Characteristics of Functional Constipation

Diagnostic Criteria and Symptoms

The American Gastroenterological Association defines functional constipation as a condition diagnosed when a patient presents with at least two of the following symptoms for at least 12 weeks in the previous 12 months: straining during bowel movements, lumpy or hard stool, sensation of incomplete evacuation, sensation of anorectal blockage or obstruction, manual evacuation procedures to remove stool, or fewer than 3 bowel movements per week 1, 2
Constipation is not merely infrequent bowel movements but encompasses a broader set of symptoms including hard stools, feeling of incomplete evacuation, abdominal discomfort, bloating, and distention 1
Excessive straining, sense of anorectal blockage during defecation, and need for manual evacuation are key symptoms suggesting a defecatory disorder 1
The Rome III criteria define chronic constipation as the presence of any two characteristic symptoms for at least 12 weeks in the previous 12 months (not necessarily consecutive) 3
Reduced stool frequency is poorly correlated with delayed colonic transit, meaning patients with daily bowel movements may still experience constipation 1

Defecatory disorders are characterized primarily by impaired rectal evacuation from inadequate rectal propulsive forces and/or increased resistance to evacuation 1
Normal Transit Constipation (NTC) is characterized by normal anorectal function and normal colonic transit, yet patients may still experience symptoms of constipation despite normal transit time 1
Slow Transit Constipation (STC) is characterized by normal anorectal function but slow colonic transit, with some patients having colonic motor disturbances 1
Combination disorders, such as STC with defecatory disorders, may be associated with features of irritable bowel syndrome 1

Normal bowel function involves colonic absorption of fluids and transport of waste through peristalsis, with an average colonic transit time of 20-72 hours 3
Constipation represents a disruption of these normal mechanisms 3
Abnormal colonic sensation has been described in chronic constipation and may explain symptoms like abdominal pain and bloating 1

Increasing fluid intake and dietary fiber can improve colonic transit in patients with constipation, as recommended by the American Gastroenterological Association 4
Physical activity should be encouraged as it benefits patients with constipation, according to the American Gastroenterological Association 4
Pelvic floor therapy should be offered to patients with evidence of an underlying defecatory disorder, as suggested by the American Gastroenterological Association 5
Osmotic and stimulant laxatives should be offered to patients with chronic constipation, with polyethylene glycol (PEG) as a recommended first-line treatment 5, 4
Stimulant laxatives such as bisacodyl or senna can be used to achieve one non-forced bowel movement every 1-2 days, as recommended by the American Gastroenterological Association 4

Constipation can be secondary to diseases of the colon, metabolic disturbances, and neurologic disorders, and requires a detailed clinical evaluation to diagnose 1
Opioid-induced constipation is defined as constipation triggered or worsened by opioid analgesics and requires specific management approaches, as defined by the American Gastroenterological Association and the Annals of Oncology 3, 6