Mainz Pouch I
The Mainz pouch I is an ileocecal reservoir, combining cecum and ascending colon with detubularized ileum. Introduced in the 1980s, the reconstruction has been used for continent cutaneous diversion, orthotopic substitution and augmentation. Those applications have different emptying and continence mechanisms and should be distinguished when interpreting outcomes.[1][2]
For cutaneous diversion, the principal outlet options are a submucosally embedded appendix or an intussuscepted ileal nipple. The technique has substantial long-term institutional experience, but published cohorts do not establish superiority over every other reservoir.[3][4]
Patient Selection
Selection requires suitable bowel, sufficient renal and hepatic function and a sustainable catheterization plan. A continent cutaneous reservoir may be chosen when an internal reservoir is desired but orthotopic substitution is unsuitable or unwanted. Assess cognition, dexterity, access to the proposed stoma and capacity for lifelong follow-up; age alone should not determine the choice.[5][6]
Oncologic suitability for an orthotopic reconstruction depends particularly on an appropriate urethral outlet and negative urethral margin. Continent cutaneous diversion remains an alternative when the urethra cannot be retained. The AUA discussion gives eGFR below 45 mL/min/1.73 m² as an example of inadequate renal function for continent diversion; individual renal, hepatic and bowel assessment is essential.[5]
Operative Principles
The original-author surgical atlas distinguishes the required bowel by the outlet selected:[7]
- Assess the appendix before bowel division. Its caliber, length, blood supply and reach must permit reliable catheterization.
- Reservoir bowel: the appendix-stoma version uses approximately 10–12 cm of cecum/ascending colon and 20–25 cm of terminal ileum. Restore ileocolic continuity while preserving reservoir perfusion.
- Reconfiguration: open the ileal loops and ascending colon for the reservoir plate. Preserve the lower cecum needed for the appendiceal continence tunnel; do not simply open every segment completely.
- Appendix outlet: embed the vascularized appendix in a submucosal cecal bed, preserving its mesenteric vessels.
- Ileal nipple alternative: retain an additional approximately 12 cm of ileum unopened for intussusception. The total ileum used therefore exceeds that of the appendix version.
- Ureters and completion: create the selected ureteral anastomoses, avoid outlet kinking or compression, complete the pouch, and secure catheter drainage.
These dimensions describe the atlas technique, not mandatory measurements for every patient. Its historical drug and catheter protocols should not substitute for a current perioperative plan. The Catheterizable Channels page covers broader outlet planning.
Reservoir modifications
Alcini's 30-patient teniamyotomy study concerned ileocecal bladder replacement without formal detubularization. It is a separate reconstruction, not evidence for routinely adding teniamyotomies to the detubularized Mainz pouch.[8]
Bowel-flap tubes are alternatives when the appendix is absent or unsuitable. Lampel's initial 17-patient report included seromuscular and full-thickness flap tubes with mean follow-up of only eight months; it establishes a described option, not comparable long-term durability.[9]
Continence Mechanisms and Complications
In the 2006 retrospective comparison of 401 patients, outlet selection was not randomized. Results reflect different anatomy, techniques and follow-up.[4]
| Outcome | Ileal nipple, n = 205 | Appendix, n = 196 |
|---|---|---|
| Complete continence | 82% | 92% |
| Stomal stenosis | 34 (17%) | 63 (32%) |
| Reservoir stones | 41 (20%) | 20 (10%) |
| Reoperation for stomal incontinence | 12 | 3 |
| Reported outlet necrosis | One nipple necrosis within the incontinence-reoperation group | Four appendiceal necroses |
Overall, 144/401 patients required an intervention for a stomal complication, and 63% of stomal complications were treated endoscopically. The appendix offers an attractive outlet when suitable, but its stenosis burden must be discussed; the ileal nipple carries its own risks, including stone formation around exposed staples. These data do not establish that one mechanism is best regardless of anatomy.[4]
An additional two-center report of more than 800 ileocecal reservoirs, mean follow-up 7.6 years, reported overall day-and-night continence of 92.8%. That is an overall result, not an appendix-only rate. Its cohorts overlap the broader institutional experience and should not be pooled as independent patients.[3]
Ureteral Implantation
Submucosal implantation into colon is the classic antireflux approach. Serosa-lined extramural tunnels were subsequently used, including for dilated ureters. Preserve ureteral perfusion and avoid tension, angulation and compression whichever reconstruction is chosen.[1][10][7]
