Bowel obstruction is defined as abnormally delayed or blocked transit through the intestinal tract (Ripamonti & Mercadante, 2004; Waller & Caroline, 2000). With obstruction, the motor activities of the small intestine and/or colon, characterized by contractile patterns that serve the requirements of each organ, become impaired (Hasler, 2003). Although not a frequent complication, bowel obstruction occurs more often in the palliative care patient than in patients in other care settings. Malignant bowel obstruction (MBO) occurs in approximately 3% of all patients with cancer, but up to 24% of patients with colon cancer and up to 42% of women with ovarian cancer may develop obstructions (Hirst & Regnard, 2003; Ripamonti & Mercadante, 2004). Less frequently, MBOs are seen with cancers of the pancreas, stomach, endometrium, bladder, and prostate (Waller & Caroline, 2000). One retrospective chart audit showed that 19% of patients with malignant small bowel obstruction also had a large bowel obstruction (Miller, Boman, Shrier et al., 2000). Bowel obstructions are most frequently caused by postoperative adhesions, occurring in about 3.5% of people who have intestinal resection (Dang, Aguilera, Dang et al., 2002; Fazio, Cohen, Fleshman et al., 2006; Ryan, Wattchow, Walker et al., 2004). The incidence of other nonmalignant causes of bowel obstruction is not as well documented. Bowel obstructions may involve the small or large bowel and can be partial or complete. Any site of the gastrointestinal tract may be involved, from the gastroduodenal junction to the rectum and anus (Hirst & Regnard, 2003).

MBO may be intraluminal due to tumors blocking the bowel, intramural due to tumor infiltration of the intestinal muscles and the accompanying inflammation that occludes bowel, or extramural due to tumors outside the lumen that compress the bowel wall (Davis & Nouneh, 2000; Hirst & Regnard, 2003; Ripamonti & Mercadante, 2004). Adhesions may contribute to malignant obstruction in people who have had previous abdominal surgery (Miller et al., 2000). In addition, patients with cancer may have motility disorders from malignant involvement of intestinal muscle or autonomic nerves. Nonmalignant causes of bowel obstruction include adhesions from previous surgery, incarcerated or strangulated hernias, pseudo-obstruction, and fecal impaction.

Improperly managed constipation may lead to impaction and symptoms of bowel obstruction (Pappagallo, 2001; Ripamonti & Mercandante, 2004). Constipation is a common problem in people with advanced illnesses due to decreased food and fluid intake and decreased mobility. This problem is compounded by the use of medications that contribute to constipation, such as opioids and anticholinergic drugs. An impaction is easily misdiagnosed as clinicians mistake hard abdominal masses of feces for tumors (Hirst & Regnard, 2003).

Pseudo-obstruction presents like a mechanical obstruction but has no anatomic cause (Sutton, Harrell, & Wo, 2006). It is sometimes called adynamic ileus and is defined as a state of inhibited motility in the gastrointestinal tract that may be temporary (reversible) or permanent (Summers, 2003). Although there are many potential causes of pseudoobstruction, the incidence is believed to be rare (Smith, Williams, & Ferris, 2003). In the palliative care setting, the more likely causes of pseudo-obstruction include the following:

When the bowel is obstructed, intestinal contents accumulate proximal to the blockage and the bowel distends. Bowel activity increases in an effort to restore peristalsis, leading to uncoordinated muscle contractions, increased intestinal secretions, and increasing bowel distention. Further, the bacterial flora of the bowel contents increases above normal levels, causing gas production and, again, increasing bowel distention. The increased pressure on the cell walls initiates the inflammatory process, resulting in even more edema and secretions. Hypoxia of the tissues develops as the increased pressure interferes with venous drainage and oxygenation. Death results when third-spacing of fluid causes hypovolemia and renal failure, when the passage of toxins from the intestine into the lymphatics and circulation leads to sepsis, or when these events occur together (Ripamonti & Mercadante, 2004).

