Skip to main content

Bowel Anastomosis

For the reconstructive urologist, bowel anastomosis is the non-urologic operation most frequently encountered — every ileal conduit, orthotopic neobladder, continent cutaneous reservoir, augmentation cystoplasty, and Mitrofanoff construction depends on a sound bowel-to-bowel reconstitution after the bowel segment has been harvested. A leak in this anastomosis is the single most consequential complication of urinary diversion. The technical principles are not urologic — they are colorectal — but the depth at which a reconstructive urologist needs to know them is high.

This article consolidates the evidence base for safe bowel anastomosis: fundamental principles, hand-sewn vs stapled, configuration selection, perfusion assessment with ICG fluorescence angiography, risk stratification, and the particular considerations for urinary diversion.

See also: Bowel Anatomy, Incisions & Closure, Wound Healing, ERAS.

Fundamental Principles​

Five non-negotiable prerequisites govern every bowel anastomosis, regardless of technique:[1]

  1. Adequate blood supply at both ends of the proposed anastomosis.
  2. Tension-free approximation.
  3. Inclusion of the submucosa — the strongest layer of the bowel wall, and the layer that holds suture.
  4. Meticulous hemostasis.
  5. Avoidance of anastomosis in a contaminated field.

Blood Supply​

Standard clinical assessment combines visual inspection of serosal color, cut-edge bleeding, and palpation of mesenteric pulsations.[2] In experienced hands, clinical assessment alone can produce anastomotic leak rates as low as 1.6%.[2] Indocyanine green fluorescence angiography (ICG-FA) provides objective perfusion assessment and reduces anastomotic leak by 31–69% in meta-analyses, with the largest effect in left-sided and rectal resections — see the dedicated section below.[3][4][5][6][7]

Tension​

Tension is the fundamental principle with the worst objective measurement — there is no validated intraoperative tension meter.[8] Mechanistic studies nevertheless estimate that tension increases anastomotic leak risk up to 10-fold.[8] Mitigation remains procedural: adequate bowel mobilization, takedown of tethering adhesions, and surgeon judgment.

Absence of Contamination​

Primary anastomosis should be avoided in frank peritonitis. Preoperative oral antibiotics with or without mechanical bowel preparation reduces anastomotic leak and SSI and is standard for elective colorectal work.[9][10] Current evidence for urinary diversion specifically favors no routine mechanical prep (per ERAS Society radical cystectomy guideline) but supports oral antibiotic prep.

Hand-Sewn vs Stapled — the Evidence​

Across all bowel anastomoses, hand-sewn and stapled techniques produce equivalent anastomotic leak rates in meta-analysis.[11] Selection is driven by location, surgeon experience, and resource availability.

Anastomosis siteHand-sewn leakStapled leakOR (stapled)Reference
Ileocolic, all-comers6%2.5%0.48[12]
Ileocolic, cancer6.7%1.3%—[12]
Ileocolic, Crohn's disease——Insufficient evidence[12]
ColorectalEquivalentEquivalentn.s.[11]

For colorectal anastomosis, stapling is faster but produces more strictures (statistically significant, clinically modest); hand-sewn requires longer operative time but matches leak rates.[11] For ileocolic anastomosis — the relevant comparison for urinary-diversion bowel re-anastomosis after ileal or ileocolonic harvest — stapled is preferred (leak 2.5% vs 6%; OR 0.48).

Hand-Sewn Technique​

Suture Material​

  • Slowly absorbable monofilament (polydioxanone / PDS, polyglyconate) is preferred.[13]
  • Retains >50% tensile strength at 6 weeks vs ~25% for fast-absorbing suture.[14]
  • Monofilament reduces anastomotic leak vs multifilament (RR 0.76).[15]
  • Typical size: 3-0 or 4-0.

Single-Layer vs Double-Layer​

Single-layer continuous closure is preferred by level 1b evidence.[13] Compared with traditional two-layer (inner full-thickness + outer Lembert) anastomosis:

  • Equivalent or lower leak rate
  • Shorter operative time
  • Less foreign material in tissues
  • Adequate burst-strength

Two-layer closure remains acceptable but offers no outcome advantage.

Continuous vs Interrupted​

Continuous suturing is the default — faster, uniform tension distribution, equal or better leak rates.[13] Interrupted stitches are reasonable in contaminated fields, friable tissue, or for teaching.

