How can constipation be characterized.
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
Describe the primary constipation (functional constipation).
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
List risk factors for primary constipation.
Lifestyle: poor diet, insufficient physical activity, obesity
Psychological and behavioral disorders
Alterations in normal gut flora, colonic dysmotility
Describe the mechanism of altered stool consistency.
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
Describe the mechanism of altered bowel motility.
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)  → altered autonomic outflow and bowel muscle contraction 
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