Update on Urethral Bulking for Stress Urinary Incontinence in Women

In vivo biocompatibility and long-term durability of nanofibrillated cellulose as a urethral bulking agent in rats and Beagle dogs

BACKGROUND

Cystoscopy-assisted submucosal injections of urethral bulking agents offer a safe and efficient alternative to surgery for treating urinary incontinence in both dogs and women. To address the concern of their transient therapeutic effect, a preclinical study evaluating the biocompatibility, safety, and durability of nanofibrillated cellulose as a bulking agent was designed. Plant-based nanofibrillated cellulose is considered renewable, biocompatible, and non-degradable in vivo. To the best of our knowledge, no studies of nanofibrillated cellulose injected into the urethral wall of experimental animals have been published to date.

METHODS

After assessing the rheological behavior of nanofibrillated cellulose, a biocompatibility study with 50 rats and a durability study with two Beagle dogs were conducted. In anesthesized rats, deposits of either nanofibrillated cellulose or sodium chloride as an inert control were injected into the urethral wall via a caudal laparotomy. The rats were euthanized for histopathological assessment after 7, 30, and 90 days. In dogs, cystoscopy-assisted injections of nanofibrillated cellulose were followed with magnetic resonance imaging at 14 days and at 2, 3, 6, and 12 months.

RESULTS

The rheological studies demonstrated a gel-like behavior under a wide range of shear stress. Nanofibrillated cellulose induced a moderate host tissue response according to the EN ISO 10993-6 standard, consisting primarily of macrophages, foreign body giant cells, lymphocytes, and plasma cells. No significant difference was observed in the tissue response at different time points. In dogs, the bulking agent was visible in 4/5 (80%) injection sites on magnetic resonance imaging at 12 months post-injection. No signs of migration, abscess formation or any major or long-term complications were observed.

CONCLUSIONS

Nanofibrillated cellulose maintains a chronic but stable and tolerable inflammatory response for up to 90 days in the urethral wall of rats. Durability in the urethral wall of dogs indicates a potential long-term effect.

Current Treatment of Stress Urinary Incontinence by Bulking Agents and Laser Therapy-An Update

Stress urinary incontinence (SUI) affects around 20% of women. In addition to the established suburethral sling insertion, two less invasive approaches are of interest today: urethral bulking agents and vaginal laser therapy. This review discusses articles through December 2023 identified by a PubMed literature search using the keywords "incontinence" and "bulking" or "laser". Although the two approaches are less effective than sling insertions, there are specific conditions in which one or the other technique is more advantageous. Injecting bulking agents into the urethra only takes some minutes and works without general anesthesia. The method is particularly suited for elderly, frail, or obese patients with multiple comorbidities, but is also applicable for all patients and in combination with other therapies. Generally, the safety profile is good but differs between bulking materials. Two laser types-the Erbium:YAG laser with SMOOTH-mode and the fractional ablative CO2 laser-deliver heat into the tissue to induce tissue tightening and regeneration. Intravaginal laser therapy improves mild to moderate SUI, while studies describe how intraurethral laser therapy is also beneficial for severe SUI. Young women between childbirths, as well as postmenopausal women, may benefit from laser therapy. The method is safe, can be performed on an outpatient basis, and does not require any artificial material.

Urethral Bulkamid® injection after failed midurethral sling: a step-by-step video

INTRODUCTION AND HYPOTHESIS

Bulking agents are a minimally invasive treatment option for women with stress urinary incontinence (SUI) or stress-predominant mixed urinary incontinence (MUI). Recurrent SUI is a major challenge for most clinicians because there is little evidence in the literature on the best option after midurethral sling (MUS) failure.

METHODS

Bulkamid® (Contura International A/S), a urethral bulking agent, is a homogenous gel without particles, consisting of a polyacrylamide hydrogel that is nonbiodegradable.

RESULTS

In this video case report, we demonstrate the Bulkamid® injection procedure. This procedure can be carried out as an office-based procedure under local anesthesia, with no down time and only minor possible complications.

CONCLUSIONS

We consider it a valid option for patients with recurrent or persistent SUI after failed MUS surgery.