CHAPTER 21. CONSTIPATION
Debra E. Heidrich
DEFINITION AND INCIDENCE
Constipation is an extremely common problem among palliative care patients. Patients with constipation often experience abdominal discomfort, cramping, and distention as well as nausea. Unresolved constipation leads to fecal impaction—a large amount of hard, dry feces that accumulates in the rectum and sigmoid colon and cannot be evacuated—and, potentially, obstipation, a functional bowel obstruction from constipation or impaction. Patients who associate constipation with the use of opioids or other medications may discontinue or decrease these medications, leading to uncontrolled symptoms and additional discomfort. As such, proper and timely management is crucial.
In the general population, the incidence of constipation may range from 5% to 20%. Studies of patients with advanced cancer and other terminal illness indicate the incidence of constipation ranges from 32% to 87% (Potter, Hami, Bryan et al., 2003; Sykes, 1998, 2004; Wirz & Klaschik, 2005). Some of this variation is likely due to the proportion of the study population using opioids. However, Sykes (1998) reported that 64% of hospice patients who were not receiving opioid analgesia had constipation. Other factors contributing to the range in the reported incidence of constipation include variations in the primary diagnoses, ages, and settings of the study participants. In addition, constipation is likely underdiagnosed (Sykes, 2004).
A general definition of constipation is the passage of small amounts of hard, dry stool less often than three times a week (Folden, Backer, Maynard et al., 2002). However, constipation has different meanings to different people (Mercadante, 2002; Sykes, 2004). Patients may report constipation if feces are hard and dry; if there is straining, difficulty, or discomfort in expelling stool; or if stools are less frequent than normal for them.
ETIOLOGY AND PATHOPHYSIOLOGY
Normal bowel function requires the interaction of many body systems to break down food, allow proper absorption and transport of fluids and nutritional elements, and move the remaining food residue through the gastrointestinal (GI) tract to form feces for excretion. These processes are mediated by an interaction of the sympathetic and parasympathetic nervous systems affecting motor, secretory, and endocrine activities (Carroll, 2005). The urge to defecate occurs when the rectum fills with stool. The voluntary relaxation of the external sphincter allows for defecation (Carroll, 2005). Alterations in any of these body systems or physiological processes negatively affect bowel functioning.
Many factors contribute to constipation in patients with advanced progressive illnesses, including the following.
Immobility
Patients with little to no activity cannot maintain normal bowel motility. Defecation requires upright posture and strong abdominal, diaphragmatic, and anal muscles (Folden et al., 2002). Individuals with generalized fatigue and weakness and those who cannot sit on a toilet or bedside commode are at great risk for constipation.
Diet and Hydration
Patients with terminal illnesses often find it difficult to eat and drink adequate amounts of food and fluid for a variety of reasons (see Chapter 20, Cachexia and Anorexia). Low-residue diets may lack the necessary bulk to propel the feces through the bowel. The resulting constipation worsens when there is inadequate fluid intake; as a result, more water is reabsorbed from the colon and hard, dry stool is produced.
Medications
▪ Opioids bind with opioid receptors in the GI tract, leading to (1) a decrease in intestinal, gastric, biliary, and pancreatic secretions, (2) a decrease in propulsive movements due to inhibition of acetylcholine release that relaxes the intestinal musculature, and (3) an increase in internal anal sphincter tone. The net effects of stimulation of the GI opioid receptors are a decrease in stool hydration and an increase in transit time in the colon, leading to constipation (Klaschik, Nauck, & Ostgathe, 2003; Sykes, 2004). Some opioids cause more constipation than others and some individuals seem to be more sensitive to the constipating effects of opioids than others. In a study of laxative use in 49 subjects on opioids, Mancini, Hanson, Neumann et al. (2000) noted that patients on morphine required more laxative than did those on methadone. Another study of 1836 patients receiving long-acting opioid therapy found that those using transdermal fentanyl had less constipation than those using controlled-release oxycodone or controlled-release morphine (Staats, Markowitz, & Schein, 2004).
▪ Anticholinergic drugs and other medications with anticholinergic effects (e.g., tricyclic antidepressants, phenothiazines, some antipsychotics, antiparkinsonian agents) slow peristalsis, increasing the risk of constipation.
▪ Other medications contributing to constipation include antacids containing calcium or aluminum, iron supplements, diuretics, antihypertensives, calcium channel blockers, and antidiarrheal medications (Hodgson & Kizior, 2004; Sykes, 2004). In addition, overuse of laxatives can lead to a weakening of the defecation reflexes, inhibiting natural bowel functioning.
Chemical Imbalances
▪ Hypercalcemia. A high serum calcium level likely depresses the contractility of the muscle walls of the GI tract. In addition, polyuria with hypercalcemia may lead to dehydration, further contributing to constipation (Bower & Cox, 2004; White, 2005).
▪ Hypokalemia can also lead to constipation or, in some situations, paralytic ileus, which probably results from the unresponsiveness of hyperpolarized GI smooth muscle (White, 2005). A common cause of hypokalemia is administration of thiazide diuretics without potassium replacement.
Pressure and Compression of Intestines
Cancer patients with tumor in the abdomen require more laxatives than do other patients on opioid therapy (Mancini et al., 2000). Patients with ascites, abdominal or pelvic tumors, or enlarged lymph nodes are at risk for abnormalities in digestion and elimination. A partial bowel obstruction from tumor growth either inside the intestinal lumen or due to compression from outside the lumen slows motility, contributing to constipation and potentially leading to a complete obstruction (Sykes, 2004). Patients with a history of abdominal surgery are also at risk for the development of adhesions. These adhesions can decrease intestinal lumen size, interfering with transit time in the bowel; partial and complete bowel obstructions are possible.
