1. 
   

   What are the risk factor(s) for developing constipation in the hospital?

   
   
2. 
   

   How do you prevent constipation in a hospitalized patient with a history of constipation?

   
   
3. 
   

   What are the likely causes of new constipation in a hospitalized patient?

   
   
4. 
   

   What is the treatment of common causes of new constipation?

Constipation has many meanings, but for the purposes of this chapter, the medical definition of constipation includes one or all of the following: fewer than three bowel movements per week; passing hard, lumpy stools; straining with defecation; or having a sense of incomplete evacuation. Constipation can newly arise in a patient hospitalized for other medical reasons, represent an exacerbation of a chronic problem, be the principal reason for hospitalization, or be a manifestation of an acute, possibly catastrophic, event.

Chronic constipation is a common complaint that compromises quality of life and frequently prompts use of health care services. Constipation results in 2.5 million physician visits and 92,000 hospitalizations per year in the United States. The prevalence of constipation in North America is estimated to range from 2% to 27%, with most studies citing a prevalence of 15%. This variation in prevalence reflects different diagnostic criteria for constipation and study design. The estimated prevalence of constipation in other developed countries is similar to that in North America at 17.1% in Europe, 14.3% in Hong Kong and 16.5% in South Korea. Constipation is reported more often by females (2-3:1 predominance), nonwhites, individuals of lower socioeconomic status, and the elderly (prevalence of 20%–24%). The cumulative incidence of constipation over more than 1 decade is about 1 in 6. This incidence increases dramatically in the setting of certain comorbidities.

Although most individuals with constipation do not specifically seek medical care constipation contributes significantly to health care expenses. In the United States, the total health care cost of constipation diagnosis per patient exceeds $2500, and in 2001, $235 million dollars were spent for constipation, with more than half of the cost incurred from inpatient care. In the California Medicaid program, 0.6% of patients presenting to a physician with a medical complaint of constipation were admitted to a hospital, averaging almost $3000 per admission. This chapter will discuss how to distinguish, evaluate, and manage the conditions in which constipation occurs.

The pathophysiology of constipation can be understood first by a very brief review of the elements required for normal colonic transit and defecation. Normal colonic transit requires segmental activity and propagated activity, which depends on both low-amplitude and high-amplitude propagated contractions. Normal defecation requires intact pelvic floor muscles and rectal compliance. The muscles of the pelvic floor include the internal anal sphincter, the external anal sphincter, and the puborectalis muscle. The internal sphincter muscle, which is tonically contracted, is innervated by the enteric nervous system. The external sphincter and puborectalis muscles are innervated by the pudendal nerves (S2, S3, and S4). During defecation, both must relax in order for normal defecation to occur. The puborectalis muscle forms a U-shaped sling around the rectum, and when contracted maintains the rectum at a 90 degree angle (that is, perpendicular) with respect to the anal canal. This muscle must relax with voluntary defecation so the angle can widen to 135 degrees to allow unobstructed passage of stool from the rectum to the anal canal. Medications, medical illness, prior surgery, and other factors can diminish colonic contractions, contribute to pelvic floor weakness, alter rectal compliance, or cause obstruction.

New constipation commonly arises in hospitalized patients and has been attributed to multiple causes (Table 78-1). Lack of physical activity, change in diet, electrolyte disturbances, use of anesthetics and narcotics, medication side effects, and failure to continue the home laxative regimen may precipitate constipation. In the elderly, acute hospitalization further increases the prevalence of constipation in an already susceptible age group, with one-third of hospitalized geriatric patients requiring laxatives 3 times daily. The incidence of new-onset constipation at 4 weeks after a first stroke exceeds 50%. The incidence of constipation among cancer patients is 60%, but increases to 87% in those using opioids. Constipation can also be part of a symptom complex representing a serious, acute event. If abdominal distention, high-pitched bowel sounds, and pain are present, then colonic obstruction must be considered. Accompanying fever and rebound tenderness should trigger an evaluation for perforation.

The patient’s history is essential to identify the cause of constipation and its management. It is important to define the duration of constipation, the frequency of bowel movements, whether there is incomplete evacuation, straining, or passage of hard (scybalous) stool. Associated symptoms may suggest a cause for constipation. Blood or mucus in the stool may indicate an obstructive process, anal fissure, rectal prolapse, or hemorrhoids. Tenesmus suggests hard stool or possibly rectal obstruction. Overflow fecal incontinence or mental status changes can be presenting symptoms of fecal impaction in elderly patients.

