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Historically less than 2-3 bowel movements/week; Excessive difficulty straining at defecation
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Rome III for functional constipation: see below under Diagnostic Studies
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Dyschezia: difficulty in defecating
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5-30% of population report symptoms; Prevalence increases with age
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Causes
Example
Idiopathic/Functional
Chronic idiopathic: Impaired colonic transit, IBS
Structural
Colonic or anorectal: cancer, stricture
Metabolic/Endocrine
Hypokalemia, Hypercalcemia, Hypocalcemia, Uremia, Hypothyroid, DM
Collagen vascular disorders
Scleroderma, Amyloidosis
Inherited muscular disorders
Familial visceral myopathy
Colonic disorders
Colonic inertia
Enteric neuro disorders
Hirschsprung’s, Chronic intestinal pseudo-obstruction
Nonenteric neuro disorders
Parkinson’s, Spinal cord injury, MS, Scleroderma (fibrotic/non-contractile)
Anorectal disorders
Anal stricture, Rectocele
Psychological
Anorexia nervosa
Medications
Opiates & antihypertensives such as calcium channel blockers (most common causes), antacids (calcium, aluminum), anticholinergics, antispasmodics, anticonvulsants, antidepressants, diuretics, iron
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Classification based upon transit time:
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Normal transit constipation: perception of disordered evacuation; Fiber supplementation may help
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Slow transit constipation: malfunction of neural network; i.e. infection, endocrine, drug, scleroderma; Fiber may worsen
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Obstructive defecation: mechanical; i.e. Hirschsprung’s, Pelvic floor dysfunction; Fiber may worsen
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Anorectal dysfunction:
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Anismus/spastic pelvic floor syndrome: spasticity of levator ani, abnormal angulated rectoanal axis; Functional problem
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Impaired rectal sensation: decrease in urge to defecate
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Megarectum: long-term fecal impaction, often seen in children, physically/mentally impaired elderly; Occasionally with neuro disorder
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Rectocele: stool directed away from anal canal into rectocele during straining, leading to retention of feces in pouch
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The colon absorbs approximately 100 mL of fluid and 1 mEq of sodium and chloride from 1,500 mL of chyme daily
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If necessary, the absorptive capacity can increased to 5-6 L and 800-1000 mEq of sodium and chloride per day
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Healthy subjects: average mouth-to-cecum time is 6 hrs, average transit through right, left and sigmoid colon is 12 hrs each (36 hrs total)
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Normally:
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First sensing in rectum via stretch receptors in the muscularis propria initiate a spinal reflex arc: relaxation of internal anal sphincter
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Then relaxation of striated muscles of pelvic floor (puborectalis, pubococcygeus), rectoanal angle opens from 90 to 130°
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Final relaxation of external anal sphincter and passage of stool, often with concomitant diaphragm & abdominal muscle contraction
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