Coyle 2015.

Study characteristics
Methods	Study design: RCT Dates study conducted: January 2012‐July 2013
Participants	Number of participants: 46 eligible; 44 randomised (22 in each arm); 35 reported (7 participants in Group A did not receive intervention, 1 participant from Group A excluded from analysis (catheter reinserted); 2 participants from Group B excluded from analysis due to medical necessity) Setting: Galway Country: Ireland Population: mixed (30 male, 14 female) Age (mean): A 63.5; B 62 Inclusion criteria: 18 years old; competent to consent for research purposes; plan to undergo elective transabdominal colectomy, proctectomy or coloproctectomy with post‐operative epidural analgesia Condition for hospitalisation: elective transabdominal colectomy, proctectomy or coloproctectomy Exclusion criteria: Pre‐operative: prior surgery to lower urinary tract; pre‐existing lower urinary tract disease; intermittent self‐catheterisation; neurogenic bladder; pregnancy; prior transabdominal pelvic surgery; known enterovesical fistula; planned; synchronous urinary tract surgery; anticholinergic therapy; IPSS ≥ 20; urethral catheter indwelling > 24 h prior to surgery Post‐operative: epidural analgesia withdrawn ≤ 12 h post‐operatively; surgical instrumentation of or dissection involving the urinary tract; delay in removal of IUC due to medical necessity; pelvic sepsis at surgery; unexpected finding of entero‐ or rectovesical fistula at surgery; premature dislodgement of urethral catheter; failed epidural catheterisation Use of antibiotic prophylaxis: not reported
Interventions	Group A: urethral catheter removal 48 h post‐op (n = 13) Group B: urethral catheter removal within 12 h of withdrawal of epidural analgesia (n = 20) Size and type of catheter used: not reported Study definition of short‐term catheterisation (days): not reported Intended duration of catheterisation for each group: A: 48 h B: 12 h after withdrawal of epidural analgesia (median duration of catheterisation was 85.5 h)
Outcomes	Development of post‐operative urinary retention (total) Bacteriuria (UTI)
Definition of CAUTI or bacteriuria	Symptomatic or asymptomatic bacteriuria used. Unclear which definition is used however
Sponsorship/funding	None
Ethical approval	“Ethical approval given by the local Clinical Research Ethics Committee (CA 661)”
Notes	In total, 9 participants (20.5%) were excluded from analysis during the post‐operative period. In SG1, 7 patients were excluded due to the following reasons: premature accidental dislodgement of IUC (n = 2); epidural catheter dislodgement < 24 h post‐operatively (n = 2), unplanned instrumentation of the urinary tract at surgery (n = 1); IUC re‐inserted post‐operatively due to oliguria (n = 1); withdrawal of consent for patient participation (n = 1). In SG2, 2 participants were excluded due to IUC removal being delayed as a result of medical necessity.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “… were randomised using a computer generated randomisation system” Comment: adequate method of randomisation
Allocation concealment (selection bias)	Low risk	Quote: “The operator was blinded as to the allocated arm, which was contained in a sealed envelope, at the time of catheter insertion.” Comment: adequate method of allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not reported – unlikely it was possible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Blinding of microbiological outcome (detection bias)	Low risk	Not reported. Likely however that samples were sent to a laboratory where the microbiologist would be unaware of the study
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Flowchart indicates that group A reported on 14 patients and group B on 20 patients – but in table there are only 13 patients in group A
Selective reporting (reporting bias)	Low risk	All outcomes in methods are reported in full in results.
Other bias	Low risk	Appears to be free from other sources of bias