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Cancer Health Center

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Gastrointestinal Complications (PDQ®): Supportive care - Health Professional Information [NCI] - Impaction

Etiology of Impaction

Five major factors precipitating impaction include the following:

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  • Opioid analgesics.
  • Prolonged inactivity.
  • Dietary alterations.
  • Psychiatric illness.
  • Chronic use of drugs for constipation.[1]

Laxatives used to decrease constipation are the drugs that contribute most to the development of constipation and impaction. Repeated and escalating dosing of laxatives renders the colon less sensitive to its intrinsic reflexes stimulated by distention. (Refer to the Etiology of Constipation section of this summary for causes of constipation that may lead to impaction.)

Signs and Symptoms of Impaction

The patient may exhibit symptoms similar to constipation or present with symptoms unrelated to the gastrointestinal system. If the impaction presses on the sacral nerves, the patient may experience back pain. If the impaction presses on the ureters, bladder, or urethra, urinary symptoms can develop. These symptoms include increased or decreased frequency or urgency of urination, or urinary retention.

When abdominal distention occurs, movement of the diaphragm is compromised, leading to insufficient aeration with subsequent hypoxia and left ventricular dysfunction. Hypoxia can, in turn, precipitate angina or tachycardia. If the vasovagal response is stimulated by the pressure of impaction, the patient may become dizzy and hypotensive.

Movement of stool around the impaction may result in diarrhea, which can be explosive. Coughing or activities that increase intra-abdominal pressure may cause leakage of stool. The leakage may be accompanied by nausea, vomiting, abdominal pain, and dehydration and is virtually diagnostic of the condition. Thus, the patient with an impaction may present in an acutely confused and disoriented state, with signs of tachycardia, diaphoresis, fever, elevated or low blood pressure, and/or abdominal fullness or rigidity.

Assessment of Impaction

Assessment includes the questions discussed previously for the patient with constipation. (Refer to the Assessment of Constipation section of this summary for the list of questions.) Additional assessment includes auscultation of bowel sounds to determine if they are present, absent, hyperactive, or hypoactive. The abdomen is inspected for distention and gently palpated for any masses, rigidity, or tenderness. A rectal examination will determine the presence of stool in the rectum or sigmoid colon. An abdominal x-ray (flat and upright) would show loss of haustral markings, gas patterns reflecting gross amounts of stool, and dilatation proximal to the impaction.[2]

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