Important elements of the past medical history include an obstetric and surgical history. A thorough review of all medications can reveal a drug-related cause of constipation. Common culprits of constipation-induced medications include prescription medications (opiates, anticholinergics, and calcium-channel blockers), over-the-counter drugs, and herbals (Table 78-2). In the elderly, home use of laxatives is the only identifiable risk factor for developing constipation in the hospital. A family history of bowel disorders should be sought. The social history should explore physical activity and dietary habits, including amount of fiber intake, fluid intake, number and timing of meals, and dehydration. Red flags for a serious underlying etiology of constipation include weight loss, abdominal pain, rectal bleeding, iron deficiency anemia, or a significant family history of colon cancer. Complaints of severe pain with abdominal distention could signal colonic obstruction or intestinal ischemia with potentially life-threatening complications.

A complete physical exam searching for signs of a systemic illness is essential, although it is often unrevealing. In particular, the abdominal exam should focus on palpating for stool in the left or right lower quadrant. Severe abdominal distention, high-pitched bowel sounds, and tenderness to palpation are suggestive of an obstructive etiology. Evaluation of the patient may sometimes reveal a fecolith palpable through the abdominal wall or on digital examination of the rectum. A complete neurologic examination may provide evidence of occult neurologic disease such as Parkinson disease. The anorectum should be inspected for hemorrhoids, anal fissures, skin tags, or rectal prolapse. If cauda equina syndrome is suspected, perineal sensation can be evaluated by using a Q-tip or sharp point of a pin to gently stroke all quadrants. An anocutaneous reflex (“anal wink”) can be elicited by stroking the perineal skin; the absence of reflex contraction of the external anal sphincter would suggest a neuropathy. The digital rectal examination can evaluate sphincter tone, the contents of the rectal vault, and allow detection of blood in the stool. Fever, tachycardia, and other signs of hemodynamic instability are clues to complications of perforation or ischemia.

Pertinent laboratory tests in the evaluation of constipation include a complete blood count, electrolytes, including calcium, phosphorous, and magnesium, blood urea nitrogen, creatinine, glucose, and thyroid function tests. Other laboratory tests, such as serum protein electrophoresis, urine porphyrins, serum parathyroid hormone, and evaluation for adrenal hypofunction should be considered, if indicated by history or physical exam.

Diagnostic imaging is not a necessary component of every evaluation of constipation, but can provide critical information in the right clinical scenario. In patients with abdominal distention, pain, and constipation, plain abdominal radiography can be helpful in assessing the degree of constipation and ruling out obstruction. Abdominal radiographs may demonstrate a dilated colon or small bowel with air fluid levels indicative of obstruction. Plain abdominal radiographs can also help diagnose a sigmoid or cecal volvulus. The presence of free air on plain abdominal radiograph would indicate perforated bowel (see Chapter 109 Plain Abdominal Imaging).

If abdominal radiography demonstrates colonic dilatation suggestive of an obstruction, additional imaging should be performed. A flexible sigmoidoscopy or colonoscopy, barium enema, or CT scan can help define a colonic obstruction. Flexible sigmoidoscopy and colonoscopy can also identify a mucosal lesion, such as a malignancy or stricture. The timing of the latter studies would depend on the risk of perforation from performing the study. For example, acute diverticulitis causing obstruction would require treatment prior to performing a colonoscopy to rule out the possibility of an occult cancer underlying the inflammation.

Differential Diagnosis of Acute Constipation

Fecal Impaction

Impaction of feces occurs in children, institutionalized individuals, and the elderly, and sometimes as a complication of opioid use. Large calcified fecoliths as well as seed bezoars have caused large bowel obstruction. Treatment of fecal impaction requires aggressive management since impaction may lead to urinary tract obstruction, perforation of the colon, dehydration, electrolyte imbalance, renal insufficiency, fecal incontinence, decubitus ulcers, stercoral ulcers, and rectal bleeding. Treatment of fecal impaction in part depends on where the impaction is located. Fecal impaction may require urgent manual disimpaction, especially in the elderly, a population in whom risk factors of immobility, dehydration, and multiple medications predispose it to complications of mental status changes, agitation, and worsening confusion.

In the left colon, manual disimpaction may be followed by enemas, which work primarily by stimulating rectal propulsion in this situation. Soapsuds enemas (composed of 6 grams castile soap/liter) are chemical irritants and promote intestinal fluid secretion. There are rare reports of colitis after administration of soapsuds enemas for more than 5 days in a row. Hypertonic solutions, like sodium phosphate, work by osmosis, drawing water into the lumen. Sodium phosphate enemas should be used with caution, because retention of the enema in the absence of defecation can lead to dehydration, hyperphosphatemia, and acute renal failure.