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, so there is no stoma, appliance or self-catheterization. Fisch and Hohenfellner described it in Mainz in the early 1990s as a low-pressure modification of classical ureterosigmoidostomy. Detubularization reduces coordinated bowel contractions but leaves the risks of ureteric obstruction, infection, metabolic acidosis and long-term neoplasia at the ureterocolonic implantation.[1][2][3][4]
This is a selected alternative to a conduit or catheterizable reservoir with lifelong follow-up requirements. For selection across diversion types, see Urinary Diversion Principles; for the undetubularized operation and its long-term complications, see Ureterosigmoidostomy.
Historical Development
Classical ureterosigmoidostomy implants the ureters into intact sigmoid colon. Its problems were high-pressure contractions with urge incontinence and upper-tract deterioration, hyperchloremic acidosis, pyelonephritis and carcinoma at the ureterocolonic junction. A review reported carcinoma in 2–15% with a latent period of 20–26 years, and attributed carcinogenesis to bacterial nitrosamine production and oxidative injury at the healing anastomosis.[18]
- 1993. Fisch reported 47 patients (mean follow-up 10 months). All were continent by day and all but one woman were dry at night, with basal and peak pressures of 24 and 35 cm H₂O.[2]
- 1994. A 72-patient series (including 15 children) followed for 1–31 months reported the same continence pattern.[6]
- 1996. The Mainz series included 73 operated patients (59 adults, 14 children), 69 of whom were followed. The authors reported 94.5% daytime and 98.6% nighttime continence, with 5 early and 8 late complications (6.8% and 10.9% relative to the 73 operated patients).[19] Gilja reported rectodynamic observations in 20 patients.[19][10]
- 1998. Gerharz reported a prospective series of 34 patients and concluded that detubularization overcomes the bowel frequency and urge incontinence of the classical operation.[13]
- 2001 to 2006. Öbek (60 patients), D'Elia (123 patients from 1990 to 2000), Hadzi-Djokic (220 patients) and Pahernik (38 children) reported series that included alkali requirements and upper-tract complications.[5][1][11][12]
- 2024. Jing reported 37 patients after robotic cystectomy with Mainz pouch II diversion.[7]
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. In Jing's 37-patient cohort, preoperative colonoscopy checked for intestinal disorders, and the authors treated a positive result as a reason not to perform Mainz II diversion.[7] 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]
Anal competence is tested before surgery with rectal manometry or a supervised retention test, in which the patient retains a water enema. Published water volumes and retention times vary, and no single cutoff is validated as an eligibility test. Fisch described the urodynamic and rectodynamic evaluation as a reliable predictor of postoperative continence. The Öbek series had one incontinent patient, a woman with previous pelvic radiotherapy.[6][4][5]
Reported indications include cystectomy for bladder cancer (92 of 123 patients in the D'Elia series), bladder exstrophy or incontinent epispadias (26), irreparable traumatic loss of the sphincteric urethra (4) and cloacal malformation (1). In children the operation has been used after failed primary reconstruction (14 of 38) and for conversion from an incontinent diversion (6 of 38).[1][12]
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 a Malawi case series of 21 women who received Mainz II diversion for irreparable fistula, 8/21 had died and 5/21 were lost to follow-up; the exact causes of seven deaths were undetermined, and one woman died in an attack.[22] The authors advised against its use in low-resource settings where late complications may be difficult to treat.[22] In the Nitkunan cohort (17 patients, mean follow-up 6.4 years), 10 of 12 patients treated after cystectomy for cancer were continent, whereas 2 of the 5 revisions of failed classical ureterosigmoidostomy needed conversion to a colonic conduit for nocturnal incontinence.[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 |
D'Elia's series stratified implantation between the submucosal and serous-lined extramural tunnel by ureteral anatomy.[1] Bastian's comparison of 81 renal units used the Goodwin-Hohenfellner tunnel in 55, the Abol-Enein modification in 23 and the Le Duc technique in 3. Ureteric stenosis requiring reimplantation occurred in 2 units (one Goodwin-Hohenfellner, one Abol-Enein).[9] Follow-up was available for 36 of 41 patients.[9]
Hohenfellner's original description adds mesosigmoid and colonic-tunnel detail. Reaching the promontory without tension may call for mobilizing the sigmoid and descending colon to the splenic flexure, taking care to avoid splenic injury. For the left ureter, a wide, vessel-free mesosigmoid window is used, preserving the longitudinal periureteral vessels and the parallel accessory gonadal branches; left ureteral dissection is described as the more critical of the two sides. In the serous-lined extramural tunnel, the short vasa recta arising from the marginal artery of Drummond[23] leave gaps between which seromuscular sutures can be placed to enlarge the tunnel, whose diameter is adapted to ureteral dilation and wall thickness; Hohenfellner marks a 3.5-cm tunnel with stay sutures in his described operation.[21]
Bowel preparation, antibiotics, thromboprophylaxis and postoperative recovery follow the contemporary perioperative pathway.
