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MAINZ Pouch: Surgical Technique (Step-by-Step) and Complications

The MAINZ pouch is a heterotopic continent urinary diversion after cystectomy. The reservoir is formed using the caecum and distal ileum, the continence mechanism is constructed with the appendix vermiformis.

Indications for a MAINZ Pouch

Heterotopic continent urinary diversion should be offered to motivated and medically suitable patients for urinary diversion after cystectomy if the urethra or the urinary sphincter is not suitable for orthotopic urinary diversion. 

Contraindications for MAINZ Pouch

• Intestinal diseases (Crohn disease, ulcerative colitis, short bowel syndrome)
• After pelvic radiation therapy
• Chronic kidney disease (GFR <60–80 ml/min)
• Poor compliance
• Low life expectancy
• Lack of ability for self-catheterization

Step-by-Step Surgical Techniques of MAINZ Pouch

Preoperative patient preparation:

Please see the section on radical cystectomy.

Bowel Dissection:

Mobilize the ascending colon. Incise the tip of the appendix vermiformis and dilate the appendicular lumen: the appendix is suitable for the continence mechanism if a 16 CH catheter can be inserted. Isolate 20 cm of ascending colon and 40 cm of ileum if the appendix is suitable for the continence mechanism. Add 20 cm of ileum if the continence mechanism is made with the ileocaecal valve [fig. MAINZ pouch 1]. Perform side-to-side ileocolonic anastomosis to restore bowel continuity. Carefully irrigate and clean the isolated bowel segment.

MAINZ pouch I: Isolate 20 cm of ascending colon and 40 cm of ileum and continue with a longitudinal incision of the bowel.

Longitudinal bowel incision:

Incise the colon following the taenia libera and cross the ileocecal valve into the ileum, if the appendix is sufficient for the continence mechanism. Spare the ileocecal valve during the longitudinal bowel incision if the continence mechanism is made with ileum. Carefully irrigate and clean the isolated bowel segment.

Detubularization:

Arrange the bowel segments like an N [fig. MAINZ pouch 2], form a bowel plate by connecting the limbs of the N with running sutures (Vicryl 3-0).

MAINZ pouch I: Detubularization and nonrefluxing ureterocolonic anastomosis.

Nonrefluxing ureterocolonic anastomosis:

Perform an antirefluxive ureteral implantation analogous to ureterocystoneostomy: submucosal tunneling with overholt clamp, implantation of the ureter as in UCN (PDS 4-0).

Pouch closure:

Fold the pouch plate in the longitudinal axis and close it with running sutures (Vicryl 3-0).

MAINZ pouch I: Continence mechanism with appendix.

Continence mechanism with appendix:

Create openings in the mesoappendix every one centimeter. Continue with a longitudinal seromuscular incision of the anterior taenia from the appendix base in the cranial direction for at least 4 cm [fig. MAINZ pouch 3]. Flip the appendix over into the colonic incision and place sutures through the openings of the mesoappendix to close the colonic incision. Knotting the placed sutures locates the appendix in the submucosa of the pouch and serves as a continence mechanism [fig. MAINZ pouch 4].

MAINZ pouch I: The pouch plate is folded in the longitudinal axis and closed with a running suture.

Umbilical stoma:

Remove the skin of the umbilicus and incise the fascia if necessary. Pass the catheter through the stoma. Create the anastomosis between the umbilical stoma and appendix with interrupted sutures 2-0 PDS. Fix the pouch with additional sutures to the ventral abdominal wall.

Postoperative Care after MAINZ Pouch

Please see the section urinary diversion for postoperative care.

Complications of MAINZ Pouch

In addition to the complications of cystectomy, see the section urinary diversion for complications of the continent urinary diversion.

References

Hautmann 2003 HAUTMANN, R. E.: Urinary diversion: ileal conduit to neobladder.
In: J Urol
169 (2003), Nr. 3, S. 834–42

Thuroff u.a. 1986 THUROFF, J. W. ; ALKEN, P. ; RIEDMILLER, H. ; ENGELMANN, U. ; JACOBI, G. H. ; HOHENFELLNER, R.: The Mainz pouch (mixed augmentation ileum and cecum) for bladder augmentation and continent diversion.
In: J Urol
136 (1986), Nr. 1, S. 17–26

  Deutsche Version: Technik und Komplikationen des MAINZ-Pouch