Constipation

Definition and EtiologyTop

Constipation refers to infrequent bowel movements (<3 per week) and/or difficult defecation with associated straining, hard stools, sensation of incomplete evacuation, or manual maneuvers.

Causes:

1) Functional/idiopathic constipation includes constipation-predominant irritable bowel syndrome (IBS) and functional constipation with associated normal colonic transit, slow colonic transit, and/or dyssynergic defecation with paradoxical contraction or lack of relaxation of the anal sphincter.

2) Diseases of the colon and small intestine: Diverticulosis, cancer or tumors, intestinal strictures due to various inflammatory diseases (Crohn disease, ulcerative colitis, ischemic inflammation, tuberculosis), hernia, intestinal torsion. Intestinal methanogen overgrowth may induce constipation and bloating.

3) Anorectal diseases: Anal stricture, cancer, hemorrhoids, anal fissure, rectal prolapse, rectal diverticulum, post neuronal blockage.

4) Drugs: Analgesics (opioids, nonsteroidal anti-inflammatory drugs [NSAIDs]), anticholinergic drugs such as antidepressants (eg, amitriptyline), antihistamines, antispasmodic and antipsychotic agents, antiepileptic drugs (eg, carbamazepine), antiparkinsonian (dopaminergic) drugs, drugs containing calcium or aluminum, iron supplements, antihypertensive agents (beta-blockers, calcium channel blockers, diuretics, clonidine), 5-HT3 receptor antagonists, oral contraceptives. Abuse of laxative agents may also cause or worsen constipation.

5) Pelvic diseases: Tumors of the ovary or uterus, endometriosis.

6) Diseases of the peripheral nervous system that may impair the colonic transit and defecation reflex: Hirschsprung disease; Chagas disease; lower back pain with impaired lumbosacral innervation of the distal colon, rectum, and anal sphincter; neuropathy associated with systemic disorders (eg, diabetes mellitus, thyrotoxicosis, chronic kidney disease, neoplasm) and systemic rheumatic diseases (systemic lupus erythematosus, mixed connective tissue disease, Sjögren syndrome, rheumatoid arthritis, vasculitis, polymyositis, systemic sclerosis and dermatomyositis); intestinal pseudo-obstruction; paraneoplastic autonomic dysfunction; post severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection.

7) Central nervous system diseases: Cerebrovascular diseases, multiple sclerosis, Parkinson disease, posttraumatic brain or spinal cord injury, spinal tumors.

8) Endocrine and metabolic diseases: Diabetes mellitus, hypothyroidism, hypopituitarism, pheochromocytoma, porphyria, uremia, hyperparathyroidism, hypercalcemia, hypokalemia.

9) Pregnancy.

10) Psychiatric disorders: Depression, anorexia nervosa.

11) Genetic disorders: Hirschsprung disease, cystic fibrosis, muscular dystrophies, familial adenomatous polyposis, multiple endocrine neoplasia syndromes, Prader-Willi syndrome, spinal muscular atrophy, Down syndrome, neurofibromatosis type 1.

DiagnosisTop

New-onset constipation requires particular diagnostic vigilance.

1. History and physical examination: Determine the frequency of bowel movements, stool consistency, duration of constipation, symptoms associated with defecation (eg, loss of bowel urgency, excessive straining, incomplete evacuation, need for manual maneuvers), coexisting symptoms (eg, fever, blood in stools, abdominal pain, vomiting), present and past illnesses, and drugs. Assess the mental status as well as the presence of symptoms of endocrine and nervous system diseases that may be accompanied by constipation. You may need to perform digital rectal examination (DRE) to assess the anal sphincter resting tone and its capability of squeezing, anal sphincter relaxation and perineal descend during straining, presence of anal fissures and ulcers, hemorrhoids, rectal bleeding, rectal mass, and rectal prolapse.

Left colon dysmotility, presenting as left colon hypertonicity and impaired defecation reflex, is common in patients with lower back pain, coccyx injury, and overlapping urologic symptoms. Clinical features of incomplete bowel movement, prolonged toilet time, difficulty passing gas, inability to pass well-formed stool, and in severe cases, intermittent symptoms of partial bowel obstruction.

Alarming symptoms increasing the risk of an organic cause of constipation include fever, unintended weight loss, blood in stool (visible or occult), anemia, abdominal mass, anal lesions, nocturnal abdominal pain that wakes the patient, and family history of colon cancer or inflammatory bowel disease.

2. Diagnostic studies:

1) Blood tests: Complete blood count (CBC); in some patients serum glucose, calcium, and thyroid-stimulating hormone (TSH) levels.

2) Fecal occult blood test (FOBT).

3) Colonoscopy is necessary for the early diagnosis of colorectal cancer in patients >50 years of age or with alarming symptoms.

4) Anorectal manometry, balloon expulsion test, defecography, and colonic transit studies using markers are sometimes performed in patients with persistent functional constipation not responding to standard management (see Management, below). Colonic manometry is recommended in patients with severe, intractable, slow-transit constipation prior to surgical interventions. Imaging studies (radiography, computed tomography [CT], magnetic resonance imaging [MRI], defecography) help identify left colon hypertonicity/luminal narrowing.

