Portal annular pancreas: An unusual pancreatic pseudotumor with clinical significance

Praveen Kumar Ravi; Pravash Ranjan Mishra; Sudipta Ranjan Singh

doi:10.4103/NJCA.NJCA_67_21

CASE REPORT

Year : 2021 | Volume : 10 | Issue : 4 | Page : 246-248

Portal annular pancreas: An unusual pancreatic pseudotumor with clinical significance

Praveen Kumar Ravi¹, Pravash Ranjan Mishra², Sudipta Ranjan Singh³
¹ Assistant Professor, Department of Anatomy, Trichy SRM Medical College Hospital and Research Centre, Trichy, Tamil Nadu; Former Senior Resident, Department of Anatomy, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
² Additional Professor, Department of Anatomy, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
³ Additional Professor, Department of Forensic Medicine and Toxicology, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India

Date of Submission	28-May-2021
Date of Decision	27-Aug-2021
Date of Acceptance	14-Oct-2021
Date of Web Publication	28-Oct-2021

Correspondence Address:
Pravash Ranjan Mishra
Department of Anatomy, All India Institute of Medical Sciences, Room No 1, Academic Block, Ground Floor, Bhubaneswar - 751 019, Odisha
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/NJCA.NJCA_67_21

Abstract

Portal annular pancreas (PAP) is a rare congenital anomaly due to abnormal fusion of ventral pancreatic bud left to the developing portal vein. Its incidence is 1.1%–3.4% in the literature. PAP is commonly involving the uncinate process; complete encircling is relatively rare. Proposed hypothesis for the congenital PAP is (1) hypertrophied ventral pancreatic bud fuses with the body of the pancreas left to the portal vein and (2) malformation of the portal vein. We found a bulky pancreas in a 51-year-old male during an autopsy. After careful dissection, we observed that the pancreas was completely encircling around the portal vein cranial to its formation. The encircled tissue was confirmed as normal pancreatic tissue by H & E and immunohistochemical staining. Pancreatic ductal pattern was observed anterior to the portal vein. This condition is usually asymptomatic; most of the time, the same was diagnosed incidentally during surgery. However, in cases of the malignant lesion in the head of the pancreas, the PAP is usually confused as the tumor's extension (pseudotumor). The management of posttransection pancreatic stump is challenging and usually results in complications such as pancreatic fistula. Knowledge about the PAP is necessary for the surgeon and radiologist for accurate diagnosis and prior planning to prevent the postoperative complications.

Keywords: Circumportal pancreas, congenital anomaly, pancreatic fistula, portal vein

How to cite this article:
Ravi PK, Mishra PR, Singh SR. Portal annular pancreas: An unusual pancreatic pseudotumor with clinical significance. Natl J Clin Anat 2021;10:246-8

How to cite this URL:
Ravi PK, Mishra PR, Singh SR. Portal annular pancreas: An unusual pancreatic pseudotumor with clinical significance. Natl J Clin Anat [serial online] 2021 [cited 2022 Jul 1];10:246-8. Available from: http://www.njca.info/text.asp?2021/10/4/246/329501

Introduction

The portal annular pancreas (PAP) is a rare developmental anomaly. The incidence of the PAP is ranging from 1.1% to 3.4% in the literature.^[1],[2] PAP commonly involves the uncinate process; complete encircling is relatively rare.^[3] It is usually asymptomatic; however, in patients with PAP, the surgical procedure near the pancreatic region is challenging, with a higher morbidity rate, usually results in postoperative complications such as pancreatic fistula.^[4],[5] In the present study, the authors report a rare complete PAP with its histological features.

Case Report

During the routine autopsy in a case of road traffic accident, the authors incidentally noticed the bulkier pancreas in a 51-year-old male. The pancreas was dissected from the posterior abdominal wall along with the duodenum and surrounding structures for further evaluation. The length and weight of the pancreas were 25.5 cm and 196 g (doubled than the usual), respectively. After careful dissection, we observed that the pancreatic tissue was completely encircling around the portal vein cranial to its formation (suprasplenic type) [Figure 1]a, [Figure 1]b and [Figure 1]c. On hematoxylin and eosin staining, the wrapped aberrant tissue shows classical pancreatic acini and islets of Langerhans. Islets of the aberrant pancreatic tissue express specific immunoreactivity with the anti-synaptophysin antibody [Figure 2].^[6],[7],[8] We noticed that the pancreatic ductal system was lying in front of the portal vein (anteportal type) on piecemeal dissection.

