Low Anterior Resection (LAR)

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Robotic LAR with total mesorectal excision is the default workflow below; laparoscopic and open approaches are covered as shorter parallel notes. For rectal cancer staging, neoadjuvant decisions, and related eponyms, see the colorectal topic review.

Procedure Snapshot

• Indication: Mid- and upper-rectal adenocarcinoma (lesion ≥ 5 cm from anal verge and ≥ 1 cm above the anorectal ring), typically after neoadjuvant chemoradiation for stage II/III disease. Also used for select benign disease (severe diverticulitis, prolapse, radiation injury).
• Expected duration: 3–5 hours robotic; longer for obese patients, narrow male pelvis, or low tumors.
• Positioning: Modified lithotomy in Yellofins, arms tucked, shoulder supports taped (steep Trendelenburg). Foley. Orogastric tube. Rectal irrigation with saline or dilute betadine after induction to wash out the distal rectum.
• Prep: Mechanical bowel prep + oral antibiotics (neomycin + metronidazole) the day prior (MOABP) — the current NSQIP / SCIP standard.¹ IV cefazolin + metronidazole within 60 min of incision.
• Robotic platform: da Vinci Xi most commonly. Single-dock, multi-quadrant operation — mobilize splenic flexure, pelvic dissection, and (if performed) ileostomy creation from one dock via boom rotation.
• Special instruments: Robotic monopolar scissors / hook, fenestrated bipolar, Cadiere grasper, robotic stapler (SureForm 45 blue and green reloads), circular EEA stapler (28 or 29 mm typical), Alexis wound protector, Lone Star retractor for low cases.
• Ureteral stents: Case-by-case — low threshold for prior pelvic radiation, bulky tumor, or reoperative pelvis.

Template Dictation — 13 Essential Steps (Bhama & Cleary)

Standardized from the Springer Operative Dictations chapter; the Step Workflow below expands on each. Use this as your pre-case mental checklist and as a scaffold for dictation.

1. Combined lithotomy–supine position.
2. Place laparoscopic / robotic cannulas.
3. Explore the abdomen for metastatic disease (liver, peritoneum, ovaries in females).
4. Mobilize the mesentery from the retroperitoneum, medial to lateral.
5. Identify the left ureter.
6. Identify and ligate the inferior mesenteric artery.
7. Mobilize the splenic flexure.
8. Mobilize the sigmoid and descending colon from remaining lateral attachments.
9. Total mesorectal excision of the rectum.
10. Staple at the pelvic floor.
11. Check the anastomosis for patency and integrity using a leak test.
12. Diverting loop ileostomy if indicated.
13. Close the abdomen.

Step Workflow — Robotic LAR with TME (primary)

