Constipation Diagnosis and Management

Pathophysiologic Mechanisms

The American Gastroenterological Association recognizes that the urge to defecate results from normal rectal distension triggering parasympathetic reflexes via the rectal sphincter, and its loss indicates defecatory disorders or slow transit constipation 1, 2
Diminished perception of rectal distension with loss of urge to defecate is a recognized pathophysiologic factor contributing to constipation, often associated with reduced rectal sensation and impaired awareness of the need to defecate 1, 2
Reduced rectal sensation may coexist with structural disturbances like rectocele or intussusception in defecatory disorders 3

The American Gastroenterological Association emphasizes that questioning must be specific to identify predominant symptom patterns, including infrequency, straining, sensation of blockage, and need for manual maneuvers 4
Prolonged excessive straining with soft stools or inability to pass enema fluid strongly indicates defecatory disorders, characterized by reduced rectal sensation and impaired awareness of the need to defecate 3, 4
Need for perineal/vaginal pressure or digital evacuation is an even stronger clue for defecatory disorders, often requiring anorectal testing and pelvic floor retraining/biofeedback therapy 3, 4
Sensation of incomplete evacuation is one of the Rome III diagnostic criteria for chronic constipation, and sensation of anorectal blockage or obstruction during defecation is another Rome III criterion 1, 2

Loss of urge to defecate, particularly when combined with other symptoms, should prompt specific diagnostic evaluation, including anorectal testing and colonic transit study 3, 4
Anorectal testing, such as manometry and balloon expulsion test, should be performed first to identify defecatory disorders, especially when patients report straining, sensation of blockage, or need for manual maneuvers 4
Colonic transit study should be evaluated if anorectal tests do not show defecatory disorder or if symptoms persist despite treatment, to guide the use of prokinetic agents targeting colonic motility 4
Pelvic floor retraining/biofeedback therapy is the primary treatment for defecatory disorders with reduced rectal sensation, while prokinetic agents are more appropriate for slow transit constipation 5, 6

Elderly patients are five times more prone to constipation than younger people, with reduced urge to defecate being a specific age-related risk factor, along with polypharmacy, reduced mobility, and reduced hydration 1, 2
Opioids cause constipation by inhibiting intestinal motility and increasing colonic fluid absorption, contributing to loss of urge in these patients 1, 2, 5