|Year : 2016 | Volume
| Issue : 4 | Page : 278-280
Imaging findings in incomplete annular pancreas in adults with crocodile jaw appearance: Report of two cases
Puneet Mittal1, Kamini Gupta2, Amit Mittal1, Ranjana Gupta1
1 Department of Radiodiagnosis, MMIMSR, Mullana, Ambala, Haryana, India
2 Department of Radiodiagnosis, Dayanand Medical College and Hospital, Ludhiana, Punjab, India
|Date of Web Publication||15-Nov-2016|
Dr. Puneet Mittal
Department of Radiodiagnosis, MMIMSR, Mullana, Ambala, Haryana
Source of Support: None, Conflict of Interest: None
Annular pancreas is a well-known developmental anomaly. It usually presents in neonatal period with duodenal obstruction due to pancreatic tissue enveloping the second part of duodenum. It is associated with other anomalies such as Down's syndrome, duodenal atresia, and Hirschsprung disease. Presentation in adults can be due to pancreatitis or obstruction. While complete annular pancreas is well described in literature, imaging appearance of incomplete annular pancreas is only described recently. We present imaging findings in two cases of partial annular pancreas.
Keywords: Annular, crocodile, incomplete, jaw, magnetic resonance imaging, multidetector computed tomography, pancreas
|How to cite this article:|
Mittal P, Gupta K, Mittal A, Gupta R. Imaging findings in incomplete annular pancreas in adults with crocodile jaw appearance: Report of two cases. Int J Health Allied Sci 2016;5:278-80
|How to cite this URL:|
Mittal P, Gupta K, Mittal A, Gupta R. Imaging findings in incomplete annular pancreas in adults with crocodile jaw appearance: Report of two cases. Int J Health Allied Sci [serial online] 2016 [cited 2019 Oct 21];5:278-80. Available from: http://www.ijhas.in/text.asp?2016/5/4/278/194134
| Introduction|| |
Annular pancreas is an uncommon congenital anomaly. Its actual incidence is unknown and has been estimated at around 0.02%, while endoscopic retrograde cholangiopancreatography (ERCP)-based studies report a higher incidence of around 0.4%. About half of the cases present in the neonatal period with obstruction. Presentation in adults is usually in the 3rd to 6th decade with pancreatitis, obstruction, or epigastric pain/discomfort. The partial annular pancreas should be looked for while imaging especially in cases of obscure causes of pancreatitis or duodenal obstruction in adults.
| Case Reports|| |
A 42-year-old male patient presented with 7 days history of epigastric pain and vomiting after meals. On ultrasound abdomen, the stomach was seen in grossly distended state with narrowing in the second part of duodenum due to pancreatic tissue partially encircling it [Figure 1]. Further evaluation with contrast-enhanced computed tomography, done on 128 slice multidetector computed tomography (CT), revealed pancreatic tissue extending anterolaterally and posterolaterally to the second part of duodenum with duodenal obstruction [Figure 2]. On magnetic resonance imaging (MRI), partial annular pancreas was seen with "crocodile jaw" appearance [Figure 3]. Diagnosis of the partial annular pancreas was confirmed at gastrojejunostomy with relief of symptoms.
|Figure 1: Ultrasound image in axial plane (a) dilated stomach (white arrow). More inferior section (b) anterior and posterior extension of pancreatic tissue (white arrows) partially encircling the second part of duodenum (dotted white arrow)|
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|Figure 2: Coronal contrast-enhanced computed tomography image (a) grossly dilated stomach. Axial contrast-enhanced computed tomography image (b) anterolateral and posterolateral extension of pancreatic tissue in relation to second part of duodenum|
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|Figure 3: Axial T1-weighted fat saturated image shows anterolateral and posterolateral extension of pancreatic tissue in relation to the second part of duodenum giving crocodile jaw appearance (white arrow)|
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A 40-year-old female patient presented with 5 days history of severe epigastric pain and vomiting. She had a history of two attacks of acute pancreatitis and intermittent episodes of bowel obstruction in past 1 year of unknown cause. CT scan showed bulky head of pancreas with associated irregular fluid collection in the lesser sac. Pancreatic tissue was seen to extend in anterolateral and posterolateral direction in relation to second part of duodenum [Figure 4]. MRI showed partial annular pancreas with "crocodile jaw appearance" [Figure 5]. The patient was initially managed conservatively for relief of pancreatitis and later on underwent duodenoduodenostomy after 2 months which also confirmed the imaging diagnosis of partial annular pancreas.
|Figure 4: Axial contrast-enhanced computed tomography image shows anterolateral and posterolateral extension of pancreatic tissue in relation to second part of duodenum (dotted white arrows). Furthermore, noted is bulky head of pancreas with peripancreatic inflammation and fluid collection consistent with acute pancreatitis (white arrow)|
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|Figure 5: Axial T1-weighted image shows anterolateral and posterolateral extension of pancreatic tissue in relation to duodenum with crocodile jaw appearance (black arrows). Decreased T1-weighted signal of pancreas is consistent with acute pancreatitis|
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| Discussion|| |
Pancreas develops from dorsal and ventral buds. Ventral bud forms the uncinate process and head of pancreas and dorsal bud forms the body and tail of pancreas. Embryogenesis of annular pancreas is uncertain; however, it is certain that annular pancreatic tissue originates from ventral bud. Various theories have been put forward. Most consistent appears to be one proposed by Kamisawa et al.,, which describes origin of annular pancreas due to adherence of ventral anlage to duodenum and subsequent duodenal rotation.
Annular pancreas can be complete or incomplete; in complete annular pancreas, there is a complete ring of pancreatic tissue surrounding the duodenum and in incomplete annular pancreas, there is an incomplete ring of pancreatic tissue surrounding the duodenum. In these cases, there may be thin rim of pancreatic tissue in the duodenal wall which may not be detectable on imaging. The complete annular pancreas is a well-known entity; however, the incomplete annular pancreas is often poorly recognized and may be undetected on routine imaging, especially in patients who do not present with duodenal obstruction. Interestingly, about one-third of patients with incomplete annular pancreas present with obstruction which is only marginally less than those with complete annular pancreas. Therefore, this finding should be sought for in those with duodenal obstruction or with pancreatitis of the unknown cause.
The preoperative diagnosis of annular pancreas has improved considerably with the development of newer techniques such as ERCP and magnetic resonance cholangiopancreatography (MRCP). With advent of multidetector CT and increasing awareness of this condition, more cases are being detected preoperatively., Imaging is also useful for defining grading of pancreatitis, any associated fluid collections and changes of chronic pancreatitis. Moreover, MRCP is useful of defining any associated ductal anomalies. While the diagnosis of complete annular pancreas is straightforward with complete ring of pancreatic tissue enveloping second part of duodenum, incomplete annular pancreas may be more subtle. Three types have been described depending on extension of pancreatic tissue in relation to duodenum: Anterolateral extension, posterolateral extension, and both anterior and posterior extension (giving crocodile jaw appearance). Out of these, anterolateral extension is least specific, while crocodile jaw appearance is considered highly specific of incomplete annular pancreas. In symptomatic cases, treatment is usually by bypassing the duodenal obstruction by duodenoduodenostomy or gastrojejunostomy.
Both the patients in this study presented with "crocodile jaw appearance" with both anterior and posterior extension of pancreatic tissue. In conclusion, crocodile jaw appearance is very useful for imaging detection of incomplete annular pancreas. It should be looked for in patients with obscure causes of duodenal obstruction or pancreatitis, so that appropriate and timely treatment can be instituted.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]