INTRODUCTION

Chronic urinary retention is a frequent condition in individuals with neurological and nonneurological bladder dysfunctions1 and requires catheterization to empty the bladder if the condition persists.2,3 Although clean intermittent catheterization (CIC) is considered one of the safest drainage methods, urinary tract infections (UTIs) remain a significant risk for morbidity. The incidence of catheter-associated UTI rates is between 0.8 and 3.5 per year, posing a high health-economic burden due to emergency visits, hospital admissions, and prolonged hospital stays.4,5 Catheter-associated risk factors for UTI have been extensively investigated over the years.5–7 Based on a literature search, Kennelly and colleagues5 proposed a risk factors model for patients with neurogenic lower urinary tract dysfunction dependent on CIC. Four domains were proposed as common risk factors: general underlying conditions, local urinary tract conditions, CIC compliance and technique, and factors related to the individual CIC device and CIC process.5

A common step in the CIC process is catheter repositioning toward the end of catheterization to ensure thorough bladder emptying.8 This maneuver may be necessary because the bladder mucosa may be sucked into the drainage holes due to a negative pressure within the catheter lumen, preventing complete bladder emptying.9,10 Catheter repositioning is therefore needed to restart the urine flow potentially leading to mucosal microtrauma.11 To address this issue, a new male and female intermittent catheter was developed, featuring a long drainage zone with multiple micro-holes for improved bladder emptying and reduced risk of mucosal suction. The objective of these trials was to evaluate the micro-hole zone catheter (MHZC) prototype compared to a conventional eyelet catheter (CEC) regarding difference in number of mucosal suctions (measured as flow-stops) bladder emptying (measured as residual urine at first flow-stop), and microtrauma (measured as hematuria).

METHODS

Three similar randomized, single-blinded, 3-arm crossover studies were conducted. Each trial included 3 data collection visits; all visits were performed at Department of Urology, Rigshospitalet, Copenhagen, Denmark. Data were collected from March 2020 to May 2021. Fifteen male and 15 female healthy volunteers (HV), 15 male and 15 female IC users, were included in 3 distinct but almost identical studies and later combined in the analysis phase. Inclusion criteria for HV were willingness to refrain from analgesics 24 hours prior to catheterization visits and a negative urinalysis (determined by Multistix® 7, Seimens, Erlangen Germany) for hematuria. Inclusion criteria for IC users were bladder management via CIC for at least 3 months with at least 2 catheterizations daily prior to study start and the ability to self-catheterize. To ensure evaluation of the catheters in a broad population, the distribution of subjects enrolled with either neurogenic vs non-neurogenic bladder dysfunctions was determined to be proportioned at 3:2 in the two IC-user studies.

Study procedures were reviewed and approved by the regional ethical committee (De Videnskabsetiske komitéer for Region Hovedstaden, case nos. H-19089779, H-20015021, and H-20020163, respectively) and the Danish Medicines Agency (record nos. 2020030463, 2020032970, and 2020032971, respectively). All participants gave oral and written informed consent before being enrolled in the study. Disclosure of results for each study is available at https://clinicaltrials.gov/, NCT04445051, NCT04543136, and NCT04557787.

Catheters

The study devices were newly designed, ready-to-use, 12 Charriere (12 French) hydrophilic-coated catheters. The male and female study devices were compositionally identical to the commercially available catheters, CE-marked* SpeediCath Flex and SpeediCath Standard (Coloplast A/S, Humlebaek, Denmark), respectively. Exemptions included the design and manufacturing method of the drainage holes and length of the drainage zone, which have several small holes (0.4 mm in diameter) (Male prototype catheters Figure 1a and Female prototype catheters Figure 1b), whereas the comparator device has 2 oval eyes measuring 2 × 4 mm by the tip, similar to other CECs currently available for CIC. Two prototypes of the study devices were tested, a short and a long drainage zone variant, differing by the number of eyelets: 21 × 4 and 38 × 4 eyelets for male, and 14 × 4 and 17 × 4 eyelets for female (Figure 1).

Figure 1.:

(a) Male and (b) female micro-hole zone catheter prototype with a short (variation 1) and long (variation 2) micro-hole drainage zone.

