Abstract
Abstract
Introduction
Bladder catheterisation is one of the most commonly performed medical procedures worldwide in hospitals. Although traditionally performed as a sterile procedure to prevent infections, it incurs a considerable carbon footprint and substantial healthcare costs. This study aimed to assess whether adopting clean bladder catheterisation as standard hospital practice is non-inferior to sterile catheterisation regarding the occurrence of catheter-associated urinary tract infections (CAUTIs), and to evaluate the carbon footprint of catheterisation sets.
Methods
This retrospective observational non-inferiority study compared the proportion of patients with a suspected CAUTI during a 6-month sterile catheterisation phase and a 6-month clean catheterisation phase. The primary outcome was the proportion of CAUTIs, with secondary outcomes including positive urine cultures, cultured microorganisms and carbon footprint. Non-inferiority of clean catheterisation was assessed using multivariable logistic regression, reporting risk differences (RDs) and 95% CIs. Non-inferiority was concluded when the upper bound of the 95% CI did not exceed the non-inferiority margin of 0.5 percentage point. Interrupted time series (ITS) analysis assessed time trends, and the carbon footprint was evaluated using life-cycle assessment.
Results
Among 3293 catheterised patients, 3.8% (62/1647) in the sterile phase and 3.3% (55/1646) in the clean phase met the criteria for a CAUTI (adjusted RD −0.44% (95% CI −1.4% to 0.5%)). ITS analysis showed no significant change in CAUTI trends following implementation. Positive urine cultures were found in 13.1% (216/1647) and 13.1% (215/1646) of patients in the sterile and clean catheterisation phases (adjusted RD 0.30% (95% CI −2.4% to 1.7%). The carbon footprint of the clean catheterisation set was 70.7%–82.3% lower compared with the sterile sets.
Conclusion
Clean bladder catheterisation was non-inferior to sterile catheterisation in suspected CAUTI rates and significantly reduced the carbon footprint. Our findings suggest that clean catheterisation may be considered as a safe alternative default practice.
Keywords: UROLOGY, Health policy, Hospitals
STRENGTHS AND LIMITATIONS OF THIS STUDY.
This study used a large hospital dataset derived from routinely collected catheterisation records, medication administration data, and microbiological laboratory results, thereby minimising recall bias and reflecting real-world clinical practice.
There were no relevant changes in patient care, infection control precautions or laboratory analysis, a prerequisite for a relevant pre–post comparison.
The observational pre–post design yields an inherent risk of residual or unmeasured temporal confounding, although interrupted time series analysis was used to assess trends over time.
Due to incomplete clinical complication registry data, the study relied on a case definition for catheter-associated urinary tract infections based on matched antibiotic prescriptions and microbiological data.
Introduction
Urinary catheterisation is one of the most frequently performed medical procedures worldwide, primarily for urinary retention or obstruction.1 2 It is estimated that annually nearly 100 million urinary catheters are sold worldwide, and in hospitals, approximately 20% of admitted patients receive a urinary catheter at some point.3 4 To prevent catheter-associated urinary tract infections (CAUTIs), catheterisation is commonly performed by a sterile technique using disposable materials. However, there is no evidence of the superiority of sterile catheterisation over a clean approach in terms of infection prevention, while the disposable materials inherently generate waste, CO₂ emissions and costs. As healthcare systems face increasing pressure to reduce their environmental footprint, re-evaluating such resource-intensive practices has become essential.
Despite a lack of high-quality studies showing the superiority of sterile catheterisation, US Centers for Disease Control and Prevention guidelines recommend inserting urinary catheters using a sterile technique with sterile gloves, a disposable drape, sterile sponges and an antiseptic.5 6 However, the preference for sterility is largely based on expert opinion. In contrast, Dutch infection prevention guidelines acknowledge the absence of high-quality studies and recently recommend clean insertion using non-sterile gloves and no antiseptics.1
In 2024, a tertiary (academic) hospital with around 22 500 annual admissions adopted a ‘clean’, non-sterile urinary catheterisation protocol. This hospital-wide implementation provides a unique opportunity to evaluate the safety of clean catheterisation with regard to CAUTI in a real-world hospital setting.
