Abstract

Annular pancreas is a rare congenital anomaly. It consists of a ring of pancreatic tissue partially or completely encircling the descending part of the duodenum. Previously the condition was detected either during surgery or autopsy. With   the improvements  achieved in imaging techniques the diagnosis of annular pancreas in adults increased in frequency.

Ductal pattern of the ring tissue is important because of its clinical implications. The exact incidence of this congenital anomaly can not be calculated because many cases may remain asymptomatic. Despite the congenital nature of the disease, the clinical manifestations may occur at any age.

Keywords : annular pancreas,  pancreatic bud,  pancreatic duct,  duodenum.

Introduction

Annular pancreas is considered as a rare congenital malformation where a ring of pancreatic tissue surrounds the second part of duodenum[1] . It is seen in one of every  20000  autopsies[2]. Men being affected more commonly than women[3]. With the improvement of imaging techniques the diagnosis of annular pancreas in adults increased in frequency [3].Many remain asymptomatic throughout life[4].Magnetic resonance pancreaticography is being used with increased frequency as a noninvasive alternative to the diagnostic endoscopic retrograde pancreaticography in the evaluation of the pancreatic ducts without the risk of inducing pacreatitis[5]. The knowledge about the ductal pattern in normal pancreas as well as  in congenital variations are important for a surgeon according to which he can modify the surgical procedures in a more satisfactory way. This will help them to prevent most of the common post operative complications like pancreatitis. It is a very interesting  topic for  anatomists because most of the clinically important variations can be clearly analysed by them on embryological basis.

Materials and methods

The specimen of annular pancreas was collected during  a study on the ductal pattern of pancreas. It was from a male cadaver of age 56  who died of road traffic accident. The second part of duodenum was encircled by a glandular  tissue which was continuous with the main  pancreas. Pancreas was removed enbloc with attached bile duct, duodenum and spleen. Later spleen was dissected away from the tail end of pancreas.

On the posterior aspect of specimen the bile duct was traced down to the junction with main  pancreatic duct. Tributaries of main and accessory pancreatic ducts were traced to see whether there is any duct entering from the pancreatic ring tissue. The duct from the annular pancreas  was traced to see its tributaries and pattern. To see the  patency of duct Indian ink was injected through the distal end using a syringe and needle and checked the appearance in the duodenal lumen. Histo pathologicalogical  examination of the ring tissue was done.

Observation

A complete, thin ring of pancreatic tissue was surrounding the 2nd part of duodenum(fig-1). The intestine showed mild dilatation above and below the ring. From the annular pancreatic tissue one duct joined the main pancreatic duct posteriorly. Duct started on the anterior aspect and showed many tributaries. It turned to the right side and after traversing the whole pancreatic tissue it joined the main pancreatic duct (fig-2) . There was no tributary to the accessory pancreatic duct from the ring tissue.  It was a patent duct. Ductal pattern is showed in diagram no-1.The annular tissue was adherent to the duodenal wall. The histological study showed a normal pancreatic tissue.

Discussion

The development of annular pancreas is still a controversial topic .According to Langman’s Embryology, the ventral pancreatic bud consists of two components (right and left) which under normal conditions fuse and rotate around the duodenum in such a manner that they come to lie below the dorsal pancreatic duct[6].This explains why the duct from annular tissue is commonly connected to main pancreatic duct.

Lecco postulated  that adhesion of the distal tip of the ventral primordium to the duodenal wall before its migration results in annular pancreas[7]. Baldwin stated that persistence and further development of left component is responsible for the formation of pancreatic ring around the duodenum[8]. The results of immuno-histochemical analysis using antipancreatic polypeptide antibody suggest that the ring formation originates from the left lobe of paired ventral pancreatic bud.[9]

Yogi et al classified annular pancreas according to the drainage of annular duct. The most common is type 1 where annular duct directly flows into the main pancreatic duct [3].The ductal pattern in the present case comes under this pattern. There was no duct from the ring tissue to duct of  santorini as observed by   Russadi et al[10]. The study conducted by  Heymann   showed a continuation of proximal end of main pancreatic duct over the ring tissue anteriorly and after winding around the duodenum it joined the common bile duct[11].

When clinical manifestations ensue at adult age, symptoms include cramping  epigastric pain, post prandial fullness and relief with vomiting[12].Besides peptic ulcer disease, acute and chronic pancreatitis, obstructive jaundice and gastric outlet obstruction may also be   associated  conditions[13]. Division or resection of the pancreatic annulus as used in the past[1]is not advised because of the duodenal leak, post operative pancreatitis and  pancreatic fistula[12].

Summary.

The pancreatic tissue  present over the duodenum can constrict the lumen and block or impair the blood flow depending upon its thickness.. Almost  two third of the patients remain asymptomatic. In this present study till death the person had, no recorded complaints related to pancreatic pathology. Even the  histological examination showed normal  glandular tissue. Annular pancreas is found concomitantly with  ampullary carcinoma. The co-existence must be considered until the absence is proved[14]. The main goal of surgical treatment of annular pancreas is the relief of duodenal obstruction and several procedures have been proposed with this intent[12]. Bypass surgery of the annulus by duodenostomy, gastrojejunostomy or duodeonojejunostomy seems to the preferred method of treatment[12]. Duodenopancreatectomy is suggested when annular pancreas is associated with neoplastic conditions[15].The differential diagnosis between focal inflammatory lesions in the head of the pancreas due to chronic pancreatitis and pancreatic cancer remains a challenging task for radiologists, pathologists and surgeons[3]. In relieving surgical operations prior knowledge of ductal pattern is important for avoiding postoperative complications.

Aknowledgement.

I express my sincere gratitude towards Dr.T.R.Kalavathi and Dr.Chrictilda Felicia who inspired me and guided me.

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