1. Positioning, Ports, Docking
   • Modified lithotomy, steep Trendelenburg with right side down for splenic flexure, then neutral for pelvic dissection.
   • Port placement (Xi): five ports in a gentle arc across the abdomen from the RLQ to the LUQ, roughly aligned along a line drawn from ASIS through the umbilicus to the costal margin. Assistant 12 mm port in the RLQ or between ports 1–2.
   • Dock over the left hip, boom to target the pelvis. Target can be shifted to the splenic flexure for takedown without re-docking.
2. Medial-to-Lateral Sigmoid / Rectal Mobilization
   • Elevate the sigmoid mesentery and score the peritoneum at the sacral promontory along the right side of the superior rectal artery. Develop the avascular presacral plane — the key TME landmark.
   • Identify and sweep the left ureter and gonadal vessels posteriorly. They cross the pelvic brim under the iliac vessels; failure to identify them before IMA ligation is the classic cause of ureteral injury.
   • Identify the superior hypogastric plexus over the sacral promontory; sweep it posteriorly away from the specimen to preserve sympathetic function (bladder, sexual).
3. IMA / IMV Ligation
   • High tie (at the aortic origin) is the default for oncologic resections — maximal lymphadenectomy (IMA nodes, “station 253”) and additional reach from the left colon.
   • Low tie (distal to the left colic takeoff) preserves left colic blood supply and may reduce anastomotic ischemia in selected cases, but sacrifices nodal yield.
   • Ligate with robotic stapler (white or tan reload) or clips + energy. Take the IMV separately at the inferior border of the pancreas during splenic flexure mobilization for additional reach.
4. Splenic Flexure Takedown
   • Almost always needed for a tension-free low pelvic anastomosis.
   • Medial-to-lateral under the IMV, then lateral release of the descending colon along the white line of Toldt, then division of the gastrocolic / splenocolic attachments. Confirm the conduit reaches the pubic symphysis easily.
5. Total Mesorectal Excision (TME)
   • Enter the avascular holy plane of Heald between the mesorectal fascia (visceral) and the presacral fascia (parietal). Sharp, bloodless dissection along the shiny mesorectal envelope.
   • Posteriorly: dissect to the coccyx / anorectal ring; violate Waldeyer’s fascia to enter the deepest plane.
   • Anteriorly: open the peritoneal reflection; Denonvilliers’ fascia separates the rectum from the seminal vesicles/prostate (men) or vagina (women). Stay on or just behind Denonvilliers — violating anteriorly injures the neurovascular bundles (GU/sexual dysfunction).
   • Laterally: divide the lateral stalks (middle rectal vessels + autonomic nerves); identify and preserve the pelvic splanchnic nerves (parasympathetic, S2–S4) running on the lateral pelvic sidewall.
   • Continue TME down to the level just above the anorectal ring for a partial TME, or all the way to the pelvic floor for a total TME on a low tumor.
6. Distal Transection
   • Confirm distal margin: ≥ 2 cm in general, ≥ 1 cm acceptable after neoadjuvant therapy. For mid-rectal tumors, the partial TME can stop 5 cm below the tumor.
   • Robotic stapler (blue or green reload) to divide the rectum — ideally in a single fire. If multiple fires are needed, minimize overlap and stagger the lines (each extra firing increases leak risk).
7. Specimen Extraction & Proximal Division
   • Extract through a Pfannenstiel or extended supraumbilical incision with a wound protector. Divide the proximal colon at a point with good pulsatile flow after splenic flexure mobilization.
   • Check the mesorectal envelope for completeness — intact (complete), nearly complete, or incomplete (Quirke grading).² Photograph for path and tumor board.
   • Place the EEA anvil in the proximal colon, secure with a purse-string.
8. Circular Stapled Colorectal Anastomosis
   • Re-insufflate the abdomen. Pass the EEA stapler (28 or 29 mm typical) transanally under direct vision. Align and dock with the anvil.
   • Spike placement — through the edge, not the middle, of the distal staple line. Advance the circular stapler spike so it exits the rectal stump through one of the corners of the transverse staple line rather than through its center. This way the circular anastomotic ring crosses the linear staple line only once (at that corner) instead of bisecting it into two ischemic “dog-ears.” Intersecting staple lines are the classic nidus for early leak — this single maneuver is the highest-yield technical pearl from the LAR video.
   • Fire; retrieve the stapler. Inspect both donuts — must be complete and intact. Partial donuts = incomplete anastomosis.
   • Air leak test (flexible sigmoidoscopy or bulb insufflation under saline): pelvis filled with saline, clamp the proximal colon, insufflate rectum — look for bubbles. A positive air leak mandates repair (Lembert sutures) or takedown with redo anastomosis.
9. Drain and Diverting Loop Ileostomy (selective)
   • Pelvic drain (closed suction) placed near the anastomosis — routine for low anastomoses; controversial for mid/upper.³
   • Diverting loop ileostomy for: ultra-low anastomosis, anastomosis < 5 cm from anal verge, positive leak test, post-radiation tissue, immunosuppressed patient, tension on the anastomosis. Create 15–20 cm from the ileocecal valve; mature with rod if needed.
10. Closure
    • Fascia with 0 PDS or looped 2-0 PDS using small-bites technique (5 mm × 5 mm, SL:WL ≥ 4:1) per STITCH.⁴ Pfannenstiel closure is low-risk for incisional hernia.
    • Skin: staples or subcuticular.

Step Workflow — Laparoscopic LAR (parallel option)

• Nearly identical sequence to robotic, performed through 5 lap ports. Harder distal pelvic dissection in a narrow male pelvis; pneumoperitoneum-driven bowel retraction is less elegant than robotic articulated graspers.
• Consider laparoscopic approach for mid-rectal / upper-rectal tumors where the deep pelvic work is less demanding.

Step Workflow — Open LAR (parallel option)

• Midline laparotomy, self-retaining pelvic retractor (St. Mark’s / Bookwalter).
• Same TME plane, hand-sewn or stapled anastomosis.
• Default for emergent presentations (obstruction, perforation) or a frozen pelvis where minimally invasive dissection is unsafe.
• Higher SSI, longer LOS, longer ileus, but equivalent oncologic outcomes.⁵

Rapid-Fire Questions

• Q: What is TME?
  A: Total mesorectal excision — sharp dissection in Heald’s avascular plane between the visceral mesorectal fascia and the parietal presacral fascia, removing the rectum and its entire lymphovascular envelope en bloc. Reduced local recurrence from ~30% to ~5%.⁶

• Q: Who described it and when?
  A: Bill Heald, 1982.⁶ St. Mark’s/Basingstoke.

• Q: High tie vs low tie of the IMA — trade-offs?
  A: High tie = better nodal yield, more conduit length. Low tie (preserves left colic) = better conduit perfusion, possibly lower leak. Oncologic outcomes are similar in modern meta-analyses.⁷ Most surgeons high-tie for cancer.