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.[2] Gilja's 20-patient study compared preoperative rectal pressures with the postoperative pouch (9–36 months):[10]
| Parameter | Before | After |
|---|---|---|
| Mean basal pressure | 21.4 cm H₂O | 19.3 cm H₂O (p > 0.05) |
| Mean contraction pressure | 27.6 cm H₂O (maximum 48) | 19.1 cm H₂O (p < 0.05) |
In Gilja's 20-patient before-and-after series, mean contraction pressure fell while basal pressure did not change significantly.[10] All 20 patients were continent day and night, emptying four times by day and once at night. The authors fixed the pouch to the promontory or psoas muscle without compromising its blood supply to reduce ureteral kinking and upper-tract dilatation, and reported hyperchloremic acidosis in most patients.[10]
Outcomes and Evidence Limits
Most evidence consists of selected, uncontrolled series. Several early Mainz publications report successive experience from the same program, so their patients overlap. Comparisons with historical classical ureterosigmoidostomy series are not randomized.
| Study | Population and follow-up | Findings |
|---|---|---|
| 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. |
| 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. |
| 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. |
| Hadzi-Djokic 2006 (early complications)[11] | Same 220-patient cohort | Early complications in 24 patients: pyelonephritis 17, unilateral ureterohydronephrosis 11, bilateral 2, incipient renal failure 5, prolonged ileus 6; late implantation-site stenosis in 11 patients (8 unilateral, 3 bilateral) |
| Gerharz 1998[13] | 34 patients aged 1.9–76.9 years (30 after cystectomy), February 1992 to September 1997, prospective | No perioperative deaths; all continent by day, one with nighttime incontinence; mild acidosis in 2 |
Gerharz's series included conversion to an ileal conduit after recurrent septicemia in one patient and nephrectomy for ureterointestinal obstruction in another, so favorable continence can coexist with serious upper-tract complications. Öbek, Gerharz and Hadzi-Djokic each reported no perioperative deaths.[13][5][11]
The Bastian quality-of-life study obtained EORTC QLQ-C30 questionnaires from 41 of 83 patients operated in Bonn and Pesaro; 28 had died and 14 were lost to follow-up. Scores on all scales except diarrhea were comparable to a German reference population, with no significant difference between men and women. Daytime continence was 100% among survey respondents, about one third of respondents urinated more than six times by day and more than three times at night, and 63% of the 31 Bonn diversion-questionnaire respondents could distinguish stool from urine. Patients did not find the nighttime frequency disturbing.[14]
Pediatric Series
Pahernik's 38 children (mean age 5 years, range 0.5–17) were operated between 1991 and 2004; 33 had bladder exstrophy or incontinent epispadias.[12]
| Parameter | Result |
|---|---|
| Followed | 35 children, mean 112 months |
| Daytime continence | 100% |
| Nighttime incontinence requiring pads | 3 children (8.6%) |
| Pyelonephritis | 6 children (15.8% of the 38 operated), mostly with anastomotic stenosis |
| Ureteral reimplantation | 10 of 69 renal units (14.5%): 7 for stenosis, 3 for reflux |
| Serum creatinine | Normal in all |
| Alkali supplementation | 24 of 35 (69%), started when base excess was below −2.5 mmol/L |
| Clinical acidosis requiring hospitalization | 1 child |
| Annual rectosigmoidoscopy after more than 10 years | No pathological findings in 16 patients |
The authors recommend annual endoscopy from postoperative year 10 in this population.[12]
Robotic Reports
Jing 2024 reported 37 patients undergoing robotic cystectomy followed by Mainz II diversion; accrual reportedly began in November 2020, and median follow-up was reported as 23 months (range 12–36.5).[7] Only two diversions were intracorporeal; 35 were open. Continence allowed no pad or one safety pad: 91.9% were continent by day, 86.5% at night and 83.8% at both times. At 30 days, 35/37 patients (94.6%) reported at least moderate continence satisfaction on an unvalidated scale, including 21/37 (56.8%) who rated themselves very satisfied.[7] Late complications occurred in 7 patients and included three enterocutaneous fistulas, ureteroenteric stricture and urosepsis.[7]
Other Rectosigmoid Configurations
Valved S-shaped and dismembered rectosigmoid reservoirs are distinct designs, each described in small series.