This study aimed to determine whether clean bladder catheterisation is non-inferior to sterile catheterisation with respect to CAUTI rates following its adoption as standard hospital practice. In addition, this study assessed the number of positive urine cultures, the cultured microorganisms and the carbon footprint of catheterisation sets.
Methods
Study design and setting
This was a retrospective observational non-inferiority study comparing the proportion of patients with a suspected CAUTI preintervention and postintervention. The study was performed in the Radboud University Medical Center, a tertiary referral hospital in the Netherlands. The intervention involved a hospital-wide transition from sterile to clean catheterisation, which was implemented from April to June 2024. Two periods were selected for comparison: a pretransition phase (August 2023 to January 2024), where sterile catheterisation was used, and a post-transition phase (October 2024 to March 2025), after the transition to clean catheterisation. No relevant alterations in patient care or microbiology analysis occurred during the period of August 2023 to March 2025.
Participants
All adult (≥18 years) inpatients who received at least one urine catheter were eligible. Exclusion criteria were patient that underwent: Synergo treatment (thermochemotherapy), conventional intravesical chemotherapy, kidney transplant, urodynamic examinations and those with catheterisations lasting less than 120 min. In our hospital, patients who underwent catheterisation over a guidewire and immunocompromised patients were catheterised by sterile protocol; however, due to registry data, it was not possible to identify and exclude these patients from the analysis.
Implementation project of clean catheterisation
Until April 2024, catheterisation was performed by a sterile technique. After transitioning to clean catheterisation, hospital-wide protocols were revised to a clean (aseptic) technique using non-sterile gloves, non-sterile gauze, anaesthetic gel and tap water (online supplemental C for a detailed protocol, an instruction video (in Dutch), online supplemental D for product specifications). This new clean protocol was uploaded to the hospital system on 3 April 2024, at which moment clean catheterisation became effective hospital-wide. Between April and June 2024, the implementation coordinator (A-KN) visited all clinical departments to introduce and explain the new protocol and provide hands-on training to the clinical and nursing staff. The post-transition phase commenced in October 2024 to allow for a 2-month wash-in period, ensuring extensive time for staff to become familiar with the protocol (figure 1).
Figure 1. Flow diagram and timeline. *Patients undergoing Synergo treatment (thermochemotherapy), conventional intravesical chemotherapy and urodynamic examinations were not included in the eligible population, as catheterisations performed during these procedures are not registered in the hospital catheter registry. Consequently, exclusion counts for these categories could not be quantified.
Protocol adherence
To assess protocol adherence, a hospital-wide questionnaire was distributed among clinical and nursing staff in December 2024. The questionnaire was disseminated by email via coordinators of all clinical departments. Staff were asked whether they worked according to the (new) clean catheterisation protocol, using a five-point Likert scale ranging from never to always. Responses of often or always were considered adherent (online supplemental A). In addition, the number of sterile catheterisation sets purchased by the hospital was obtained from the purchasing department and assessed monthly during the pretransition and post-transition phases. Data from the children’s hospital were excluded as they did not follow the new protocol, as well as data from the training institute. To note, the sterile sets are primarily used in the operating room, while catheterisations on the wards were sterile but did not involve these sets. Relevant purchasing data on the ward procedures could not be obtained, as the products used for sterile catheterisations are also used for other medical purposes (online supplemental D).
Variables and outcomes
The primary outcome was the proportion of patients with an indwelling catheter who met the criteria for a suspected CAUTI. The secondary outcomes included (1) the proportion of positive urine cultures, (2) the spectrum of cultured microorganisms and (3) the carbon footprint of the sterile and clean catheterisation set.
