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Annular pancreas results from a band of pancreatic parenchyma that
encircles a section of the second part of the duodenum. The embryologic
anomaly is secondary to the malrotation of the ventral bud, which wraps
around the duodenum to fuse with the dorsal bud.
This malformation can
be isolated or can be accompanied by a digestive tract malrotation or
atresia. Its frequency is also increased by Trisomy 21.
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Embryological Development of Annular Pancreas |
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Shirkhoda et al.: Anomalies and anatomic varients of
the pancreas. In Gore & Levine, Textbook of Gastrointestinal
Radiology, 2n Ed. Phila: W. B. Saunders Co., 2000, p 1761
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The clinical
consequences of annular pancreas depend on the degree of duodenal obstruction. In cases of
complete obstruction, the diagnosis is readily evident in the neonate.
Plain films reveal two asymmetrical air-fluid levels, one gastric, the
other duodenal, with little distal bowel gas. This is the "double
bubble" sign. The diagnosis
can be suggested by prenatal US, which would demonstrate the two
constant liquid-containing abdominal structures, possibly accompanied by hydroamnios. This anomaly may present later, and into adulthood, as
partial duodenal obstruction or pancreatitis. The treatment of
significant
obstruction is always surgical.
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