Hypothesis / aims of study
The aim of the study was to investigate the feasibility of measuring a closing pressure in continent catheterizable channels (CCC).
For patients with impaired bladder emptying and difficult transurethral access, a CCC may be a solution. Although satisfaction of patients with a CCC is generally high, leakage of the channel is a common complication. In order to prevent leakage, the pressure in the CCC should be higher than in the bladder at at least one point. It is unknown which factor of the channel contributes most to continence: the length of the channel or a pressure point such as the passage through the rectus fascia, the abdominal muscle or skin, or the intravesical submucosal tunnel. Watson et al found in 1995 that in children, the length of the channel was most predictive of stomal continence. [1] In the literature, no further studies could be found embracing this concept. Furthermore, CCC pressure profilometry in adults has not been reported. In this feasibility study, we measured the CCC pressure profile in patients with various types of CCC’s with and without leakage.
Study design, materials and methods
In this feasibility study, adult patients with a CCC on (augmented) bladder or pouch who underwent a urodynamic study between January and March 2023 were included. All patients gave informed consent. Besides standard filling cysto-/pouchometry, a continuous stomal pressure measurement (CSP) and stomal pressure profile (SPP) of the CCC was performed, analogous to the measurement of a urethral pressure profile. [2]
Starting with an empty bladder or pouch, an air-charged catheter (T-DOC CAT 880, Laborie, Portsmouth, NH) with two pressure channels (vesical and stomal pressure) was passed through the CCC into the bladder or pouch. To obtain SPP-1 (SPP with empty bladder) the catheter was retracted through the channel by hand with approximately 1 cm/s while measuring the pressure. Hereafter the catheter was inserted deeper in bladder or pouch again, with the stomal pressure measurement manually positioned at the point of maximal closure pressure. To obtain CSP, the catheter was secured at this point and a cough test was executed to check the pressures. After filling the bladder/pouch, at maximum bladder capacity, SPP-2 was obtained by reinserting the catheter deeper in the bladder / pouch and retracting it through the CCC while measuring the pressure.
The primary goal was to investigate the feasibility of the measurement of CSP and SPP; the secondary objective was to describe the pressure profilometry by extracting data on leakage during the study, vesical/pouch pressure, maximal stomal pressure during SPP-1 and SPP-2, number of peaks in the SPP, and stomal pressure changes during CSP measurement. In case leakage was observed during the urodynamic study, a distinction was made between leakage due to detrusor overactivity or low compliance and leakage with low bladder/pouch pressure (<20 cm H2O). SPP-1, SPP-2 and CSP of patients with leakage with low bladder/pouch pressure (group 1) and those without leakage or with leakage due to high bladder pressure (group 2) were compared.
Results
A total of 14 patients were included in this study. Baseline characteristics are shown in Table 1.
In all 14 patients it was technically possible to perform a SPP and in 13/14 patients a CSP could be measured. All patients showed a positive stomal pressure and stomal pressure changes during SPP-1 and SPP-2, as well as stomal pressure changes during filling cystometry, Valsalva maneuver, and cough tests. An example of a stomal pressure profile is presented in figure 1. The number of closing pressure peaks in SPP-1 and SPP-2 varied between 1 and 3. CSP showed variation over time.
Median maximal stomal pressure was 114 (range 48-201) cmH2O in SPP-1 and 125 (range 58-283) cmH2O in SPP-2. Seven patients had stomal leakage during urodynamic study; four patients with low bladder pressure (group 1) and three patients with detrusor overactivity (group 2). Seven patients without leakage were also assigned to group 2. SPP-1, SPP-2 and CSP were higher in group 1 than in group 2 (median 117 versus 99 cm H2O, median 134 versus 106 cm H2O, and median 95 versus 80 cm H2O).
Interpretation of results
In this feasibility study, we found that it is possible to measure the stomal pressure and to perform a stomal pressure profile in patients with CCC. In our results, it was striking that measured stomal pressures were rather high, much higher than urethral pressures . This is consistent with earlier findings in children.[1] Stomal leakage despite high (maximal) stomal pressures may be explained by periodical stomal relaxation in the context of peristalsis. If relaxation is indeed the case, drug treatment of stomal leakage might be an option. In some patients, but not all, we found three peaks in the SPP. We hypothesize that these are the submucosal intravesical tunnel, passage through the fascia and through the skin, respectively. Further study, with additional fluoroscopy (with fluid filled catheter) for example in order to determine the exact position of the pressure measuring point of the catheter, might help to elucidate this question. As the catheter was pulled manually, it was difficult to determine stomal length. The use of an automated puller could solve this problem. We found a trend towards lower maximum closing pressures in patients with leakage while bladder pressure was low. Whether this represents ‘stomal stress incontinence’ needs to be established, as well as the clinical meaning of this finding. Due to the small sample size, we could not make a distinction between different types of stomas (bladder flap, detubularized ileum or appendix). Measurements in a larger cohort might provide better and more interpretable information. Results could help in understanding the dynamics of CCCs and in treatment of complications.