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Constipation           See also constipation_rx.pdf    

* Passage of material from the cecum through the colon to the rectum ordinarily takes about 24 hours.
   Defecation involves peristaltic waves, relaxation of the pelvic floor muscles & the external anal sphincter.

Possible mechanisms of constipation include excessive absorption of fluids, impaired evacuation, & slow colonic transit (colonic inertia).  

Possible Causes of chronic constipation:

• Functional - IBS (Irritable Bowel Synd)  
• Drugs - barium,  opiates, iron pill, calcium pill, calcium blockers, anticholinergics, antidepressants, antiparkinsonian agents, diuretics, NSAID, etc.
• Mechanical - neoplasms, rectal intussusception or prolapse, rectocele
• Metabolic - hypothyroidism, hypercalcemia, diabetes
• Neurogenic - intestinal pseudo-obstruction, multiple sclerosis, Parkinson's disease, Hirschsprung disease (aganglionosis)
• Others - pregnancy, slow colonic transit (colonic inertia), pelvic floor dysfunction, chronic laxatives use, collagen-vascular diseases.

Diagnostic Approach:

1. History & physical examination
2. Lab. tests: CBC, TSH, lytes, calcium, glucose, creatinine, fecal occult blood, barium enema x-ray, sigmoidoscopy or colonoscopy.
3. Colonic transit test with high-fiber diet & ingestion of markers, then x-ray for several days; anorectal manometry; air or water-filled balloon expulsion test; defecography with artificial stool in the rectum.
   * Colonic Transit Test is studied by giving patients radiopaque markers orally & performing radiographic studies daiy or 5-7 days later.  A total transit time of up to about 70 hours is condidered normal.  

Treatment Options:

• Bulk-forming laxatives as dietary or synthetic fiber promote peristalsis & reduce transit time.  The biggest disadvantage is bloating.
• Sorbitol & lactulose are carbohydrates that have an osmotic effect.  They increase the water content of & soften the stool.  The advantage is gas.
• PEG solution as Golytely or Colyte are used as laxatives.  They have an unplesant salty taste.
  MiraLax is a new dry powder form of PEG without electrolytes approved for use by adults for occasional constipation.  It is soluble in water & forms a tasteless solution.
• Mineral oil, a lubricant laxative that inhibits water absorption in the colon, is not particularly useful compared with the alternatives.  There is a danger of aspiration & lipid pneumonitis in elderly patients with impaired swallowing mechanisms or reflux.
• The saline laxative Milk of Magnesia - for a more rapid onset of effect.  The magnesium has an osmotic effect that causes water retention in the colon as well as a cathartic effect.
• Bisacodyl (a diphenylmethane) - the stimulant laxative.
• Anthraquinone (senna, cascara sagrada, aloe, frangula) are mild laxatives.  They may cause melanosis coli.  They also may cause pink, red, brown, or black discoloration of the urine.
• Tegaserod, a partial 5-HT4 agonist, accelerated colonic transit in pts with constipation-predominat irritable bowel syndrome.
  Prucalopride, a selective & specific 5-HT4 agonist, accelerated proximal colonic transit.  Adverse effects included headache, nausea, flatulence, & diarrhea.

Empirical Rx Steps:

1. Adequate hydration & dietary fiber intake (25-35 g/d), exercise, dedicated time for bowel movements
2. Processed or synthetic fiber as  Metamucil powder (psyllium), methylcellulose
   Stool softeners as Docusate-Na  (Colace)100-200 mg 1-2x/d, docusate-Ca (Surfak) 240 mg 1-2x/d, mineral oil 15-45 mL/d.  
3. Osmotic laxatives:
   Mg-sulfate 15-45 mL/d, Mg-citrate 200 mL/d, Fleet Phospha-soda 20-45 mL prn, Lactulose 5-60 mL 1-2/d, Sorbitol 70% 15-60 mL 1-2x/d, Poly-ethylene glycol PEG solution (GoLytely or Colyte) 300-1,000 mL up to 2 L/d or
   MiraLax powder is a new dry powder form of PEG without electrolytes approved for use by adults for occasional constipation.  It is soluble in water & forms a tasteless solution.
4. Stimulant laxatives:
   Senna (Senokot) 8.6-17 mg 1-2x/d,  Disacodyl (Dulcolax, Correctol ) 5 mg tab 2 tab/d or 10 mg supp/day, or phenolphthalein  (Alophen pill) or anthraquinone compounds, to promote colonic secretion & motility

RX of Fecal Impaction:

• Manual removal with local anesthetic lubricant use
• Enema - oil retention, tap water
• Suppositories - glycerin or bisacodyl (Dulcolax)
• Miscellaneous - polyethylene glycol solution (GoLytely, Colyte), water-soluble contrast media enema                       

REF:
Cleveland Clinic Journal of Med 1/1999;66:41 - Edy Soffer
Mayo Clin Proc 9/1998;73:881 - Charlene Prather

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The Tome II  Diagnostic Criteria for Constipation:
At least 12 weeks, which need not be consecutive, in the preceding 12 months of two or more of the following:

1. Straining in more than 1 of 4 defecations.
2. Lumpy or hard stools in more than 1 of 4 defecations
3. Sensation of incomplete evacuation in more than 1 or 4 defecations
4. Sensation of anorectal obstruction/blockade in more than 1 of 4 defecations
5. Manual maneuvers to facilitate more than 1 in 4 defecations (e.g. digital evacuation, support of the pelvic floor) and/or
6. Less than 3 defecations/week
   * Loose stools are not present, and there are insufficient criteria for irritable bowel syndrome.

The Rome II Criteria for Irritable Bowel Syndrome:
At least 12 weeks, which need not be consecutive, in the preceding 12 months of abdominal discomfort or pain that has 2 of 3 features:

1. Relieved with defecation; and/or
2. Onset associated with a change in frequency of stools; and/or
3. Onset associated with a change in form (appearance) of stool.

The following symptoms cumulately support the diagnosis of irritable bowel syndrome:

• Abnormal stool frequency (>3 times per day or < 3 times per week)
• Abnormal stool form (lumpy/hard or loose/watery stools
• Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation)
• Passage of mucus
• Bloating or feeling of abdominal distention.