Changes in the Innervation of the Gastrointestinal Tract
Constipation has been noted in many patients with motor disorders, such as spinal cord lesions and neurological diseases. This constipation is likely the result of visceral neuropathy and a disturbance in the nerve supply of the colon that slows the colonic transit time. In addition, patients who have neurological diseases may experience failure of the puborectalis and anal sphincter muscles to relax, causing intractable constipation (Mercadante, 2002). The innervation of the intestinal tract can also be interrupted by surgery. A history of abdominal surgery provides helpful information for assessing constipation. Neuropathy is a complication of some cancer chemotherapy agents, in particular, the vinca alkaloids. Although constipation is a well-documented side effect of these medications in patients undergoing active treatment, the long-term effects are not clear. Patients who received high cumulative doses of the vinca alkaloids may be at risk for persistent constipation (Mercadante, 2002).
The elderly may experience sensory changes affecting bowel functioning. In particular, rectal insensitivity may lead to a decrease in the urge to defecate (Sykes, 2004). When the urge to defecate is ignored, the anal muscles become weakened, resulting in a risk for constipation and impaction.
Psychosocial Concerns
Under conditions of fear, anxiety, stress, and depression, epinephrine is released as a sympathetic stress response. Epinephrine decreases peristalsis, leading to a risk for constipation. However, the stress response can also increase intestinal mucus formation and cause pain and cramping. Thus, some patients, when stressed, have alternating bouts of diarrhea and constipation. Patients who are embarrassed about using bedpans or bedside commodes may ignore the need to defecate to preserve their privacy. In addition, those who are confused, lethargic, weak, or in pain may not respond to the defecation reflex. As noted, this inattention to the urge to defecate can result in weakened anal muscles.
ASSESSMENT AND MEASUREMENT
Constipation is identified via patient report of infrequent or absent bowel movements, difficulty or pain in defecating, incomplete defecation, or hard, dry stool. Although patients may associate symptoms such as abdominal pain, bloating, flatulence, nausea, malaise, and headache with constipation, these symptoms are not specific to constipation (Sykes, 2004). Stool amount, consistency, and frequency and the length of time since the last bowel movement are important assessment data.
It is important to identify the patient’s definition of constipation. Some may report constipation if a day passes without a bowel movement despite the lack of other symptoms. This may or may not indicate actual constipation. “Normal” bowel habits can range from a bowel movement one to three times a week to daily or several daily bowel movements.
HISTORY AND PHYSICAL EXAMINATION
When performing the history and physical examination, be sensitive to the fact that many people are at least uncomfortable, if not extremely embarrassed, by questioning about bowels and bowel functioning. Maintain an environment as conducive to patient privacy as possible during history taking and examination.
General Assessment
▪ Patient’s medical history and presence of any disease affecting bowel function
▪ Fluid and food intake, including amounts and types of fluids and food
▪ Hydration status: skin turgor, condition of mucous membranes, urinary output, orthostatic blood pressure measurements
▪ Current medications, especially any opioids, tricyclic antidepressants, anticholinergics, sedatives, antiemetics, antipsychotics, antihypertensives, antacids, and diuretics
▪ Activity level and ability to use a toilet or bedside commode
History Related to Complaint of Constipation
▪ Normal bowel patterns and history of any constipation problems
▪ Patient’s definition or description of “constipation”
▪ Date of the last bowel movement as well as the amount, color, and consistency of stool
▪ Any discomfort or bleeding with bowel movements
▪ Interventions the individual uses or has used to prevent or relieve constipation, including medications, enemas, or any special teas, juices, or foods
▪ Patient’s evaluation of the effectiveness or side effects of these interventions
▪ Any use of manual manipulation, such as the application of anal pressure or digital removal of stool
Gastrointestinal Assessment
▪ Reports of abdominal pain or cramping
Note: The pain of constipation may be mistaken for pain related to the disease and “treated” with additional opioids instead of treating the problem of constipation (Sykes, 2004). Do not withhold opioids from patients with pain and constipation; perform a thorough assessment to determine the potential cause of pain and treat it appropriately.
▪ Reports of nausea or vomiting
▪ Abdominal assessment
Distention
Bowel sounds
Increased activity occurs in early intestinal obstruction
Decreased or absent bowel sounds, which may indicate ileus or peritonitis
High-pitched tinkling sounds, indicating fluid and air under tension in a dilated bowel
Rushes of high-pitched sounds with abdominal cramping, which indicate intestinal obstruction (Bickley & Szilagyi, 2003)
Masses and areas of tenderness on palpation
Ascites or trapped air that may be noted with percussion
Rectal Examination
▪ Inspect the rectum for fissures, tears, hemorrhoids, fistulas, or tumors.
▪ Perform a digital examination to identify stool or tumors in the rectum.
▪ Avoid digital examination if the patient is neutropenic or thrombocytopenic or has known tumors.
Psychoemotional Assessment
▪ Assess the patient’s ability to maintain privacy for toileting.
▪ Evaluate the patient’s stress and anxiety level.
▪ Assess for confusion or dementia.
DIAGNOSTICS
As with all symptom evaluation in palliative care, radiographic and laboratory procedures should be performed only when confirmation of the underlying problem will change the course of treatment. If the cause of constipation can be identified on the basis of the medical diagnosis, treatments, or other presenting symptoms, confirmation by radiography or blood work may not be necessary to determine an appropriate course of treatment.
▪ An abdominal film may differentiate between constipation and obstruction (Mercadante, 2002). It is performed only if there is persistent doubt and is rarely necessary (Sykes, 2004). (See Chapter 19, Bowel Obstruction.)
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