Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the formal ranking system used by the PDQ Editorial Boards to assess evidence supporting the use of specific interventions or approaches. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
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 should be 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.
If a diagnosis of fecal impaction is uncertain, a laboratory workup can rule out other problems. A complete blood cell count, appropriate blood chemistries, chest x-ray, and an electrocardiogram can be performed. If the patient has become dehydrated, the blood urea nitrogen, creatinine, and serum osmolality will be elevated. There may be an elevation of the hemoglobin and hematocrit indicating hemoconcentration. The white blood cell (WBC) count may be slightly elevated in the presence of a fever. If the WBC count is extremely elevated and the patient is exhibiting a high fever and abdominal pain, an obstruction, perforation, infection, or inflammatory process must be ruled out. With marked distention of the cecum (diameter ≥12 cm), there is a risk of bowel perforation.