Figure 1: Dissected portal annular pancreas. (a) Antero-inferior view of pancreas showing the formation of portal vein and entry of the same into the substance of pancreas. (b) Posterior view of the pancreas with colored (blue) portal vein insitu. (c) Inferior view of pancreas showing the opening for portal vein within the pancreas

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Figure 2: Immunohistochemical staining with anti-synaptophysin antibody showing the islets (brown – DAB positive areas) with background hematoxylin stain (exocrine area)

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Discussion

The annular pancreas is the most common congenital anomaly seen in the pancreas, in which the duodenal annular pancreas is the usual variant. The PAP is relatively rare when compared with other variants of the annular pancreas. The PAP may be due to abnormal fusion of ventral bud left to the developing portal vein resulting in the PAP [Figure 3].^[1],[9],[10] Like this, rarely pancreatic bud encircles the superior mesenteric vessels (SMV) results in entrapment of SMV into the substance of the pancreas.^[3] PAP is frequently seen in some animals such as swine.^[10],[11] PAP commonly involves only the uncinate process; complete encircling is relatively rare.^[10],[11] Variant hepatic artery was found to associated with the 25% of PAP which is similar to that of its incidence with nonportal anular pancreas.^[2]

Figure 3: (a-c) Line diagrams show the mechanism of the normal development of the pancreas; D shows the hypertrophic ventral pancreatic bud (V) fusing to the dorsal bud (d) left to the portal vein; F – primitive foregut. The figure was adapted and modified from Yilmaz and Celik

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The pancreas develops from the two endodermal evaginations from the caudal region of the foregut, namely dorsal and ventral pancreatic buds. During the pancreas development, the ventral bud rotates to the left in the axis of the developing duodenum to fuse posteriorly with the dorsal pancreatic bud.^[12] Researchers proposed two hypotheses for congenital PAP. (1) Hypertrophied ventral pancreatic bud fuses with the body of the pancreas left to the portal vein and (2) malformation of the portal vein.^[1],[13] In the present case, a bulky pancreas (doubled the weight of normal pancreas) strongly suggests the former hypothesis.

Based on its relation to the commencement of the portal vein, the PAP was classified into three types, namely suprasplenic (aberrant pancreatic parenchyma cranial to the formation of the portal vein), infrasplenic (caudal to its), and mixed type.^[14] Further, based on the relation of the pancreatic ductal pattern, it is classified into three more types, namely anteportal, retroportal, and retroportal with pancreatic divisium.^{[9],[15],[16]} In the present case, it belongs to the suprasplenic anteportal type of the PAP, the most common (92%) type of PAP.

This variation is usually asymptomatic. In cases of the malignant lesion in the head of the pancreas, the PAP was confused with the tumor's extension (pseudo tumour).^[1] In other way, if there is an extension of the tumor into the PAP, it may lead to incomplete removal of tumor cells. Contrast-enhanced computed tomography scan is the investigation of choice for diagnosing the PAP; magnetic resonance cholangiopancreatography may be required for further evaluation of ductal pattern before surgery.^[4],[16] Precise planning of surgical procedures is necessary to avoid complications.^[4],[17] Previous studies reported that the PAP is missed in more than half of the cases in preoperative magnetic resonance imaging (MRI) and computed tomography (CT) scans.^[9] A higher incidence of surgical complications is reported in this anomaly, especially the postoperative pancreatic fistula (45% of cases).^[4],[11] Unlike the normal pancreas, the surgical procedure in this cases is different and challenging. There are no proper guidelines in the stump management of PAP. In classical pancreatoduodenectomy (Whipple resection), posttransection of the pancreatic head, two pancreatic stumps (i.e., one stump anterior to the portal vein and another posterior to it) have to be managed in cases of the PAP. Dhanapal et al. reported a similar intra-operative case of anteportal type of PAP. They performed “duct to mucosa” pancreaticojejunostomy in the anterior stump and the posterior stump without ductal opening was managed with interrupted polypropylene sutures.^[4]

Conclusion

In conclusion, the PAP is predominently asymptomatic in nature. However, in cases of a malignant lesion in the head of the pancreas, the PAP is usually confused as the extension of the tumor (pseudotumor). Postoperative pancreatic fistula is the most common complication in cases of PAP, thus the prior planning of pancreatic stumps management is necessary. Knowledge about the PAP is necessary for the surgeon and radiologist for the accurate diagnosis since the condition is missed in more than half of the cases in preoperative MRI and CT scans.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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