CAUTIs were not routinely and systematically monitored in the healthcare-associated infection surveillance of Radboudumc. Additionally, because CAUTIs are presumed under-reported in the clinical registries and our own hospital complication registry, we could not use this routine registration for the purpose of this study.7 The following case definitions were applied: patients were classified as having a suspected CAUTI if they had an indwelling urine catheter, a positive urine culture from a urine sample collected during catheterisation and received antibiotics that are prescribed for treating a urinary tract infection. The first antibiotic dose had to be administered between 2 days after catheter insertion and up to 7 days after catheter removal. This definition was based on literature and the National Institute for Public Health and the Environment definitions.8 9 Antibiotics were selected based on the Dutch SWAB-ID guidelines (the national electronic antimicrobial guide of the Dutch Working Party on Antibiotic Policy) and in consultation with the medical microbiology department in our institution (online supplemental B for the list of selected antibiotics).10 Regarding the decision to perform a urine culture, there is no hospital-wide guideline; it is based on the clinical judgement of the treating physician.
Data sources
Information on urinary catheter insertion and removal was extracted from the Bedside Input Application, which is used by nursing staff to document device placement and removal at the bedside in the electronic health record. Data on antibiotic administration were retrieved from the medication administration module of the electronic health record system EPIC (Epic Systems Corporation, Verona, WI, USA). Microbiological results, including urine culture outcomes and isolated microorganisms, were obtained from the microbiological laboratory information system GLIMS (MIPS, Gent, Belgium). The clinical information officer performed the data linkage and validation using identifiable patient numbers across all systems to ensure data matching accuracy. Afterwards, the researchers will be provided with a fully anonymised dataset for analysis. No individual patient records were accessed by the research team.
Sustainability: life cycle assessment
A life cycle assessment (LCA) of the catheterisation kits used at the Radboud University Medical Center was conducted. This included two sterile sets and one clean set (online supplemental D).11 The LCA calculated the emissions in kilograms carbon dioxide equivalent (CO2 eq) for each catheterisation set. This cradle-to-grave assessment considered all carbon emissions related to the production, use, and disposal of the equipment. The catheter itself and the anaesthetic gel used during catheterisation were excluded from the assessment, as these were not affected by the transition to the non-sterile catheterisation protocol. The ISO14040 and ReCiPe2016 methodologies were applied.12 13
Data for the assessment were gathered through direct observation and waste audits conducted on the catheterisation sets used within the institution. Data were entered into a life cycle inventory in SimaPro LCA software (PRé Consultants, Amersfoort, the Netherlands) and integrated with the ecoinvent 3.9 and STREAM databases (for Dutch transport processes).13,15 The carbon footprint was calculated using the ReCiPe 2016 method (Midpoint (H)).13
Statistical analyses
Continuous variables are presented as mean±SD or median±IQR, depending on data distribution. Patient and care type characteristics were compared by univariable standardised mean differences (SMDs) between the pretransition and post-transition phases. SMDs directly quantify the magnitude of differences, with an SMD <0.1 suggesting a negligible imbalance within that variable.16 17
Each patient was included only once in the analysis, as some patients received multiple catheters during their admission or across different hospitalisations. If a patient had one catheter without a suspected CAUTI and one with a suspected CAUTI, the latter was selected for the analysis to provide a conservative estimation of CAUTI risk.
No formal sample size calculation was performed. Instead, a pragmatic sampling strategy was used by evaluating all consecutive bladder catheterisations over a 12-month period (two 6-month periods) at a large tertiary university hospital.
A complete case analysis was performed, and missing data were negligible (table 1).
Table 1. Patient, hospital admission and catheter characteristics of 3293 patients with urinary catheters during the study period.
