Case Report Singapore Med J 2009; 50(1) : e29

Annular in an adult patient: diagnosis with endoscopic ultrasonography and magnetic resonance cholangiopancreatography Kandpal H, Bhatia V, Garg P, Sharma R

ABSTRACT is an uncommon congenital anomaly that usually presents early in childhood. The role of endoscopic ultrasonography in the diagnosis of this condition has been only sparsely reported. We present annular pancreas in a 50-year-old man; the anomaly was initially suspected during endoscopy and endoscopic ultrasonography, and subsequently confirmed on magnetic resonance cholangiopancreatography.

Keywords: annular pancreas, endoscopic ultrasonography, magnetic resonance cholangiopancreatography, pancreatic anomaly Singapore Med J 2009; 50(1): e29-e31 Fig. 1 Radial EUS image from the second part of the . The pancreatic tissue (white arrows) along with its duct (black Introduction arrow) are seen to completely encircle the lumen of the duodenum. H: head of the pancreas. Annular pancreas is a rare congenital anomaly in which a portion of the pancreatic tissue surrounds the duodenum. Imaging modalities, including radiograph the descending duodenum (Fig. 1). The pancreatic of the abdomen, barium meal study and, more recently, duct was seen coursing through this tissue around the computed tomography (CT), magnetic resonance (MR) duodenum. EUS features raised a suspicion of annular Department of imaging and MR cholangiopancreatography (MRCP), pancreas. The findings were subsequently corroborated Radiodiagnosis, All India Institute of have all assisted in the preoperative diagnosis. The on MR imaging, which revealed a near complete ring Medical Sciences, role of endoscopic ultrasonography (EUS), however, of pancreatic tissue encircling the duodenum (Fig. 2a Ansari Nagar, (1) New Delhi 110029, has received little attention. We present a case of & b), suggesting the presence of annular pancreas. India incidentally-detected annular pancreas in an adult The encircling annular duct and its opening into the Kandpal H, MD patient. EUS and MRCP features are highlighted. main were clearly seen on the MRCP Senior Research Associate images (Fig. 2c). The patient’s symptoms resolved with Case Report conservative management. Sharma R, MD Additional Professor A 50-year-old man presented with epigastric pain of Discussion Department of one month duration. There was no associated Gastroenterology or abdominal distension. He had no significant past Annular pancreas is an uncommon congenital anomaly Bhatia V, MD illness. Physical examination was unremarkable. (one in 20,000 live births) in which the pancreatic tissue Senior Research Standard biochemistry, serum biochemical parameters forms a complete (25%) or partial (75%) ring around the Associate and abdominal ultrasonography were normal. An descending duodenum.(1) Several hypotheses regarding Garg P, MD Associate Professor upper gastrointestinal endoscopy showed an extrinsic its development have been proposed,(2) although the impression on the second part of the duodenum, the exact aetiology is still unknown. According to the Correspondence to: Dr Raju Sharma cause of which was further evaluated with EUS. most current theory, the tip of the left ventral anlage Tel: (91) 98 1020 8551 Fax: (91) 11 2686 2663 EUS revealed a band-like structure, isoechoic and adheres to the duodenum and stretches to form a ring Email: raju152@ continuous with the head of the pancreas, encircling during development.(3) Histologically, the annular yahoo.com Singapore Med J 2009; 50(1) : e30

2a 2b

Fig. 2 (a,b) Axial T1-W MR images show the annular pancreas 2c (arrowhead) encircling the second part of the duodenum. (c) MRCP image shows the annular duct (arrow) surrounding the duodenum. The annular duct opens into the main pancreatic duct (duct of Wirsung) (arrowhead). CD: common ; A: gastric antrum; GB: gall bladder; D: duodenum.

