resetting your password
The risk of urinary tract infection (UTI) among women undergoing elective gynecological surgery during which a catheter is placed is high: 10-64% following catheter removal. We conducted the first randomized, double-blind, placebo-controlled trial of the therapeutic efficacy of cranberry juice capsules in preventing UTI after surgery.
We recruited patients from a single hospital between August 2011 and January 2013. Eligible participants were undergoing elective gynecological surgery that did not involve a fistula repair or vaginal mesh removal. One hundred sixty patients were randomized and received 2 cranberry juice capsules 2 times a day, equivalent to 2 8 ounce servings of cranberry juice, for 6 weeks after surgery or matching placebo. The primary endpoint was the proportion of participants who experienced clinically diagnosed and treated UTI with or without positive urine culture. Kaplan-Meier plots and log rank tests compared the 2 treatment groups.
The occurrence of UTI was significantly lower in the cranberry treatment group compared with the placebo group (15 of 80 [19%] vs 30 of 80 [38%]; odds ratio, 0.38; 95% confidence interval, 0.19–0.79; P = .008). After adjustment for known confounders, including the frequency of intermittent self-catheterization in the postoperative period, the protective effects of cranberry remained (odds ratio, 0.42; 95% confidence interval, 0.18–0.94). There were no treatment differences in the incidence of adverse events, including gastrointestinal upset (56% vs 61% for cranberry vs placebo).
Among women undergoing elective benign gynecological surgery involving urinary catheterization, the use of cranberry extract capsules during the postoperative period reduced the rate of UTI by half.
A metaanalysis of 7 studies of short-term catheterized patients (including men and women and surgeries of various types) found that antibiotics given at the time of catheter removal reduced UTI incidence by approximately 50%, but the risk remained significant: 4.7% within 4 weeks.
However, antibiotic prophylaxis is not an ideal solution because the prevalence of antibiotic resistance among urinary bacterial isolates is very high and continues to increase. Escherichia coli is the most common urinary pathogen; among hospitalized patients in the United States and Europe, approximately 10% of E coli from urinary-associated bacteremia had the extended spectrum beta-lactamase phenotype, and approximately 26% were resistant to levofloxacin.
The American cranberry (Vaccinium macrocarpon) has been widely used for the prevention of urinary tract infections. Cranberry juice may prevent UTIs by selecting against more adhesive strains in the stool, by directly preventing E coli from adhering to uroepithelial cells, or by both of these mechanisms.
A 2012 systematic review and metaanalysis found an overall protective effect of cranberry on UTIs, but there was considerable heterogeneity in results across trials that varied in dose administered, population study, and sample size.
No previous studies of cranberry have addressed effectiveness in reducing the risk of UTIs after catheterization. We begin to fill this gap by conducting a randomized clinical trial of the effectiveness of cranberry juice capsules in preventing UTIs among women undergoing elective gynecological surgery in which a catheter is in place. This is an especially high-risk group because these operations involve surgery adjacent to the bladder and delayed bladder emptying is common. Because catheter insertion and removal introduces bacteria and causes trauma that may increase UTI risk, we also take into account frequency of intermittent catheterization following removal of the Foley catheter.
Materials and Methods
We conducted a randomized, double-blind, placebo-controlled study of the therapeutic efficacy of 2 cranberry juice capsules 2 times a day, equivalent to 2 8 ounce servings of cranberry juice, for approximately 6 weeks after elective gynecological surgery in preventing UTIs after catheterization.
The Institutional Review Board at the University of Michigan approved the study protocol; all participants gave written informed consent. The use of cranberry capsules for this trial was approved by the Food and Drug Administration (IND 111959) (ClinicalTrials.gov identifier NCT01346774).
We recruited study participants between August 2011, and January 2013, from patients referred by physicians from the Urogynecology and Minimally Invasive Surgery clinics of the University of Michigan Division of Gynecology at the time of their preoperative visit for elective gynecological surgery. The urogynecology clinic specializes in the surgical management of pelvic organ prolapse, urinary incontinence, and anal incontinence; the Minimally Invasive Surgery clinic specializes in the surgical management of fibroids, endometriosis, and pelvic pain. All surgeries were performed within the University of Michigan Hospital System and followed the hospital’s standard operating procedures.
