Anne-Marie Boller, MD and Joel M. Sternbach, MD, MBA
You are called to the bedside of a 79-year-old male patient for evaluation of his altered mental status. The patient is a nursing home resident, now POD 3 from a right total hip replacement, with complaints of abdominal distention and diffuse crampy abdominal pain for two days. There is no record of him having had a bowel movement since being admitted from his nursing home four days ago. A review of the patient’s medication list reveals the addition of acetaminophen/hydrocodone for pain control. He was started on a general diet and his home verapamil, furosemide, and clonidine today but was not given any of his home over-the-counter medications (including Miralax and Metamucil). There is no nausea or vomiting, vital signs are WNL and stable, and the patient has adequate urine output. He is passing flatus on a regular basis. On examination, his abdomen is distended but soft and mildly tender to palpation diffusely.
1. What should be included in the initial evaluation of this patient?
2. What additional testing (labs, imaging) could help guide your management?
3. What are your options for treating constipation? Given their mechanisms, which would you choose for this patient?
4. You are concerned that the patient might have a fecal impaction. How do you diagnose and treat this condition? What prophylactic measures could have been taken to prevent this?
Constipation as described by individual patients varies widely but is generally defined by decreased frequency (less than 3 bowel movements per week) and/or symptoms such as straining, passage of lumpy or hard stool, sensation of blockage or obstruction, need for manual assistance (digitations or splinting), and sensation of incomplete evacuation (in >25% of stools).
Rome III criteria provide some standardization when enrolling patients in clinical trials.
Rome III Criteria for Functional Constipation
Diagnostic criteria (criteria fulfilled for the past 3 months with symptom onset at least 6 months prior to diagnosis):
1. Must include 2 or more of the following:
A. Straining during at least 25% of defecations
B. Lumpy or hard stools in at least 25% of defecations
C. Sensation of incomplete evacuation for at least 25% of defecations
D. Sensation of anorectal obstruction/blockage for at least 25% of defecations
E. Manual maneuvers to facilitate at least 25% of defecations (eg, digital evacuation, support of the pelvic floor)
F. Fewer than 3 defecations per week
2. Loose stools are rarely present without the use of laxatives.
3. Insufficient criteria for irritable bowel syndrome.
At-risk populations include the elderly, especially hospitalized or nursing home residents, and women, who are diagnosed 3 times more commonly than men. A western diet, low in dietary fiber, and inadequate fluid intake combined with prolonged immobility or a generally sedentary lifestyle all contribute to the development of constipation.
Other common causes of constipation include:
1. Medication side effects:
A. Opiates—slow transit causing increased desiccation of stool
B. Antihypertensives, especially calcium channel blockers (verapamil)
C. Diuretics (furosemide)
D. Anticholinergics (including antihistamines and many antidepressants)
E. Iron supplements
F. Antacids with calcium or aluminum, calcium supplements
G. Antidiarrheal agents
H. Long-term laxative use/abuse
2. Medical conditions:
E. Spinal cord injury
3. Structural abnormalities:
A. Prior abdominal surgery causing adhesions
B. Pregnancies or history of obstetric surgery
C. Colonic stricture due to cancer, IBD, or radiation exposure
1. The evaluation of the patient should start with a comprehensive history, focusing on establishing the onset and duration of symptoms. Constipation can be the first symptom and/or accompanying symptom of a bowel obstruction. Bowel obstructions must be thought of as organic in origin or functional in origin. Organic causes typically present acutely and can indicate the need for early imaging:
2. Colorectal cancer
4. Sigmoid or cecal volvulus
6. Fecal impaction
7. Foreign body
Functional causes are typically more chronic and warrant a more extensive outpatient evaluation:
1. Normal-transit constipation
2. Slow-transit constipation
3. Outlet obstruction/constipation (pelvic floor dysfunction)
Alarm or “red flag” symptoms in addition to constipation include acute onset, nausea or vomiting, fever/chills, change in stool quality (caliber or consistency), inability to pass flatus (obstipation), severe abdominal pain and distention, unintended weight loss (>10 lb), rectal bleeding or melena, unexplained iron-deficiency anemia, or age >50 years with no prior screening for colorectal cancer with or without a family history of colon cancer. These “red flag” symptoms must be reviewed in the historical examination; they may indicate an organic cause for the patient’s constipation.
