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Hemi-Kock Continent Stoma

A Hemi-Kock continent stoma uses an intussuscepted ileal nipple as the catheterizable continence mechanism for a retained bladder, with or without bowel augmentation.[3][4] The term hemi-Kock also describes a different configuration using a nipple as an afferent antireflux valve. These are alternative applications: one nipple does not simultaneously provide both a continent abdominal outlet and an antireflux ureteral inlet.[1][2][3]

For shared reservoir and catheterization principles, see Augmentation Cystoplasty and Principles of Continent Catheterizable Channels.

Concept and Background​

The Hemi-Kock derives from the Kock continent ileal reservoir, which Kock first used for continent cutaneous urinary diversion in Göteborg in 1975.[12] The full Kock pouch is a stand-alone reservoir with two nipple valves: an afferent valve that prevents reflux and an efferent valve that forms the continent stoma.[13] The Hemi-Kock was developed at the University of Southern California by Weinberg and colleagues in 1988. It keeps one nipple valve and joins a detubularized ileal plate to the native bladder.[2]

FeatureFull Kock pouchHemi-Kock
ReservoirStand-alone ileal pouchRetained bladder with an ileal or sigmoid augment, or a stoma alone in selected cases; the original ileal plate could be converted to a complete reservoir[1][3][4]
Nipple valvesTwo (afferent antireflux and efferent stoma)One, used as the efferent stoma or as an afferent antireflux limb
IleumLarger segmentAbout 40 cm[1]
UretersImplanted into the afferent limbNative insertions can remain when the nipple is the efferent stoma; ureters or a previous conduit are joined to the afferent limb when the nipple is antireflux
Typical settingDiversion after cystectomyAugmentation with a continent stoma, or undiversion, in a patient with a retained bladder

Configurations and Selection​

ConfigurationFunctionUreteral implications
Continent abdominal stoma with augmentationEfferent nipple provides the catheterizable continence mechanismNative ureteral insertions can remain when appropriate; additional ureteral reconstruction is not automatically required
Antireflux augmentation / undiversionAfferent nipple separates a ureteral or previous conduit inlet from the reservoirUreters or a previous ileal conduit are connected to the afferent limb

Kreder's 30-patient series included both applications as well as conversion to a complete reservoir. Weinberg's initial seven-patient report concerned a nonrefluxing augmentation.[1][2] The two series describe different Hemi-Kock operations.[1][2]

Candidates need a reconstructable reservoir, acceptable bowel and metabolic reserve, a stoma they or a caregiver can catheterize, and a dependable lifelong follow-up plan. A damaged outlet may require a separate continence procedure or bladder-neck closure. Closure is a definitive choice requiring a reliable alternate drainage route. In Herschorn's 18-patient series, the aim was to keep a competent urethra for additional access when possible. Ten patients had an anti-incontinence procedure and three had bladder-neck closure.[4][3]

An afferent nipple has been used for markedly dilated ureters or undiversion. Nieh favored a nipple over a tunneled implant for dilated ureters as expert opinion.[24] In a different population with low-pressure orthotopic ileal substitutes, a randomized trial found severe stenosis-related upper-tract dilation in 9/67 evaluable renal units with antireflux nipples versus 2/69 with isoperistaltic afferent limbs at median follow-up of 57 versus 45 months.[24] A continent stoma alone may also be constructed in selected patients without needing a large augment.[1][4][20]

Indications and patient selection​

The Hemi-Kock has been used in these settings:[1][3][4]

  • Adults with a complex lower urinary tract disorder who need both augmentation and a continent catheterizable channel.
  • A devastated bladder outlet that requires bladder-neck closure.
  • Dilated ureters that need an antireflux implant.
  • Undiversion of a previous ileal conduit or other supravesical diversion.
  • An unavailable appendix when a Monti channel alone would not give enough augmentation.