| Total (N=3293) | Pretransition (N=1647) | Post-transition (N=1646) | SMD* | |
|---|---|---|---|---|
| Female, n (%) | 1629 (49.5) | 797 (48.4) | 832 (50.5) | 0.043 |
| Age, mean±SD | 62.5±17.5 | 62.3±17.4 | 62.8±17.5 | 0.030 |
| Admission duration, median±IQR | 4 (1–11) | 4 (1–10) | 4 (2–11) | 0.021 |
| Type of care at admission, n (%) | ||||
| Emergency, n (%) | 1446 (43.9) | 715 (43.4) | 731 (44.4) | 0.020 |
| MC/IC, n (%) | 41 (1.2) | 19 (1.1) | 22 (1.3) | 0.017 |
| Other, n (%) | 1806 (54.8) | 913 (55.4) | 893 (54.3) | −0.024 |
| Duration of catheterisation (days), median IQR | 1.92 (0.86–4.46) | 1.94 (0.83–4.33) | 1.89 (0.88–4.63) | −0.071 |
| 0–2 days, n (%) | 1697 (51.5) | 840 (49.5) | 857 (50.5) | 0.021 |
| 3–7 days, n (%) | 1139 (34.6) | 600 (52.7) | 539 (47.3) | −0.078 |
| >7 days, n (%) | 457 (13.9) | 207 (45.3) | 250 (54.7) | 0.076 |
| Type of catheter | ||||
| Silicone, n (%) | 1444 (43.9) | 746 (45.3) | 698 (42.4) | −0.058 |
| Latex, n (%) | 31 (0.9) | 14 (0.9) | 17 (1.0) | 0.019 |
| Foley (coated), n (%) | 90 (2.7) | 61 (3.7) | 29 (1.8) | −0.119 |
| Foley (Thermistor), n (%) | 5 (0.2) | 4 (0.2) | 1 (0.1) | −0.047 |
| Unknown, n (%) | 1723 (52.3) | 822 (49.9) | 901 (54.7) | 0.097 |
Missing data: gender (n = 1), admission duration (n = 13).
SMD <0.1 indicates a negligible difference within that variable.
IC, Intensive care; MC, Medium care; SMD, standardised mean difference.
A directed acyclic graph was constructed to identify potential confounders and precision variables in the association between method of catheterisation (clean vs sterile) and development of CAUTIs (online supplemental E). These included sex, age, duration of admission, duration of catheterisation, way of hospital admission (emergency vs other) and type of catheter (eg, silicone).
Non-inferiority of clean catheterisation was assessed by comparing the proportions of suspected CAUTIs between the pretransition and post-transition phases. Proportions were compared using multivariable logistic regression. Adjusted risk differences (RDs) and corresponding two-sided 95% CIs were estimated using marginal standardisation. Non-inferiority was concluded if the upper bound of the 95% CI did not exceed the non-inferiority margin of 0.5 percentage point. The non-inferiority margin of 0.5 percentage point was defined a priori and deliberately kept narrow. An increase beyond this threshold was considered clinically undesirable from a patient safety and hospital-level perspective.
To assess time trends in the occurrence of CAUTIs in the two periods, an interrupted time series (ITS) was conducted. Given the well-established association between longer catheterisation duration and increased CAUTI risk, an interaction analysis was conducted to evaluate whether the effect of clean versus sterile catheterisation differed across catheterisation duration strata. Three exploratory duration strata were chosen: 0–2 days, 3–7 days and >7 days. In this model, the monthly proportion of patients with a suspected CAUTI was modelled per catheter-duration category, with the date of catheter insertion as the exposure moment.
Regarding the microbiology urinary culture data, the top 10 most frequently cultured microorganisms were analysed and visualised. For explorative analysis, univariable logistic regression analyses were performed, reporting RDs with corresponding 95% CIs, comparing preintervention and postintervention microbiological pathogen distributions.
All statistical analyses were performed using R (V.4.5.1; R Foundation for Statistical Computing, Vienna, Austria).
Ethical considerations and patient and public involvement
The study was conducted in accordance with the ethical principles of the updated Helsinki Declaration of 2013, and reporting adhered to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.18 The study was reviewed by the medical ethics committee (METC 2025-18602), which granted a waiver of the requirement for ethical approval under the Dutch Medical Research Involving Human Subjects Act. The analyses were performed using anonymised data from clinical information systems, containing no directly or indirectly identifiable information, in accordance with privacy regulations. This registry-based study did not involve patients or the public in the design, conduct, reporting, or dissemination plans of the research.
Results
Patient characteristics
A total of 3894 patients were eligible, of whom 3293 were included in the analysis. Among these, 1647 patients were included in the pretransition phase, and 1646 patients in the post-transition phase (figure 1). No relevant difference regarding patient-, care type- and catheter characteristics was observed between phases, based on univariable SMDs. On average, a catheter was in situ for 1.92 days (IQR 0.86–4.46). For detailed characteristics, see table 1.