Eligible participants were nonpregnant women at least 18 years of age without a history of nephrolithiasis, congenital urogenital anomaly or neurogenic bladder, or any known allergy to cranberry products and who did not require therapeutic anticoagulant medicine during the 6 weeks after surgery or whose surgery did not involve a fistula repair or a vaginal mesh removal.
The primary endpoint was the proportion of participants who experienced clinically diagnosed and treated UTI whether or not results from a urine culture were available. Diagnosis and treatment were up to the treating physician. Secondary endpoints included the incidence of UTI caused by E coli and time from randomization to UTI. Safety endpoints included adverse events and serious adverse events.
TheraCran cranberry and placebo capsules were provided by Theralogix, LLC (Rockville, MD), gratis, asking only that results be made available to them at the time of publication. Based on proanthocyanidin content, the 4 cranberry capsules are equivalent to 2 8 ounce servings of cranberry juice.
Participants were directed to take 2 capsules by mouth twice each day (once in the morning and once in the evening), starting at the time of discharge for 4-6 weeks, or until their return for their postoperative doctor’s visit. Participants were instructed to drink an 8 ounce glass of water while taking the capsule with or without food.
Concomitant medications, foods, and beverages
Participants were instructed not to consume any cranberry products (including whole fruit, jellies, juices, or dietary supplement capsules containing cranberry) or vitamin C supplements beyond the assigned regimen. Compliance was assessed at each follow-up contact.
Participants were randomized at time of surgery, a median of 18.5 days following enrollment (range, 0–146 days). Because bacteriuria increases with age, we balanced treatment groups by age (younger than 60 years vs 60 years or older), based on the expected median age of our study population. Stratified randomization (1:1 Theracran cranberry capsules–placebo) was performed using computer-generated permuted blocks, with a block size known only to the Data Coordinating Center. The Data Coordinating Center provided a randomization schedule for the supplier who printed labels that were placed on each bottle of capsules.
After participants were deemed eligible, study coordinators performed the randomization using the next available randomization number on a stratum-specific list provided by the Data Coordinating Center.
All study personnel (with the exception of designated individuals at the Data Coordinating Center), treating physicians, and patients were masked to treatment assignment. The Investigational Drug Service at the University of Michigan stored and managed the capsules and conducted drug accountability.
Study procedures and data collection
After giving informed consent, each participant completed a self-administered questionnaire regarding her medical and sexual history, health behaviors, and symptoms. Following hospital admission, a urine specimen was collected upon catheter insertion in the operating room and catheter removal (from the catheter port). At the time of hospital discharge, research staff provided the participant with enough capsules for 8 weeks of the assigned regimen and administered the first dose. Participants were reminded to take the cranberry capsules daily, continuing 2 times per day until their postoperative visit, usually at 6 weeks.
Research staff also instructed the participants to collect a urine sample if they experienced urinary symptoms consistent with a UTI (painful urination, an urgent need to urinate, pain/pressure in the lower abdomen or pubic area, fever of 100°F or more, or flank pain), provided a urine collection kit (containing a preservative), orders for a urine culture (if needed) that included instructions to the laboratory to forward results to the treating physician at the University of Michigan Health System if the culture was performed elsewhere, and written instructions for at-home urine collection. Participants were given a symptom diary to record any urinary symptoms.
Participants were advised to contact research staff immediately and to collect a urine specimen should they experience urinary symptoms consistent with UTI. When participants contacted research staff, they were administered a brief structured interview regarding the type and duration of symptoms and referred to their physicians for diagnosis and treatment. Urine was cultured using standard microbiological techniques for the presence of uropathogens at the clinical laboratory selected by their treating physician.
Study staff contacted participants within 3 days, and at 2 and 4 weeks after hospital discharge to assess compliance to study protocol, to identify whether the participant had urinary symptoms consistent with UTI, and to elicit any adverse events. These items were also assessed at the 6 week postoperative doctor’s visit using a self-administered questionnaire. At study exit, capsule bottles were collected so capsules could be counted to assess compliance.
Medical records of all randomized study participants were reviewed to identify any missed postoperative symptomatic UTI episodes, adverse events, and medications prescribed. All study participants received an intravenous antibiotic administration prior to the start of the surgical procedure, including urinary catheter insertion (as per hospital protocol).
There were no changes to the methods or trial outcomes after the trial began. There were no interim analyses or stopping guidelines.
The study protocol, including definitions of adverse events, is available upon request.
