What is pelvic dyssynergia and hypertonic pelvic floor muscle (pelvic‑floor muscle hypertonicity)?

What is Pelvic Dyssynergia and Hypertonic Pelvic Floor?

Pelvic dyssynergia (also called dyssynergic defecation or anismus) is a functional defecatory disorder in which the pelvic floor muscles paradoxically contract or fail to relax during attempted defecation, creating a functional outlet obstruction despite adequate propulsive forces, while hypertonic pelvic floor refers to chronically elevated resting tone of the pelvic floor muscles that can cause pain, voiding dysfunction, and constipation. 1, 2

Core Pathophysiology

Dyssynergic Defecation:

• The puborectalis muscle and/or external anal sphincter contract paradoxically or fail to relax adequately (< 20% relaxation) during straining, blocking rectal evacuation even when stool is soft. 1, 2
• This is a behavioral disorder with no underlying morphological or neurological abnormality in most cases—the muscles are structurally normal but functionally uncoordinated. 3
• The condition creates functional outlet obstruction: the rectum generates normal propulsive pressure, but the pelvic floor acts as a closed gate. 4

Hypertonic Pelvic Floor:

• Chronically elevated resting tone of the pelvic floor muscles (puborectalis, external anal sphincter, levator ani) that persists even at rest. 5, 6
• High resting anal sphincter pressure on digital rectal examination is the hallmark physical finding. 5
• Can result from chronic straining, muscular injury, scar tissue formation, neuropathies, or neurologic conditions such as hereditary spastic paraplegia. 6
• Leads to a constellation of symptoms beyond constipation: pelvic pain, dyspareunia (painful intercourse), voiding dysfunction, and pudendal nerve compression. 5, 6, 7

Clinical Presentation

Hallmark Symptoms of Dyssynergia:

• Prolonged excessive straining with soft stools—this is the single most specific clue that distinguishes outlet obstruction from slow-transit constipation. 2
• Need for manual digital evacuation or perineal/vaginal pressure to pass stool (≈85% specificity for dyssynergia). 2, 5
• Sensation of incomplete evacuation or anorectal blockage despite prolonged effort. 2
• Small, soft stools mixed with mucus that require manual extraction. 2
• Inability to pass enema fluid despite adequate rectal distension. 2

Hallmark Symptoms of Hypertonic Pelvic Floor:

• Chronic pelvic pain, often localized to the pudendal nerve distribution (perineum, rectum, genitals). 5, 6
• Dyspareunia (pain during intercourse) due to inability to relax pelvic floor muscles. 6, 7
• Urinary retention or urgency with difficulty voiding, especially after pelvic surgery (e.g., hemorrhoidectomy). 5
• Acute localized tenderness over the puborectalis muscle on digital rectal examination (levator ani syndrome). 2, 5
• Symptoms worsen with activities that increase pelvic floor tension (prolonged sitting, straining, sexual activity). 6

Diagnostic Approach

Physical Examination (Digital Rectal Examination):

• High resting anal tone indicates hypertonicity; low/lax tone suggests weakness or neuropathy. 5
• Paradoxical puborectalis contraction during simulated defecation (ask patient to "bear down as if having a bowel movement") confirms dyssynergia. 2, 5
• Reduced perineal descent (< 1 cm movement) during simulated evacuation reflects impaired pelvic floor relaxation. 5
• Inability to "expel the examiner's finger" during push maneuver is diagnostic of dyssynergia. 2, 5
• Important caveat: A normal digital rectal exam does not exclude dyssynergia—up to 30% of confirmed cases have an unremarkable exam. 2, 5

First-Line Objective Testing:

• Anorectal manometry is the essential diagnostic tool, measuring resting and squeeze pressures, anal sphincter relaxation during simulated defecation, and rectal sensory thresholds. 1, 2, 5
• Dyssynergia pattern: Paradoxical anal contraction or < 20% sphincter relaxation during three push attempts. 1, 2, 5
• Hypertonicity pattern: Elevated resting anal pressure (typically > 80 mmHg; normal 40–80 mmHg) with high squeeze pressure. 5
• Balloon expulsion test: Failure to expel a 50 mL water-filled balloon within 1–3 minutes is abnormal and confirms outlet obstruction. 1, 2, 5

Second-Line Testing (When Manometry and Balloon Expulsion Are Discordant):