Inverting vs Everting​

Inverting (Lembert, Connell) patterns create serosa-to-serosa apposition and are traditional. Everting technique shows no clear advantage or disadvantage in experimental comparison.[13] Modern preference is a single-layer continuous inverting or simple-apposition technique with submucosal inclusion.

Bowel Anastomotic Stitches​

The classic two-layer hand-sewn bowel anastomosis combines an inverting full-thickness inner layer with a seromuscular outer layer. Four named stitches make up the working repertoire:

StitchPatternLayer / role
ConnellContinuous full-thickness invertingInner layer of two-layer hand-sewn anastomosis
CushingContinuous seromuscular inverting (Lembert's continuous variant)Outer layer; preferred for speed
LembertInterrupted seromuscular invertingOuter layer; the founding bowel-anastomotic technique (Lembert 1826)
HalstedInterrupted seromuscular inverting (double-bite Lembert variant)Outer layer; high-tension reinforcement

The Parker-Kerr stitch (over-the-clamp baseball + Lembert) is the corresponding two-layer stump closure used during urinary diversion.

Specifications​

Evidence-supported parameters:[13]

  • Bite depth: ~5 mm from the anastomotic edge.
  • Stitch spacing: ~5–6 mm between bites.
  • Layer inclusion: must include submucosa (the strongest layer of the bowel wall).
  • Tension: approximate, do not strangulate.
  • Mucosal eversion: slight eversion acceptable.

A caveat worth internalizing: hand-sewn technique is inherently less standardized than stapled — the precise bite, spacing, and tension vary surgeon to surgeon in a way that staplers control by design.[13]

Step-by-Step (Single-Layer Continuous)​

The most evidence-supported approach:[13][16][17]

  1. Preparation — mobilize bowel, confirm perfusion, align ends without tension.
  2. Posterior wall —
    • Stay sutures at mesenteric and antimesenteric corners.
    • Begin continuous suture at one corner, tying inside the lumen.
    • Full-thickness bites 5 mm from edge, 5–6 mm apart, with emphasis on capturing submucosa.
    • Progress to opposite corner.
  3. Anterior wall —
    • Continue the same suture anteriorly.
    • Maintain consistent bite and spacing.
    • Complete the anastomosis by tying to the initial suture.
  4. Verification — hemostasis, no gaps, no tension.

A reported non-inverting two-layer technique (full-thickness continuous 5 mm/6 mm + seromuscular-only second layer at the same dimensions) achieved 0% leak rate in 80 patients with shorter operative time and lower cost than stapling, though in a single-center series.[17]

Configuration Selection​

End-to-End​

Traditional configuration — maintains normal caliber, straightforward technique. Can be hand-sewn or performed with a circular stapler (EEA device). Higher leak rate than end-to-side for low anterior resection.[13][18]

End-to-Side​

For low anterior resection, end-to-side reduces anastomotic leak by 63% vs end-to-end (RR 0.37) and produces improved Wexner (bowel function) scores for 6 months.[18] Preferred for the lowest rectal anastomoses.

Side-to-Side / Functional End-to-End​

The GIA-stapled side-to-side ("functional end-to-end") construction is the standard for ileocolic and ileoileal anastomosis — the relevant configuration for nearly every urologic bowel-diversion bowel re-anastomosis. See the dedicated Staplers article for cartridge selection, complication data, and the broader evidence base across urologic applications.

Cartridge selection. Always use a tissue cartridge (3.5–4.8 mm staple height) for bowel work — never a vascular cartridge (2.0–2.5 mm, designed for thin vascular tissue). Loading the wrong cartridge is one of the commonest preventable stapler errors.[24]

Stapler size. Ghanaat et al. (2018) compared GIA-60 vs. GIA-80 for bowel reanastomosis during radical cystectomy in 511 patients — stapler size was not independently associated with postoperative ileus (OR 1.11, p = 0.6). Positive fluid balance was the strongest predictor of ileus.[24]

Robotic stapled ileo-ileal anastomosis during RARC. Saxena et al. (2025), 170 patients — postoperative ileus 7.0%, small-bowel obstruction 4.7%, zero intraoperative bowel injuries across ileal conduit (75.8%), neobladder (21%), and continent pouch (2.3%).[25]

Stapler malfunction. Chan et al. (2000) reported a 1.7% endovascular-GIA malfunction rate across 565 laparoscopic nephrectomies, with 70% of failures attributable to preventable causes — improper loading, incomplete jaw closure, or tissue bunching.[26] The same human-factors lesson applies to bowel-anastomosis firings.

