To compare the efficacy and time-to-discharge of two methods of trial of void (TOV): bladder infusion versus standard catheter removal. Our hypothesis is that bladder infusion prior to TOV will lead to improved time-to-discharge.

Electronic searches for randomised controlled trials (RCTs) comparing bladder infusion versus standard catheter removal were performed using multiple electronic databases from dates of inception to June 2020. Participants underwent TOV after acute urinary retention or post-operatively after intraoperative indwelling catheter (IDC) placement. Quality assessment and meta-analyses were performed, with odds ratio and mean time difference used as the outcome measures.

Eight studies, comprising 977 patients, were included in the final analysis. Pooled meta-analysis demonstrated that successful TOV was significantly higher in the bladder infusion group compared to standard TOV (OR 2.41, 95% CI 1.53-3.8, P=0.0005), without significant heterogeneity (I2=19%). The bladder infusion group had a significantly shorter time-to-decision in compared to standard TOV (weighted mean difference(WMD) – 148.96 minutes, 95% CI -242.29, -55.63, P=0.002) and shorter time-to-discharge (WMD -89.68 minutes, 95% CI -160.55, -18.88, P=0.01). There was no significant difference in complication rates between the two groups.

The current study has several limitations. Firstly, the relatively small sample size of included studies limits certainty in reaching definitive conclusions, while the magnitude of effect is of uncertain significance without robust and dedicated cost-effectiveness analysis. Secondly, individualised patient data were not available for each study, so adjustment for heterogeneity in factors known to contribute to TOV success was not possible.  These important factors may include factors related to patient selection (IDC insertion for acute or chronic urinary retention, postoperatively, success/failure definition), duration or complexity of surgery, or pre-existing patient factors (e.g. TURP for IDC dependence due to detrusor failure, medications including diuretics and alpha blockers, co-morbidities). Fortunately, the subgroup analysis according to specialty (urological, gynaecological and other/combined surgeries) was possible, which grouped similar patient demographics and definitions of TOV success/failure. While the significance and explanation for heterogeneity in meta-analysis is complex, the more homogeneous results according to specialty and gender may suggest a greater benefit in women postoperatively, compared to men or following urinary retention. 

The significant benefits observed with bladder infusion indicate this method is worth considering in the general population and particularly surgical patients when acute urinary retention affects 5%-70% of patients postoperatively[1-3] Thirdly, it is difficult to blind ward nursing staff to intervention as part of the trials, and this represents a source of potential bias influencing outcomes. Time to discharge is variable according to institutional and patient factors.  For example, Mowat and colleagues identified difficulty ensuring that participants are committed to discharge from recovery if eligibility criteria are met, and not all staff following strict TOV protocols, as possible confounding variables[2]. These factors, as well as cost-analyses, were not well described in all the included studies, but could considerably affect the outcomes of this meta-analysis.

In conclusion, our pooled analysis of the current literature demonstrates that the bladder infusion technique of TOV may be associated with significantly increased likelihood of successful TOV and subsequently reduced times to discharge in postoperative patients and those with acute urinary retention.  These findings require confirmation in larger, phase III trials specific for the clinical situation (postoperative, acute urinary retention) with appropriate cost-effectiveness analysis to definitively demonstrate an  expected benefit to both individual patients and health systems.

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Mowat A, Brown B, Pelecanos A, Mowat V, Frazer M (2018) Infusion-fill method versus standard auto-fill trial of void protocol following a TVT-exact procedure: A randomised controlled trial. The Australian & New Zealand journal of obstetrics & gynaecology 58 (5):564-569. doi:10.1111/ajo.12780
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