Study Procedures

The study consisted of 1 inclusion visit (V0) and 3 single test visits (V1-3) (Figure 2). For visits 1 to 3, participants were requested to arrive with a full bladder and a first urine sample was tested for baseline hematuria. Catheterizations were performed at each visit with 1 of the 3 catheters according to a randomization scheme, generated automatically by a computer. A first catheterization was performed by study nurse, after which the participants were asked to drink and wait 1 to 2 hours to ensure bladder refilling. Healthy volunteers were then asked for a second urine sample obtained by urination, while IC users provided a second sample obtained via self-catheterization.

Figure 2.:

Flow diagram of participants randomized to either a short or long catheter variant, or comparator, at 3 test visits. The diagram shows the pooled study population consisting of 15 male and 15 female healthy volunteers from the first study, 14 male IC users from the second study, and 15 female IC users from the third study. AE indicates adverse effect; DD, device deficiency; IIT, intention to treat; UTI, urinary tract infection.

Similar to self-CIC taught to persons managed by IC, catheters were repositioned when a flow-stop was experienced. The number of flow-stops was detected as a pressure change coinciding with a stop of urine flow using an electronic pressure sensor attached to the outlet of the catheter (the sensor was developed by Coloplast A/S). Urine volume emptied at the first flow-stop, and at end of catheterization, was measured by a time-logged scale (sampling rate ∼2.5 Hz). Post void residual volume (PVR) left in the bladder immediately post catheterization was measured in triplicate using an ultrasound scanner (model BK3000, HB Medical, Horsholm, Denmark) in triplicate (Figure 3).

Figure 3.:

Catheterization process and measurement of the flow (voided urine [g]/ time [s]), flow-stops (coinciding change in pressure [mbar], and flow [g/s]), which also marks the point for repositioning the catheter in order to let the urine to flow again. At first flow-stop and at the end of catheterization, voided urine is measured and the difference (total urine voided-urine voided at first flow-stop) equals the residual urine at first flow-stop (RV1). After the catheterization, post void residual (PVR) urine volume is measured with a bladder scanner.

Hematuria was measured with a dipstick test post catheterization for all participants and following urination for HV. Finally and immediately after each catheterization, participants were asked to indicate the degree of discomfort associated with the catheterization process on a 10-cm visual analog scale (VAS), ranging from “no discomfort” (0 cm) to “worst possible discomfort” (10 cm).

Data Analysis

The intention-to-treat population (full analysis set) comprised all randomized participants who had been exposed to at least 1 product, with valid information on at least 1 end point. The primary end point, RV1, was calculated as the delta value between total volume catheterized minus the volume catheterized at first flow-stop (Figure 3). Secondary end points, PVR and discomfort rankings, were analyzed in a general linear mixed model with participants included as a random component, and visit, treatment (comparator [standard catheter]), study devices (a short and long catheter variant), and sex (male and female) as fixed effects. The number of flow-stop incidents per catheterization, number of incidents of visual blood on the catheter post catheterization, and number of incidents of positive hematuria (as a proxy for microtrauma) were included as exploratory end points and analyzed in a general linear mixed model, modeling the probability (expressed as odds ratio, OR) of a positive outcome in favor of the MHZC and the 95% confidence interval (CI). The incidence of adverse events (AE) has been reported by descriptive statistics for each group.

For the statistical meta-analyses, several assumptions were made for each end point. Hence, for RV1, number of flow-stop incidents, and PVR, data were combined across the 3 studies assuming same effect across participants (HV and IC user), catheters (short and long variant), and catheterization (HCP and self-catheterization). However, results were not combined on sex, assuming different effects according to the length of the male and female catheters.

For number of hematuria incidents, an effect according to underlying conditions was assumed and results were therefore separated for HV and IC users. Instead, these end points were combined on sex, short and long catheter variants, and who performed catheterization (HCP vs self-catheterization). These analyses were based on an assumption that hematuria would be independent of sex, length of drainage zone of the study catheter, and who performed the catheterization. Supplemental Digital Content 1, Table S1, available at: https://links.lww.com/JWOCN/A101, presents average values and corresponding SD for each end point separately for each study.

A significance level of α value of .05 (2-sided) was applied. All treatment differences (catheters), as well as 95% CIs, were estimated by using Proc Mixed in SAS, version 9.4 (SAS Institute Inc, Cary, North Carolina).