For right hemicolectomy:[19]

  • Leak rate comparable to end-to-side
  • Higher postoperative ileus rate: 4.9% vs 1.3% (p=0.017)
  • Shorter anastomotic construction time
  • Wider luminal caliber

Side-limb length: 3 cm and 6 cm side-limbs show no difference in leak.[13]

Configuration Summary​

AnastomosisPreferred configuration
Low anterior resectionEnd-to-side (lower leak rate)
Right hemicolectomyFunctional end-to-end or end-to-side
Ileocolic (for urinary diversion bowel re-anastomosis)Stapled functional end-to-end
High colorectalEnd-to-end or side-to-side equivalent

Perfusion Assessment — ICG Fluorescence Angiography​

ICG-FA has accumulated the most robust evidence base of any technical adjunct to bowel anastomosis.

Meta-analytic outcomes:[3][4][5][6][7]

  • Overall leak reduction: 31–69% (OR 0.39–0.69)
  • Left-sided / rectal resection: most pronounced benefit (NNT 14–23)
  • All ISGRC leak grades (A, B, C) reduced
  • LOS reduction: 0.72 days
  • Added operative time: +2.4 min (not significant)
  • No adverse events from ICG injection

Technique:[3][4][6]

  1. Administer 0.05–0.2 mg/kg ICG IV.
  2. Switch camera to near-infrared fluorescence mode.
  3. Assess perfusion at the proposed transection site before division.
  4. Reassess after anastomotic construction.
  5. Modify the plan if perfusion is inadequate.

ICG-FA changes surgical decision-making in 16.3% of cases — typically by altering the level of bowel transection.[5]

Evidence maturity: moderate-certainty evidence from 9 RCTs with 4,754 patients; trial-sequential analysis indicates the required information size has been exceeded for left-sided / rectal resections, meaning further RCTs are unlikely to change the conclusion.[6][7]

Alternatives: hyperspectral imaging and laser speckle contrast imaging show comparable leak reduction to ICG-FA; diffuse reflectance spectroscopy has fewer data.[3]

Anastomotic Leak​

Site-Specific Leak Rates[20][23]​

AnastomosisLeak rate
Coloanal19–25%
Low anterior resection10–19%
Left-sided colorectal5–10%
Right hemicolectomy0.5–3%
Ileocolic0.5–2.5%

For urinary-diversion bowel re-anastomosis (ileoileal or ileocolic), expected leak rates are at the low end (0.5–2.5%), but the consequences — combined urinary + enteric peritonitis — are devastating.

Risk Factors​

Patient (non-modifiable):[9][10][20][21][22]

  • Male sex (OR 1.6)
  • ASA ≥3
  • Obesity (OR 2.7, BMI >30)
  • Diabetes
  • Chronic kidney disease
  • Immunosuppression (OR 2.5)
  • Thrombocytosis (platelets >400 × 10⁹/L)
  • Hypertension

Modifiable (preoperative):[9][10][20]

  • Smoking (OR 3.93)
  • Alcohol excess
  • Low serum albumin / malnutrition
  • Anemia

Operative / tumor-related:[9][20][21][22]

  • Distal location (rectal > left colon > right colon)
  • Tumor >3 cm, advanced stage
  • Emergency surgery
  • Metastatic disease
  • Blood loss / transfusion
  • Operative time >4 hours
  • Intraoperative complication (OR 2.2)

Postoperative:[9][20]

  • NSAIDs increase leak risk — avoid in the early postoperative period (a specific concern for ERAS programs that lean on ketorolac / ibuprofen for opioid-sparing analgesia after bowel surgery).

Protective Factors​

  • Preoperative oral antibiotics ± mechanical bowel prep — reduces leak.[9][10]
  • ICG-FA perfusion assessment — 31–69% leak reduction.[3][4][5][6][7]
  • Diverting stoma — lessens the consequences of leak but does not reduce its prevalence.[20]

ISGRC Grading[23]​

GradeManagement
ANo change — subclinical / radiographic finding
BActive intervention without reoperation (drainage, antibiotics, endoscopic)
CReoperation required

Early leaks (within the first few postoperative days) are typically technical or perfusion-related and present with rapid clinical deterioration; later leaks are more often associated with local ischemia or infection.

