BACKGROUND: People requiring long-term bladder draining with an indwelling catheter can experience catheter blockage. Regimens involving different solutions can be used to washout catheters with the aim of preventing blockage. OBJECTIVES: To determine if certain washout regimens are better than others in terms of effectiveness, acceptability, complications, quality of life and economics for the management of long-term indwelling urinary catheterisation in adults. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Specialised Trials Register, MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, CINAHL and EMBASE (searches last updated April 2009). Additionally, we examined all reference lists of identified trials. SELECTION CRITERIA: All randomised and quasi-randomised trials comparing catheter washout policies (e.g. washout versus no washout, different washout solutions, frequency, duration, volume, concentration, method of administration) in adults (16 years and above) in any setting (i.e. hospital, nursing/residential home, community) with an indwelling urethral or suprapubic catheter for more than 28 days. DATA COLLECTION AND ANALYSIS: Data were extracted by three reviewers independently and compared. Disagreements were resolved by discussion. Data were processed as described in the Cochrane Handbook. If the data in trials were not fully reported, clarification was sought from the authors. For categorical outcomes, the numbers reporting an outcome were related to the numbers at risk in each group to derive an risk ratio (RR). For continuous outcomes, means and standard deviations were used to derive weighted mean differences (WMD). No meta-analysis of study results was possible. MAIN RESULTS: Five trials met the inclusion criteria involving 242 patients (132 completed) in two cross-over and three parallel-group randomised controlled trials. Only three of the eight pre-stated comparisons were addressed in these trials. Some trials addressed more than one comparison (e.g. washout versus no washout and one type of washout solution versus another). The analyses reported for the two cross-over trials were inappropriate as they were based on differences between groups rather than differences within individuals receiving sequential interventions. Two parallel-group trials had limited value: one combined results for suprapubic and urethral catheters and one had data on only four participants. Only one trial was free of significant methodological limitations, but its sample size was small. Three trials compared no washout with one or more washout solution (saline or acidic solutions) and authors tended to conclude no difference in clinical outcomes between washout and no washout. In the one trial which had data of sufficient quality to allow interpretation, no difference was detected between washout and no washout groups in the rate of symptomatic urinary tract infection or time to first catheter change. Three trials compared different types of solution: saline versus acidic solutions (two trials); saline versus acidic solution versus antibiotic solution (one trial). Authors tended to report no difference between different washout solutions but the data were too few to support their conclusions. The one trial which warranted consideration concluded no difference between saline and an acidic solution in terms of symptomatic urinary tract infections or time to first catheter change. AUTHORS' CONCLUSIONS: The data from five trials comparing differing washout policies were sparse and trials were generally of poor quality or poorly reported. The evidence was too scanty to conclude whether or not washouts were beneficial. In the first instance we require further rigorous, high quality trials with adequate power to detect any benefit from washout being performed as opposed to none. Then trials comparing different washout solutions, washout volumes, frequencies/timings and routes of administration are needed.