After the history is complete, a thorough physical examination should include an assessment of the patient’s general clinical condition and review of vital signs and should focus on an abdominal examination. All abdominal examinations should assess for distention, tenderness, or tympani, rule out hernias or masses, and evaluate for signs of peritonitis. Bowel sounds are generally decreased in slow gut transit and increased or high-pitched in obstruction. External examination of the perianal region can identify anal fissures, hemorrhoids, abscesses, or protruding masses. Results of a digital rectal examination should include the following:
1. Description of the amount and consistency of stool in the rectum
2. Palpation for rectal masses
3. Identification of gross blood or stool leakage
4. Testing of the ability to contract/relax the anal sphincter voluntarily
2. Laboratory evaluation should include a complete blood count and basic chemistry panel to screen for anemia and identify hypomagnesemia, hypercalcemia, and hypokalemia. Thyroid function tests for suspected hypothyroidism and serum lead and iron levels are also useful in evaluating the patient.
Early imaging may be considered in demented or delirious patients with constipation, as the history and physical examination may not be adequate to rule out obstruction. Plain films (KUB or acute abdominal series) may reveal megacolon or megarectum in patients with stricture or obstructing mass and can delineate the extent of fecal impaction. Evidence of bowel obstruction and perforation may also be obvious on plain films (see Figure 39-1).
Figure 39-1. Plain film with dilated loops of bowel and, more ominously, free intraperitoneal air.
A water-soluble contrast enema with Gastrografin (diatrizoate meglumine) or Hypaque (diatrizoate sodium) can pass an impacted area and evaluate for a more proximal mass, stricture, or perforation. It can also be therapeutic in cases of fecal impaction.
A CT scan will assist in evaluation of any obstructing mechanical or inflammatory process. If these have been ruled out, it is most efficacious to get the patient’s colon cleared of fecal debris and perform a colonoscopy, but this is not always possible in the patient with functional constipation.
3. The first step in almost all patient populations is optimizing modifiable dietary and lifestyle factors. These include:
1. Increasing dietary fiber to a goal of 20 to 30 g daily
2. Ensuring adequate fluid intake with at least 6 to 8 glasses (1.5-2 L) of water daily
3. Encouraging ambulation/regular exercise
4. Correcting underlying electrolyte/metabolic abnormalities (and determining their cause):
F. Hyperglycemia (DM)
5. Reviewing all medications for their constipation effects
6. Reviewing all past and current medical/surgical problems for their possible constipating effects
After optimizing dietary, lifestyle, and behavior factors, medications can often be helpful in addressing the problem of functional constipation. There are many different mechanisms and types of laxatives that are utilized in the treatment of constipation:
Bulk laxatives—these work by colonic distention, triggering peristalsis:
1. Psyllium (Metamucil) 1 tbsp BID—hygroscopic husks absorb water and become mucilaginous (jello-like).
2. Methylcellulose (Citrucel).
3. Calcium polycarbophil (Fibercon).
4. Guar gum (Benefiber).
Osmotic laxatives—as a class, these act as hyperosmolar agents, drawing water into the lumen of the intestine as well as stimulating colonic activity via cholecystokinin:
1. Lactulose/70% sorbitol—poorly absorbed sugars:
A. Sorbitol is sweeter than sucrose with ~1/3 fewer calories.
B. Sorbitol is significantly less expensive than lactulose.
C. Lactulose converts ammonia to nonabsorbable ammonium ion.
2. Magnesium salts:
A. Magnesium ions stimulate the activity of nitric oxide (NO) synthase and increase levels of the proinflammatory mediator platelet activating factor (PAF) in the GI tract.
B. NO may stimulate intestinal secretion via prostaglandin- and cyclic GMP–dependent mechanisms while PAF produces significant stimulation of colonic secretion and gastrointestinal motility.