Considerations Specific to Urinary Diversion​

Universal anastomotic principles apply, but several points deserve urologic emphasis:

  • Bowel prep: oral antibiotic prep is favored; the EAU / ERAS Society cystectomy guideline does not recommend routine mechanical bowel preparation.
  • Configuration: GIA-stapled functional end-to-end is the standard for bowel-to-bowel reconstitution after ileal or ileocolic segment harvest for conduit, neobladder, or continent reservoir.
  • Mesenteric windows must be closed after bowel harvest to prevent internal hernia — a well-described late cause of obstruction after ileal conduit.
  • Perfusion: ICG-FA is particularly useful at the urinary-reservoir / ileal-segment boundary. A dual-leak (urinary + enteric) event is the worst postoperative complication of urinary diversion, and the margin for error is narrow.
  • Tension: especially critical in neobladder construction, where the reconfigured bowel must reach the urethra.
  • Luminal environment: the intestinal limb re-anastomosis is re-exposed to feces; the urinary reservoir sees urine, which alters healing (mucus production, crystallization, urothelial metaplasia over time) but does not typically change the 30-day technical leak rate.
  • Ileal length: for ileal conduit, 15–20 cm of terminal ileum is typical; at least 20 cm should be preserved proximal to the ileocecal valve to protect B12 and bile-salt absorption.

Videos​

Technique demonstrations — hand-sewn bowel anastomosis.

Hand-sewn bowel anastomosis
Hand-sewn bowel anastomosis
Hand-sewn bowel anastomosis
Hand-sewn bowel anastomosis
Hand-sewn bowel anastomosis

References​

1. Curley SA, Allison DC, Smith DE, Doberneck RC. "Analysis of Techniques and Results in 347 Consecutive Colon Anastomoses." Am J Surg. 1988;155(4):597–601. doi:10.1016/s0002-9610(88)80417-3

2. Kream J, Ludwig KA, Ridolfi TJ, Peterson CY. "Achieving Low Anastomotic Leak Rates Utilizing Clinical Perfusion Assessment." Surgery. 2016;160(4):960–967. doi:10.1016/j.surg.2016.06.007

3. Renna MS, Grzeda MT, Bailey J, et al. "Intraoperative Bowel Perfusion Assessment Methods and Their Effects on Anastomotic Leak Rates: Meta-Analysis." Br J Surg. 2023;110(9):1131–1142. doi:10.1093/bjs/znad154

4. Trastulli S, Munzi G, Desiderio J, et al. "Indocyanine Green Fluorescence Angiography Versus Standard Intraoperative Methods for Prevention of Anastomotic Leak in Colorectal Surgery: Meta-Analysis." Br J Surg. 2021;108(4):359–372. doi:10.1093/bjs/znaa139

5. Hussain K, Balamurugan G, Ravindra C, et al. "The Impact of Indocyanine Green Fluorescence Angiography (ICG-FA) on Anastomotic Leak Rates and Postoperative Outcomes in Colorectal Anastomoses: A Systematic Review." Surg Endosc. 2025;39(2):749–765. doi:10.1007/s00464-025-11547-1

6. Ryan ÉJ, Ryan OK, Corrigan N, et al. "Indocyanine Green Fluorescence Angiography for Anastomotic Perfusion Assessment in Colorectal Surgery: A Systematic Review With Meta-Analysis, Meta-Regression, and Trial Sequential Analyses." Lancet Gastroenterol Hepatol. 2026. doi:10.1016/S2468-1253(25)00373-5

7. Mirza W, Iqbal H, Saeeda Y, et al. "Indocyanine Green Fluorescence-Guided Perfusion vs Standard Assessment to Prevent Clinical Anastomotic Leak After Colorectal Resection: A GRADE-Assessed Systematic Review and Meta-Analysis of RCTs With Site-Specific Subgroup Analysis." World J Surg Oncol. 2025;23(1):454. doi:10.1186/s12957-025-04163-9

8. Khalid MU, Ali D, Wu JY, Lee H, Khan A. "Impact and Measurement of Mechanical Tension in Bowel Anastomosis: A Scoping Review of the Current Literature." J Surg Res. 2025;308:161–173. doi:10.1016/j.jss.2025.02.011

9. Bao X, Yi K, Cheng J, et al. "Risk and Protective Factors for Postoperative Anastomotic Leakage in Esophageal and Gastrointestinal Surgery: An Umbrella Review of Meta-Analyses and Systematic Reviews." Int J Surg. 2025. doi:10.1097/JS9.0000000000003308