Prerequisites are adequate renal function for the metabolic load of an ileal segment, the ability to catheterize the stoma, motivation for lifelong catheterization and follow-up, and a surgeon familiar with continent ileal reservoir principles.[2]

Operative Principles​

The details depend on whether the nipple is afferent or efferent and on the chosen modification. The following is an orientation guide:

  1. Define the complete reconstruction. Plan reservoir capacity, ureteral drainage, native outlet management, stoma site, and postoperative access before bowel isolation.
  2. Select a vascularized ileal segment. The historical hemi-Kock used approximately 40 cm of terminal ileum, divided between the augment and valve/channel. In the original descriptions, about 20–25 cm formed the plate and 15–17 cm the efferent limb and nipple, taken 15–20 cm proximal to the ileocecal valve, with ileoileal continuity restored. Preserve terminal ileum and bowel blood supply as anatomy permits; a fixed length is not appropriate for every patient.[1][2]
  3. Prepare the intussuscepted nipple. Preserve the mesenteric vascular arcades and confirm perfusion. In Herschorn's efferent modification, three staple lines stabilize the nipple; the third fixes it to the augment wall.[3] For an efferent catheterizable valve, Herschorn's adult modification removes peritoneum and fat alongside the segment to be intussuscepted and creates a mesenteric window under 1 cm only at the point of maximum tension. Skinner's 8-cm and Boyd's 7-cm mesenteric-stripping dimensions describe historical full-Kock and canine afferent valves, respectively; they are not default dimensions for an adult efferent stoma.[3][13][14]
  4. Detubularize and reconfigure the augment. Open the remaining segment along its antimesenteric border and fold it into a U or W shape. Join it broadly to the opened native bladder to support low-pressure storage.
  5. Orient the valve for its intended role. An efferent continence nipple and an afferent antireflux nipple have different flow paths. Construct the catheterizable limb. In Herschorn's efferent modification, taper it over a 14-Fr catheter and imbricate the staple line with 2-0 absorbable suture.[3] Route the limb without tension or kinking and confirm easy catheter passage. The stoma is usually brought out at the umbilicus or the right lower quadrant; Hanna placed it at the umbilicus in children.[16]
  6. Establish drainage and follow-up. Ensure accessible catheter drainage and an explicit plan for an obstructed or uncatheterizable stoma.[1][4][3]

Historical Kock reservoirs used nonabsorbable staples and collars that could become stone foci or contribute to erosion and obstruction. Later modifications altered fixation, collar use, and channel tapering.[5][6][7][3]

Nipple valve compared with flap valve​

Nipple valve (Kock, Hemi-Kock)Flap valve (Mitrofanoff, Monti)
GeometryIntussuscepted bowel protrudes into the reservoir lumenCatheterizable tube lies in a submucosal tunnel or serosa-lined extramural trough[25]
Closing forceFilling pressure compresses the nipple from outsideFilling pressure compresses the channel against the backing wall
Characteristic failureDesussception (slippage), stenosis, stones on fixation materialTunnel inadequacy, stenosis, erosion

Nieh's review describes the nipple valves as technically demanding, with early and late complications and occasional catheterization problems, and reports that simple modifications in fixation, limited use of staples and mesh collars, and tapering of the stoma resolved much of this.[20]

Fixation and modifications​

Fixation of the intussuscepted nipple has changed over time:

  • Original technique. Metal staples and a nonabsorbable collar secured the nipple. In canine hemi-Kock reservoirs, calculi formed on exposed metal staples and Marlex collars, while absorbable (Polysorb) staples promoted healing and never served as a stone nidus. The authors recommended proper staple placement and no anchoring collar.[14] In a separate randomized study of urethral hemi-Kock antireflux valves, pouch stones occurred in 1/21 evaluable men with absorbable staples versus 6/20 with metal staples over 6–88 months.[22]
  • Mesentery exclusion and seromuscular diathermy. In dogs, excluding mesentery from the intussusception and applying deep seromuscular diathermy gave a stable valve. Autosuture GIA stapling shortened operating time but did not improve stability.[15]
  • Seromuscular stripping (Mori). The nipple was created without metal staples in 17 patients with a Mainz pouch. Results were satisfactory in 15; two were incontinent, one from nipple prolapse and one from ischemic change of the valve.[17]
  • Modified efferent fixation (Soulié). In a 40-patient Kock pouch series, extussusception (8%) and efferent nipple prolapse (3%) occurred only in the 23 patients with the earlier technique, not in the 17 with modified fixation. Continence at 6 months was 78% and 94%, a difference that was not significant (P = 0.13).[18]
  • Hanna modification in children. Afferent and efferent limbs were fixed at two points, internally to the pouch wall and externally by apposed incisions and sutures, without staples or a Marlex collar. A continent, nonrefluxing reservoir was achieved in all 10 children.[16]
  • Contemporary Hemi-Kock. Herschorn's later cohort describes modified valve construction and tapering of the catheterizable limb (see below).[3]

