Etiology

Constipation can be chronic or acute. Chronic constipation is typically classified as primary or secondary depending on the etiology. Acute constipation may be caused by lifestyle changes , hospitalization, immobility, or the acute onset of secondary causes of constipation

Subtypes

• Normal transit constipation (most common): symptoms of constipation despite normal colonic transit time

• Defecatory disorders (also known as outlet obstruction or pelvic floor dyssynergia): difficulty evacuating stool once it reaches the rectum

  • Can manifest with prolonged straining, rectal discomfort, and trouble passing even soft stools

  • May be caused by inadequate rectal propulsion, increased resistance to evacuation , or other factors

• Slow transit constipation (least common): constipation with slow colonic transit time

• Lifestyle: poor diet, insufficient physical activity, obesity

• Genetic predisposition

• Psychological and behavioral disorders

• Alterations in normal gut flora, colonic dysmotility

• External factors such as lack of exercise or inadequate fluid and fiber intake (primary constipation)/internal factors such as changes within the colon or rectum (secondary constipation) → slow passage of stool → prolonged absorption of water by the bowel → dry, hard stool → painful defecation → sensation of incomplete and irregular bowel emptying → constipation

• Effective peristalsis of the bowel is controlled by intrinsic (e.g., myenteric plexus) and extrinsic (e.g., sympathetic and parasympathetic) innervation.

• Any alteration in bowel innervation may lead to ineffective peristalsis.

  • Drugs (e.g., calcium channel blockers, opiates, antispasmodics, antidepressants) [10] → altered autonomic outflow and bowel muscle contraction [11]

  • Endocrine pathology (e.g., hypothyroidism) → downregulated bowel motility

  • Neurological pathology (e.g., spinal injury, enteric neuropathy) → disease or trauma of bowel innervation

• Ineffective peristalsis → difficult passage of stool regardless of stool consistency → sensation of incomplete and irregular bowel emptying