Dyssynergic Defecation (Pelvic Floor Dysfunction)
You have classic symptoms of dyssynergic defecation—a functional outlet obstruction where your pelvic floor muscles paradoxically contract instead of relaxing during attempted bowel movements, trapping soft stool and gas in the rectum. 1
Why This Is Happening
Your constellation of symptoms—straining to pass soft stool, rectal distension, trapped gas that won't come out, and abdominal pain—points directly to a defecatory disorder rather than slow-transit constipation or irritable bowel syndrome. 2, 1 The key diagnostic clue is that you are straining even though your stool is soft; this indicates the problem is at the outlet (pelvic floor) rather than in colonic motility. 2, 1
- Dyssynergic defecation occurs when the puborectalis muscle and external anal sphincter contract paradoxically or fail to relax adequately (less than 20% relaxation) during attempted defecation, creating a functional blockage. 1
- This causes incomplete evacuation, the sensation of rectal fullness, and the need to strain repeatedly—even with soft stool—because the pelvic floor won't "open the door." 2, 1
- The trapped gas and bloating you feel are secondary to retained stool and gas from outlet obstruction, not from excessive gas production. 2, 1
What You Should Do Now
Step 1: Immediate Symptomatic Relief (First 1–2 Weeks)
While awaiting definitive testing and treatment, take these measures to reduce straining and soften stool:
- Stop any constipating medications if possible—opioids, anticholinergics (e.g., antihistamines, bladder medications), calcium-channel blockers, iron supplements. 1
- Start polyethylene glycol (MiraLAX®) 17 g once daily to soften stool and reduce straining. 1
- Add bisacodyl (Dulcolax®) 10 mg once daily to promote regular bowel movements. 1
- Drink at least 1.5 liters of water daily. 1
- Optimize toileting habits:
- Avoid high-dose fiber or bulk laxatives (e.g., psyllium, methylcellulose) until you are well-hydrated, as they can worsen outlet obstruction by increasing stool volume that cannot be evacuated. 1
Do not treat this as irritable bowel syndrome or slow-transit constipation with fiber or prokinetics—the primary problem is outlet obstruction, not colonic inertia. 1
Step 2: Confirm the Diagnosis
You need anorectal manometry combined with a balloon expulsion test to objectively confirm dyssynergic defecation. 1, 3
- Anorectal manometry measures resting and squeeze pressures, evaluates anal sphincter relaxation during simulated defecation, and assesses rectal sensory thresholds. 1
- Balloon expulsion test is abnormal when you cannot expel a 50 mL water-filled balloon within 1–3 minutes, confirming outlet obstruction. 1
- Expected findings in dyssynergia:
Do not order colonoscopy unless you have alarm features (rectal bleeding, anemia, unintentional weight loss, sudden onset after age 50). 1 Do not order colonic transit studies before anorectal testing—up to one-third of patients have secondary slowing due to untreated dyssynergia. 1
Step 3: Definitive Treatment—Biofeedback Therapy
Biofeedback therapy is the first-line definitive treatment for dyssynergic defecation, with a Grade A recommendation and 70–80% success rate. 1, 4
- How it works: Visual or auditory feedback trains you to relax your pelvic floor muscles during straining, restoring normal recto-anal coordination through operant conditioning. 1
- Typical protocol: 4–6 sessions over 8–12 weeks with a trained pelvic-floor therapist. 1
- Predictors of success: Lower baseline rectal sensory thresholds and absence of depression. 1, 4
- Predictors of failure: Elevated first-sensation threshold and presence of depression. 1, 4
Biofeedback is completely safe, free of morbidity, and superior to laxatives for defecatory disorders. 4 It also improves rectal and pelvic sensory perception in over 70% of patients with reduced sensation. 4
Step 4: If Biofeedback Fails or Is Unavailable
- Rectal bisacodyl suppositories 10 mg once daily for local stimulation. 1
- After 8–12 weeks of biofeedback, order a colonic transit study because approximately 30% of patients have combined dyssynergic defecation and slow-transit constipation. 1
Common Pitfalls to Avoid
- Do not continue escalating laxatives indefinitely—this will not address the underlying pelvic floor dysfunction and delays definitive treatment. 4
- Do not assume irritable bowel syndrome without first excluding a defecatory disorder; the two conditions overlap in approximately 30% of cases but require different therapies. 1
- Do not prescribe high-dose fiber or bulk laxatives, as they increase stool volume that cannot be evacuated. 1
- Do not proceed to surgical interventions (e.g., colectomy) without confirming normal anorectal function—unrecognized dyssynergia leads to disastrous surgical outcomes. 1
When to Refer
Refer to gastroenterology or a pelvic-floor specialist for:
- Anorectal manometry and balloon expulsion testing. 1
- Biofeedback therapy. 1
- Management of refractory symptoms after failed biofeedback. 1
Refer to colorectal surgery when:
- Defecography reveals structural pelvic-floor abnormalities (e.g., large rectocele, rectal prolapse) requiring repair. 1
- True slow-transit constipation persists after exhaustive medical management. 1
What to Expect
- Bloating and abdominal fullness are secondary to retained stool and gas from outlet obstruction; they improve with successful biofeedback. 1
- Timing matters: The earlier you start biofeedback therapy, the better the recovery of sensory function. 4
- Realistic timeline: Gradual improvement over weeks to months with proper biofeedback therapy. 4