Urethral bulking

From Dog

Urethral bulking is a surgical technique for correction of canine urinary incontinence.

If the results of medical or surgical treatment of USMI are incomplete or unsatisfactory, endoscopic submucosal implantation of urethral bulking agents such as polytetrafluoroethylene (Teflon) or medical-grade collagen can be performed to create intraluminal resistance to urine outflow.20"22 Successful urethral bulking with submucosal collagen has been reported in women and dogs[1].

Collagen products are commonly used in people to correct defects of the skin and soft tissues. A specific collagen product for urologic use (Contingen, Bard Urological, Covington, GA) has been commercially developed and approved for use in humans. This product is composed of highly purified bovine dermal collagen that is cross-linked with glutaraldehyde and dispersed in phosphate-buffered saline. The collagen component is composed of approximately 95% type I collagen and 5% or less type III collagen. This product is packaged in a sterile 2.5-mL syringe for single use. Collagen has a higher degree of biocompatibility compared with other products previously reported for urethral bulking (e.g., polytetrafluoroethylene).

Initial reports showed a control rate (complete continence) of 53% for USMI treated with one or two series of submucosal injections of collagen. This rate improved to 75% when PPA was administered to dogs in which collagen injections provided inadequate urinary control.21 More recently, a success rate of 68% was reported in 40 female dogs with USMI treated with submucosal collagen injections. Some dogs may require a second series of collagen injections if incontinence is uncontrolled or relapses. Repeat injection procedures are usually easier to complete because the previous urethral bulking site is readily identified and augmented[2].

Position the patient in right lateral recumbency under general anesthesia. Clip and aseptically prepare the vulva and perivulvar region. A 19- or 14-French rigid cystoscope with a 30° angle is used for uroendoscopy and the injection procedure. Endoscopy is performed using a sterile fluid infusion to create a clear visual field. Mucosal hemorrhage can be controlled with the infusion of cold fluids. An assistant with sterile gloves should prepare the collagen and injection device.

Perform a complete evaluation of the lower urinary and reproductive structures to rule out anatomic causes of urinary incontinence before injecting the collagen. Position the tip of the cystoscope within the proximal urethra to visualize the vesicourethral junction, and aseptically pass the injection device through the biopsy channel of the cystoscope until the beveled needle end is visible in the optical field. The recommended site for collagen injection is approximately 1.5 to 2 cm caudal to the vesicourethral junction. Position the cystoscope to facilitate insertion of the beveled tip of the injection device immediately below the urethral mucosa into the submucosal layer. Slowly inject the collagen, watching for immediate elevation of the urethral mucosa to create a mounding effect. If the needle is positioned too deep, there is minimal to no intraluminal deformation of the urethral mucosa. The collagen is commonly injected at three to four sites in a circle. The amount of collagen injected at each site is determined visually. Injection of excessive collagen at any given site can result in mucosal disruption and leakage of collagen from the site. The procedure is considered complete when the injection sites appose one another, achieving visual obstruction of the urethral lumen.

Patients should be continent immediately after this procedure. Dogs with moderate to severe inflammation or urinary tract infection may experience some minor incontinence until the infection/inflammation is resolved medically. If incontinence persists after the initial collagen injections, this procedure can be repeated, enhancing the previously injected sites. Administration of PPA has been shown to further enhance control of urinary continence after collagen injection. Complete urinary outflow obstruction has not been reported in dogs. Follow-up endoscopic examinations have uniformly demonstrated that the submucosal collagen deposits can remain visually unchanged for years. Relapse of incontinence after prolonged successful control with collagen injections may be related to absorption of the phosphate buffer component of the collagen preparation.


  1. Arnold S, Hubler M, Lott-Stolz G, Rusch P. (1996) Treatment of urinary incontinence in bitches by endoscopic injection of glutaraldehyde cross-linked collagen. J Small Anim Pract 37:163-168
  2. Barth A, Reichler IM, Hubler M, et al (2005) Evaluation of long-term effects of endoscopic injection of collagen into the urethral submucosa for treatment of urethral sphincter incompetence in female dogs: 40 cases (1993-2000). JAVMA 226(1):73-76