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Mainz Pouch I

The Mainz pouch I (Mixed Augmentation Ileum 'N Zecum) is a detubularized ileocecal reservoir made from cecum, ascending colon and two ileal loops. Thüroff, Alken, Riedmiller, Jacobi and Hohenfellner developed it in Mainz from 1983. It has been used for continent cutaneous diversion, orthotopic substitution and augmentation, which differ in emptying and continence mechanisms, so outcomes are reported separately below.[1][2][18][19]

For cutaneous diversion, the outlet is a submucosally embedded appendix or an intussuscepted ileal nipple. Most published data come from two German centers (Mainz and Wuppertal), including a series of more than 800 patients with mean follow-up of 7.6 years.[3][4]

Historical Development​

  • 1983. The first Mainz pouches were made for bladder augmentation and continent cutaneous diversion.[19]
  • 1985. The first description reported 10 patients (4 augmentations, 6 diversions). It described the low-pressure reservoir from cecum and two ileal loops and submucosal-tunnel ureteral implantation into the cecum; of six cutaneous diversions, two achieved continence with ileoileal intussusception, two relied on an alloplastic stomal prosthesis, and two awaited a sphincteric device.[18]
  • 1986. The J Urol description reported 11 augmentations and 12 diversions; the same three functional features were retained.[1]
  • 1988. The 100-patient report (34 augmentations, 15 orthotopic substitutions, 51 cutaneous diversions) recorded that stapling the nipple to the bowel wall and ileocecal valve solved nipple prolapse. The umbilicus was adopted as the stomal site for cosmetic reasons.[2]
  • 1990. The in situ, submucosally embedded appendix was introduced as the continent outlet.[9]
  • 1995. Seromuscular and full-thickness bowel-flap tubes were described for patients without a usable appendix.[9]
  • 1996. A report of 561 patients from Mainz and Wuppertal included 60 augmentations, 61 orthotopic substitutions and 440 cutaneous diversions.[19]

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. Cognition, dexterity, access to the proposed stoma, expected survival and capacity for lifelong follow-up are assessed.[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 guideline discussion lists inadequate renal or hepatic function (for example, an eGFR below 45) among the absolute contraindications to continent diversion. Renal, hepatic and bowel status are each assessed for the individual patient.[5]

After pelvic irradiation, the Mainz group built continent cutaneous reservoirs from nonirradiated colon only, the Mainz pouch III, because irradiated bowel is associated with more early and late complications.[25]

Operative Principles​

The original-author surgical atlas distinguishes the required bowel by the outlet selected:[7]

  1. Assess the appendix before bowel division. Its caliber, length, blood supply and reach must permit reliable catheterization. Calibrate the lumen before choosing bowel length, because an appendix that appears normal may be obliterated.[7]
  2. 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.
  3. 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.
  4. Appendix outlet: embed the vascularized appendix in a submucosal cecal bed, preserving its mesenteric vessels.
  5. 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. The 1988 technique fixed the nipple to the bowel wall and ileocecal valve to address prolapse.[2]
  6. Ureters and completion: create the selected ureteral anastomoses, avoid outlet kinking or compression, and complete the pouch. In the original-author technique, a transumbilical Foley and separate transcutaneous pigtail drain the pouch; bilateral ureteral stents are externalized and secured.[7]

These dimensions come from the atlas technique and vary with the patient. The 1988 series described the same reservoir as 10–15 cm of cecum and ascending colon plus two ileal loops of equal length.[2] The Catheterizable Channels page covers broader outlet planning.