RESULTS

Fifty-nine participants were randomized and included in 3 test visits, undergoing catheterization with a new catheter at each visit (Figure 2). One participant discontinued after visit 2; this participant was included in the intention-to-treat population. Participant characteristics are presented in Table 1. The age range was lower for HV participants than for IC users (age range: 20-57 years vs 21-82 years, respectively). An overweight of participants in the IC-user group had neurogenic lower urinary tract dysfunction (3:2); the predominant neurological disorders among males were spinal cord injury; and the predominant causes among female participants were multiple sclerosis and spina bifida.

TABLE 1. - Characteristics of Participants Female Male HV (N = 15) IC User (N = 15) HV (N = 15) IC User (N = 14) Age, mean (range), y 31.2 (20-57) 47 (21-71) 32.3 (24-52) 55 (30-82) Neurogenic lower urinary tract dysfunction 0 9 0 9 Underlying disease Multiple sclerosis ... 4 ... 1 Spina bifida ... 3 ... 1 Spinal cord injury ... 0 ... 6 Other ... 2 ... 1 Nonneurogenic lower urinary tract dysfunction 0 6 0 5 Underlying condition Benign prostate hyperplasia (BPH) ... 0 ... 1 LUTS due to previous bladder tumor ... 0 ... 2 LUTS due to other reasons ... 6 ... 2 Catheter of choice Hydrophilic-coated cathetera ... 3 ... 2 Hydrophilic-coated catheter with omnidirectional tipb ... 0 ... 2 Hydrophilic-coated catheter about half length of standard catheterc ... 12 ... 8 GentleCath glide ... 0 ... 1 Unknown ... 0 ... 1 Positive baseline hematuria, n (%) 0 (0) 2 (13) 0 (0) 4 (29) Concomitant medication, n (%) 7 (47) 15 (100) 0 (0) 14 (100) Prophylactic antibiotics, n (%) 0 (0) 0 (0) 0 (0) 2 (14)

Abbreviations: HV, healthy volunteers; IC, intermittent catheter; LUTS, lower urinary tract syndrome;

aHydrophilic-coated catheter (LoFric: Wellspect, Mölndal Sweden).

bHydrophilic-coated catheter with flexible tip (Coloplast, Humlebæk Denmark).

cHydrophilic-coated standard and compact catheters (SpeediCath Standard and SpeediCath Compact, Coloplast, Humlebæk Denmark).

Bladder Emptying and Catheter Flow-Stops

The primary end point, residual urine volume at first flow-stop (RV1), combined for HV and IC users, was significantly higher for CEC than for MHZC, with mean differences and 95% CI of 49 mL ([33-65) for male and 32 mL (16-47) for female (both P < .001; Figure 4a). The combined average number of flow-stop incidents was 8 times more frequent in males (95% CI, 4.08-14.50) and 21 times more frequent in females (95% CI, 10.27-44.46) for catheterizations with CEC than for MHZC (both P < .001; Figure 4b). Approximately 70% of catheterizations with CEC had more than 1 flow-stop as compared to approximately 10% of catheterizations with MHZC (both sexes, P < .001; Table 2).

Figure 4.:

Catheter performance for CEC versus the MHZC evaluated and presented as (a) scatter plot of residual urine at first flow-stop (RV1) with mean and 95% confidence interval (CI) and (b) mean plot of average number of flow-stop with 95% CI in male and female participants (HV and IC users combined). P values for RV1 represent difference in mean values. P values for flow-stops represent difference in mean flow-stop counts. CEC indicates conventional eyelet catheter; MHZC, micro-hole zone catheter.

TABLE 2. - Proportion of Flow-Stops, RV1, and Mean PVR for Male and Female (Combined for HV and IC Users) Male Female CEC MHZC CEC MHZC Number of patients 29 29 30 30 Number of catheterizations 29 56 30 60 Percentage of catheterizations with flow-stops ≥1 72.1a 12.9 75.6a 7.8 Percentage of catheterizations with RV1 >50 mL 25.6a 3.6 17.8a 1.1 Percentage of catheterizations with RV1 >100 mL 14 0 8.9 0 Mean PVRb (SD), mL 21 (36) 25 (51) 4 (10) 8 (45)

Abbreviations: CEC, conventional eyelet catheter; MHZC, micro-hole zone catheter; PVR, post void residual; RV1, residual urine volume at first flow-stop.

aP < .001 for the difference between proportion of catheterizations.

bRounded to nearest number.

