Diagnosis

Hirschsprung's disease (colonic aganglionosis) with resulting megacolon

Findings

Plain film of the abdomen demonstrates massive distention of the sigmoid colon and rectum with inspissated feces in a ground-glass appearance (Figure 1). The sigmoid colon fills the entire pelvis and much of the abdomen. The colon is dilated to the splenic flexure, as seen on the chest film from the abdominal series (Figure 2).

The patient underwent subtotal colectomy for the removal of the dilated segment of colon. Grossly, the resected colon had a proximal diameter of 6.5 cm and a distal diameter of
16 cm. Microscopically, there was hypoganglionosis throughout the resected sigmoid colon. A section from the distal resected colon at the rectosigmoid junction demonstrated focal aganglionosis involving the surgical margin with associated hypertrophy of the muscularis. There may be additional aganglionic colon incorporated into the Hartmann's pouch, which can be confirmed after the pouch is resected to allow completion of the operation with pull-through.

Discussion

Hirschsprung's disease (congenital colonic aganglionosis) is a condition normally associated with newborns and infants. It can present in the newborn period as a failure to pass meconium in the first 24 hours of life.¹ In infants and toddlers it is associated with a history of constipation, abdominal distention, and failure to thrive.² The degree of aganglionosis can be quite variable, with some patients having aganglionosis of just the internal anal sphincter (termed ultrashort-segment Hirschsprung's disease) and some having aganglionosis of the entire colon.³ The majority of patients with this condition fall between these extremes. The incidence of Hirschsprung's disease is 1 in 4000 live births, with males affected 4 times more frequently than females.¹

The differential diagnosis of megacolon is broad, so classifying the various causes as either congenital or acquired is helpful. Congenital causes include Hirschsprung's disease, the neuronal intestinal dysplasias, myelodysplasia, and anorectal malformations.⁴ In adults, megacolon is usually from an acquired cause, since congenital causes are usually diagnosed in childhood. Acquired causes of megacolon can be further subclassified by the underlying mechanism. Neurologic causes include Chaga's disease, central nervous system dysfunction, diabetic neuropathy, and myotonic dystrophy. Diseases affecting smooth muscle, such as scleroderma and amyloidosis, can also cause megacolon, as can certain metabolic disorders and drugs. Finally, acquired megacolon can be idiopathic (Ogilvie's syndrome) or secondary to mechanical obstruction.³

Diagnosis of Hirschsprung's disease in the pediatric population is best made using rectal manometry and rectal suction biopsy.⁵ Rectal manometry involves measuring the tone of the anal sphincter while a balloon is inflated in the rectum. In suction biopsy, specimens of mucosa and submucosa are obtained to evaluate for the presence of ganglion cells and for histochemical staining. This specimen should be taken at least 3 cm proximal to the dentate line to avoid an area of normal hypoganglionosis.³ In adults, diagnostic imaging in the form of an abdominal series and a barium enema precedes biopsy. Classically, the barium enema would reveal a narrowed rectum, representing the aganglionic segment, distal to the dilated sigmoid. A cone-shaped zone of transition may be present, best visualized in the lateral projection.⁶ These classic findings may be absent in disease limited to the external anal sphincter.

Treatment of Hirschsprung's disease involves surgical removal of the defective segment of the colon.² The diagnosis and operative repair are usually made before the patient reaches age 5. The original operative repair was described by Swenson⁷ in 1948 and is termed the Swenson procedure. Though there have been several modifications to the original Swenson procedure, operative repair generally involves resecting the aganglionic segment of colon, using frozen sections to determine the proximal extent of the aganglionosis, and creating an anastomosis between the normally innervated bowel and the anal canal.² The prognosis after surgery is good, and the majority of patients achieve fecal continence.⁵

CONCLUSION

In the appropriate clinical setting, Hirschsprung's disease should be considered in the differential diagnosis of an adult with megacolon.

Prepared by Richard W. Skinner, DO, MBA, a Transitional Intern at San Joaquin General Hospital, French Camp, CA.

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2. Swenson O. Hirschsprung's disease: A review. Pediatrics. 2002;109:914-918.

3. Phillips SF, Pemberton JH. Megacolon: Congenital and acquired. In: Feldman M, Scharschmidt BF, Sleisenger MH (eds). Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 6th ed. Philadelphia, PA: W.B. Saunders; 1998:1810-1819.

4. Di Lorenzo C, Hyman P. Gastrointestinal motility in neonatal and pediatric practice. Gastroenterol Clin North Am. 1996;25:203-224.

5. Wyllie R. Motility disorders and Hirschsprung disease. In: Behrman RE, Kliegman RM, Jenson HB, eds. Nelson Textbook of Pediatrics. 16th ed. Philadelphia, PA: W.B. Saunders; 2000:1138-1141.

6. Mindelzun RE, Hicks SM. Adult Hirschprung disease: Radiographic findings. Radiology. 1986;160:623-625.

7. Swenson O, Bill AH. Resection of the rectum and rectosigmoid with preservation of the sphincter for benign spastic lesions producing megacolon. Surgery. 1948;24:212-220.