Reservoir modifications​

Alcini reported 30 patients with ileocecal bladder replacement using multiple transverse teniamyotomies instead of formal detubularization. All were continent by day; at one year mean capacity was 396 mL with a mean full-filling pressure of 28 cm H₂O. This is a separate reconstruction from the detubularized Mainz pouch.[8]

Bowel-flap tubes are alternatives when the appendix is absent or unsuitable. Lampel's initial report of 17 patients used a seromuscular flap tube in 11 and a full-thickness flap tube in 6. At mean follow-up of 8 months, 16 of 17 catheterized every 4 to more than 6 hours with 14–16 F catheters and were continent day and night.[9]

Continence Mechanisms and Complications​

Wiesner's 2006 retrospective comparison of 401 patients was not randomized; groups differed in anatomy, technique and follow-up.[4]

OutcomeIleal nipple, n = 205Appendix, n = 196
Complete continence82%92%
Stomal stenosis34 (17%)63 (32%)
Reservoir stones41 (20%)20 (10%)
Reoperation for stomal incontinence123
Reported outlet necrosisOne nipple necrosis within the incontinence-reoperation groupFour appendiceal necroses
Mean time to first stenosis43.8 months31.4 months
Mean time to first stone62.8 months47.5 months

Overall, 144/401 patients (36%) required an intervention for a stomal complication, and 63% of stomal complications were treated endoscopically.[4] The authors attributed the higher stenosis rate with the appendix to its smaller diameter and the higher stone rate with the nipple to metal staples. The nipple outlet produced somewhat more mucus.[4] In a single-center series of 28 secondary ileal-nipple revisions for failed pouch outlets, 24 patients were continent day and night and four used a safety pad at mean 65.4-month follow-up; two later required a third continence mechanism.[26]

Gerharz reported 96 appendix and 106 ileal-nipple outlets, with mean follow-up of about 3 years; the abstract also calls the cohort 193 consecutive cases, so its overall denominator is inconsistent.[20] Appendix stenosis (15.6%) was corrected as a minor outpatient procedure, and two complete appendix necroses were replaced with an ileal nipple. Reoperation was needed in 13 of 106 nipples (12.3%) for necrosis (4), dislocation from the ileocecal valve (3), detachment from fascia (4) or stenosis (2). Stones occurred in 3 nipples and no appendix. The authors advised using the appendix whenever a suitable one is available.[20]

The two-center series of more than 800 ileocecal reservoirs, mean follow-up 7.6 years, reported overall day-and-night continence of 92.8%.[3] Stomal stenosis occurred in 23.5% with an appendix and 15.3% with an ileal nipple, and stones in 5.6% and 10.8%.[3] Eleven patients (8 appendix, 3 nipple) required reoperation for ischemic degeneration of the continence mechanism. These patients overlap those in the 401-patient report.[3] In the 561-patient series (mean follow-up 57 months), early and late complications occurred in 12% and 37%, and stoma failure in 11% of cutaneous diversions.[19]

Ureteral Implantation​

Submucosal implantation into colon is the classic antireflux approach. Serosa-lined extramural tunnels were subsequently used, including for dilated ureters. Ureteral perfusion is preserved and tension, angulation and compression are avoided with either reconstruction.[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]

OutcomeSubmucosal tunnelSerosa-lined extramural tunnel
Obstruction59/809 renal units (7.3%)3/74 (4.1%)
Obstruction in previously dilated upper tracts13.9%3.1%
Obstruction in patients with neurogenic bladder17.1%7.1%
Obstruction-free at 1 / 5 / 10 years97% / 93% / 91%100% / 96% / 96%
Patients with serum creatinine ≤ 1.6 mg/dL at last follow-up97%98%

In this retrospective series, the extramural tunnel was associated with lower observed obstruction rates, especially with previously dilated upper tracts or neurogenic bladder; the authors preferred it in those settings. Renal function remained stable with both techniques. A normal serum creatinine does not exclude unilateral obstruction.[10]

The larger two-center cohort above (more than 800 patients, mean follow-up 7.6 years) separately reported anastomotic stricture of the afferent limb in 6.5% of renal units with a submucosal tunnel versus 5.0% with a serosa-lined extramural tunnel, consistent in direction with the 2007 comparison.[3]

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]