The proportions of catheterizations with RV1 greater than 50 mL and RV1 greater than 100 mL were calculated. As presented in Table 2, a significantly higher proportion of catheterizations with CEC (26% for male and 18% for female) led to RV1 greater than 50 mL compared to MHZC (4% for male and 1% for female). In addition, 14% and 9% of catheterizations with CEC led to RV1 greater than 100 mL (male and female, respectively) whereas there were zero occurrences for MHZC.

Finally, to evaluate efficiency of urine evacuation from the bladder vesicle at the end of catheterization, mean PVRs for males were less than 25 mL and for females less than 10 mL, with large variations for all catheters (Table 2). Mean PVR differences and 95% CI between CEC and MHZC were low and insignificant, corresponding to male catheters: −4.30 (−17.42 to 8.82), P = .551 and female catheters: −4.09 (−17.60 to 9.41), P = .519 (Table 2).

Hematuria

We hypothesized that hematuria in IC users may represent a transient condition related to catheterization or the underlying condition leading to the need for IC. In contrast, the prevalence of hematuria in HV participants was 0% (Table 1), and this group was identified as providing a more reliable surrogate for catheter-associated microtrauma. In the catheterized urine from HCP, the likelihood for hematuria was similar for CEC and MHZC (OR [95% CI] = 0.95 [0.11-7.86], P = .961) (Table 3). However, when incidents of hematuria in HV were measured during normal micturition after catheterizations, the likelihood was now 5.84 higher for CEC than for MHZC (95% CI = 0.97-35.05; P = .053) (Table 3). In IC users, there was an indication of a higher likelihood of hematuria in the catheterized urine with CEC (17.2%) compared with MHZC (9.6%) (OR [95% CI] = 2.00 [0.76-5.23]; P = .156). Gross hematuria was not observed during any catheterization.

TABLE 3. - Proportion of Hematuria Post catheterization and During Normal Micturition Post catheterization HV Odds Ratio (P) IC User Odds Ratioa (P) CEC MHZC CEC MHZC Number of patients 30 30 ... 29 29 ... Number of catheterizations 30 59 ... 58 114 ... Incidents of hematuria, post catheterization, % 3.3 3.4 0.95 (.961) 17.2 9.6 2.00 (0.156) Incidents of hematuria in normal micturition after catheterization, % 23.3 5.1 5.84 (.053) ... ... ...

Abbreviations: CEC, conventional eyelet catheter; HV, healthy volunteers; IC, intermittent catheter; MHZC, micro-hole zone catheter.

aStatistical analysis of hematuria (positive urine dipstick) for conventional eyelet catheter (CEC) and micro-hole zone catheter (MHZC) in the catheterized urine (post catheterization) in HV and IC users and additionally in normal micturition after catheterization in HV only.

Comfort and AE

Discomfort ratings revealed higher mean scoring in HV than in IC users (mean VAS: ∼1 cm) and higher mean scoring in HV males than in HCP females (mean VAS: ∼1 cm) (Figure 5). Mean overall discomfort ratings were less than 3 cm in male HV, less than 1.5 cm in female HCP, and less than 1 cm in both male and female IC users, and there was no difference in scores between catheters on any of the discomfort assessments.

Figure 5.:

Scatterplot of individual overall discomfort ratings (cm) during catheterization, assessed via the visual analog scale (VAS) ranging from “no discomfort” (0 cm) to “worst possible discomfort” (10 cm), in male and female HV and IC users and with corresponding mean values and standard deviations for CEC (gray) and MHZC (turquoise).CEC indicates conventional eyelet catheter; IC, intermittent catheter; MHZC, micro-hole zone catheter.

Out of 266 catheterizations across the 3 studies, 7 AE were observed; none were deemed serious AEs. Two participants were diagnosed with a UTI, both possibly related to MHZC.

DISCUSSION

These trials with IC users and HV are the first to evaluate the MHZC compared to CECs, in male and female participants. Findings indicate significantly improved bladder emptying at first flow-stop, significantly reduced number of flow-stops, and a trend toward reduced hematuria (measured as a proxy for microtrauma) for MHZC compared to CEC, without influence on discomfort.

