Mainz Pouch II
The Mainz Pouch II (sigma-rectum pouch) is a detubularized rectosigmoid reservoir that empties through the anus. Continence depends on the native anal sphincter; there is no catheterizable skin stoma. Detubularization reduces coordinated bowel contractions, but does not eliminate ureteric obstruction, infection, metabolic acidosis or the long-term neoplasia risk associated with ureterocolonic implantation.[1][2][3]
This is a selected alternative to a conduit or catheterizable reservoir, with substantial lifelong follow-up requirements. For selection across diversion types, see Urinary Diversion Principles; for the undetubularized operation and its long-term complications, see Ureterosigmoidostomy.
Selection and Counseling
Assess renal function, electrolytes and acid–base status; bowel disease and colorectal neoplasia risk; previous pelvic treatment; anal continence and rectal function; and the patient's ability to follow a lifelong medication and endoscopy plan. Renal impairment, active bowel disease, poor anal continence and inability to obtain reliable follow-up weigh strongly against this diversion. Pelvic radiation requires particular assessment of rectal tissue and sphincter function.[4][5][3]
Rectal manometry or a supervised retention test may help characterize function. Published water-volume and retention-time protocols vary; a single water-enema cutoff is not a universally validated eligibility test. A normal test cannot guarantee postoperative continence.[6][4][7]
Discuss daytime and nighttime emptying, urine–stool mixing, diarrhea or leakage, medication costs, access to urgent care, and the possible need for later conversion. Avoid presenting the absence of an external appliance as freedom from ongoing care. In the small long-term Nitkunan cohort, results after revision of a failed classical ureterosigmoidostomy were less favorable than after primary diversion; detubularization cannot reliably compensate for a deficient anal outlet.[8]
Operative Design
The original design opens the rectosigmoid along its antimesenteric surface and reconfigures the bowel plate with a side-to-side closure to form a reservoir. The mesenteric blood supply must remain intact. Ureteral implantation and reservoir fixation must leave a well-perfused, tension-free course without angulation or compression.[6][2]
| Component | Operative purpose and limitation |
|---|---|
| Detubularization and reconfiguration | Reduce the effect of coordinated bowel contractions and increase functional reservoir capacity; individual pressure and emptying behavior still require follow-up |
| Ureteral implantation | A submucosal tunnel or serous-lined extramural tunnel can be used according to ureteral caliber and local anatomy; antireflux construction must not sacrifice perfusion or produce obstruction |
| Fixation | Original reports describe fixation near the promontory to limit pouch descent and ureteral kinking; assess the mesentery, ureters and adjacent structures rather than using fixation as a substitute for adequate reach |
| Temporary drainage | Ureteral stents and rectal drainage are described in operative protocols; their route and removal timing depend on the reconstruction and postoperative course |
Small series of different implantation techniques do not establish a universally superior antireflux method. The Bastian comparison followed 36 of 41 operated patients, with unequal groups and only a few Le Duc implantations; absence of a detected difference is not proof of equivalence.[9]
The sequence above describes the reconstruction's principles. Bowel preparation, antibiotics, thromboprophylaxis and postoperative recovery should follow the applicable contemporary perioperative pathway; historical series do not establish a universal preparation or drainage schedule.
Urodynamic Evidence
The initial Fisch series included 47 patients with mean follow-up of 10 months (range 1–20); reported full-reservoir basal and highest peak pressures were 24 and 35 cm H₂O. These are cohort observations, not guaranteed pressures or treatment targets.[2] In Gilja's 20-patient study, basal pressure did not significantly change, although phasic contraction behavior improved. Detubularization should therefore be described as reducing high-pressure contractions, rather than eliminating every high-pressure event.[10]
Outcomes and Evidence Limits
Most evidence consists of selected, uncontrolled series. Several early Mainz publications represent successive experience from the same program. Their patients must not be pooled as independent cohorts, and differences from historical classical ureterosigmoidostomy series do not establish a randomized comparative benefit.
