Knight 1996.

Methods	RCT or quasi‐RCT: RCT Setting: USA
Participants	Population: patients undergoing total hip or knee arthroplasty Inclusion criteria:patients undergoing a primary total hip arthroplasty or total knee arthroplasty with sterile urine cultures Exclusion criteria:History of chronic UTIs or a structural urinary abnormality, revision arthroplasty, long‐term suppressive antibiotic therapy Age (mean, range): 66 (35 ‐ 86) years. Number of participants: Eligible: 174 Randomised: 174 Reported: 119 Dropouts (n of participants + reasons): 55 participants were excluded: 35 did not have cultures obtained on postoperative day 5; 5 allocated to treatment group received a urethral catheter; 7 allocated to control group received an IC; 8 required prolonged use of a urethral catheter for medical reasons Follow‐up: until participants were voiding without problems
Interventions	A (n = 62): Indwelling urethral catheter (Foley) placed just prior to surgery. Remained in place for 48 hours. Thereafter, urinary retention was treated with intermittent catheterisation. B (n = 57): Intermittent catheterisation every 6 hours if participants were unable to void or were voiding in volumes of ≤ 50 ml.
Outcomes	Primary outcome (symptomatic UTI): not reported Bacteriuria: A: 5/62; B: 7/57 (P = 0.45) Definition of bacteriuria: > 105 colonies of a predominant organism Number of participants with urinary retention 48 hours after surgery: A:12/62; B:20/57 Costs per participant for the first 48 hours after surgery: A: USD 8.33; B: USD 53.20
Sponsorship/Funding	Not reported
Notes	Urinary retention was defined as the inability to pass urine or if participants were voiding in volumes of ≤ 50 ml Analysis of cost was conducted for the 2 methods of management based on both materials and nursing time components of costs. Antibiotics: All participants received routine antibiotic prophylaxis (cefazolin) every 8 hours for 48 hours; it was not explicitly stated whether other antibiotics except prophylaxis were administered pre‐ or postoperatively. Participant‐controlled analgesia was given to those who had a general anaesthetic. Participants who had an epidural anaesthetic were maintained on the epidural for analgesia for 48 hours. The average number of intermittent catheterisations was 8 per participant (participants were catheterised more frequently than the planned 6‐hour trial interval)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	“Eligible patients were randomized into one of two groups according to the last digit of their medical record number without regard to age, sex or procedure” – sequence generated by rule based on medical record number; not truly random
Allocation concealment (selection bias)	High risk	“Eligible patients were randomized into one of two groups according to the last digit of their medical record number without regard to age, sex or procedure” – allocation not concealed as participant could be identified by medical record number
Blinding of participants	High risk	No information provided but can assume participants were not blinded as indwelling vs intermittent
Blinding of personnel	High risk	“Patients... received an indwelling Foley catheter in the operating room just prior to start of surgery” “Patients… were intermittently straight catheterized every six hours” – can assume that clinicians were not blinded during insertion of catheter and in postoperative care
Blinding of microbiological outcome assessment	Low risk	Urine culture for symptomatic UTI would be assessed by microbiologist, who would not know the allocation of participant to either type of catheter
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No information given for other outcomes
Incomplete outcome data (attrition bias) All outcomes	High risk	“Fifty‐five patients who were enrolled in the trial were eliminated for various reasons: 35 patients did not have cultures obtained on postoperative day 5; five patients to be in group 2 received a Foley; 7 patients to be in group 1 did not receive a Foley catheter; eight patients required prolonged use of a Foley catheter (to accurately monitor intake and output) for medical reasons.” – dropout rate of 55 participants is high.
Selective reporting (reporting bias)	Low risk	Reported all expected outcomes. Unable to access protocol, some uncertainty about selective reporting
Other bias	Unclear risk	"five patients to be in group 2 received a Foley, 7 patients to be in group 1 did not receive a Foley" ‐ these participants were excluded from analysis