Best Direct Long-Term Evidence​

Herschorn 2022 retrospectively reviewed 109 adults, median age 38 years, after Hemi-Kock catheterizable stoma with cystoplasty. At mean follow-up 10.4 years:[3]

OutcomeFindingInterpretation
Maintaining CIC with social continence (at most one pad)98/109 (90%)63/109 (58%) reported no stomal leakage at last follow-up
Any secondary intervention70/109 (64.2%), including 46/109 (42.2%) with bladder-stone proceduresA substantial long-term maintenance burden; the stone count uses all 109 patients as denominator
Less invasive interventionsMore than 60% were endoscopic or under local anesthesia, mainly for stones—
Valve revision14/109 (12.8%)—
Revision before versus after modifications8/44 (18.2%) versus 6/65 (9.3%)Sequential observational groups

The earlier 18-patient Herschorn series reported 17 dry patients and one lost to follow-up at mean 26 months. Fifteen had augmentation and three a stoma alone; some also had outlet procedures.[4]

The broader Cochrane review of intestinal urinary reconstruction found sparse, low-quality comparative trials.[8]

Long-term durability of the Kock system​

In the Göteborg series of 176 patients who had a Kock reservoir for continent urinary diversion between 1975 and 1999, almost 90% of the 126 known survivors had a well-functioning reservoir.[12] Reoperation was frequent, mainly for nipple problems.[12] Nieh's 1997 review described the orthotopic Hemi-Kock reservoir as one of the most dependable and stable neobladders, an expert assessment of a related configuration.[20]

Complications and Troubleshooting​

  • Difficult catheterization, retention, or obstruction. Assess promptly for channel angulation, stenosis, valve dysfunction, mucus, or stones. Avoid repeated forceful catheter attempts. Acute loss of drainage requires urgent urologic management.
  • Leakage. Reassess reservoir pressure, emptying, and valve integrity before assuming the valve alone has failed.
  • Valve slippage, stenosis, ischemia, or erosion. Management may require endoscopic treatment, valve revision, channel replacement, or conversion to a different drainage strategy.
  • Stones and recurrent symptomatic infection. They remain causes of reintervention. EAU recommends regular saline irrigation to reduce bladder-stone recurrence after augmentation or continent cutaneous urinary diversion when there is no history of autonomic dysreflexia . During trans-stomal stone removal in continent diversion, protect the continence mechanism; before percutaneous access, assess for overlying bowel on CT.[23]
  • Augmentation-related morbidity. Bowel obstruction, metabolic acidosis, nutritional deficiency, perforation, and long-latency malignancy still require lifelong attention.[3][9]

The following figures come from full Kock pouch series and give the range of nipple-valve problems.

ComplicationReported frequencySource and setting
Urinary stones18/68 (26.5%) of Kock patients followed 12 months or longer, usually on exposed staples or the eroded nonabsorbable collar; 5.4% among 37 Indiana pouch patients followed 12 months or longerArai 1993 (mean follow-up 53 months for Kock and 34 months for Indiana)[5]
Urinary stones42/95 (44%) after Kock pouch and 11/59 (19%) after Indiana pouch, among patients followed more than 3 monthsOkada 1996[6]
Efferent nipple malfunction21/95 (22%) of Kock pouch patients followed more than 3 months, mostly in the first yearOkada 1996[6]
Afferent nipple malfunction26/95 (27%) of Kock pouch patients followed more than 3 months, arising several years after surgeryOkada 1996[6]
Afferent nipple malfunction10/42 (24%): collar erosion (5), afferent limb stenosis (2), obstruction by a mucous plug or fungus ball (3)Arai 1991 (mean follow-up 38 months)[7]
Afferent antireflux valve complications79/802 (9.8%) patients had 84 events: stones on staples 42, stenoses 35, and prolapses 7. Surgical correction was reported in 81: 56 endoscopic (7.0%) and 25 open revisions (3.1%)Stein 1996 (USC)[19]

Arai attributed most late afferent malfunction to the nonabsorbable collar and considered it avoidable.[5][7] In the fecal Kock continent ileostomy, Fasth reported a 29% revision rate for late nipple valve dysfunction, mainly from sliding, and stapling did not significantly reduce sliding.[21]