A modified orthotopic arrangement keeps the ileocecal valve intact as the antireflux mechanism and implants the ureters directly into the retained pre-valvular ileum rather than into colon. When tumor involvement or prior radiation has shortened the ureters, this pre-valvular ileal segment can be lengthened to bridge part or all of the ureteral defect; when the ileocolic pedicle is too short to bring the pouch down to the urethra without tension, rotating it 180 degrees counter-clockwise has been described to achieve a tension-free urethrointestinal anastomosis.[24]

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; another 33% used a safety pad. Fifteen of 205 renal units developed ureteroenteric stenosis.[11]

Augmentation retains native bladder and outlet structures, so continence depends on the native bladder neck and urethral mechanism. In the 100-patient report, 32 of 34 augmentation patients were completely dry day and night, and 3 relied on intermittent catheterization. In the 561-patient series, 93% of augmentation patients were completely continent and all but 3 voided by abdominal straining.[2][19]

Bedük compared 19 Mainz and 36 Abol-Enein and Ghoneim orthotopic neobladders (median follow-up 36 and 31 months).[21] Urodynamic findings did not differ significantly between the groups.[21]

OutcomeMainz (19 patients)Abol-Enein and Ghoneim (36 patients)
Ureterointestinal stenosis10.5%5.7%
Pouch-ureteral reflux7.9%4.2%
Pyelonephritis15.8%13.8%
Daytime incontinence5.3%5.5%
Nighttime incontinence (twice weekly or more)21%8.4%
Capacity at 12 months (urodynamics in 39 of 55 patients)426 ± 34 mL442 ± 27 mL

Santucci's urodynamic comparison of five reservoir types included 11 Mainz stomal reservoirs and 8 Mainz neobladders. Continence was 91% for the Mainz stomal reservoir and 75% for the Mainz neobladder, in a 40-patient series with mean urodynamic assessment at 9.1 months.[22]

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 a reported follow-up of 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. Ureteral stenosis requiring revision occurred in 16% of renal units with a submucosal tunnel and 3% with an extramural tunnel. Revisions were also needed for outlet incontinence (9%), stoma stenosis (23%), pouch calculi (15%), stoma prolapse (2%) and symptomatic reflux (1%). These are single-institution results with continuing 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. Mean follow-up was 11.8 years. Upper tracts improved or remained stable in 97% of renal units with a colonic conduit or Mainz pouch I and in 95% with orthotopic substitution.[13] Complete continence was achieved in 98% of those with a continent stoma.[13] The 97% upper-tract figure combines colonic conduits and Mainz pouch I; the 95% orthotopic-substitution and 98% continent-stoma continence figures describe separate groups.[13] In the companion report of orthotopic reservoirs in children and adolescents, upper tracts were stable or improved in all augmentation patients and in 20 of 23 renal units after substitution.[23] Reconstruction follows assessment of storage pressure, renal risk, outlet function and the patient's ability to catheterize. That ability is reassessed 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. Clinical examination revealed no signs of megaloblastic anemia, funicular myelosis or osteoporosis. Bone density was measured in only 18 patients, and the authors suggested, without demonstrating, that systematic blood-gas follow-up with alkali may have prevented bone demineralization.[14]

The appendix-outlet version uses less ileum than a nipple-outlet reconstruction. Bowel length is one determinant of metabolic risk, alongside segment location, renal function, urine contact and prior bowel surgery.[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.[15] The reported tumor prevalence was 0.14% in ileocecal pouches and 1.29% in the separately analyzed category of orthotopic (ileo-)colonic neobladders; the study did not isolate orthotopic Mainz I.[15] The authors recommended endoscopy for catheterizable ileocecal pouches when hematuria, chronic urinary infection or hydronephrosis is present; they recommended regular endoscopic evaluation from at least the fifth postoperative year for the separate category of orthotopic (ileo-)colonic neobladders.[15] The 0.14% figure did not differ significantly from ileal neobladders (0.05%, p = 0.46) but was lower than ureterosigmoidostomy (2.58%) and cystoplasty (1.58%).[15]

