Constipation occurs in 15% of adults and up to one-third of elderly adults and is a common reason for seeking medical attention. It is more common in women. Older individuals are predisposed due to comorbid medical conditions, medications, poor eating habits, decreased mobility, and in some cases, inability to sit on a toilet (bed-bound patients). The first step in evaluating the patient is to determine what is meant by “constipation.” Patients may define constipation as infrequent stools (fewer than three in a week), hard stools, excessive straining, or a sense of incomplete evacuation. Table 15–3 summarizes the many causes of constipation, which are discussed below.
Table 15–3.Causes of constipation in adults. |Favorite Table|Download (.pdf) Table 15–3. Causes of constipation in adults.
Inadequate fiber or fluid intake
Poor bowel habits
Endocrine: hypothyroidism, hyperparathyroidism, diabetes mellitus
Metabolic: hypokalemia, hypercalcemia, uremia, porphyria
Neurologic: Parkinson disease, multiple sclerosis, sacral nerve damage (prior pelvic surgery, tumor), paraplegia, autonomic neuropathy
Calcium channel blockers
Calcium and iron supplements
Anorectal: rectal prolapse, rectocele, rectal intussusception, anorectal stricture, anal fissure, solitary rectal ulcer syndrome
Colonic mass with obstruction: adenocarcinoma
Colonic stricture: radiation, ischemia, diverticulosis
Slow colonic transit
Idiopathic: isolated to colon
Chronic intestinal pseudo-obstruction
Pelvic floor dyssynergia
Irritable bowel syndrome
Most patients have constipation that cannot be attributed to any structural abnormalities or systemic disease. Some of these patients have normal colonic transit time; however, a subset have slow colonic transit or defecatory disorders. Normal colonic transit time is approximately 35 hours; more than 72 hours is significantly abnormal. Slow colonic transit is commonly idiopathic but may be part of a generalized gastrointestinal dysmotility syndrome. Patients may complain of infrequent bowel movements and abdominal bloating. Slow transit is more common in women, some of whom have a history of psychosocial problems (depression, anxiety, eating disorder, childhood trauma) or sexual abuse. Normal defecation requires coordination between relaxation of the anal sphincter and pelvic floor musculature while abdominal pressure is increased. Patients with defecatory disorders (also known dyssynergic defecation)—women more often than men—have impaired relaxation or paradoxical contraction of the anal sphincter and/or pelvic floor muscles during attempted defecation that impedes the bowel movement. This problem may be acquired during childhood or adulthood. Patients may complain of excessive straining, sense of incomplete evacuation, or need for digital manipulation. Patients with primary complaints of abdominal pain or bloating with alterations in bowel habits (constipation, or alternating constipation and diarrhea) may have irritable bowel syndrome.
B. Secondary Constipation
Constipation may be caused by systemic disorders, medications, or obstructing colonic lesions. Systemic disorders can cause constipation because of neurologic gut dysfunction, myopathies, endocrine disorders, or electrolyte abnormalities (eg, hypercalcemia or ...