duodenal ulcers in 26%–48% and with in 15%–30% of cases.(5) An awareness of the wide range of clinical severity and age of presentation as well as a high index of clinical suspicion are important for a correct diagnosis. Imaging plays a vital role in the diagnosis and management of annular pancreas. Although contrast-enhanced CT can demonstrate the enhancing pancreatic tissue around the duodenum, findings can be non-specific if the duodenum is not sufficiently opacified, or there is insufficient contrast pancreatic tissue is intermixed with the smooth muscle enhancement of the pancreatic tissue.(1) EUS is feasible, of the duodenal wall and extends close to the mucosal even in cases with descending duodenal obstruction, layer.(1) Other associated congenital anomalies including by scanning from the duodenal bulb.(1) Although not a trisomy 21, tracheo-oesophageal fistula, imperforate primary imaging modality in the diagnosis of annular anus and Hirschsprung’s disease are seen in up to 75% pancreas, EUS may help clarify the cause of an extrinsic of cases.(4) impression on the second part of the duodenum. EUS, Annular pancreas represents the second most unlike ERCP, can not only delineate the duct but also common congenital pancreatic abnormality after the pancreatic parenchyma surrounding the duodenum. .(4) It usually presents in neonates MRCP has the added advantage of being noninvasive with vomiting due to severe duodenal obstruction. and operator-independent, and is capable of delineating Radiographs in these cases often reveal the characteristic the precise ductal .(6) The annular duct usually double-bubble sign, representing air in the dilated connects with the main pancreatic duct or the common stomach and the duodenal bulb. Duodenal obstruction bile duct near the ampulla but may uncommonly drain in annular pancreas may also result from associated directly into the duodenum.(2,6) anomalies like duodenal web or stenosis. At the other Endoscopic cholangiopancreaticography (ERCP) end of the clinical spectrum, this entity is asymptomatic has a reported diagnostic accuracy of 85% when the and remains undetected or only incidentally detected. annular duct opens into the main pancreatic duct.(4) In others, symptoms of duodenal obstruction or However, ERCP via selective cannulation of the major may manifest for the first time in adult papilla alone is unrewarding in cases where the annular life. Obstruction may be heralded by an episode of duct opens into the minor papilla or directly into the pancreatitis which causes a narrowing of the duodenum. duodenum.(4) ERCP is also technically difficult in cases Annular pancreas can be associated with gastric and with duodenal obstruction. It may aggravate or induce Singapore Med J 2009; 50(1) : e31

pancreatitis.(1) Barium studies provide only indirect References evidence of annular pancreas by revealing eccentric 1. Gress F, Yiengpruksawan A, Sherman S, et al. Diagnosis of annular pancreas by endoscopic ultrasound. Gastrointest Endosc narrowing and medial retraction of the duodenal sweep 1996; 44:485-9. at the level of the annulus.(7) This appearance can also 2. Mortele KJ, Rocha TC, Streeter JL, Taylor AJ. Multimodality be seen in pancreatitis, pancreatic carcinoma and post- imaging of pancreatic and biliary congenital anomalies. bulbar ulcer.(7) Radiographics 2006; 26:715-31. Symptomatic duodenal obstruction due to annular 3. Kamisawa T, Yuyang T, Egawa N, Ishiwata J, Okamoto pancreas is treated with duodeno-duodenostomy A. A new embryologic hypothesis of annular pancreas. Hepatogastroenterology 2001; 48:277-8. or duodeno-jejunostomy.(7) Division of the annular 4. Faerber EN, Friedman AC, Dabezies MA. Annular pancreas. In: ring is not recommended, due to a high incidence of Friedman AC, Dachman AH, eds. Radiology of the Liver, Biliary postoperative complications like fistula formation, Tract, Pancreas. St Louis: Mosby-Year Book, 1994: 745-8. pancreatitis, pancreatic laceration or recurrent duodenal 5. Shirkhoda A, Gore RM, Ghahremani GG. Anomalies and anatomic stenosis secondary to local fibrosis.(7) In conclusion, MR variants of the pancreas. In: Ghore RM, Levine MS, eds. Textbook imaging coupled with MRCP is the ideal technique for of Gastrointestinal Radiology. 2nd ed. St Louis: WB Saunders, 2000:1754-66. the noninvasive diagnosis of annular pancreas. EUS 6. Choi JY, Kim MJ, Kim JH, et al. Annular pancreas: emphasis on is an emerging and excellent modality to diagnose magnetic resonance cholangiopancreatography findings. J Comput annular pancreas and should be preferred over ERCP Assist Tomogr 2004; 28:528-32. in cases where the diagnosis is first suspected during 7. Jadvar H, Mindelzun RE. Annular pancreas in adults: imaging endoscopy. features in seven patients. Abdom Imaging 1999; 24:174-7.