Management of Fecal Impaction

Introduction

Fecal impaction may be defined as a large compacted mass of feces (fecaloma) that becomes stuck in the colon or rectum and cannot be evacuated by the patient. Fecal impaction is common and causes significant morbidity. Although it can occur at all ages, some groups of patients are more susceptible, such as children and institutionalized elderly persons. Others at particular risk include the physically and mentally incapacitated, persons who are bedridden or dependent on narcotics, and those who have a long history of laxative use.

Etiopathology

Several anatomic and physiologic factors contribute to symptoms of chronic constipation and fecal impaction. The sensory function of the rectum and anus may be decreased with age or by neurologic disorders resulting in a higher threshold for sensing rectal distension and urgency. In addition, constipation and slow colonic motility produce harder, more compact stools, causing less rectal distension and eventually leading to restriction in their passage through the relatively fixed diameter of the anus. If this cycle perpetuates, formed stool becomes impacted and overflow may occur, leading to passive, intermittent soiling.

The most common factor predisposing to fecal impaction is constipation, and thus the underlying causes and risk factors are the same ( Boxes 21-1 and 21-2 ). Numerous medications are associated with constipation ( Box 21-3 ). In children, the most frequent cause of fecal impaction is the development of a withholding behavior that may occur after a painful or frightening experience with evacuation at one time, which then perpetuates a cycle of fear of defecation and further stool retention.