• Q: Required distal margin?
  A: ≥ 2 cm without neoadjuvant; ≥ 1 cm after neoadjuvant is acceptable.⁸

• Q: Anastomotic leak rate after LAR?
  A: ~10% overall; higher for low/ultra-low anastomoses, male pelvis, smoking, obesity, post-radiation, steroids.⁹

• Q: When do you divert?
  A: Anastomosis within ~5 cm of the anal verge, positive air leak test, tension, post-radiation, malnutrition / steroids / immunosuppression. Meta-analyses show loop ileostomy reduces the clinical consequences of leak but not the leak rate itself.¹⁰

• Q: LAR syndrome — what is it?
  A: Constellation of urgency, frequency, clustering, incontinence, and incomplete evacuation after low rectal resection. Seen in ~50–90% of patients with ultra-low anastomosis.¹¹ Improves over 12–24 months but often persists.

• Q: Key autonomic structures at risk?
  A: Superior hypogastric plexus (sympathetic) at the sacral promontory → retrograde ejaculation / bladder dysfunction if injured. Hypogastric nerves running along the lateral pelvis. Pelvic splanchnic nerves (S2–S4 parasympathetic) → erectile and bladder parasympathetic function.

• Q: Why Denonvilliers’ fascia matters?
  A: It separates the rectum from the seminal vesicles/prostate (men) or posterior vagina (women). Dissecting anterior to it injures the neurovascular bundles → erectile / vaginal dysfunction. Dissect on or just posterior to Denonvilliers when the anterior tumor is small; take it with the specimen when the tumor abuts the anterior wall.

• Q: How do you check the mesorectal specimen?
  A: Inspect the mesorectal envelope grossly — complete (intact, shiny, no defects), nearly complete (minor defects not to muscularis propria), or incomplete (muscularis propria visible, Quirke grade).² Predicts local recurrence.

• Q: Donut incomplete after circular stapler fire?
  A: Anastomosis is not complete. Options: laparoscopic/robotic Lembert oversewing, redo the anastomosis, or take down and reconstruct. Never close skin over an incomplete anastomosis.

• Q: ROLARR trial — what did it show?
  A: Robotic vs laparoscopic LAR — no significant difference in conversion rate or oncologic outcomes.¹² Supports robotic as equivalent to lap; does not prove superiority.

• Q: Indications for neoadjuvant chemoradiation?
  A: Locally advanced rectal cancer: cT3–T4 or node-positive disease. Short-course RT (25 Gy in 5 fx) vs long-course CRT (~50 Gy + fluoropyrimidine). Total neoadjuvant therapy (TNT) is increasingly standard.⁸

• Q: Tumor response to neoadjuvant — complete pathologic response rate?
  A: ~10–20% pCR with conventional CRT; higher with TNT regimens. Some centers pursue watch-and-wait for clinical complete responders.¹³

Critical Anatomy

• Rectal arterial supply: superior rectal (IMA branch), middle rectal (internal iliac), inferior rectal (pudendal/internal iliac). TME ligates the superior rectal; middle rectal is in the lateral stalks; inferior rectal is below the levators (not encountered unless doing APR).
• Heald’s plane: avascular areolar tissue between visceral mesorectal fascia and parietal presacral fascia. The shiny plane you follow posteriorly.
• Waldeyer’s fascia: dense rectosacral fascia at S4 — must be divided sharply to get to the anorectal ring.
• Denonvilliers’ fascia: anterior rectal fascia separating rectum from seminal vesicles/prostate (men) or vagina (women).
• Autonomic nerves:
  • Superior hypogastric plexus — over the sacral promontory; sympathetic.
  • Hypogastric nerves (L/R) — descend along the lateral pelvis.
  • Pelvic splanchnic nerves (nervi erigentes) — S2–S4 parasympathetic; preserved on the pelvic sidewall.
• Ureters: cross the pelvic brim at the bifurcation of the common iliac, medial to the gonadal vessels. Identify before IMA ligation.
• Danger zones:
  • Presacral venous plexus (brutal bleeding — do not cauterize, consider thumbtack, bone wax, or packing).
  • Left ureter during IMA ligation.
  • Autonomic nerves at all four quadrants of the pelvic dissection.
  • Small bowel retained in the pelvis during specimen extraction.

