Abstract

In order to understand the anatomical variations and congenital anomalies of the pancreas, many of which have practical surgical implications, it is important to realize that this organ originates from two separate embryonic anlagen: a ventral and a dorsal primordium. An annular pancreas is a rare malformation, and it is generally accepted that the ring formation originates from a single ventral pancreas, as suggested by Lecco. However, an annular pancreas may also originate from paired ventral pancreata, thus supporting Baldwin's hypothesis. Here, we attempt to clarify the pathogenesis of the annular pancreas.

Copyright © 2007 S. Karger AG, Basel

An annular pancreas is a rare malformation in which a band of pancreatic tissue surrounds the descending portion of the duodenum, either completely or incompletely, and is in continuity with the head of the pancreas. The anomaly is often discovered incidentally and/or at autopsy. Some patients with this anomaly develop duodenal stenosis, obstructive jaundice and pancreatitis; however, many remain asymptomatic and the anomaly is only discovered accidentally in adulthood.

Many infants with this anomaly also have various other congenital anomalies such as Down's syndrome, malrotation, esophageal atresia, duodenal atre-sia, duodenal diverticulum, pancreas divisum, imperforate anus and congenital heart disease. The diagnosis is usually obtained by endoscopic retrograde cholangiopancreatography (ERCP) and/or histological analyses. Although several theories have been proposed to explain the origins of annular pancreas, the pathogenesis is still controversial [1-4]. It is generally accepted that the ring formation originates from the ventral pancreas, as suggested by Lecco and Baldwin [1, 2]. The difference between Lecco's and Baldwin's hypotheses is whether the ventral pancreatic anlage is single or paired. On the basis of embry-ologic analyses, many gastroenterologists and pathologists have come to believe that the ventral pancreatic anlage is initially paired, with the left lobe normally disappearing during development, as described by Odgers [5]. However, the histogenesis of the ventral pancreatic anlage is also controversial because most of the resected and/or autopsied annular pancreata that have been investigated histopathologically support Lecco's hypothesis. We present an annular pancreas that was investigated histopathologically and immunohisto-chemically, which supports Baldwin's hypothesis with reference to the histogenesis of the ventral pancreatic anlage [6].

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