Clean catheterisation protocol adherence
Overall adherence to the clean catheterisation protocol was high, with 91% (218/240) of respondents reporting use of the clean technique often or always (online supplemental A). Purchasing data showed that a total of 4274 sterile catheterisation sets were used during the 6-month pretransition phase (range: 644–773 sets per month), compared with 141 sets in the post-transition phase (range: 15–39 sets per month). This represents a 96.7% reduction in the use of sterile catheterisation sets.
Proportion of suspected CAUTIs
In total, 3.8% (62/1647) of patients in the sterile catheterisation phase and 3.3% (55/1646) in the clean catheterisation phase met the criteria for suspected CAUTI. The adjusted RD was −0.44% (95% CI −1.4% to 0.5%) in favour of clean catheterisation. The two-sided 95% CI did not exceed the 0.5 percentage point non-inferiority margin (table 2).
Table 2. Proportion of patients with catheter-associated urinary tract infection.
| Total | Pretransition | Post-transition | Unadjusted RD (95% CI) | Adjusted RD (95% CI) | |
|---|---|---|---|---|---|
| Overall, n (%) | 117/3293 (3.6) | 62/1646 (3.3) | 55/1647 (3.8) | −0.4% (−1.7% to 0.8%) | −0.4% (−1.4% to 0.5%) |
| Sex |
|
||||
| Female, n (%) | 70/1629 (4.3) | 34/797 (4.3) | 36/832 (4.3) | 0.1% (−1.9% to 2.0%) | |
| Male, n (%) | 47/1663 (2.8) | 28/850 (3.3) | 19/813 (2.3) | −1.0% (−2.5% to 0.6%) | |
| Age | |||||
| ≤70 years old, n (%) | 52/1895 (2.7) | 26/973 (2.7) | 29/1011 (2.8) | 0.2% (−1.2% to 1.6%) | |
| >70 years old, n (%) | 65/1309 (4.6) | 36/674 (5.3) | 26/635 (4.1) | −1.2% (−3.5% to 1.0%) | |
| Type of care at admission | |||||
| Emergency, n (%) | 84/1446 (5.8) | 40/715 (5.6) | 44/731 (6.0) | 0.4% (−0.2% to 2.8%) | |
| MC/IC, n (%) | 2/41 (4.9) | 1/19 (5.3) | 1/22 (4.5) | −0.7 (−14.0 to 12.6) | |
| Other, n (%) | 31/1806 (1.7) | 21/913 (2.3) | 10/893 (1.1) | −1.2 (−2.4 to 0.0) | |
| Duration of catheterisation | |||||
| 0–2 days, n (%) | 24/1697 (1.4) | 13/840 (1.5) | 11/857 (1.3) | −0.3 (−1.4 to 0.9) | |
| 3–7 days, n (%) | 57/1139 (5.0) | 32/600 (5.3) | 25/539 (4.6) | −0.7 (−3.2 to 1.8) | |
| >7 days, n (%) | 36/457 (7.9) | 17/207 (8.2) | 19/250 (7.6) | −0.6 (−5.6 to 4.4) | |
| Type of catheter | |||||
| Silicone, n (%) | 44/1444 (3.0) | 24/746 (3.2) | 20/698 (2.9) | −0.4 (−2.1 to 1.4) | |
| Other, n (%) | 73/1849 (3.9) | 38/901 (4.2) | 35/948 (3.7) | −0.5 (2.3 to 1.3) |
RDs were estimated using marginal standardisation based on the univariable and multivariable logistic regression models.
IC, intensive care; MC, medium care; RDs, risk differences.
Assessment of time trends stratified by catheterisation duration
To examine time trends during the sterile and clean catheterisation periods, an ITS analysis was conducted. The analysis revealed no significant preintervention trend, with an OR of 1.06 per month (95% CI 0.91 to 1.23), and no statistically significant change in trend after implementation (OR 0.89 (95% CI 0.71 to 1.10)) (figure 2).
Figure 2. Binominal interrupted time series. The grey area indicates the 8-month transition phase. Bullets indicate monthly proportions of patients with a suspected CAUTI. CAUTI, catheter-associated urinary tract infection.