| Study | Population and follow-up actually assessed | Findings useful for counseling |
|---|---|---|
| D'Elia 2004[1] | 123 operated during 1990–2000; 102 with at least 12 months of follow-up analyzed, mean 46.2 months | Reported day/night continence 97%/95%; 14/194 renal–ureteric units developed implantation stenosis; 69% used alkali. “Ten years' experience” describes accrual, not ten-year follow-up for every patient |
| Öbek 2001[5] | 60 operated; 50 had longer-term data, median 31 months | 30/50 required alkali; 3/50 were hospitalized for severe acidosis/hypokalemia. Two later deaths were attributed to probable malnutrition/metabolic abnormalities, without proof of a single causal mechanism |
| Hadzi-Djokic 2006[11] | 220 operated; 177 followed, median 21 months | Three patients reported incontinence; 92/177 required alkali and potassium. The large operative cohort does not mean all 220 had complete follow-up |
| Pahernik 2006[12] | 38 children; 35 followed, mean 112 months | Reported daytime continence in all followed children, but 24/35 required alkali and 10/69 renal units required ureteric reimplantation. These selected results do not remove lifelong metabolic and neoplasia concerns |
Gerharz's prospective 34-patient series included conversion to an ileal conduit after recurrent septicemia and nephrectomy for ureterointestinal obstruction. Favorable continence can coexist with serious upper-tract complications.[13]
The Bastian quality-of-life study obtained questionnaires from 41 of 83 operated patients; 28 had died and 14 were lost to follow-up. Its generally favorable scores and diarrhea signal describe respondents, with substantial survivor and response selection. They do not establish better quality of life than another diversion.[14]
Robotic Reports
Jing 2024 reported 37 patients undergoing robotic cystectomy followed by Mainz II diversion, but only two diversions were intracorporeal; 35 were open. Continence allowed either no pad or one safety pad. The observational report supports feasibility in a selected setting, not superiority of robotic pouch construction or a preferred diversion for women. Enterocutaneous fistula, stricture and urosepsis were among the reported complications.[7]
Other Rectosigmoid Configurations
Valved S-shaped and dismembered rectosigmoid reservoirs are distinct designs. The Sundin S-pouch report contained 15 patients with mean follow-up of 11 months. Elabbady's dismembered reservoir report contained 20 patients; occasional passage of clear urine in some patients did not demonstrate complete separation of urine and feces or abolition of cancer risk. These small technical series should not determine a preferred operation.[15][16]
Lifelong Follow-up
Renal, Infectious and Metabolic Complications
Assess emptying and continence, hydration, renal function, electrolytes including bicarbonate and potassium, and upper-tract imaging. Frequency should reflect baseline renal reserve, previous obstruction, biochemical instability and symptoms. Hyperchloremic acidosis is often treated with oral alkali, but may be severe; dosing and potassium replacement require laboratory monitoring. Refer to the alkali pharmacology hub.[1][5][12]
Fever, flank pain, rising creatinine, reduced output, new hydronephrosis or a marked change in emptying require prompt assessment for infection or obstruction. New confusion, profound weakness, dehydration or vomiting can accompany serious metabolic illness. Persistent acidosis also warrants attention to nutrition and bone health. Vitamin B12 surveillance is driven by concomitant ileal resection, malabsorption or other risk factors; a purely rectosigmoid reservoir does not itself remove the terminal ileum.
Colorectal Neoplasia and Endoscopy
Detubularization does not make the ureterocolonic cancer risk merely theoretical. Urine-exposed ureterocolonic anastomoses require lifelong surveillance planning. Historical estimates vary with the population, duration and whether the endpoint includes adenomas as well as cancer; a single relative risk or a pooled diversion prevalence is not a Mainz-II-specific lifetime cancer probability.[17][3]
The 2010 BSG/ACPGBI guideline specifies annual flexible sigmoidoscopy from the tenth anniversary, extending just beyond the higher ureteric implantation, with a grade C recommendation. Older urological reviews proposed surveillance starting around five to six years. Agree an explicit plan with gastroenterology and urology that accounts for prior findings, anatomy and local guidance; investigate bleeding, unexplained anemia, bowel changes or new ureteric obstruction without waiting for a scheduled examination.[3][18]
A ureterocolonic anastomosis can resemble a small polyp. The BSG/ACPGBI guideline advises against snare resection of a polypoid lesion at the anastomosis, because it may create a urinary leak. A suspicious lesion needs a planned specialist assessment; biopsy may be appropriate. This precaution differs from management of a lesion clearly remote from the implantation.[3]
Surveillance remains necessary after conversion to another diversion unless the original ureteric anastomoses have been removed. Document retained anatomy explicitly in the handoff to endoscopy.[3]
References
1. D'Elia G, Pahernik S, Fisch M, Hohenfellner R, Thüroff JW. "Mainz Pouch II Technique: 10 Years' Experience." BJU Int. 2004;93(7):1037–42. doi:10.1111/j.1464-410X.2003.04777.x
2. Fisch M, Wammack R, Müller SC, Hohenfellner R. "The Mainz Pouch II (Sigma Rectum Pouch)." J Urol. 1993;149(2):258–63. doi:10.1016/s0022-5347(17)36050-0
3. Cairns SR, Scholefield JH, Steele RJ, et al. Guidelines for colorectal cancer screening and surveillance in moderate and high risk groups (update from 2002). Gut. 2010;59:666–690. Ureterosigmoidostomy section, pp674–675. doi:10.1136/gut.2009.179804.
