Development of an ex-vivo porcine lower urinary tract model to evaluate the performance of urinary catheters

Abstract

Intermittent catheterization is the gold standard method for bladder management in individuals with urinary retention and/or incontinence. It is therefore important to understand the performance of urinary catheters, especially on parameters associated to risks of developing urinary tract infections, and that may impact the quality of life for urinary catheter users. Examples of such parameters include, urine flowrate, occurrence of flow-stops, and residual urine left in the bladder after flow-stop. Reliable in-vitro and/or ex-vivo laboratory models represent a strong asset to assess the performance of urinary catheters, preceding and guiding in-vivo animal studies and/or human clinical studies. Existing laboratory models are generally simplified, covering only portions of the catheterization process, or poorly reflect clinical procedures. In this work, we developed an ex-vivo porcine lower urinary tract model that better reflects the catheterization procedure in humans and allows to investigate the performance of standard of care catheters. The performance of three standard of care catheters was investigated in the developed model showing significant differences in terms of flowrate. No differences were detected in terms of residual volume in the bladder at first flow-stop also when tuning the abdominal pressure to mimic a sitting down and standing up position. A newly discovered phenomenon named hammering was detected and measured. Lastly, mucosal suction was observed and measured in all standard of care catheters, raising the concern for microtrauma during catheterization and a need for new and improved urinary catheter designs. Results obtained with the ex-vivo model were compared to in-vivo studies, highlighting similar concerns.

Improved emptying performance with a new micro‐hole zone catheter in adult male intermittent catheter users: A comparative multi‐center randomized controlled cross‐over study

“…Additional implications of higher intra‐catheter pressure peaks and flow‐stop concern the effect of repositioning the catheter to release the surrounding mucosa from the eyelets. Mucosal oedemas, hemorrhages, tissue residues on the edge of catheter eyelets, and floating tissue agglomerates in the catheterized urine are indications of iatrogenic microtrauma observed after catheterizations through eyelets of conventional size 11–16 . Despite the lack of hematuria differences between catheters in the current study ( p > 0.05), a 74% reduced likelihood for dipstick hematuria was observed post catheterization with the MHZC compared to VaPro as a comparator ( p = 0.043) in another recent study 20 .…”

“…This facilitates a free urinary flow where the pressure is distributed along the length of the drainage zone and abrupt flow stops are prevented because there will always be some micro‐holes uncovered. This in turn eliminates the need to adjust or reposition the catheter towards the end of catheterization and theoretically reduces the risk of iatrogenic microtrauma 16 …”

Catheter‐associated bladder mucosal trauma during intermittent voiding: An experimental study in pigs

“…[13][14][15] Identical catheter size is critical when analysing mucosal trauma, as the shape and size of eyelets and catheter shaft are shown to influence the hydrodynamic pressure gradient that ultimately dictates mucosal suction and associated trauma. 6 Arguably, the use of pigs makes the results more translatable to human; however, pigs are more expensive than smaller animal models precluding the use of large sample sizes. A limitation to this study is the experimental approach of 20 repeated drainages which does not truly reflect the use in human patients of roughly five to six drainage per day.…”

“…Others have used mice, rabbits, and dogs for investigating catheter‐associated urinary tract infection, but these animals are not large enough to accurately recapitulate the human bladder anatomy or to support catheter sizes designed for adults 13–15 . Identical catheter size is critical when analysing mucosal trauma, as the shape and size of eyelets and catheter shaft are shown to influence the hydrodynamic pressure gradient that ultimately dictates mucosal suction and associated trauma 6 . Arguably, the use of pigs makes the results more translatable to human; however, pigs are more expensive than smaller animal models precluding the use of large sample sizes.…”

“…Ex vivo studies have demonstrated that flow stops are associated with the occurrence of a hydrodynamically generated negative pressure gradient with peak pressures at the site of the catheter eyelets that facilitates transient suction events of the urothelium. [4][5][6] The resulting mucosal trauma from these suction events compromises the urothelial barrier which may be an overlooked risk factor of urinary tract infection (UTI) in patients using IC or indwelling catheters. 7 Catheter-associated suction events have been reported in humans.…”