• Fluoroscopic or MR defecography visualizes the defecation process in real time, identifying paradoxical sphincter contraction, impaired anorectal angle change (< 15° excursion), and structural abnormalities (rectoceles, intussusception). 1, 2, 8, 4
• Defecography shows prolonged evacuation time (> 30 seconds), retained contrast (> 1/3 of initial volume), and narrowed anal canal (< 12 mm diameter) during straining in dyssynergia. 4
• Critical technical requirement: Patients must perform maximal straining and complete rectal emptying during imaging; incomplete evacuation misses enteroceles and underestimates dysfunction. 8

Distinguishing Dyssynergia from Weakness

This distinction is critical because treatments are opposite:

Feature	Dyssynergia/Hypertonicity	Muscle Weakness
Resting anal tone	High (> 80 mmHg)	Low (< 40 mmHg)
Puborectalis response during push	Paradoxical contraction	Weak/absent contraction
Balloon expulsion	Fails to expel	May expel but with weak force
Fecal incontinence	Absent	Present (leakage)
Straining with soft stool	Yes (hallmark)	No
Manual evacuation needed	Yes	No

2, 5

Treatment

First-Line Definitive Therapy for Dyssynergia:

• Biofeedback therapy carries a Grade A recommendation with 70–80% success rates in clinical trials. 1, 2, 3, 9
• Mechanism: Uses visual (computer monitor) or auditory feedback to train patients to relax pelvic floor muscles during straining, restoring normal recto-anal coordination through operant conditioning. 1, 2
• Typical protocol: 4–6 sessions over 8–12 weeks with a trained pelvic floor therapist. 2, 5
• Predictors of success: Lower baseline rectal sensory thresholds, absence of depression, shorter colonic transit times. 1, 2
• Predictors of failure: Elevated first-sensation threshold, presence of depression. 1, 2

First-Line Therapy for Hypertonic Pelvic Floor:

• Pelvic floor physical therapy with manual trigger-point release, perineal stretching, and myofascial release techniques. 5, 6, 7
• Avoid standard Kegel exercises—they worsen hypertonicity by further contracting already tight muscles. 5
• Intravaginal massage and perineal stretching have demonstrated efficacy for reducing tone and improving symptoms. 6, 7
• For associated pudendal neuralgia: low-dose tricyclic antidepressants (e.g., nortriptyline) or gabapentinoids. 5

Immediate Symptomatic Management (First 1–2 Weeks):

• Discontinue all constipating medications (opioids, anticholinergics, calcium-channel blockers, iron supplements). 2
• Polyethylene glycol 17 g daily to soften stools and reduce straining. 2
• Avoid high-dose fiber or bulk laxatives—they increase stool volume that cannot be evacuated and worsen outlet obstruction. 2
• Toileting habits: defecate 30 minutes after meals (gastrocolic reflex), use footstool for squatting position, limit straining to ≤ 5 minutes. 2

Common Pitfalls

• Do not attribute symptoms to irritable bowel syndrome without first excluding a defecatory disorder—up to one-third of chronically constipated patients have dyssynergia. 2
• Do not order colonic transit studies before anorectal testing—secondary slowing from untreated dyssynergia is common. 2
• Do not prescribe standard Kegel exercises for hypertonicity—they exacerbate pelvic floor spasm. 5
• Do not rely on a normal digital rectal exam to exclude dyssynergia—objective testing is mandatory. 2, 5
• Do not assume prostate enlargement causes bowel symptoms—pelvic floor dysfunction commonly affects both urinary and defecatory systems through shared neuromuscular pathways. 2
• Do not order MR defecography acutely—reserve it for chronic refractory cases (> 8–12 weeks) or when structural lesions are suspected. 5, 8

Special Populations

Post-Surgical Patients:

• Nonrelaxing pelvic floor dysfunction occurs in 75% of patients with ileal pouch-anal anastomosis (IPAA), especially those with chronic pouchitis (83.3% vs. 62.2% without pouchitis). 9
• Biofeedback remains effective in this population: 68.2% achieve mild-moderate improvement and 22.7% achieve significant improvement. 9
• Post-hemorrhoidectomy urinary retention is typically due to reflex pelvic floor spasm (hypertonicity), not sphincter weakness. 5

Neurologic Conditions:

• Patients with hereditary spastic paraplegia or other spastic neurologic disorders often have severe pelvic floor hypertonicity requiring intensive physical therapy with stretching protocols. 6