Sample size was based on logistical and statistical principles. Estimates of the incidence of symptomatic UTI in our patient population were unavailable, and thus, we assumed the UTI rate to be similar to that in the literature for patients receiving prophylactic antibiotics (15–18%).
We believed we could enroll approximately 200 participants (100 per treatment group) and calculated that this sample size would provide at least 80% power with a 2-sided type I error of 5% to detect a large treatment difference (65–75% relative risk reduction) if the UTI rate was 15–20% in the placebo group (based on a 2-sample binomial test, performed using EAST, version 5.1, 2007; Cytel, Cambridge, MA). Recruitment was stopped at 160 randomized participants because of budgetary and timing constraints.
Baseline sociodemographic and medical history characteristics were summarized using descriptive statistics. Primary analyses used an intent-to-treat approach. We used logistic regression to model the incidence of the primary endpoint and to take into account all prespecified risk factors including age, UTI history, the presence of a Foley catheter, and intermittent self-catheterization.
We also summarized treatment differences in the time to UTI using Kaplan-Meier methods and tested these differences with log rank tests. A sensitivity analysis was performed for the primary endpoint, using a modified intent-to-treat analysis population that included only randomized participants who took at least 1 dose of the study medication. In addition, we assessed treatment differences in culture-confirmed UTI and culture-confirmed when E coli was the pathogen. We tested for differences in compliance and safety using the χ2 test.
All analyses were performed using SAS software, version 9.3 (SAS Institute, Cary, NC).
Between August 2011 and January 2013, 359 women presenting for elective gynecological surgery were screened for eligibility; 160 met the inclusion criteria, agreed to participate and were randomized. Almost all (94%) received the allocated intervention (cranberry: 74 of 80 vs placebo: 76 of 80). Reasons for not receiving the intervention included the patient was discharged when staff were not available (n = 2), the participant could not swallow the capsules or returned the bottle unopened (n = 4), the capsules were lost (n = 1), the participant’s physician told her to avoid cranberry (n = 1), the surgery was cancelled (n = 1), or the participant withdrew (n = 1) (Figure 1).
Follow-up was not statistically different by group: 73 of 80 of those allocated to cranberry (91%) and 72 of 80 assigned to the placebo (90%) completed at least 1 follow-up (P = .79); and 41 of 80 of those allocated to cranberry (51%) and 32 of 80 allocated to placebo (40%) completed all 3 follow-up visits. The primary endpoint was obtained for all randomized participants via a review of medical records.
Participants ranged in age from 23 to 88 years (mean ± SD for cranberry: 56 ± 12.5; placebo: 56 ± 14.3). Sociodemographic characteristics and most medical history features were not statistically significantly different by treatment group (Table 1), including the number of UTIs in the 12 months prior to surgery (cranberry: 0.39 ± 0.88; placebo: 0.38 ± 0.80) and treating physician (data not shown). However, those assigned to cranberry were significantly less likely to have required intermittent self-catheterization during the recovery period (31% vs 50%; P = .02), and reported a lower number of self-catheterization episodes per day (cranberry 3.7 ± 3.1 vs placebo 5.5 ± 4.9; P = .08).
Table 1Sociodemographic, baseline, and postoperative characteristics of randomized participants by treatment group
Percentages are based on total responses. Incomplete responses were received for marital status (cranberry: n = 1); income (cranberry: n = 2, placebo: n = 6); race (cranberry: n = 1); NSAID use in the postoperative period (cranberry: n = 14, placebo: n = 20); UTI history (cranberry: n = 3, placebo: n = 2); and postmenopausal status (cranberry: n = 2).
Participants who self-catheterized were more likely to have a history of UTI (72% vs 54%; P = .01; data not shown). Seven women used an indwelling Foley catheter at home for part of the follow-up period (cranberry: n = 3; placebo: n = 4). The decision to discharge a patient with intermittent self-catheterization or a Foley catheter was left to the individual physicians. Patients discharged with a Foley catheter usually are unable to perform catheterization or decline to do so.
Association of cranberry with UTI
Overall, 45 of the 160 participants (28%) had a UTI. The incidence of UTI was significantly lower in the cranberry than the placebo group (15 of 80 [19%] vs 30 of 80 [38%]; odds ratio [OR], 0.38; 95% confidence interval [CI], 0.19–0.79; P = .008). Among participants with a UTI diagnosis, the percentage of those confirmed by culture did not differ between the women assigned placebo or cranberry (77% [23 of 35] vs 80% [12 of 15]; P = .31). When the endpoint was limited to those with culture confirmed diagnosis (>103 CFU/mL urine
), the incidence of UTI was also significantly lower in the cranberry than the placebo group (12 of 18 [15%] vs 23 of 80 [29%]; OR, 0.44; 95% CI, 0.20–0.96; P = .037).
