Low Anterior Resection (LAR)
What the Examiner Expects
Resection of the rectum with a colorectal or coloanal anastomosis, preserving the anal sphincter complex. The cornerstone of rectal cancer surgery is total mesorectal excision (TME) — sharp dissection in the avascular areolar plane between the visceral (mesorectal) and parietal (presacral) fascia, removing all mesorectal fat and lymph nodes as an intact envelope. The examiner expects you to stage the patient (MRI pelvis for local staging, CT for distant staging), determine need for neoadjuvant therapy (chemoradiation for T3/T4 or N+ by NCCN guidelines), and understand the technical nuances: a 1 cm distal mucosal margin is adequate for rectal cancer (not the traditional 5 cm), but the mesorectum must be excised completely regardless.
Key Examiner Focus Points
- Indicated for upper and mid rectal cancers (above the levator ani)
- Total mesorectal excision (TME) is mandatory for oncologic quality
- Neoadjuvant chemoradiation for T3/T4 or node-positive rectal cancer
- Diverting loop ileostomy for low anastomoses (typically < 7 cm from anal verge)
- Low anterior resection syndrome (LARS): urgency, frequency, incontinence
Common Curveballs
MRI shows a T3N1 mid-rectal tumor — the patient wants to go straight to surgery
No. Neoadjuvant chemoradiation (long-course: 5-FU/capecitabine with 50.4 Gy radiation over 5–6 weeks) followed by surgery 8–12 weeks later is the standard of care for locally advanced rectal cancer. Total neoadjuvant therapy (TNT) with induction chemo followed by chemoradiation is an emerging approach. Surgery alone risks incomplete resection and local recurrence.
After the anastomosis, you notice the donuts are incomplete
Incomplete donuts indicate a potential anastomotic defect. Test the anastomosis: fill the pelvis with saline, insufflate air transanally via a rigid proctoscope or flexible endoscope. If there are bubbles, take down and redo the anastomosis or add reinforcing sutures. An untested anastomosis with incomplete donuts has a high leak rate.
Patient develops an anastomotic leak 6 days postop
If the patient has a diverting loop ileostomy in place, this is usually manageable nonoperatively: IV antibiotics, percutaneous drainage of any pelvic collection, and the proximal diversion protects the leak. If no diversion is present and the patient is septic, return to the OR for washout and creation of a proximal diverting stoma.
Practice this topic with an AI-powered mock oral exam.
Browse Practice Cases