Urinary salvage reports include conversion of a failed efferent limb to a flap-valve channel and construction of a secondary ileal nipple. Waldner transversely retubularized the short intact ileal segment of the original efferent limb in five women with a Kock pouch and embedded it in an extramural trough as a Mitrofanoff-type flap valve. All five were continent, without catheterization problems, at 6–28 months.[10] A 28-patient ileocecal-pouch series reported 24 fully continent patients, four using a safety pad, and two needing a third continence mechanism at mean 65.4 months.[11] Its reported 92% overall success is not the same as complete dryness and is not Hemi-Kock-specific.[11] These are specialist salvage options.

Choosing Among Catheterizable Channels​

OptionRelevant distinction
AppendicovesicostomyUses a suitable appendix and a flap-valve tunnel; additional augmentation may be needed
Yang-MontiUses a short retubularized bowel segment; availability depends on bowel health, mesenteric reach, and prior surgery
Hemi-KockProvides an ileal augment with an intussuscepted continence mechanism; the trade-offs are greater bowel use and valve-related maintenance

The Hemi-Kock has not been widely adopted compared with the flap-valve and ileocecal-valve procedures.[3] Nieh's review cites its technically demanding valve construction and its early and late complications.[20] The efferent Hemi-Kock configuration serves adults who need simultaneous augmentation and a continent catheterizable stoma. An afferent antireflux Hemi-Kock is a separate configuration used for selected patients with dilated ureters or during undiversion.[1][3] The direct Hemi-Kock evidence is largely institutional observational experience.[3][8]

Lifelong Follow-Up​

For adult NLUTD reconstruction incorporating bowel, AUA/SUFU advises annual focused history, examination and symptom assessment, a basic metabolic panel and urinary tract imaging ; the supporting discussion also advises monitoring B12 over time when terminal ileum is used.[9] Review catheterization, mucus management, stoma function, and nutritional risks. AUA/SUFU states that clinicians should perform cystoscopy for gross hematuria or symptomatic recurrent urinary tract infection [9] and should not perform screening cystoscopy .[26] Unexplained suprapubic pain also warrants evaluation, and acute abdominal pain or sepsis may indicate perforation.[9]

See also Full Kock Pouch and Bladder-Neck Closure.

References​

1. Kreder K, Das AK, Webster GD. The hemi-Kock ileocystoplasty: a versatile procedure in reconstructive urology. J Urol. 1992;147(5):1248–1251. doi:10.1016/s0022-5347(17)37530-4

2. Weinberg AC, Boyd SD, Lieskovsky G, Ahlering TE, Skinner DG. The hemi-Kock augmentation ileocystoplasty: a low pressure anti-refluxing system. J Urol. 1988;140(6):1380–1384. doi:10.1016/s0022-5347(17)42050-7

3. Herschorn S, Locke J, Vigil H. Hemi-Kock continent stoma with augmentation cystoplasty: modifications and outcomes. Urology. 2022;160:217–222. doi:10.1016/j.urology.2021.10.004

4. Herschorn S, Thijssen AJ, Radomski SB. Experience with the hemi-Kock ileocystoplasty with a continent abdominal stoma. J Urol. 1993;149(5):998–1001. doi:10.1016/s0022-5347(17)36278-x

5. Arai Y, Kawakita M, Terachi T, et al. Long-term followup of the Kock and Indiana pouch procedures. J Urol. 1993;150(1):51–55. doi:10.1016/s0022-5347(17)35394-6

6. Okada Y, Shichiri Y, Terai A, et al. Management of late complications of continent urinary diversion using the Kock pouch and the Indiana pouch procedures. Int J Urol. 1996;3(5):334–339. doi:10.1111/j.1442-2042.1996.tb00549.x

7. Arai Y, Okada Y, Matsuda T, et al. Afferent nipple valve malfunction caused by anchoring collar: an unexpected late complication of the Kock continent ileal reservoir. J Urol. 1991;145(1):29–32; discussion 33. doi:10.1016/s0022-5347(17)38238-1

8. Cody JD, Nabi G, Dublin N, et al. Urinary diversion and bladder reconstruction/replacement using intestinal segments for intractable incontinence or following cystectomy. Cochrane Database Syst Rev. 2012;(2):CD003306. doi:10.1002/14651858.CD003306.pub2