The median time to UTI was significantly longer among those in the cranberry than the placebo group (18 days vs 8.5 days, Figure 2, log rank test, P = .0005). Results did not change in the sensitivity analysis using the modified intent-to-treat analysis population, which excluded the 10 participants who did not take a single dose of study medication.
The beneficial effect of cranberry treatment remained after adjusting for frequency of postoperative self-catheterization and having an indwelling Foley catheter at home in a logistic regression model (OR, 0.42; 95% CI, 0.18–0.94; P = .037) (Table 2). Women who self-catheterized during the postoperative period had a significantly higher incidence of UTI (33 of 65 [51%] vs 12 of 95 [13%]; OR, 7.13; 95% CI, 15.5–3.28; P < .001), but there was no interaction between frequency of self-catheterization and treatment (P = .63). Furthermore, of the 7 participants with an indwelling catheter for part or all of the postoperative recovery period, 1 of 3 assigned to cranberry and 3 of 4 assigned to placebo had a UTI. (The one woman who had a Foley catheter throughout the entire study period developed a UTI based on endpoint criteria.)
Table 2Effect of cranberry juice pills on risk of urinary tract infection, adjusting for having an indwelling catheter at home, and frequency of self-catheterization
The increased risk of UTI associated with discharge with an indwelling Foley catheter remained after adjusting for frequency of intermittent catheterization following Foley removal during the postoperative period and the effects of cranberry (OR, 7.3; 95% CI, 1.42–42.07; P = .018 [Table 2]). There was no association between UTI history (both in the previous 12 months and any time during life) and UTI risk after surgery (data not shown).
E coli was the most common infecting organism (cranberry: 38%; placebo: 46% [Table 3]). Considering only those with a UTI caused by E coli, the risk of UTI among those taking cranberry was reduced by an estimated 62% (OR, 0.38; 95% CI, 0.13–1.13; P = .07). The second most common infecting bacterial species was Klebsiella pneumoniae among the cranberry group (23%) and Enterococcus among the placebo group (23%). The vast majority of cultures had 105 CFU/mL urine or greater of the infecting bacteria (92% for cranberry and 81% for placebo), and all urine cultures had at least 1 species occurring at greater than 104 CFU/mL urine; 4 positive cultures reported 2 bacterial species.
Table 3Distribution of microorganisms causing urinary tract infection by treatment group
Of the 45 participants who had a primary outcome (UTI) culture results were not available for 10 participants (cranberry: n = 3, placebo: n = 7) with clinically diagnosed and treated urinary tract infection. Numbers may not sum to totals because more than 1 species was present in 4 cultures (cranberry: n = 1, placebo: n = 3). Greater than 104 CFU/mL urine of a potential uropathogen were detected in all positive cultures. In the culture positive for yeast, there were 105 CFU/mL urine; the culture positive for Lactobacillus (103 CFU/mL urine) also had 105 CFU/mL urine of Escherichia coli. There were 105 CFU/mL urine reported for the mixed culture.
Cranberry (n = 12)
Placebo (n =23)
Total species detected
UTI, urinary tract infection.
Foxman. Cranberry juice capsules and UTI. Am J Obstet Gynecol 2015.
a Of the 45 participants who had a primary outcome (UTI) culture results were not available for 10 participants (cranberry: n = 3, placebo: n = 7) with clinically diagnosed and treated urinary tract infection. Numbers may not sum to totals because more than 1 species was present in 4 cultures (cranberry: n = 1, placebo: n = 3). Greater than 104 CFU/mL urine of a potential uropathogen were detected in all positive cultures. In the culture positive for yeast, there were 105 CFU/mL urine; the culture positive for Lactobacillus (103 CFU/mL urine) also had 105 CFU/mL urine of Escherichia coli. There were 105 CFU/mL urine reported for the mixed culture.
