Chronic Constipation with Incomplete Evacuation | ODS Guide

Chronic constipation combined with persistent incomplete evacuation - feeling that stool remains after defecation, excessive straining, and sometimes needing manual assistance - is the hallmark cluster of obstructed defecation syndrome (ODS). This cluster requires specialist anorectal evaluation including manometry and defecography. It does not fully respond to dietary changes and laxatives alone.

Classic ODS Presentation

• Chronic constipation with prolonged straining at each attempt
• Persistent feeling of incomplete evacuation after defecation
• Sensation of rectal or anal blockage - "something is in the way"
• Multiple trips to toilet for one bowel movement
• Pressing around the perineum or manually assisting evacuation
• Years of symptoms, typically in women (often after childbirth)
• Laxatives partially help but never fully resolve the problem

Causes of ODS

• Paradoxical puborectalis contraction - the puborectalis muscle, which normally relaxes during defecation, instead contracts and narrows the anorectal angle. The most common functional cause. Very treatable with biofeedback.
• Rectocele - forward bulging of the rectum into the posterior vaginal wall. Stool preferentially fills the rectocele pocket rather than the anal canal. Surgical repair when large and symptomatic.
• Rectal intussusception - internal telescoping of the rectal wall. Diagnosed on defecography. May respond to biofeedback or require surgery.
• Enterocele - small bowel loops prolapse into the rectovaginal space. Obstructs defecation. Surgical repair.
• Rectal prolapse (internal) - full-thickness rectal fold intussusception. Laparoscopic mesh rectopexy.

Investigations

• Anorectal manometry: Identifies paradoxical puborectalis contraction, reduced sphincter relaxation, and impaired defecation reflex
• Defecography (dynamic proctography): X-ray or MRI imaging of the defecation process; identifies rectocele size, rectal intussusception, enterocele, and pelvic floor descent
• Colonoscopy: To exclude structural colorectal causes - done before or alongside manometry and defecography

Treatment

Functional ODS - Biofeedback physiotherapy

For paradoxical puborectalis contraction - biofeedback is the most effective treatment. A pelvic floor physiotherapist uses real-time visual or electromyographic feedback to teach the patient to correctly relax the puborectalis during defecation. Success rates of 60-80% for symptom improvement. Requires 4-6 sessions. No medications or surgery needed for this subtype.

Structural ODS - Surgery

• Rectocele repair: Transvaginal or transanal approaches to reinforce the rectovaginal wall
• STARR procedure (Stapled TransAnal Rectal Resection): Endorectal stapling to remove redundant rectal tissue causing internal intussusception
• Laparoscopic ventral mesh rectopexy: Secures the rectum with mesh to the sacrum; addresses prolapse, rectocele, and enterocele simultaneously; preferred for complex ODS

Frequently Asked Questions