Post operative urinary retention (POUR) after a urethral bulking agent (UBA) procedure is a common adverse event reported in up to 20% of cases[1]. Although the majority of these events are transient, lasting less than 24 hours, they are undesirable outcomes causing psychological stress for both patient and clinician, as well as diminished patient satisfaction scores. Risk factors for POUR after urogynecologic procedures are bladder outlet obstruction, poor outlet relaxation, strain voiding, and voiding without a detrusor contraction, all of which require preoperative multichannel urodynamic evaluation to confirm the diagnosis. However, due to the poor predictability of these studies prior to anti-incontinence procedures, routine testing is no longer recommended.  Overall, patients’ reporting of their own voiding patterns (ie: do you push to pee?) fail to correlate with objective measures such elevated intra-abdominal pressure or non-relaxing EMG on preoperative testing, which makes it difficult to judge who will be at increased risk of POUR. Educating patients about proper toileting habits, such as relaxing to void and not pushing or straining is important, but may not be effective in correcting these patterns, particularly in adult women with previously undiagnosed childhood voiding dysfunction. Functional voiding, or the ability to coordinate the outlet and the bladder during urination, may be an acquired sensorimotor skill necessary to ensure the unobstructed release of urine.  The success of biofeedback and urotherapy for treating dysfunctional voiding patterns suggests that pelvic floor proprioception is a likely prerequisite to the ability to voluntarily relax the urethral sphincter. We explored this concept by employing a novel sensorimotor training method that uses sniff-enhanced respiration, which is an expansion of the volitional neuromuscular reflex that elicits simultaneous diaphragmatic contraction and sphincter relaxation [2]. We hypothesized that women who received this training in the weeks prior to injection would have a decreased rate of POUR compared to women who did not receive this training.

This is a retrospective cohort study comparing two groups of consecutive women receiving SUI treatment using polyacrylamide hydrogel (PAHG) injection, performed in the distal urethra to augment the sphincter mechanism.   Internal Review Board approval was obtained prior to study commencement. We had broad inclusion criteria such as patients with occult SUI who had concomitant urogynecologic procedures, patients who had prior history of SUI surgery and patients with mixed urinary incontinence (table 1). Prior to injection, we gave verbal instructions to the first group to relax and not push to pee. For the second group, we provided one formal sensorimotor training (SMT) session on how to feel the drop of the puborectalis/pubococcygeal muscle to its posterior position, using the sniff-enhanced respiration reflex in 3 separate postures 1) semi-supine (figure 1) 2) sitting up/lean forward (tripod) “toileting” posture  3) and standing. We encouraged patients to routinely practice lean forward toilet posture, with continuous sniff-enhanced respiration to initiate, continue and complete urination while becoming aware of the sensation of dropping the muscle down. POUR was defined as need for more than one episode of clean intermittent catheterization before resumption of spontaneous voiding or need for catheterization within 24 hours of leaving the hospital in the case of ambulatory procedures.

195 patients with SUI were treated with PAHG injection. Group 1 (n=129) was treated between November 1st, 2022 and March 15th, 2023. Group 2 (n=66) was treated from Nov 1st, 2023 to March 15th, 2024. Descriptive statistics were performed. 28 women total (14%) had POUR. 26 patients were in group 1 (no SMT) compared to only 2 patients in group 2 (SMT). Among women who underwent concomitant sacrocolpopexy, 53% (16/30) of those who did not have SMT had POUR as compared to 7% (2/27) of those who had prior SMT. No patient in either group required a post-op catheter more than 24 hours after procedure.

The sniff reflex is a well known method for assessment of diaphragmatic function through its stimulation of the phrenic nerve. Sniff nasal inspiratory pressure (SNIP) is a common noninvasive test of inspiratory muscle strength and the integrity of the bulbospinal nerve pathway in patients with neuromuscular disease. The sniff reflex coincidentally activates volitional sphincter relaxation and, when enhanced with respiration, is a useful tool to facilitate the coordinated release of urine [3].  Women with SUI receiving sniff-enhanced respiration SMT prior to distal urethral injection of PAHG had decreased POUR compared to those who received only verbal instructions to relax. This difference was most pronounced in patients receiving additional procedures for pelvic floor reconstruction. These findings suggest that a percentage of women with SUI may have underlying voiding dysfunction which, when addressed on a sensorimotor level, can potentially improve their ability to release urine after a UBA procedure.

In the present study, women receiving pelvic muscle SMT using sniff-enhanced respiration for urination had decreased POUR after injection of PAHG compared to those who only received a verbal direction to “relax to pee”.  Because patients with undiagnosed voiding dysfunction are at increased risk for POUR, SMT is a precautionary measure to be taught to women who are preparing for urethral injection.

Hoe V, Haller B, Yao HH, O'Connell HE. Urethral bulking agents for the treatment of stress urinary incontinence in women: A systematic review. Neurourol Urodyn. 2021 Aug;40(6):1349-1388. doi: 10.1002/nau.24696. Epub 2021 May 20. PMID: 34015151.
Tomori Z, Benacka R, Donic V. Mechanisms and clinicophysiological implications of the sniff- and gasp-like aspiration reflex. Respir Physiol. 1998 Oct;114(1):83-98. doi: 10.1016/s0034-5687(98)00077-2. PMID: 9858054.
Keller JA, Chen J, Simpson S, Wang EH, Lilascharoen V, George O, Lim BK, Stowers L. Voluntary urination control by brainstem neurons that relax the urethral sphincter. Nat Neurosci. 2018 Sep;21(9):1229-1238. doi: 10.1038/s41593-018-0204-3. Epub 2018 Aug 13. PMID: 30104734; PMCID: PMC6119086.

Continence 12S (2024) 101348
DOI: 10.1016/j.cont.2024.101348