10. Parthasarathy M, Greensmith M, Bowers D, Groot-Wassink T. "Risk Factors for Anastomotic Leakage After Colorectal Resection: A Retrospective Analysis of 17,518 Patients." Colorectal Dis. 2017;19(3):288–298. doi:10.1111/codi.13476

11. Neutzling CB, Lustosa SA, Proenca IM, da Silva EM, Matos D. "Stapled Versus Handsewn Methods for Colorectal Anastomosis Surgery." Cochrane Database Syst Rev. 2012;(2):CD003144. doi:10.1002/14651858.CD003144.pub2

12. Choy PY, Bissett IP, Docherty JG, et al. "Stapled Versus Handsewn Methods for Ileocolic Anastomoses." Cochrane Database Syst Rev. 2011;(9):CD004320. doi:10.1002/14651858.CD004320.pub3

13. Slieker JC, Daams F, Mulder IM, Jeekel J, Lange JF. "Systematic Review of the Technique of Colorectal Anastomosis." JAMA Surg. 2013;148(2):190–201. doi:10.1001/2013.jamasurg.33

14. Deerenberg EB, Henriksen NA, Antoniou GA, et al. "Updated Guideline for Closure of Abdominal Wall Incisions From the European and American Hernia Societies." Br J Surg. 2022;109(12):1239–1250. doi:10.1093/bjs/znac302

15. Patel SV, Paskar DD, Nelson RL, Vedula SS, Steele SR. "Closure Methods for Laparotomy Incisions for Preventing Incisional Hernias and Other Wound Complications." Cochrane Database Syst Rev. 2017;11:CD005661. doi:10.1002/14651858.CD005661.pub2

16. Siri Pathamanathan S, Jayasena W, Due S, Singh H. "How to Do a Continuous Inverting Bowel Anastomosis Employing Counter-Traction." ANZ J Surg. 2026. doi:10.1111/ans.70515

17. Yao L, Li C, Zhu X, et al. "An Effective New Intestinal Anastomosis Method." Med Sci Monit. 2016;22:4570–4576. doi:10.12659/msm.902000

18. McKechnie T, Sharma S, Daniel R, Eskicioglu C. "End-to-End Versus End-to-Side Anastomosis for Low Anterior Resection: A Systematic Review and Meta-Analysis of RCTs." Surgery. 2021;170(2):397–404. doi:10.1016/j.surg.2020.12.030

19. Kim S, Huh JW, Lee WY, et al. "Comparative Analysis of Functional End-to-End and End-to-Side Anastomosis in Laparoscopic Right Hemicolectomy for Colon Cancer." Surgery. 2025;180:109051. doi:10.1016/j.surg.2024.109051

20. McDermott FD, Heeney A, Kelly ME, et al. "Systematic Review of Preoperative, Intraoperative and Postoperative Risk Factors for Colorectal Anastomotic Leaks." Br J Surg. 2015;102(5):462–79. doi:10.1002/bjs.9697

21. Frasson M, Flor-Lorente B, Rodríguez JL, et al. "Risk Factors for Anastomotic Leak After Colon Resection for Cancer: Multivariate Analysis and Nomogram From a Multicentric, Prospective, National Study With 3193 Patients." Ann Surg. 2015;262(2):321–30. doi:10.1097/SLA.0000000000000973

22. Nikolian VC, Kamdar NS, Regenbogen SE, et al. "Anastomotic Leak After Colorectal Resection: A Population-Based Study of Risk Factors and Hospital Variation." Surgery. 2017;161(6):1619–1627. doi:10.1016/j.surg.2016.12.033

23. Aaron AE, Amabile A, Andolfi C, et al. Gastrointestinal Surgical Emergencies. American College of Surgeons; 2021.

24. Ghanaat M, Winer AG, Sjoberg DD, et al. "Comparison of postradical cystectomy ileus rates using GIA-80 versus GIA-60 intestinal stapler device." Urology. 2018;122:121–126. doi:10.1016/j.urology.2018.09.010

25. Saxena S, Kim K, Billah MS, et al. "Outcomes of stapled ileo-ileal anastomosis during robot-assisted radical cystectomy with urinary diversion: points of technique." J Endourol. 2025. doi:10.1177/08927790251390881

26. Chan D, Bishoff JT, Ratner L, Kavoussi LR, Jarrett TW. "Endovascular gastrointestinal stapler device malfunction during laparoscopic nephrectomy: early recognition and management." J Urol. 2000;164(2):319–321.