Definition
There is no single definition for constipation. It can be described as hard stools, infrequent stools (<3/week), need for excessive strain while stooling or the feeling of incomplete evacuation.
Etiology and Risk Factors
- Small or Large bowel obstruction:
- Volvulus, intra-abdominal adhesions, or masses
- Ileus
- Medication related:
- Opioids
- Calcium channel blockers
- Metabolic disturbances: hypothyroidism, hypercalcemia
- Pelvic floor muscle and anal sphincter dysfunction
- Fecal impaction
- Irritable bowel syndrome
- Slow transit constipation: common in young women, delayed emptying of the proximal colon often.
- “Functional” constipation: have a normal colonic transit time.
Evaluation and Differential Diagnosis
- Evaluate for potential medication related causes (opioids, anticholinergics, iron)
- Is the patient on a bowel regimen if they are on chronic opioids?
- Does the patient pass flatus?
- When was the last bowel movement?
- Consider a rectal exam and abdominal x-ray to evaluate for obstruction if there is a suggestion of bowel obstruction or the patient has had prolonged constipation or new abdominal pain.
Management
- Bulk Laxatives: psyllium, methylcellulose
- Osmotic laxatives: sodium phosphate, magnesium citrate, magnesium hydroxide
- Poorly absorbed sugars: lactulose, sorbitol, polyethylene glycol and electrolytes (Go-lytely), polyethylene glycol 3350 (Miralax).
- Stimulant laxatives: senna, castor oil, mineral oil and bisacodyl.
- Docusate, though popular, is ineffective.
- Enema/suppository: Phosphate enema (Fleet), tap-water (500cc/day), lactulose retention enema, bisacodyl suppository.
- Avoid fleet enemas in patients with CKD.
- Manual disimpaction is often required to help remove stool from the bowel.
Key points
- “Afterload before preload”: suppository/enema before stimulant.
- All patients on chronic opioids should be on a bowel regimen including stool softeners and stimulant laxatives.
- A reasonable starting regimen to treat uncomplicated constipation is senna and miralax; if not effective, add bisacodyl suppository, an enema, and/or manual disimpaction.
- Exercise caution before adding powerful oral laxatives such as lactulose or Mg citrate for a patient with refractory constipation. First examine the patient; if the abdomen is firm or distended, obtain a KUB to rule out bowel obstruction.
- Methyl-naltrexone can be helpful for refractory opioid induced constipation.
Lembo, A; Camilleri, M. “Chronic Constipation.” New England Journal of Medicine.349:14, 1360-68.
Pandolfino JE, Howden CW, Kahrilas PJ. Motility-modifying agents and management of disorders of gastrointestinal motility. Gastroenterology 2000;118(2 Suppl 1):S32-47.