Obstructions in the proximal bowel cause vomiting and severe dehydration and electrolyte disturbances but minimal distention. Blockage in the distal bowel causes a large amount of fluid to accumulate in the bowel, third-spacing of fluids and dehydration, abdominal distention, and feculent vomiting (Dang et al., 2002; Hirst & Regnard, 2003). Malignant obstructions may present acutely but are more likely to have a gradual onset over weeks or months (Hirst & Regnard, 2003).

The assessment of bowel obstruction is based primarily on the presenting symptoms of pain, vomiting, and obstipation (Dang et al., 2002). Abdominal pain is present in about 90% of patients presenting with a bowel obstruction (Hirst & Regnard, 2003). The pain is usually described as colicky, meaning it worsens when the intestines contract in their attempt to restore peristalsis but lessens when the muscles relax. Pain usually presents in the suprapubic region when the obstruction is low in the colon (Waller & Caroline, 2000). As the distention worsens, so does the pain; it may become constant. Assessment measures include noting the onset, location, and severity of pain, noting whether the pain is intermittent or continuous, and noting any worsening of the pain over time.

Because there is less distention with proximal obstructions (e.g., jejunal or small bowel obstructions), there may be less pain but significantly more vomiting. Vomiting develops later in obstructions of the distal ileum and colon and may be feculent (Dang et al., 2002; Hirst & Regnard, 2003). Assess the amount, color, and odor of emesis. Remember that some patients may have concurrent large and small bowel obstructions.

Dehydration is a concern with high-volume emesis and poor intake, so assessment must include evaluation of hydration status. Assess skin turgor, blood pressure, heart rate, urinary output, and subjective symptoms of dehydration, such as headache and dry mouth.

While patients with complete bowel obstruction are usually obstipated, those with partial or intermittent bowel obstructions may have constipation or diarrhea. Ask about frequency, amount, and consistency of bowel movements. Be aware that what is reported as diarrhea may be overflow of liquefied fecal material (Waller & Caroline, 2000).

Abdominal obstruction can also compromise respiratory function due to pressure on the diaphragm secondary to abdominal distention. Patients with cardiorespiratory problems at baseline are especially vulnerable (Summers, 2003). Assess changes in respiratory rate and effort, as well as any report of dyspnea.

The diagnosis of bowel obstruction can present challenges for the clinician. Some patients advance from a partial to complete occlusion in an insidious manner, whereas other patients may develop an intermittent obstruction, causing fluctuating symptoms. It is essential that clinicians complete a detailed history, including:

A comprehensive physical examination includes assessing the patient’s general appearance, signs of hydration, fever, hypotension, and respiratory compromise. Perform a thorough assessment of the abdomen. Note any laparotomy scars or abdominal distention. Palpate for masses, noting that a fecal impaction can be mistaken for a tumor. Note any tenderness to palpation. Listen to bowel sounds. In early bowel obstruction, bowel sounds may be high pitched and tinkling. Be aware, however, that classic tinkling sounds are actually rare (Twycross & Wilcock, 2001). Bowel sounds may be absent with complete bowel obstruction. Complete a rectal examination to assess rectal tone and the presence of masses, fecal impaction, or liquid stool.

When the clinical evaluation suggests obstruction or ileus, radiographic examination is helpful to confirm the diagnosis, differentiate ileus from obstruction, or, at least, contribute to an understanding of the cause (Jenkins, Taylor, & Behrns, 2000). In patients in the end stage of advanced cancer, abdominal films are indicated only when the patient may be a candidate for palliative surgery to relieve the obstruction or to distinguish between mechanical obstruction and severe constipation (Waller & Caroline, 2000). Multislice spiral computed tomography, computed tomography colonography, and magnetic resonance imaging are more accurate than plain radiographs and can determine the extent of intraabdominal cancer, an important factor in determining if a patient is a surgical candidate (Low, Chen, & Barone, 2003; Taourel, Kessler, Lesnick et al., 2003). In addition to radiographic studies, blood chemistries may be obtained to evaluate fluid and electrolyte status.