5) Rectal full-thickness biopsy in patients with suspected Hirschsprung disease.

6) Glucose hydrogen breath and methane tests for intestinal methanogen overgrowth.

3. Diagnostic criteria (Rome IV) for functional constipation:

1) Onset of constipation ≥6 months ago persisting for ≥3 months.

2) At least 2 of the following:

a) Straining during >25% of defecations.

b) Lumpy or hard stools (Bristol stool scale types 1-2 [see Figure 1 in Diarrhea]) in >25% of defecations.

c) Sensation of incomplete evacuation for >25% of defecations.

d) Sensation of anorectal obstruction or blockage for >25% of defecations.

e) Manual maneuvers to facilitate >25% of defecations (eg, digital evacuation, support of the pelvic floor).

f) Fewer than 3 spontaneous bowel movements per week.

In addition, loose stools are rare without the use of laxative agents and the criteria for IBS are not met (see Irritable Bowel Syndrome). There are also no features suggestive of an underlying organic condition (or organic causes excluded by results of diagnostic studies).

ManagementTop

Patient education plays an important role in maintaining regular bowel movements with or without pharmacologic treatment. It includes regular toilet time in the morning (waking response) and postprandially (gastrocolic reflex) and efforts to reduce dependency on laxative drugs. Treat the primary cause of constipation if possible. Treatment options address specific pathophysiology of constipation, such as prokinetics for slow colonic transit, optimizing stool consistency for dyssynergic defecation, and managing lower back pain due to left colon dysmotility.

1. Nonpharmacologic management:

1) Dietary modifications: A balanced high-calorie meal may improve colonic transit through the gastrocolic reflex. Adequate fiber, fluids, and prunes or prune juice are recommended.

2) Lifestyle modifications: Lack of regular physical activity or sedentary lifestyle and prolonged sitting may worsen constipation. Optimal management of lower back pain improves extrinsic innervation to the left colon and defecation reflex.

3) Discontinue drugs that can cause constipation (if possible).

4) Manual maneuvers: Digital disimpaction for removal of stool from the rectum, pelvic floor support during defecation in patients with rectocele or pelvic floor weakness.

5) Anorectal biofeedback training for patients with anal dyssynergia to correct inappropriate contraction of the pelvic floor muscles and external anal sphincter during defecation in patients with anal dyssynergia. To enhance the defecation reflex and continence mechanisms, regular Kegel exercises should be performed (to learn more, visit mayoclinic.org and clevelandclinic.org).

6) Noninvasive sacral neuromodulation therapy (such as transcutaneous electrical nerve stimulation) to enhance defecation reflex and to improve extrinsic innervation to the left colon. Long-term effectiveness requires further studies.

2. Pharmacotherapy:

1) Stool softeners: Docusate sodium to soften stool consistency.

2) Bulk-forming laxatives to stimulate colonic motility: Patients with intestinal stricture, megacolon, severe slow colonic transit, impaired smooth muscle contractility, or dyssynergic defecation may respond differently to psyllium and methylcellulose.

3) Osmotic laxatives (polyethylene glycol and lactulose) induce intestinal water secretion, thereby changing stool consistency and increasing stool frequency (see below).

4) Linaclotide is a minimally absorbed peptide agonist of the guanylate cyclase C receptor that stimulates intestinal fluid secretion and transit.

5) Prucalopride, a 5-HT4 receptor agonist, shows prokinetic effects to improve colonic motility.

6) Bisacodyl, a stimulant oral laxative, used only as needed to avoid dependence.

7) Tenapanor, a sodium/hydrogen exchanger 3 inhibitor, which acts locally to reduce sodium absorption from the small intestine and colon, resulting in increased intestinal lumen water secretion to soften stool.

8) Plecanatide stimulates guanylate cyclase C on the luminal surface of the intestinal epithelium to increase intestinal fluid.

9) Disimpaction: Suppositories (glycerin or bisacodyl) help to initiate the defecation reflex and empty the rectum. Enemas with warm water, mineral oil, or sodium phosphate enema (the last one should be avoided in older patients) help to lubricate stool, liquify hard stool in the rectum, and initiate the defecation reflex, emptying the rectum and overcoming obstructive defecation. For patients with severe proximal impaction, endoscopic interventions may be considered.

10) Management of severe left colon dysmotility: Optimal management of the primary causes such as lumbar spine abnormality, pinaverium (a specific calcium channel blocker of the smooth muscle cells of the gut), noninvasive sacral neuromodulation (such as transcutaneous electrical nerve stimulation) to enhance defecation reflex and to improve extrinsic innervation to the left colon.

11) Management of intestinal methanogen overgrowth.

12) Herbal medication such as senna, only as needed to avoid dependence.

3. Surgery: For patients with disabling symptoms from severe slow colonic transit who are unresponsive to medical therapy, a comprehensive assessment of pancolonic motility and its regulation systems, such as the autonomic nervous system and sacral spinal pathway, is recommended to investigate the pathophysiology in detail prior to surgical consideration, such as ileostomy, subtotal colectomy, or total colectomy.