Wiesner's 2007 retrospective study included 458 patients, with 809 renal units receiving a submucosal tunnel and 74 an extramural tunnel; median overall follow-up was 89 months.[10]
| Outcome | Submucosal tunnel | Serosa-lined extramural tunnel |
|---|---|---|
| Obstruction | 59/809 renal units (7.3%) | 3/74 (4.1%) |
| Obstruction in previously dilated upper tracts | 13.9% | 3.1% |
| Obstruction in patients with neurogenic bladder | 17.1% | 7.1% |
The lower observed obstruction in the extramural group informed the authors' preference, especially for dilated upper tracts. The comparison was neither randomized nor balanced in size; it is not a universal guideline requirement or proof of superior renal preservation. A normal serum creatinine alone does not exclude unilateral obstruction.[10]
Orthotopic and Augmentation Applications
Orthotopic Mainz reconstruction omits a cutaneous outlet and joins the reservoir to the retained urethra. Emptying relies on an appropriate outlet, pelvic-floor relaxation and abdominal pressure; some patients need intermittent catheterization.[11]
Leissner's 1999 series included 108 men, 103 evaluable, with mean follow-up 42 months. Reported daytime continence was 88%, including 17% using a safety pad. At night, 34% were completely continent while sleeping through the night and another 33% used a safety pad; nighttime results should not be collapsed into a single “dry” percentage. Fifteen of 205 renal units developed ureteroenteric stenosis.[11]
Augmentation retains native bladder and outlet structures. In the early 100-case experience, 34 patients underwent augmentation, 15 orthotopic substitution and 51 cutaneous diversion. These groups should not share one continence or catheterization estimate.[2]
Neurogenic and Pediatric Experience
Stein's 2005 cutaneous-diversion report included 70 children and adolescents, of whom 65 had follow-up after five deaths unrelated to diversion. At median 8.7 years, upper tracts were stable or improved in 113/118 renal units; reported continence was 97%. Revision burdens included stomal stenosis, outlet incontinence, stones and ureteral obstruction. These are selected institutional results, not a guarantee of protection without surveillance.[12]
The earlier 2000 report covered 149 operations with follow-up in 129 patients, comprising 59 colonic conduits, 12 orthotopic reconstructions and 58 Mainz I diversions. Its long-term outcomes must not be described as a 149-patient Mainz-pouch cohort.[13] Reconstruction follows assessment of storage pressure, renal risk, outlet function and the patient's ability to catheterize; the ability to maintain care must be reconsidered during transition to adulthood.
Metabolic Outcomes
Pfitzenmaier reevaluated 94 of 458 operated patients, median follow-up nine years. B12 supplementation was recommended in 32% because levels were low-normal or low, and 37% continued citrate for acidosis prevention. Absence of overt clinical metabolic symptoms in this selected, monitored cohort does not establish freedom from biochemical deficiency or prove that alkali prevented bone disease. Bone density was measured in only 18 patients.[14]
The appendix-outlet version uses less ileum than a nipple-outlet reconstruction, but bowel length alone does not determine metabolic risk. Segment location, renal function, urine contact and prior bowel surgery also matter. Neither the 32% supplementation figure nor older Schilling-test results from other reservoirs constitute a direct comparative B12-deficiency rate.[14][7]
See Vitamin B12 Supplementation, Urinary Acidifiers and Alkalinizers, and Mucus Management.
Secondary Malignancy and Follow-up
Kälble's 2011 analysis recorded 32 secondary tumors among 17,758 diversions reported by German centers. The reported prevalence in ileocecal pouches was 0.14%; this is not a lifetime incidence estimate. The authors recommended endoscopy of catheterizable ileocecal pouches for concerning symptoms such as hematuria, recurrent infection or hydronephrosis, rather than mandatory routine endoscopy for every asymptomatic pouch.[15]
Lifelong functional follow-up should cover catheterization and stomal access, continence, renal drainage, stones, metabolic abnormalities and bowel symptoms. For cancer cystectomy, AUA recommends laboratory assessment every 3–6 months for 2–3 years and then annually; EAU recommends annual B12 testing after bowel diversion. Tailor imaging and additional testing to the original disease and functional risk.[5][16]
Do not routinely screen or treat asymptomatic bacteriuria because an intestinal reservoir is colonized. Culture and treat for clinical indications, including established exceptions such as preparation for mucosa-breaching urological procedures.[17] Difficulty passing a catheter, newly impaired drainage or suspected pouch injury requires prompt assessment and a drainage plan.