In subgroup analysis, the absolute risk of suspected CAUTI is: 1.4% (24/1697) among patients with a catheter in situ for 0–2 days, 5.0% (57/1139) for those catheterised for 3–7 days, 7.88% (36/457) for those catheterised for >7 days. In an exploratory interaction analysis with catheterisation duration, no evidence of a statistically significant level change was observed after implementation of a clean catheterisation protocol for patients with a catheter for 3–7 days (OR 0.70 (95% CI 0.24 to 2.08)) or more than >7 days (OR 1.08 (95% CI 0.31 to 3.74)). No statistically significant change in post implementation trend was observed for either patients with a catheter for 3–7 days (OR 0.97 (95% CI 0.24 to 2.08)) or >7 days (OR 0.87 (95% CI 0.63 to 1.21)) (figure 3)
Figure 3. Binominal interrupted time series per subgroup (catheterisation duration 0–2, 3–7 days and >7 days). The grey area indicates the 8-month transition phase. Bullets indicate monthly proportions of patients with a suspected CAUTI. CAUTI, catheter-associated urinary tract infection.
Total number of positive urine cultures and cultured microorganisms
Analysis of all positive cultures revealed that 13.1% (215/1647) of catheterised patients had a positive culture in the pretransition phase and 13.1% (215/1646) in the post-transition phase (adjusted RD 0.2% (95% CI −1.7% to 1.2%)).
In total, 831 isolates were cultured, with 434 in the pretransition phase and 397 in the post-transition phase. The 10 most cultured microorganisms are visualised in table 3. In total, 11.8% (51/434) of isolates in the pretransition phase and 17.9% (71/397) in the post-transition phase did not belong to the 10 most cultured organisms. Escherichia coli remained the most frequently isolated organism in both periods (31.6% vs 27.2%), followed by mixed flora and Klebsiella pneumoniae. Staphylococcus aureus was found in 1.8% (8/434) of the cultures in the pretransition phase versus 2.0% (8/397) in the post-transition phase. In an exploratory analysis, no statistically significant differences were observed between the prephase and postphase (table 3).
Table 3. Culture data.
| Type | Pretransition (N=434) n (%) | Post-transition (N=397) n (%) | Univariable RD (95% CI) | |
|---|---|---|---|---|
| Escherichia coli | Neg, rod | 137 (31.6) | 108 (27.2) | −4.4% (−10.6% to 1.8%) |
| Gram-positive flora | Pos | 93 (21.4) | 68 (17.1) | −4.3% (−9.7% to 1.1%) |
| Klebsiella pneumoniae | Neg, rod | 53 (12.2) | 32 (8.1) | −4.2% (−8.2% to −0.1%) |
| Mixed bacterial flora | – | 41 (9.4) | 39 (9.8) | 0.4% (−3.6% to 4.4%) |
| Proteus mirabilis | Neg, rod | 14 (3.2) | 22 (5.5) | 2.3% (−0.5% to 5.1%) |
| Aerococcus urinae | Pos, coc | 11 (2.5) | 11 (2.8) | 0.2% (−2.0% to 2.4%) |
| Candida albicans | Yeast | 7 (1.6) | 15 (3.8) | 2.2% (−0.1% to 4.4%) |
| Pseudomonas aeruginosa | Neg, rod | 11 (2.5) | 10 (2.5) | 0.0% (−2.2% to 2.1%) |
| Enterococcus faecalis | Pos, coc | 7 (1.6) | 13 (3.3) | 1.7% (−0.5% to 3.8%) |
| Enterobacter cloacae | Neg, rod | 9 (2.1) | 8 (2.0) | −0.1% (−2.0% to 1.9%) |
Culture data of the 10 most frequent cultured isolates per total number of cultures.
Coc, coccus; Neg, negative; Pos, positive; RD, risk difference.
