What is dyssynergic defecation?

What is Dyssynergic Defecation?

Dyssynergic defecation is a functional defecatory disorder characterized by paradoxical contraction or inadequate relaxation of the pelvic floor muscles during attempted defecation, resulting in impaired rectal evacuation despite adequate propulsive forces. 1

Core Pathophysiology

• This is an acquired behavioral disorder where patients lose the ability to coordinate their abdominal and pelvic floor muscles to evacuate stool normally 2, 3
• The pelvic floor muscles paradoxically contract rather than relax during straining, creating a functional obstruction at the anal outlet 4, 2
• There are no associated morphological or neurological abnormalities—this is purely a coordination problem, not structural damage 5
• The condition causes reduced rectal sensation and impaired awareness of the need to defecate due to chronic straining and pelvic floor dysfunction 4

Clinical Presentation: Key Features to Recognize

• Prolonged excessive straining with soft stools is the hallmark clinical clue—if patients struggle to pass soft stool or cannot evacuate enema fluid, dyssynergic defecation should be strongly suspected 6
• Sensation of incomplete evacuation after bowel movements 6, 3
• Need for digital evacuation or perineal/vaginal pressure to facilitate defecation 1, 6
• Sensation of anorectal blockage during attempted defecation 6
• Inability to pass a water-filled balloon during balloon expulsion testing 1

Diagnostic Approach

Essential Tests

• Anorectal manometry combined with balloon expulsion test is essential for diagnosis and should be performed first when defecatory disorder is suspected 1, 6
• Digital rectal examination should assess pelvic floor motion during simulated evacuation, looking for paradoxical contraction or failure to relax the puborectalis muscle 6
• High-resolution manometry and magnetic resonance defecography can provide additional mechanistic insights when needed 2, 7

When to Test

• Test patients who fail initial conservative measures with fiber and laxatives 6
• Test when clinical features suggest difficult evacuation: straining with soft stools, need for manual maneuvers, or sensation of blockage 1, 6
• In cases of discordant anorectal manometry and balloon expulsion test results, consider fluoroscopic or magnetic resonance defecography to confirm pelvic floor dysfunction 1

Prevalence and Impact

• Dyssynergic defecation affects up to one-half of patients with chronic constipation, making it one of the most common forms of functional constipation 2, 3
• About one-third of chronically constipated patients have an evacuation disorder, with dyssynergic defecation being a common cause 3

First-Line Treatment: Biofeedback Therapy

• Biofeedback therapy is the definitive first-line treatment with a Grade A recommendation, demonstrating superior efficacy to laxatives and other modalities 1
• Success rates exceed 70-80% in clinical trials for patients with dyssynergic defecation 1, 2
• The therapy trains patients to relax their pelvic floor muscles during straining and restores normal rectoanal coordination through operant conditioning principles 1
• Treatment involves visual (computer monitor) or audible/verbal feedback to inform patients of muscle contraction strength and coordinated pressure changes during attempted defecation 1
• Biofeedback is completely free of morbidity and safe for long-term use 4

Predictors of Treatment Success

• Patients with lower or more normal baseline thresholds for first rectal sensation and urge are more likely to respond to biofeedback 1
• Depression and elevated first rectal sensory threshold volume are independent predictors of poor biofeedback efficacy 1
• Lower baseline constipation scores, shorter colonic transit times, and lower intolerable urgency thresholds predict better outcomes 1

Critical Pitfalls to Avoid

• Do not continue escalating laxatives indefinitely in patients with defecatory disorders—this will not address the underlying pelvic floor dysfunction and delays definitive treatment 4
• Do not assume constipation is purely a colonic motility problem; failure to recognize the pelvic floor component is a frequent reason for therapeutic failure 4
• Do not skip anorectal testing in patients who fail initial conservative measures, as this is essential to identify the specific dysfunction 4
• Do not attribute bowel symptoms solely to irritable bowel syndrome without first excluding a defecatory disorder 6

Alternative Treatment Options

• Sacral nerve stimulation may improve rectal sensation in patients with rectal hyposensitivity when biofeedback fails or is unavailable 4
• Botulinum toxin type A injection has been studied but evidence is poor with heterogeneous outcomes (symptomatic improvement ranging from 29.2% to 100%) and should not be considered first-line 8