DDx (med/ surg) constipation + ab pain

Constipation

Common causes

  1. Low-fibre diet
  2. Inadequate fluid intake/ dehydration
  3. Immobility/ lack of PA
  4. Irritable bowel syndrome
  5. Old age
  6. Post-op pain
  7. Hosp env (¯ privacy, bed pan)

Anorectal disease

  1. Anal fissure
  2. Anal stricture
  3. Rectal prolapse

Intestinal obstruction

  1. Strictures (eg. Crohn's)
  2. CRC
  3. Pelvic mass (eg. foetus, fibroids)
  4. Diverticulosis (but rectal bleeding commoner)
  5. Congenital abn
  6. Psuedo-obstruction

Metabolis/ Endocrine

  1. Hypothyroid
  2. Hyper-Ca++
  3. Hypo-K+
  4. Porphyria
  5. Lead poisoning

Drugs

  1. Opiate analgesics (eg. morphine, codeine)
  2. Anticholinergics (eg. tricyclics, phenothiazines)

NM

  1. Spinal/ pelvic n inj
  2. Aganglionosis (eg. Chaga's, Hirschsrpung's dis)
  3. Systemic sclerosis
  4. DM neuropathy

Other

  1. Chronic laxative abuse (diarrhoea commoner)
  2. Idiopathic slow transit
  3. Idiopathic megarectum/ colon

Tx of Constipation

  1. Treat cause
  1. High fibre diet
  2. ­ fluid intake (exc. Obstruction, megacolon, inertia/hypotonia)
  3. PA
  1. Drugs (only if above fails, short dur only)
  1. Bulking agents: ­ faecal mass ® (+) peristalsis, taken with ­ fluid (not 4: difficulty swallowing, obstruction, atony, impaction)
  2. Stool softeners: arachis oil enemas lubricate and soften (liquid paraffin short dur only - S/E: anal seepage, lipoid pneum, malabsorption of fat-sol Vits)
  3. Osmotic laxatives: retain fluid and bowel (eg. Lactulose - semi-synthetic disacc; Mg salts) (avoid Na salts - cause Na+ and water retention)
  4. Stimulant laxatives: ­ intestinal mobility (not for obstruction), prolonged use - atony, hypo-K+