The average amount of time from a participant’s surgery, when they started study drug, to their termination from the study was 38 days (SD, 24; range, 0–227). At study exit, of the 130 participants with information available, 110 (85%) reported taking 2 capsules twice a day most or all of the time. Most participants reported following the prescribed regimen at the 2 week (89%) and 4 week (82%) follow-up contacts. Pill counts were available for a similar number of participants by treatment assignment (cranberry: n = 57, placebo: n = 60); participants averaged 3 capsules per day in both treatment groups. Compliance was not statistically significantly different by treatment group using any measure of compliance.
The proportion of participants with adverse events and serious adverse events did not differ by treatment groups (P = .28 and P = 1.00, respectively). Seventy-five participants experienced 328 adverse events in the cranberry group, and 78 participants experienced 423 adverse events in the placebo group. Four participants experienced 5 severe adverse events in the cranberry group and 4 participants experienced 7 adverse events in the placebo group. Gastrointestinal upset was the most commonly reported event in both groups (cranberry: n = 45 [56%]; placebo: 49 [61%]).
This is the first report of a double-blind, placebo-controlled randomized clinical trial demonstrating a statistically and clinically significant benefit of taking cranberry in preventing UTI after elective gynecological surgery during which a urinary catheter is placed. This reduction in UTI risk is similar in magnitude to that reportedly obtained by administering antibiotics at the time of catheter removal
In our previous cranberry trial conducted among college students during which we used juice, the placebo juice contained similar levels of vitamin C to that found in cranberry juice. We observed no effect of cranberry in that trial, perhaps because vitamin C has been observed to have a beneficial effect on UTI risk.
Several strengths in the study design and analysis of this trial make it unlikely that the difference in outcome was due to (alpha) error. The design, conduct, and analysis of the trial, including randomization scheme, blinding of study personnel and participants, and active surveillance for outcomes, were held to the highest standards. Furthermore, after analyses took into account known risk factors (the need for intermittent self-catheterization, UTI history, and age), the findings remained consistent, with cranberry mitigating the risk for UTI. This suggests that our results might be generalized to women undergoing laparoscopic or vaginal surgery for benign gynecological procedures in which a catheter is placed.
Developing practices to reduce UTI risk is a promising area for quality improvement. Considering the use of intermittent catheterization is a potential example. Each time a catheter is inserted, the bladder is inoculated with bacteria, and there is some subtle trauma, increasing a risk of infection. Among the 65 women who reported intermittent catheterization, the median number of times was 15 (mean, 32; range, 1–216 times) during the postoperative period. Developing patient education to reduce the number of times that intermittent catheterization is undertaken might reduce UTI risk. Moreover, our results suggest that discharging a patient from the hospital with an indwelling catheter in place should be avoided if possible. These women experienced a 7-fold increase in UTI risk after adjusting for cranberry use and frequency of intermittent catheterization.
Future studies might aim to optimize the time of catheter insertion and removal and to develop strategies to reduce the frequency of intermittent catheterization. At least 1 previous trial compared different timings of urinary catheter removal following abdominal hysterectomy. Removal immediately following surgery was associated with increased urinary retention and removal after 24 hours with increased risk of UTI; removal at 6 hours resulted in the fewest adverse events.
Strategies to decrease the length of time associated with catheterization may need to be carefully considered in each case, weighing the risks of postoperative urinary retention and overdistension against that of UTI, but are promising areas for future research to decrease this common infection.
We thank Dr Jack Sobel for serving as data and safety monitor; the staff at Statistical Analysis of Biomedical and Educational Research unit for technical assistance; the participating patients, physicians, physician assistants, and nurses at the Urogynecology and Minimally Invasive Gynecologic Surgery clinics and University of Michigan Hospitals; and Alexandra Beach, Erin Case, and Marian Turner for outstanding work as recruiters. We are also very grateful to Bill Reisdorph of the Michigan Institute for Clinical and Health Research (MICHR) (2UL1TR000433-06) for his assistance with obtaining the reporting requirements for an investigational new drug designation, and Michigan Institute for Clinical and Health Research for clinical monitoring. We also thank Theralogix, LLC (Rockville, MD) for providing cranberry juice capsules and placebo for use in this study.
Prevalence of healthcare-associated infections in acute care hospitals in Jacksonville, Florida.
This work was supported by the National Institutes of Health (grant R21-DK-085290 ). M.B.B. received investigator support through the University of Michigan Building Interdisciplinary Research Careers in Women’s Health Career Development Program (grant K12-HD-001438).
The authors report no conflicts of interest.
Cite this article as: 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.