- Valved S-shaped pouch (Sundin and Mansi). Thirty cm of rectum and sigmoid are detubularized and reconfigured into an S, with an intussuscepted valve to prevent reflux to the proximal colon and a transverse colostomy for 6 to 8 weeks. In 15 patients (mean follow-up 11 months) all were continent day and night; capacity was 400–900 mL and pressure at maximal filling was 22 cm H₂O.[15]
- Dismembered detubularized rectosigmoid (Elabbady). The sigmoid is divided about 30 cm proximal to the peritoneal reflection, the proximal two-thirds is detubularized into the pouch, and the terminal colon is anastomosed end to side to the anterior rectum. In 20 patients (4–36 months), 8 voided clear urine separated from stool in most instances. Mean basal pressure was 9.7 cm H₂O with compliance of 32.3.[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. Alkali use was 69% among 102 evaluated D'Elia patients, 60% among 50 followed Öbek patients, 52% among 177 followed Hadzi-Djokic patients and 69% among 35 followed Pahernik children, with severe acidosis requiring hospitalization in 3 of the 50 Öbek patients and 1 of the 35 children. Two Öbek patients died of probable malnutrition and metabolic abnormalities. See the alkali pharmacology hub.[1][5][12][11]
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. With otherwise unexplained confusion or seizures, include serum ammonia in the evaluation; hyperammonemic encephalopathy has been reported decades after ureterosigmoidostomy without hepatic failure.[24] Persistent acidosis also warrants attention to nutrition and bone health. Vitamin B12 surveillance is driven by concomitant ileal resection, malabsorption or other risk factors.
For the large share of patients whose Mainz II diversion follows cystectomy for muscle-invasive bladder cancer, the AUA/ASCO/SUO 2024 guideline recommends laboratory assessment at three- to six-month intervals for two to three years and then annually thereafter, with electrolytes and renal function checked because of the variable risk of hypokalemia, hyponatremia and hyperchloremic acidosis with bowel-based diversion .[20] See the Renal Function & Metabolic Surveillance hub for the full annual lab panel, eGFR interpretation pitfalls, B12 metabolite interpretation and bone-density monitoring shared across bowel-based reconstructions.
Colorectal Neoplasia and Endoscopy
Detubularization does not remove the ureterocolonic cancer risk. Urine-exposed ureterocolonic anastomoses require lifelong surveillance planning. In a multicenter German analysis of 17,758 diversions, secondary tumors occurred in 2.58% of ureterosigmoidostomies and 1.58% of cystoplasties, compared with 0.14% of ileocecal pouches and 0.05% of ileal neobladders.[17] No anastomotic neoplasm appeared in the Nitkunan series or in 16 children examined after more than 10 years, but Mainz II follow-up is mostly shorter than the 20–26 year latency described for classical ureterosigmoidostomy.[8][12][18]
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.[3] A colorectal review advised annual colonoscopy starting no later than five to six years after surgery; Kälble and colleagues recommended regular endoscopic evaluation from at least year 5 for ureterosigmoidostomy; and the pediatric Mainz series advised annual endoscopy from year 10.[18][17][12] 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][12]
A ureterocolonic anastomosis can resemble a small polyp. The BSG/ACPGBI guideline notes that clinical experience suggests avoiding snare resection of a polypoid lesion thought to be at the ureteric anastomosis, because it may damage the anastomosis and cause urinary leakage. 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
19. Fisch M, Wammack R, Hohenfellner R. "The Sigma Rectum Pouch (Mainz Pouch II)." World J Urol. 1996;14(2):68–72. doi:10.1007/BF00182560
20. Holzbeierlein J, Bixler BR, Buckley DI, et al. Treatment of Non-Metastatic Muscle-Invasive Bladder Cancer: AUA/ASCO/SUO Guideline (2017; Amended 2020, 2024). J Urol. 2024;212(1):3–10. doi:10.1097/JU.0000000000003981
21. Hohenfellner R. Urinary diversion into the rectosigmoid Mainz pouch II. In: Montague DK, Gill IS, Angermeier KW, Ross JH, eds. Textbook of Reconstructive Urologic Surgery. Informa Healthcare; 2008:383–391.
22. Patel TD, Chipungu EB, Draganchuk JM, Chalamanda C, Wilkinson JP. "Mainz II urinary diversion in low-resource settings: patient outcomes in women with irreparable fistula in Malawi." AJOG Glob Rep. 2024;4(2):100350. doi:10.1016/j.xagr.2024.100350
23. McDermott S, Deipolyi A, Walker T, Ganguli S, Wicky S, Oklu R. "Role of preoperative angiography in colon interposition surgery." Diagn Interv Radiol. 2012;18(3):314–318. doi:10.4261/1305-3825.DIR.4986-11.1
24. Jäger W, Viertmann AO, Janßen C, Birklein F, Thüroff JW, Stein R. "Intermittent hyperammonemic encephalopathy after ureterosigmoidostomy: spontaneous onset in the absence of hepatic failure." Cent European J Urol. 2015;68(1):121–124. doi:10.5173/ceju.2015.01.459