Inadequate bladder emptying in IC users is one of several identified risk factors for catheter-associated UTI, possibly attributable to product design, incorrect handling, and anatomy of the lower urinary tract.5 In the European Urology Guideline for Nurses and in Instructions for Use leaflets, IC users are advised to pull out their catheter slowly, or to reposition their catheter, to ensure thorough bladder emptying.8,12–14 As previously described, catheter repositioning is designed to alleviate mucosal suction and restart urine flow.9–11 Thus, the MHZC design serves 2 functions: to avoid mucosal suction and urothelial microtrauma and to ensure thorough bladder emptying at the first appearance of a flow-stop.

Since catheter-associated UTI is a multifactorial condition and the definition of catheter-associated UTI has not been standardized, clear cutoff values of residual urine at which patients are at an increased risk for UTI are challenging. Accordingly, residual urine thresholds vary between 50 and 300 mL across guidelines2,3,15–16 and clinical studies.17–23 Even so, certain criteria make some individuals more susceptible or vulnerable than others and therefore call for greater attention to UTI risk factors.5,6 Susceptibly to recurring catheter-associated UTI susceptibility is higher due to multiple factors.5,6 The correlation between residual urine and bacteriuria in spinal cord injury patients under a retraining program, aimed to reduce their residual urine upon emptying using different voiding techniques, was investigated and a direct correlation was found when residual urine was between 50 and 250 mL.24 Another study of male patients, who underwent biopsy for prostatic hyperplasia, found significantly higher mean PVR urine volume (113 mL) in those with UTI than in patients without (41 mL).22 Nevertheless, other studies have failed to find a direct link between residual urine and UTI.24,25 Considered collectively, a preponderance of evidence strongly suggests that residual urine is a clinically relevant risk factor for UTI.5,15,16,26,27

Study findings indicate that CECs are associated with a significantly higher number of flow-stops and RV1 than MHZC. Hence, 70% of catheterizations with CEC led to flow-stops and 9% to 14% risk for residual urine volumes of more than 100 mL as opposed to 10% of catheterizations with the MHCZ and no instances of residual volume of more than 100 mL (Table 2).

Results from the current studies potentially indicate an association between bladder wall suction and microtrauma as previously shown with indwelling catheters.9–11,28,29 Stensballe and colleagues30 found less urethral friction and less microtrauma, determined by the level of hematuria, when using hydrophilic-coated catheters as compared to uncoated catheters. Although bacteriuria could not be linked with a specific catheter in that study, we hypothesize that recurring microtrauma to the bladder wall comes with a risk of impairing its natural barrier function, thus affecting susceptibility to UTI.6,31 Additional research evaluating bladder wall trauma, hematuria, and UTI is warranted. Similarly, while results from these trials revealed beneficial effects of MHZC on bladder emptying and flow-stops, the influence of this design feature on recurrent UTI among IC users is warranted.

We measured discomfort to determine whether the MHZC catheter features (multiple micro-holes and length of drainage zone) influenced comfort during catheter insertion, bladder evacuation, and withdrawal. Mean discomfort ratings were generally low for all participants (<2.5 cm) and independent of catheter type. In the literature, the mean or median VAS scoring is generally in the 0- to 3-cm range32–35 where previous IC experience, pain anticipation, and type of catheter (coated vs uncoated) are some factors that seem to affect VAS discomfort ratings. Therefore, higher discomfort rating in HV compared to IC users in the current studies was expected and correlates with a study by Girotti and colleagues36 where adjustment to IC affected the mean VAS scoring scale for discomfort over time from 3.7 cm at 3 months to 2.5 cm at 6 months was reported. In addition, we found that the male MHZC also differed in catheter design containing a flexible tip and a sleeve as compared to the standard CEC catheter. Nevertheless, this difference did not appear to significantly influence discomfort ratings.

Limitations

Study findings are based on single catheterizations from single test days and do not represent the effect of prolonged catheter use. Large but similar variations in post-IC residual volumes were observed for all catheters across studies. This can be attributed to the specific scanner applied in the present studies that derives the volume based on multiplication of length × width × height × 0.57. Hence, once either 1 of 3 dimensions has an unmeasurable or neglectable urine volume measured as zero, this will be interpreted as an empty bladder on the scanner, or 0 mL. Similar variations in residual volumes post catheterization have been observed in other studies, and the ultrasound scanner measurements must be evaluated cautiously depending on the specific scanner used and the extent to which personnel are properly trained.

