Summary: Attempts at treating this patient's obstipation medically with
rectal tube decompression, bowel rest, and enemas failed. He was
taken to surgery for subtotal colectomy with disimpaction and
colostomy. Postoperatively, the patient had a well-functioning
colostomy and became asymptomatic.
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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neonatal intestinal obstruction.
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1999;60:2043-2050.
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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.
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and pediatric practice. Gastroenterol Clin North Am.
1996;25:203-224.
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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.