Carbon footprint of clean versus sterile catheterisation sets
The sterile catheterisation set used at the wards and emergency department included a set of sterile gloves, two non-sterile gloves, a cellulose mat, two sterile gauzes and 100 mL tap water, resulting in a carbon footprint of 0.191 kg CO2 eq per set per use. The sterile catheterisation set used in the operating room consists of a set of sterile gloves, 15 mL aseptic solution and a sterile package containing a sterile drape, tweezers, five sterile gauzes and an aluminium container, producing 0.316 kg CO2 eq per set per use. The clean catheterisation set consists of two non-sterile gauzes, 100 mL of tap water and non-sterile gloves, producing a total carbon footprint of 0.056 kg CO2 eq. This is 70.7% and 82.3% lower than the sterile method used at the wards/emergency room and operating room, respectively. This is equivalent to an estimated annual carbon footprint reduction of ~1300 kg CO2 eq, based on 3293 indwelling catheterisations at this institution. For the most relevant contributors to the carbon footprint, see figure 4.
Figure 4. Stacked bar graph showing the relative contribution of each material to the carbon footprint of two sterile and one non-sterile catheterisation sets. The percentages indicate the proportion of each material’s contribution to the total carbon footprint of its respective catheterisation set. ER, emergency room; OR, operating room.
Discussion
This study indicates the non-inferiority of clean catheterisation compared with sterile catheterisation in terms of the proportion of suspected CAUTIs across a large cohort of 3293 catheterised patients. The microbiological analysis showed a similar number of positive urine cultures and no increase in skin-bound bacteria during clean catheterisation. In addition to suggesting comparable clinical infection outcomes, switching to clean catheterisation reduces the carbon footprint of urine catheterisation sets by 71%–82%. Given the observed non-inferiority of clean catheterisation from an infection prevention perspective and the significant reduction in carbon footprint, this study provides support for the reconsideration of a clean urinary catheterisation protocol.
Findings of this study align with previous studies showing no benefit of sterility measures in catheterisation. However, available evidence is scarce and consists of heterogeneous populations and interventions. Three small randomised controlled trials exist. Firstly, Duffy et al randomised 80 veterans in nursing homes between clean and sterile ‘intermittent’ catheterisation.19 They showed no statistically significant change in symptomatic bacteriuria (55% clean vs 62% sterile, 0.89 (95% CI 0.62 to 1.29)) up to 125 days of follow-up. Secondly, Carapeti et al randomised 156 general surgical patients to sterile or clean catheterisation and showed no statistically significant change in bacteriuria (9.5% in the sterile and 11% in the non-sterile group, χ2 test: p >0.1).20 Thirdly, Mittal et al randomised 346 patients within a single centre setting between clean and sterile catheterisation and reported non-inferiority (CAUTI rate: clean group: 7.5% vs 6.9% sterile group). However, their results should be interpreted with caution; their study relied on an exceptionally broad 12% non-inferiority margin, lacked a formal non-inferiority test and lacked an intention-to-treat analysis.21 Subsequently, in the 2024 Dutch infection prevention guidelines, a pooled risk ratio was calculated to assess the effectiveness of non-antiseptic versus antiseptic meatal cleaning prior to catheter insertion on the incidence of bacteriuria. The pooled RR was 1.24 (95% CI 0.93 to 1.66), indicating no statistically significant difference, with low heterogeneity (I2=25%).1 This pooled estimate included the same studies as the systematic review by Mitchel et al and the trial by Khahakawe et al.1 22 23 Our study adds substantially to the evidence by analysing a much larger hospital population than previous small, randomised trials, allowing for a robust, real-world assessment of the safety of clean catheterisation and adds a sustainability perspective.
In the current study, we did not observe relevant differences in the cultured microorganisms between the preintervention and postintervention periods, particularly no increase in skin-bound bacteria. This supports the hypothesis that the pathogenesis of CAUTIs is not due to the introduction of bacteria by non-sterile catheterisation, but rather that late exoluminal colonisation (bacteria migrating along the outside of the catheter) is more relevant. This is in line with the study of Aumeran et al assessing the pathogenesis of catheter-associated bacteriuria among 64 patients at the intensive care unit. The study showed that 88.5% of catheter-associated bacteriuria were exoluminal, with 69.5% of microorganisms already identified in urinary meatus samples, indicating that the urethra is already colonised with bacteria that are not eliminated by meatal cleaning. Subsequently, 50% of exoluminal colonisations were late exoluminal cases (bacteria identified after day 1) where microorganisms likely ascend from the perineum alongside the catheter. In the current study, we could not differentiate between extraluminal or intraluminal origins of CAUTIs. However, our findings support the notion that CAUTI prevention is less dependent on the catheterisation technique itself and more on avoiding unnecessary catheterisation through careful patient selection and timely catheter removal once the indication resolves.24 25
A strength of this study is that it provides real-world data from a large and diverse patient population following the successful implementation of clean catheterisation. Because the hospital registry prospectively captures routine clinical data, recall bias was minimised. This is an advantage often lacking in implementation studies. In addition, there were no major changes in patient care, infection control precautions or laboratory policies at our institution during the pretransition and post-transition periods, a requirement for relevant comparison of periods. In addition, the interrupted time series analysis corrects for potential underlying temporal trends.