9. Ginsberg DA, Boone TB, Cameron AP, et al. The AUA/SUFU Guideline on Adult Neurogenic Lower Urinary Tract Dysfunction: Treatment and Follow-Up. J Urol. 2021;206(5):1106–1113. doi:10.1097/JU.0000000000002239

10. Waldner M, Hertle L, Roth S. Revision of nonfunctioning Kock pouch efferent limb: continent, tissue preserving technique. J Urol. 2000;163(6):1810–1813. doi:10.1016/s0022-5347(05)67549-0. PMID 10799188

11. 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

12. Jonsson O, Olofsson G, Lindholm E, Törnqvist H. Long-time experience with the Kock ileal reservoir for continent urinary diversion. Eur Urol. 2001;40(6):632–640. doi:10.1159/000049849

13. Skinner DG, Boyd SD, Lieskovsky G. Clinical experience with the Kock continent ileal reservoir for urinary diversion. J Urol. 1984;132(6):1101–1107. doi:10.1016/s0022-5347(17)50052-x

14. Boyd SD, Skinner DG, Lieskovsky G, Kawachi MH, Ahlering TE. Study of antireflux nipple valves of Kock ileal urinary reservoir: experimental investigation in dogs. Urology. 1991;37(1):80–87. doi:10.1016/0090-4295(91)80086-m

15. Cranley B, McKelvey ST. The Kock ileostomy reservoir: an experimental study of methods of improving valve stability and competence. Br J Surg. 1981;68(8):545–550. doi:10.1002/bjs.1800680809

16. Hanna MK, Bloiso G. Continent diversion in children: modification of Kock pouch. J Urol. 1987;137(6):1206–1208. doi:10.1016/s0022-5347(17)44450-8

17. Mori Y, Shima H, Ikoma F. A seromuscular stripping method to create a nipple valve without metal stapling for continent urinary reservoir. J Urol. 1991;145(3):492–494. doi:10.1016/s0022-5347(17)38377-5

18. Soulié M, Seguin P, Martel P, et al. A modified intussuscepted nipple in the Kock pouch urinary diversion: assessment of perioperative complications and functional results. BJU Int. 2002;90(4):397–402. doi:10.1046/j.1464-410x.2002.02909.x

19. Stein JP, Freeman JA, Esrig D, et al. Complications of the afferent antireflux valve mechanism in the Kock ileal reservoir. J Urol. 1996;155(5):1579–1584. doi:10.1016/s0022-5347(01)66131-7. PMID 8627827

20. Nieh PT. The Kock pouch urinary reservoir. Urol Clin North Am. 1997;24(4):755–772. doi:10.1016/s0094-0143(05)70418-3

21. Fasth S, Hultén L, Svaninger G. The Kock continent ileostomy: influence of a defunctioning ileostomy and nipple valve stapling on early and late morbidity. Int J Colorectal Dis. 1987;2(2):82–86. doi:10.1007/BF01647697

22. Arif H, Madbouly K, Mahran MR, Ashamallah A, Ghoneim MA. "A prospective randomized study comparing absorbable and nonabsorbable staples in constructing antireflux valves of urethral hemi-Kock pouches." BJU Int. 1999;84(4):440-443. doi:10.1046/j.1464-410x.1999.00211.x

23. European Association of Urology. "EAU Guidelines on Urolithiasis." EAU Guidelines Office; 2026. Stones in urinary diversion; Bladder stones.

24. Studer UE, Danuser H, Thalmann GN, Springer JP, Turner WH. "Antireflux nipples or afferent tubular segments in 70 patients with ileal low pressure bladder substitutes: long-term results of a prospective randomized trial." J Urol. 1996;156(6):1913-1917. doi:10.1016/S0022-5347(01)65390-4

25. Elshal AM, Abol-Enein H, Sarhan O, et al. "Catheterizable serous lined urinary outlet in children and adolescents: a choice when other treatments fail." J Urol. 2011;185(3):1083-1087. doi:10.1016/j.juro.2010.10.041

26. Ginsberg DA, Boone TB, Cameron AP, et al. "The AUA/SUFU Guideline on Adult Neurogenic Lower Urinary Tract Dysfunction: Diagnosis and Evaluation." J Urol. 2021;206(5):1097-1105. doi:10.1097/JU.0000000000002235