CONGENITAL ANOMALIES OF THE PANCREAS
In the fourth week of gestation, the human pancreas develops as 2 outpouchings of the duodenal endoderm. The larger dorsal bud develops into the tail, body, and a portion of the head of the pancreas. The ventral bud fuses with the dorsal bud at about the 17th week of gestation to create the remainder of the head of the pancreas and the uncinate process. Each bud possesses its own ductal system; variations in fusion, which occur in 15% of the population, lead to developmental anomalies. These anatomic anomalies of the pancreas may be normal variants or result in symptomatic pathologic disease.
The most common pancreatic congenital anomaly is pancreas divisum, with an identified prevalence of 5% to 10% in the general population based on postmortem studies. The majority of individuals with pancreas divisum will remain asymptomatic; however, it appears that a minority of adults and children who will develop symptoms in part from the presence of pancreas divisum most often manifest as acute recurrent pancreatitis that may progress to chronic pancreatitis. In support of its pathologic role as a disease entity, adult studies have shown a higher rate of this anomaly in those with idiopathic pancreatitis. A similar observation has been made from a recent large series of children undergoing endoscopic retrograde cholangiopancreatography (ERCP) for pancreatic disease in which the prevalence of pancreas divisum was nearly 25%. This series likely represents a select patient population but does suggest the pathologic role of pancreas divisum in a subpopulation of children with this anomaly. Therapy includes supportive care during occurrences of acute pancreatitis, with a potential benefit from endoscopic or surgical sphincterotomy/sphincteroplasty to improve pancreatic drainage and alleviate intraductal hypertension.
Annular pancreas remains a rare anomaly; however, with more advanced imaging capabilities, the incidence is now reported to be approximately 1 in 1000 (Table 412-1). The development of symptoms can occur at any age, from birth to adulthood, and it is no longer considered a disease limited to infancy. The clinical symptoms are age dependent, with neonates most often presenting with bilious emesis, abdominal distention, or growth failure secondary to feeding intolerance. The majority of adults with annular pancreas will present with pain and 1 or more conditions including nausea, vomiting, bloating, recurrent pancreatitis, and jaundice. From one series of pediatric and adult patients with annular pancreas, 71% of children were found to have an associated congenital anomaly (eg, congenital heart disease, intestinal malrotation, tracheoesophageal fistula). The associated findings in adults were less frequent (16%) and somewhat different (eg, intestinal malrotation, duodenal web, Schatzki ring). Therapeutic interventions may depend on the individual clinical manifestations, with duodenal bypass (duodenoduodenostomy) reserved for intestinal obstruction and the option of ERCP or pancreatic surgery for those presenting with pancreatic disease.
Table 412-1GENETIC PANCREATIC DISORDERS