Another limitation was the difference in catheter design between the male MHZC and CEC. Whereas the male MHZCs were sleeved catheters with a flexible tip, the comparator (CEC) was a straight unsleeved catheter. Nevertheless, we hypothesize that bladder emptying and number of flow-stops are not anticipated to be affected by these differences.

CONCLUSIONS

Study findings indicate that the MHZC catheter reduces several UTI risk factors as including reduced microtrauma due to suctioning urothelium into the eyelets of the catheter, reduced residual volumes, and signs of reduced hematuria. This novel design supports IC users with a new approach to reduce the risk of residual urine through a simple catheterization process.

ACKNOWLEDGMENTS

The authors thank Brit Grønholt Schrøder, Frederikke Hedegaard, Jane Hannibalsen, and Rikke Permild for clinical support in the clinical conduct of the study; Betina Suldvart and Christian Kamp Nielsen for their technical support; and Signe Cremer and Omar Feix do Nascimento for scientific review of the manuscript.

REFERENCES 1. Kaplan SA, Wein AJ, Staskin DR, Roehrborn CG, Steers WD. Urinary retention and post-void residual urine in men: separating truth from tradition. J Urol. 2008;180(1):47–54. doi:10.1016/j.juro.2008.03.027. 2. Blok B C-DD, del Popolo G, Groen J, Hamid R, Karsenty G, Kessler TM, Pannek J. EAU Guidelines on Neuro-Urology (ISBN 78-94-92671-07-3, 2020 http://uroweb.org/guidelines/compilations-of-all-guidelines/). Published November 16, 2002, 2020. Accessed Nov 16, 2020. 3. Stoffel JT, Peterson AC, Sandhu JS, Suskind AM, Wei JT, Lightner DJ. AUA white paper on nonneurogenic chronic urinary retention: consensus definition, treatment algorithm, and outcome end points. J Urol. 2017;198(1):153–160. doi:10.1016/j.juro.2017.01.075. 4. Dinh A, Davido B, Duran C, et al. Urinary tract infections in patients with neurogenic bladder. Med Mal Infect. 2019;49(7):495–504. doi:10.1016/j.medmal.2019.02.006. 5. Kennelly M, Thiruchelvam N, Averbeck MA, et al. Adult neurogenic lower urinary tract dysfunction and intermittent catheterisation in a community setting: risk factors model for urinary tract infections. Adv Urol. 2019;2019:2757862. doi:10.1155/2019/2757862. 6. Vasudeva P, Madersbacher H. Factors implicated in pathogenesis of urinary tract infections in neurogenic bladders: some revered, few forgotten, others ignored. Neurourol Urodyn. 2014;33(1):95–100. doi:10.1002/nau.22378. 7. Wyndaele JJ, Brauner A, Geerlings SE, Bela K, Peter T, Bjerklund-Johanson TE. Clean intermittent catheterization and urinary tract infection: review and guide for future research. BJU Int. 2012;110(11, pt C):E910–E917. doi:10.1111/j.1464-410X.2012.11549.x. 8. Vahr S. HC-B, Eikenboom J., Geng V., et al. Evidence-based guidelines for best practice in urological health care. Catheterisation urethral intermittent in adults. Eur Assoc Urol Nurs. 9. Glahn BE. Influence of drainage conditions on mucosal bladder damage by indwelling catheters. I. Pressure study. Scand J Urol Nephrol. 1988;22(2):87–92. doi:10.1080/00365599.1988.11690391. 10. Glahn BE, Braendstrup O, Olesen HP. Influence of drainage conditions on mucosal bladder damage by indwelling catheters. II. Histological study. Scand J Urol Nephrol. 1988;22(2):93–99. doi:10.1080/00365599.1988.11690392. 11. Grocela JA, Jura YH. Top-vented urinary drainage catheters cause fewer epithelial and vascular changes in the bladder mucosa compared to conventional catheters and may reduce susceptibility to urinary tract infections. Current Urology. 2010;4(3):136–141. doi:10.1159/000253440. 12. Wellspect Healthcare. Instructions for preparing the LoFric catheter for use. https://medicalmonks.com/wp-content/uploads/2014/12/LoFric-Instruction-Sheet.pdf. Accessed February 27, 2023. 