Low Anterior Resection Syndrome (LARS)

Rather than a true surgical complication, LARS is a consequence of low anterior resection and coloanal anastomosis (see Total Mesorectal Excision (TME) & Sphincter-Sparing Resection) — a syndrome, not a technical failure. Content below is from a textbook reference chapter (Sabiston Ch52 - Rectal Cancer Surgery), not primary literature.

Definition and incidence

May be present in up to 80% of patients undergoing low anterior resection. Characterized by a mixture of multiple symptoms: frequency, multiple fragmented bowel movements, a sensation of incomplete emptying, incontinence, constipation, and diarrhea. Most symptoms improve 1 year or more after resection, but long-term dysfunction is described in the majority of patients.

Cause

Multifactorial. May be due to: injury of the internal sphincter, loss of sensitivity in the anorectal mucosa, loss or impairment of the rectoanal-inhibitory reflex, reduction in the capacity of the rectal reservoir, and/or loss of compliance of the transposed colon.

Incidence is higher in patients undergoing TME, those with a coloanal anastomosis, those who received neoadjuvant chemoradiation, and those who had an anastomotic leak (see Colorectal Anastomotic Complications) — i.e. the same factors that make for a more difficult, lower resection also predispose to worse functional outcomes afterward.

Prevention

Technical mechanisms currently used to reduce LARS symptoms, by increasing the capacity of the neorectum:

• Anastomosis with a 5–6 cm colonic J-pouch.
• Transverse coloplasty, or a side-to-end colorectal anastomosis.

Coloplasty is a possible alternative in obese patients in whom a J-pouch doesn’t fit into the narrow pelvis: a 10-cm longitudinal colotomy is made about 5 cm from the distal end of the transposed colon, then sutured transversely to widen the colon and increase its compliance.

Treatment

Often empirical, based on: dietary control; balanced use of loperamide combined with fiber products; physical therapy including biofeedback; and transanal irrigation. In a minority of highly symptomatic patients with low quality of life, after failure of conservative treatment, construction of a stoma may be necessary as a definitive treatment.

Open items / gaps

• No primary trial data yet comparing J-pouch vs. coloplasty vs. side-to-end anastomosis outcomes head-to-head.
• No specific LARS score/questionnaire detail (a validated instrument exists in the literature but isn’t described in this chapter chunk) — worth ingesting if a source becomes available.