C. Can cause hypermagnesemia and hypocalcemia.
3. Sodium salts:
A. Phospho-soda (OsmoPrep).
B. Fleet Enema (sodium phosphate)—can cause hyperphosphatemia and hypocalcemia.
4. Polyethylene glycol 3350 (Miralax):
A. Seventeen grams in 8 oz liquid once or twice daily.
B. Safe in renal failure.
Stimulant laxatives—these alter water and electrolyte transport in the colon and increase colonic motility by causing low-grade inflammation in the colon through activation of prostaglandin/cyclic AMP and NO/cyclic GMP pathways:
1. Bisacodyl (Dulcolax)—diphenylmethanes inhibit water absorption in the small intestine and act via direct parasympathetic stimulation of mucosal sensory nerves, increasing peristaltic contractions.
2. Senna extracts (Ex-lax, Senokot)—anthraquinones act on enteric neurons and intestinal muscle to produce giant migrating colonic contractions in addition to stimulating water and electrolyte secretion.
3. Importantly, perforation and obstruction must be ruled out prior to giving stimulant laxatives!
Emollient laxatives—these act as stool softeners and are more effective in conjunction with stimulant laxatives:
1. Docusate sodium (Colace).
2. Glycerin suppository—exerts a hyperosmotic effect drawing water into the rectum; allows water and fat to penetrate the fecal mass.
3. Mineral oil:
A. Poor oral choice.
B. Aspiration causes lipoid pneumonia; depletes fat-soluble vitamins.
C. Lubricates stool when given as an enema.
4. Soapsuds enema—should not be used due to irritation of the colonic mucosa and risk for hemorrhagic colitis.
1. Methylnaltrexone (Relistor):
A. Mu-opioid antagonist that does not cross the blood–brain barrier.
B. Indicated only for opioid-induced constipation.
2. Lubiprostone (Amitiza)—bicyclic fatty acid, activates type II chloride channels in the apical membrane of the GI epithelium resulting in increased secretion of chloride and subsequently water:
A. Contraindicated in pregnancy.
4. Fecal impaction: a firm mass of immovable stool in the rectum or distal colon; relatively common in the elderly, especially the bed-bound nursing home population. In one study, fecal impaction was found to be responsible for 55% of cases of diarrhea in hospitalized elderly patients (see Figure 39-2A and B).
Figure 39-2. (A and B) CT images of a patient with fecal impaction and a hx of stercoral colitis.
Steps in manual disimpaction:
1. Consider analgesia and/or sedation.
2. Position the patient in the lateral decubitus or dorsal lithotomy position.
3. Soften impaction with mineral oil enema or glycerin suppository.
4. Lubricate impaction.
5. Break up impaction with scissoring motion of 2 fingers.
6. Can follow with tap water or sodium phosphate enema.
7. Start regular bowel regimen to prevent recurrence.
Impaction of stool may be prevented by following a high-fiber, fluid-rich diet; getting regular exercise; limiting intake of constipating drugs; routinely using stool softeners or laxatives; and learning biofeedback and habit training.
TIPS TO REMEMBER
More than 50% of patients taking narcotic pain relievers will develop dose-dependent constipation. A reasonable prophylactic regimen includes a combination of a bulking agent and a stimulant laxative.
Plain films of the abdomen can reveal impacted stool, dilated proximal loops of bowel, air–fluid levels, and the presence of free intra-abdominal air (in the case of perforation). The normal maximal diameter of the colon is 6 cm and that of the rectum is 4 cm.
Manual disimpaction involves softening, lubricating, and fragmenting the hardened stool.
1. Which of the following is contraindicated in patients with renal failure?
B. Sodium phosphate (Fleet Enema)
D. Polyethylene glycol
2. Which of the following is not associated with constipation?
1. B. Sodium phosphate can cause hyperphosphatemia. In high-risk patients, it can cause an acute nephropathy.
2. D. Although a treatment for diarrhea caused by C. difficile colitis, metronidazole is more commonly implicated in antibiotic-associated diarrhea itself.