Prophylactic antibiotics to reduce the risk of urinary tract infections after urodynamic studies

Urodynamics is an invasive test which involves inserting a catheter into the bladder in order to help with diagnosis of bladder symptoms. It carries the risk of causing a urinary tract infection. We need to balance the risk of a urinary tract infection and the symptoms associated with such an infection (such as fever, pain passing urine) against the risk and cost of giving prophylactic antibiotics. Some people also pick up an increased number of bacteria in the urine but do not develop the signs of an infection (asymptomatic bacteriuria). We looked at the use of prophylactic antibiotics for the prevention of urinary tract infections and bacteriuria. We identified nine trials including 973 people. We found that people were less likely to have bacteria in their urine after urodynamic studies if they had antibiotics (4% versus 12%). While they did have fewer urinary tract infections (20% compared with 28% with no antibiotics), this did not reach statistical significance. There were too few adverse effects, such as fever, pain when passing urine or a reaction to the antibiotics, for the findings to be reliable. However, people were less likely to have blood in their urine with antibiotics. There was no information about other treatments which might help reduce infections, nor about different doses or types of antibiotics.

Authors' conclusions: 

Prophylactic antibiotics did reduce the risk of bacteriuria after urodynamic studies but there was not enough evidence to suggest that this effect reduced symptomatic urinary tract infections. There was no statistically significant difference in the risk of fever, dysuria or adverse reactions. Potential benefits have to be weighed against clinical and financial implications, and the risk of adverse effects.

Read the full abstract...

There is a risk that people who have invasive urodynamic studies (cystometry) will develop urinary tract infections or bacteria in the urine or blood. However, the use of prophylactic antibiotics before or immediately after invasive cystometry or urodynamic studies is not without risks of adverse effects and emergence of resistant microbes.


To assess the effectiveness and safety of administering prophylactic antibiotics in reducing the risk of urinary tract infections after urodynamic studies. The hypothesis was that administering prophylactic antibiotics reduces urinary tract infections after urodynamic studies.

Search strategy: 

We searched the Cochrane Incontinence Group Specialised Trial Register, MEDLINE (January 1966 to January 2009), CINAHL (January 1982 to January 2009), EMBASE (January 1966 to January 2009), PubMed (1 January 1980 to January 2009), LILACS (up to January 2009), TRIP database (up to January 2009), and the UK NHS Evidence Health Information Resources (searched 10 December 2009). We searched the reference lists of relevant articles, the primary trials and the proceedings of the International Urogynaecological Association International Continence Society and the American Urological Association for the years 1999 to 2009 to identify articles not captured by electronic searches. There were no language restrictions.

Selection criteria: 

All randomized controlled trials and quasi-randomized trials comparing the use of prophylactic antibiotics versus a placebo or no treatment in patients having urodynamic studies were selected. Two authors (PL and RF) independently performed the selection of trials for inclusion and any disagreements were resolved by discussion.

Data collection and analysis: 

All assessments of the quality of trials and data extraction were performed independently by two authors of the review (PL and RF) using forms designed according to Cochrane guidelines. We attempted to contact authors of the included trials for any missing data. Data were extracted on characteristics of the study participants including details of previously administered treatments, interventions used, the methods used to measure infection and adverse events.

Statistical analyses were performed according to Cochrane Collaboration guidelines. Data from intention-to-treat analyses were used where available. For the dichotomous data, results for each study were expressed as a risk ratio (RR) with 95% confidence interval (CI) and combined for meta-analysis using the Mantel-Haenszel method.

The primary outcome was urinary tract infection. Heterogeneity was assessed by the P value and I2 statistic.

Main results: 

Nine randomized controlled trials involving the prophylactic use of antibiotics in patients having urodynamic studies were identified and these included 973 patients in total; one study was an abstract. Two further trials were excluded from the review. The methods of the included trials were poorly described.

The primary outcome in all trials was the rate of developing significant bacteriuria, defined as the presence of more than 100,000 bacteria per millilitre of a mid-stream urine sample on culture and sensitivity testing. The other outcomes included pyrexia, haematuria, dysuria and adverse reactions to antibiotics.

The administration of prophylactic antibiotics when compared to a placebo reduced the risk of significant bacteriuria (4% with antibiotics versus 12% without, risk ratio (RR) 0.35, 95% CI 0.22 to 0.56) in both men and women. The administration of prophylactic antibiotics also reduced the risk of haematuria (RR 0.46, 95% CI 0.23 to 0.91). However, there was no statistically significant difference in the primary outcome, risk of symptomatic urinary tract infection (40/201, 20% versus 59/214, 28%; RR 0.73, 95% CI 0.52 to 1.03); or in the risk of fever (RR 5.16, 95% CI 0.94 to 28.16) or dysuria (RR 0.83, 95% CI 0.5 to 1.36). Only two of 135 people had an adverse reaction to the antibiotics. The number of patients needed to treat with antibiotics to prevent bacteriuria was 12.3. Amongst women, the number needed to treat to prevent bacteriuria was 13.4; while amongst men it was 9.1 (number needed to treat = 1/ absolute risk reduction).