4. Hadzi-Djokic J, Milojević B, Pejčić T, et al. Sigma-rectum pouch (Mainz pouch II). Acta Chir Iugosl. 2014;61(1):29–34. doi:10.2298/ACI1401029H. PMID:25782222.
5. Obek C, Kural AR, Ataus S, et al. "Complications of the Mainz Pouch II (Sigma Rectum Pouch)." Eur Urol. 2001;39(2):204–11. doi:10.1159/000052437
6. Fisch M, Wammack R, Müller SC, Hohenfellner R. "The Mainz Pouch II." Eur Urol. 1994;25(1):7–15. doi:10.1159/000475238
7. Jing S, Yang E, Luo Z, et al. "Perioperative Outcomes and Continence Following Robotic-Assisted Radical Cystectomy With Mainz Pouch II Urinary Diversion in Patients With Bladder Cancer." BMC Cancer. 2024;24(1):127. doi:10.1186/s12885-024-11874-x
8. Nitkunan T, Leaver R, Patel HR, Woodhouse CR. "Modified Ureterosigmoidostomy (Mainz II): A Long-Term Follow-Up." BJU Int. 2004;93(7):1043–7. doi:10.1111/j.1464-410X.2004.04778.x
9. Bastian PJ, Albers P, Haferkamp A, Schumacher S, Müller SC. "Modified Ureterosigmoidostomy (Mainz Pouch II) in Different Age Groups and With Different Techniques of Ureteric Implantation." BJU Int. 2004;94(3):345–9. doi:10.1111/j.1464-410X.2004.04963.x
10. Gilja I, Kovačić M, Radej M, et al. The sigmoidorectal pouch (Mainz pouch II). Eur Urol. 1996;29(2):210–215. PMID:8647149.
11. Hadzi-Djokic JB, Basic DT. "A Modified Sigma-Rectum Pouch (Mainz Pouch II) Technique: Analysis of Outcomes and Complications on 220 Patients." BJU Int. 2006;97(3):587–91. doi:10.1111/j.1464-410X.2006.05995.x
12. Pahernik S, Beetz R, Schede J, Stein R, Thüroff JW. "Rectosigmoid Pouch (Mainz Pouch II) in Children." J Urol. 2006;175(1):284–7. doi:10.1016/S0022-5347(05)00035-2
13. Gerharz EW, Köhl UN, Weingärtner K, et al. "Experience With the Mainz Modification of Ureterosigmoidostomy." Br J Surg. 1998;85(11):1512–6. doi:10.1046/j.1365-2168.1998.00904.x
14. Bastian PJ, Albers P, Hanitzsch H, et al. "Health-Related Quality-of-Life Following Modified Ureterosigmoidostomy (Mainz Pouch II) as Continent Urinary Diversion." Eur Urol. 2004;46(5):591–7. doi:10.1016/j.eururo.2004.06.007
15. Sundin T, Mansi MK. "The Valved S-Shaped Rectosigmoid Pouch for Continent Urinary Diversion." J Urol. 1993;150(3):838–42. doi:10.1016/s0022-5347(17)35627-6
16. Elabbady AA, Elabbasy WI, Arafa AF, Atta MA, Abdel-Rahman M. "A Simple Technique for Urinary Diversion: The Dismembered Detubularized Rectosigmoid Bladder With Distal Colorectostomy." J Urol. 1998;160(3 Pt 1):714–7. doi:10.1016/S0022-5347(01)62765-4
17. 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
18. Azimuddin K, Khubchandani IT, Stasik JJ, Rosen L, Riether RD. "Neoplasia After Ureterosigmoidostomy." Dis Colon Rectum. 1999;42(12):1632–8. doi:10.1007/BF02236220