Informed Consent Highlights

• Risks:
  • Anastomotic leak ~ 10% overall;⁹ 15–20% for ultra-low anastomoses.
  • Bleeding (presacral venous plexus is the classic unfixable bleeder).
  • Ureteral / bladder injury ~ 1–2%.
  • Urinary dysfunction (incomplete emptying, retention) ~ 30% at 1 month, most improve.
  • Sexual dysfunction: erectile dysfunction in men ~ 25–50%, dyspareunia in women.
  • LAR syndrome ~ 50–90% of ultra-low patients.¹¹
  • Diverting ileostomy if planned or for leak — most reversed at 3–6 months.
  • Anastomotic stricture, local recurrence, incisional hernia at extraction site.
  • Standard: bleeding, infection, VTE, cardiac/pulmonary events, death.
• Benefits: Oncologic resection with sphincter preservation; improved quality of life vs APR for candidates.
• Alternatives:
  • APR (abdominoperineal resection) for tumors involving the sphincter complex.
  • Watch-and-wait for clinical complete responders after TNT in select patients.
  • Local excision (TEM/TAMIS) for early (T1) tumors with favorable features.
  • Palliation with diversion only for unresectable disease.

Post-Op Considerations (ERAS)

• Diet: Clear liquids on POD 0 once awake; advance to regular as tolerated. No NG tube routinely.
• Mobilization: Out of bed to chair same day; ambulate POD 1.
• Foley: Out on POD 2–3 for uncomplicated cases; longer (POD 5–7) for ultra-low dissection or significant pelvic neural dissection (higher retention risk).
• Drain: Pelvic drain out when output is low, non-bilious, and non-feculent (typically POD 3–5).
• Analgesia: Multimodal, opioid-sparing. TAP block or continuous epidural for open cases.
• Anticoagulation: DVT prophylaxis with LMWH; continue for 4 weeks post-discharge for cancer patients.¹⁴
• Ostomy care: NPO reversal not required; teach output monitoring (high-output risk for loop ileostomy > 1.5 L/day → dehydration, AKI).
• Red flags:
  • Leak symptoms POD 3–7: fever, tachycardia, rising WBC, pelvic pain, high drain output, feculent drain, ileus not resolving.
  • First-line imaging for suspected leak: CT with rectal contrast.
• Follow-up:
  • Clinic visit at 2 weeks.
  • Stoma reversal at 8–12 weeks once the anastomosis is confirmed intact (contrast enema / flexible sigmoidoscopy).
  • Surveillance: CEA, CT chest/abdomen/pelvis, colonoscopy at 1 year, then per NCCN.

Clinical Pearls

• Identify the ureter before you ligate the IMA. Every time. The case is not safe without this.
• Tension, tension, tension. Mobilize the splenic flexure aggressively — a conduit that barely reaches dry is a conduit that leaks under anesthesia breath-holds.
• Pulsatile flow at the proximal transection point is more important than the absolute level of transection. ICG angiography is a reasonable adjunct when available.
• Keep the presacral plane dry. Enter presacral venous plexus = consider packing and moving on; cautery rarely helps and can worsen it.
• The deepest, lowest bite of the TME is often the hardest. Consider a transanal-assisted (TaTME) approach for very low tumors in a narrow male pelvis.
• Diverting ileostomy doesn’t prevent leaks, it softens their consequences. Low threshold in post-radiation or ultra-low cases.
• Single-firing the distal stapler matters — each additional firing roughly doubles leak risk in observational data.¹⁵
• Spike the anvil through the edge of the distal staple line, not the middle. The circular anastomotic line will intersect the linear staple line only once instead of bisecting it, sparing the two ischemic “dog-ear” corners that leak. (Key pearl from the LAR video linked at the top.)
• Mesorectal grade is a key path finding that belongs in the op note and goes to tumor board.
• Rectal washout before transection reduces implantation of luminal tumor cells at the anastomosis — low cost, some oncologic benefit.
• LARS syndrome discussion preoperatively — set expectations; 50–90% of ultra-low anastomosis patients will have some degree of it.

Quick Reference Table

Quick-Reference Cards

Related Topic Reviews

• Colorectal — rectal cancer staging, anatomy, and adjuncts.

Related Landmark Papers

• STITCH — small-bites fascial closure for the extraction-site incision.

References

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8. NCCN Clinical Practice Guidelines in Oncology — Rectal Cancer. Current version, NCCN.org.
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12. Jayne D, Pigazzi A, Marshall H, et al. Effect of robotic-assisted vs conventional laparoscopic surgery on risk of conversion to open laparotomy among patients undergoing resection for rectal cancer (ROLARR). JAMA. 2017; 318(16): 1569–1580.
13. Habr-Gama A, Perez RO, Nadalin W, et al. Operative versus nonoperative treatment for stage 0 distal rectal cancer following chemoradiation therapy: long-term results. Ann Surg. 2004; 240(4): 711–717.
14. Rasmussen MS, Jorgensen LN, Wille-Jørgensen P. Prolonged thromboprophylaxis with LMWH for abdominal or pelvic surgery. Cochrane Database Syst Rev. 2009.
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