Several limitations should also be acknowledged. First, as clinical CAUTI complication registration is incomplete in our hospital, we needed to use a CAUTI case definition based on clinical and microbiological registration data. This introduces a risk of non-differential misclassification, as we cannot rule out that some patients with asymptomatic bacteriuria were treated and included as CAUTIs. To minimise the risk of including unrelated infections, antibiotic prescriptions were strictly matched within a window of 2–7 days postcatheterisation. Although this approach may still capture some asymptomatic patients. However, as this potential misclassification was non-differential (ie, likely to occur to an equal extent in the preintervention and postintervention period), we do not believe that this could have influenced our main outcome measure. Second, our primary analysis was pragmatically restricted to each patient’s first CAUTI episode due to data linkage limitations. As a result, patients who developed a CAUTI in the prephase could not reappear in the postphase, introducing a slight advantage for the postphase; however, since only four patients had a positive culture in both phases, this effect was marginal. Furthermore, our secondary analysis of all positive urine cultures captured all repeated episodes and showed comparable rates between phases (13.1% vs 13.1%). Third, we could not identify and exclude immunocompromised patients or those requiring guide-wire catheterisation. Since these procedures remained sterile in both phases, their inclusion may have somewhat diluted the observed differences between the periods. Fourth, protocol adherence was assessed by self-reported questionnaires and purchase data. Although this provides an indication of protocol adherence, the lack of direct observation or audit data is a limitation. Finally, the implementation of a clean catheterisation protocol is generalisable to other settings, including low-resource settings, under the condition of reliable availability of clean water and basic infection prevention and control practices.
This study supports the broader implementation of clean catheterisation protocols in hospitals worldwide. In the Netherlands, several hospitals have adopted the clean protocol, and likely it can be extended into nursing homes and home care as well, provided that standard infection prevention and control precautions are considered at the same level as in hospitals. This is supported by the recent update in the Dutch infection prevention guidelines for extramural long-term care, which also adapted the new clean protocol.26 We want to stimulate policymakers, guidelines developers and other care providers to consider replacing the sterile urine catheter insertion protocol with the ‘clean’ protocol.
Further, the implementation of non-sterile catheterisation serves as an example of how many procedures have, over time, adopted increasingly sterile protocols without a clear evidence base. When such practices are finally questioned, proposed reversals often trigger calls for rigorous re-evaluation, even though the original escalation was never held to the same standard. The move from sterile to clean catheterisation exemplifies how we can rethink the efficient use of healthcare resources: sterility without clinical benefit no longer fits within modern, value-based care. In a time of workforce strain, rising costs and the urgent need for low-carbon healthcare, sustainable change often begins not with new innovations but with the courage to let go of outdated routines.
In conclusion, given the absence of increased CAUTI risk and the substantial reduction in carbon footprint of catheterisation sets, routine sterile catheterisation for standard in-hospital urinary catheter placement may represent low-value care. Our findings suggest that clean catheterisation may be considered as a safe alternative default practice.
Supplementary material
Footnotes
Funding: Betaalbaar beter, VGZ (insurance company)
Prepublication history and additional supplemental material for this paper are available online. To view these files, please visit the journal online (https://doi.org/10.1136/bmjopen-2026-118759)
Provenance and peer review: Not commissioned; externally peer reviewed.
Patient consent for publication: Not applicable.
Patient and public involvement: Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.
Data availability statement
Data are available upon reasonable request.
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