A 4-week-old boy is hospitalized with persistent vomiting, fussiness, and feeding intolerance. The emesis was initially clear but became bilious in the last few hours. The infant had been breastfeeding exclusively. His temperature is 37.2 C (99.0 F). Blood pressure and pulse are normal. Physical examination shows a normal abdomen with no rebound or guarding. An upper gastrointestinal series is obtained urgently to evaluate for malrotation and volvulus and shows normal rotation but constriction of the duodenum. An abdominal CT scan reveals pancreatic tissue encircling the duodenum. Which of the following is the most likely cause of this patient's condition?

Question

A 4-week-old boy is hospitalized with persistent vomiting, fussiness, and feeding intolerance.  The emesis was initially clear but became bilious in the last few hours.  The infant had been breastfeeding exclusively.  His temperature is 37.2 C (99.0 F).  Blood pressure and pulse are normal.  Physical examination shows a normal abdomen with no rebound or guarding.  An upper gastrointestinal series is obtained urgently to evaluate for malrotation and volvulus and shows normal rotation but constriction of the duodenum.  An abdominal CT scan reveals pancreatic tissue encircling the duodenum.  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

11ec160b_3740_131f_9249_2762bda5fc77_MD0001_00 This patient has acute pancreatitis and radiographic evidence of annular pancreas, which results from abnormal migration of the ventral pancreatic bud. This bud is a foregut derivative that appears by the fifth week of gestation and rotates behind the duodenum during the seventh week of fetal development. The ventral bud moves toward the midline, where it fuses with the dorsal pancreatic bud during the eighth week. The ventral pancreatic bud gives rise to the uncinate process portion of the head and the main pancreatic duct (of Wirsung). The pancreatic tail, body, and the remainder of head derive from the dorsal bud. Abnormal migration of the ventral pancreatic bud can be caused by adherence to either the dorsal bud or duodenum before the rotation begins. This abnormal migration leads to annular pancreas, a rare congenital anomaly in which pancreatic tissue completely surrounds the second part of the duodenum. Annular pancreas can compress the duodenal lumen (causing obstruction) or result in obstructed pancreatic drainage (acute or chronic pancreatitis). However, the majority of patients with annular pancreas are asymptomatic. (Choice A) The pancreas is not derived from the midgut. Both ventral and dorsal pancreatic buds form from the duodenal portion of the foregut. (Choice C) Ectopic rests, or fragments of embryonic tissue that persist beyond the fetal period, can be found throughout the gastrointestinal tract. However, the pancreatic tissue in annular pancreas is contiguous with the rest of the pancreas by definition. (Choice D) Neither the dorsal nor ventral pancreatic bud undergoes apoptosis in normal development. (Choice E) Incomplete fusion of the ventral and dorsal pancreatic buds (pancreas divisum) is usually asymptomatic and much more common than annular pancreas. Pancreas divisum does not cause obstruction as the duodenum is not completely encircled but may predispose to the development of acute or chronic pancreatitis. Educational objective: Annular pancreas, or pancreatic tissue encircling the descending duodenum, is caused by failure of the ventral pancreatic bud to properly migrate and fuse with the dorsal bud during the seventh and eighth week of fetal development. Annular pancreas is usually asymptomatic but may present with duodenal obstruction or pancreatitis. __________ References: Annular pancreas in adults: a report of two cases and review of literature. (http://www.ncbi.nlm.nih.gov/pubmed/23669479) Disorders of the pediatric pancreas: imaging features. (http://www.ncbi.nlm.nih.gov/pubmed/15536562)

A 4-Week-Old Boy Is Hospitalized with Persistent Vomiting, Fussiness, and Feeding