15. Hooton TM, Bradley SF, Cardenas DD, et al. Diagnosis, prevention, and treatment of catheter-associated urinary tract infection in adults: 2009 International Clinical Practice Guidelines from the Infectious Diseases Society of America. Clin Infect Dis. 2010;50(5):625–663. doi:10.1086/650482. 16. Stöhrer M, Blok B, Castro-Diaz D, et al. EAU guidelines on neurogenic lower urinary tract dysfunction. Eur Urol. 2009;56(1):81–88. doi:10.1016/j.eururo.2009.04.028. 17. Chen C-M, Hsu H-C, Tsai W-S, Chang C-H, Chen K-H, Hong C-Z. Infections in acute older stroke inpatients undergoing rehabilitation. Article. Am J Phys Med Rehabil. 2012;91(3):211–219. 18. Dromerick AW, Edwards DF. Relation of postvoid residual to urinary tract infection during stroke rehabilitation. Arch Phys Med Rehabil. 2003;84(9):1369–1372. doi:10.1016/s0003-9993(03)00201-6. 19. Haylen BT, Lee J, Husselbee S, Law M, Zhou J. Recurrent urinary tract infections in women with symptoms of pelvic floor dysfunction. Int Urogynecol J Pelvic Floor Dysfunct. 2009;20(7):837–842. doi:10.1007/s00192-009-0856-3. 20. Kim BR, Lim JH, Lee SA, et al. The relation between postvoid residual and occurrence of urinary tract infection after stroke in rehabilitation unit. Ann Rehabil Med. 2012;36(2):248–253. doi:10.5535/arm.2012.36.2.248. 21. May M, Brookman-Amissah S, Hoschke B, Gilfrich C, Braun K-P, Kendel F. Post-void residual urine as a predictor of urinary tract infection—is there a cutoff value in asymptomatic men? J Urol. 2009;181(6):2540–2544. 22. Stern JA, Hsieh Y-C, Schaeffer AJ. Residual urine in an elderly female population: Novel implications for oral estrogen replacement and impact on recurrent urinary tract infection. J Urol. 2004;171(2, pt 1):768–770. 23. Truzzi JC, Almeida FM, Nunes EC, Sadi MV. Residual urinary volume and urinary tract infection—when are they linked?. J Urol. 2008;180(1):182–185. doi:10.1016/j.juro.2008.03.044. 24. Jensen AE, Hjeltnes N, Berstad J, Stanghelle JK. Residual urine following intermittent catheterisation in patients with spinal cord injuries. Paraplegia. 1995;33(12):693–696. doi:10.1038/sc.1995.145. 25. Krebs J, Bartel P, Pannek J. Residual urine volumes after intermittent catheterization in men with spinal cord injury. Spinal Cord. 2013;51(10):776–779. 26. Averbeck MA, Madersbacher H. Follow-up of the neuro-urological patient: a systematic review. BJU Int. 2015;115(suppl 6):39–46. doi:10.1111/bju.13084. 27. Monti Bragadin M, Motta R, Messmer Uccelli M, et al. Lower urinary tract dysfunction in patients with multiple sclerosis: A post-void residual analysis of 501 cases. Mult Scler Relat Disord. 2020;45:102378. doi:10.1016/j.msard.2020.102378. 28. Milles G. Catheter-induced hemorrhagic pseudopolyps of the urinary bladder. JAMA. 1965;193:968–969. doi:10.1001/jama.1965.03090110106036. 29. Isaacs JH, McWhorter DM. Foley catheter drainage systems and bladder damage. Surg Gynecol Obstet. 1971;132(5):889–891. 30. Stensballe J, Looms D, Nielsen PN, Tvede M. Hydrophilic-coated catheters for intermittent catheterisation reduce urethral micro trauma: a prospective, randomised, participant-blinded, crossover study of three different types of catheters. Eur Urol. 2005;48(6):978–983. doi:10.1016/j.eururo.2005.07.009. 31. Abarbanel J, Engelstein D, Lask D, Livne PM. Urinary tract infection in men younger than 45 years of age: is there a need for urologic investigation? Urology. 2003;62(1):27–29. 32. Bagi P, Hannibalsen J, Permild R, Stilling S, Looms DK. Safety of a new compact male intermittent catheter: randomized, cross-over, single-blind study in healthy male volunteers. Urol Int. 2011;86(2):179–184. doi:10.1159/000321900. 33. Chartier-Kastler E, Denys P. Intermittent catheterization with hydrophilic catheters as a treatment of chronic neurogenic urinary retention.