Lifelong functional follow-up should cover catheterization and stomal access, continence, renal drainage, stones, metabolic abnormalities and bowel symptoms. After cystectomy for bladder cancer, the AUA/ASCO/SUO guideline advises laboratory assessment every 3–6 months for 2–3 years and then annually [5], and the EAU bladder cancer guideline states that vitamin B12 should be measured annually after bowel diversion (guideline text, not a graded recommendation).[16] Imaging and additional testing follow the original disease and the functional risk.[5][16] For children with spinal dysraphism after bowel-based urinary reconstruction, the 2025 joint guideline states that follow-up is lifelong and includes regular renal-function and acid-base testing, with vitamin B12 testing when ileum is used; after augmentation, it also includes physical examination and ultrasound.[27]

The EAU 2026 guideline recommends against routine screening or treatment of asymptomatic bacteriuria in reconstructed lower urinary tracts , which frequently become colonized.[17] 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 / American Society of Clinical Oncology / Society of Urologic Oncology. Treatment of Non-Metastatic Muscle-Invasive Bladder Cancer: AUA/ASCO/SUO Guideline (2017; Amended 2020, 2024). 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. doi:10.1016/s0022-5347(05)67933-5. 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.

18. Thüroff JW, Alken P, Engelmann U, et al. "The Mainz Pouch (Mixed Augmentation Ileum 'N Zecum) for Bladder Augmentation and Continent Urinary Diversion." Eur Urol. 1985;11(3):152–60. doi:10.1159/000472481

19. Lampel A, Fisch M, Stein R, et al. "Continent Diversion With the Mainz Pouch." World J Urol. 1996;14(2):85–91. doi:10.1007/BF00182563

20. Gerharz EW, Köhl U, Weingärtner K, et al. "Complications Related to Different Continence Mechanisms in Ileocecal Reservoirs." J Urol. 1997;158(5):1709–13. doi:10.1016/s0022-5347(01)64105-3

21. Bedük Y, Türkölmez K, Baltaci S, Göğüş C. "Comparison of Clinical and Urodynamic Outcome in Orthotopic Ileocaecal and Ileal Neobladder." Eur Urol. 2003;43(3):258–62. doi:10.1016/s0302-2838(03)00042-3

22. Santucci RA, Park CH, Mayo ME, Lange PH. "Continence and Urodynamic Parameters of Continent Urinary Reservoirs: Comparison of Gastric, Ileal, Ileocolic, Right Colon, and Sigmoid Segments." Urology. 1999;54(2):252–7. doi:10.1016/s0090-4295(99)00098-9

23. Stein R, Wiesner C, Beetz R, Schwarz M, Thüroff JW. "Urinary Diversion in Children and Adolescents With Neurogenic Bladder: The Mainz Experience. Part I: Bladder Augmentation and Bladder Substitution: Therapeutic Algorithms." Pediatr Nephrol. 2005;20(7):920–5. doi:10.1007/s00467-005-1847-3

24. Franzaring L, Thüroff JW. Right Colon Neobladder. In: Montague DK, Gill IS, Angermeier KW, Ross JH, eds. Textbook of Reconstructive Urologic Surgery. Informa Healthcare; 2008:336-344.

25. Leissner J, Black P, Fisch M, Höckel M, Hohenfellner R. "Colon Pouch (Mainz Pouch III) for Continent Urinary Diversion After Pelvic Irradiation." Urology. 2000;56(5):798–802. doi:10.1016/s0090-4295(00)00789-5

26. Kalogirou C, Schwinger M, Kocot A, Riedmiller H. "Troubleshooting of failed continence mechanisms in the ileocecal pouch: Operative technique and long-term results of the intussuscepted ileal nipple valve." Int J Urol. 2021;28(11):1105–1111. doi:10.1111/iju.14654

27. Abrahamson K, et al. EAU–ESPU–ERN eUROGEN–ERN ITHACA–ERN ERKNet–IFSBH Guidelines on Spinal Dysraphism in Children and Adolescents. Clinical Guideline. EAU Guidelines Office, Arnhem, the Netherlands; January 2025 edition. Sections 7.8 and 12. Guideline.