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Megacolon and Hirschsprung Disease
Megacolon is divided into the congenital and acquired types. The congenital form is Hirschsprung disease and includes classic, short-segment, and ultrashort-segment types as well as total colonic aganglionosis ( Fig. 87.1 ).
Megacolon (Hirschsprung Disease).
Acquired megacolon includes many disorders. However, idiopathic acquired megacolon has no cause and is often associated with an acute form of Ogilvie syndrome (see Chapter 60 ). Acquired forms are also associated with a variety of neurologic diseases, intestinal smooth muscle disease, and metabolic disorders (see Chapter 59 ).
Congenital megacolon usually presents during infancy (although it is now well documented in adolescents and adults). It is more common in males than in females and classically has an aganglionic segment in the rectum or sigmoid with a dilated segment above. Findings from anal manometry are classically abnormal. The pathophysiology is attributed to a loss of ganglionic cells in the segment of bowel. It is reported as being linked with both dominant and recessive inheritance. In addition, patients have classic cases of the idiopathic form.
Clinical Picture
Constipation is the symptom that drives the parent or patient to seek medical advice. Functional constipation brings more children to medical attention than does aganglionic megacolon, but the differential diagnosis includes these two conditions. Great variations in clinical signs and symptoms are expected, but typical situations are readily characterized. The child with chronic functional constipation is a healthy-looking youngster of normal body appearance, whereas a child with aganglionic megacolon appears to be chronically ill, has a protuberant abdomen, and bears the stigma of malnutrition in growth and development. However, well-documented cases of normal growth and development show the disease progressing into adolescence, with rare reports in adults, up to age 40.
Typically, the child or adolescent has never had a normal bowel movement and requires laxatives and enemas to evacuate. Occasionally the presentation is diarrhea, characterized by liquid stool moving around an impaction. On rectal examination, the sphincter may be normal or relaxed, and stool or a dilated rectum is palpated; fecal impaction is often severe, and the rectal sphincter may be extremely tight.
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