See Also
References
1. Thüroff JW, Alken P, Riedmiller H, et al. "The Mainz Pouch (Mixed Augmentation Ileum and Cecum) for Bladder Augmentation and Continent Diversion." J Urol. 1986;136(1):17–26. doi:10.1016/s0022-5347(17)44714-8
2. Thüroff JW, Alken P, Riedmiller H, Jacobi GH, Hohenfellner R. "100 Cases of Mainz Pouch: Continuing Experience and Evolution." J Urol. 1988;140(2):283–8. doi:10.1016/s0022-5347(17)41584-9
3. Wiesner C, Bonfig R, Stein R, et al. "Continent Cutaneous Urinary Diversion: Long-Term Follow-Up of More Than 800 Patients With Ileocecal Reservoirs." World J Urol. 2006;24(3):315–8. doi:10.1007/s00345-006-0078-y
4. Wiesner C, Stein R, Pahernik S, et al. "Long-Term Followup of the Intussuscepted Ileal Nipple and the in Situ, Submucosally Embedded Appendix as Continence Mechanisms of Continent Urinary Diversion With the Cutaneous Ileocecal Pouch (Mainz Pouch I)." J Urol. 2006;176(1):155–9. doi:10.1016/S0022-5347(06)00571-4
5. American Urological Association / ASCO / ASTRO / SUO. Treatment of Non-Metastatic Muscle-Invasive Bladder Cancer. 2024 amendment. Statements 13–14 and 31–32 and discussions. Guideline.
6. European Association of Urology. EAU Guidelines on Muscle-invasive and Metastatic Bladder Cancer. 2026. Urinary diversion, section 6.7.5. Guideline.
7. Thüroff JW, Riedmiller H, Fisch M, Stein R, Hampel C, Hohenfellner R. Mainz pouch continent cutaneous diversion. BJU Int. 2010;106(11):1830–1854. doi:10.1111/j.1464-410X.2010.09773.x.
8. Alcini E, D'Addessi A, Racioppi M, et al. "Results of 4 Years of Experience With Bladder Replacement Using an Ileocecal Segment With Multiple Transverse Teniamyotomies." J Urol. 1993;149(4):735–8. doi:10.1016/s0022-5347(17)36195-5
9. Lampel A, Hohenfellner M, Schultz-Lampel D, Thüroff JW. "In Situ Tunneled Bowel Flap Tubes: 2 New Techniques of a Continent Outlet for Mainz Pouch Cutaneous Diversion." J Urol. 1995;153(2):308–15. doi:10.1097/00005392-199502000-00004
10. Wiesner C, Pahernik S, Stein R, et al. "Long-Term Follow-Up of Submucosal Tunnel and Serosa-Lined Extramural Tunnel Ureter Implantation in Ileocaecal Continent Cutaneous Urinary Diversion (Mainz Pouch I)." BJU Int. 2007;100(3):633–7. doi:10.1111/j.1464-410X.2007.06991.x
11. Leissner J, Stein R, Hohenfellner R, et al. "Radical Cystoprostatectomy Combined With Mainz Pouch Bladder Substitution to the Urethra: Long-Term Results." BJU Int. 1999;83(9):964–70. doi:10.1046/j.1464-410x.1999.00049.x
12. Stein R, Wiesner C, Beetz R, et al. "Urinary Diversion in Children and Adolescents With Neurogenic Bladder: The Mainz Experience. Part II: Continent Cutaneous Diversion Using the Mainz Pouch I." Pediatr Nephrol. 2005;20(7):926–31. doi:10.1007/s00467-005-1848-2
13. Stein R, Fisch M, Ermert A, et al. Urinary diversion and orthotopic bladder substitution in children and young adults with neurogenic bladder: a safe option for treatment? J Urol. 2000;163(2):568–573. PMID:10647686.
14. Pfitzenmaier J, Lotz J, Faldum A, et al. "Metabolic Evaluation of 94 Patients 5 to 16 Years After Ileocecal Pouch (Mainz Pouch 1) Continent Urinary Diversion." J Urol. 2003;170(5):1884–7. doi:10.1097/01.ju.0000091900.57347.ee
15. Kälble T, Hofmann I, Riedmiller H, Vergho D. "Tumor Growth in Urinary Diversion: A Multicenter Analysis." Eur Urol. 2011;60(5):1081–6. doi:10.1016/j.eururo.2011.07.006
16. European Association of Urology. EAU Guidelines on Muscle-invasive and Metastatic Bladder Cancer. 2026. Functional follow-up, section 7.4. Guideline.
17. European Association of Urology. EAU Guidelines on Urological Infections. 2026. Reconstructed lower urinary tracts and asymptomatic bacteriuria, sections 3.3.5.d.5 and 3.3.7. Guideline.