Annular Pancreas Accompanied by Hematochezia

Zhigang Gong, AST; Xiaoqing Ding, RT; Wenli Tan, MD, PhD; Xi Zhao*, MD
Department of Radiology, Shuguang Hospital, Affiliated with Shanghai TCM University, Shanghai, P. R. China
*Siemens Healthineers China
|14/01/2020

A 46-year-old male patient, suffering from acute hematochezia and unconsciousness, was transferred to our hospital. He had a history of recurrent hematochezia over the past 5 years and had undergone colonoscopy in the referring hospital. This had revealed multiple right-sided hemorrhagic diverticula. His past treatments included endovascular embolization and pharmacotherapy. A Dual Energy (DE) CT was performed for evaluation.

CT images revealed multiple diverticula in the ascending colon. The descending duodenum appeared to be narrowed, with localized wall thickening and inhomogeneous enhancement. The boundaries of the duodenal wall to the head of the pancreas were unclear (Fig. 1). These findings raised the suspicion of a duodenal tumor, potentially invading the pancreatic head. As the scan was performed using DE, images could be displayed at 45 keV using Monoenergetic Plus. This significantly enhanced the image contrast, demonstrating clearer boundaries of the duodenum wall to the pancreatic head. A partial encircling of the annulus, giving a ‘crocodile jaw’ appearance, without signs of a significant duodenal narrowing or pancreatic duct obstruction, was also visualized (Fig. 2). An annular pancreas was diagnosed and subsequently confirmed during a right hemicolectomy due to an uncontrollable hematochezia.

A Dual Energy (DE) CT was performed to further evaluate acute hematochezia and unconsciousness.
Courtesy of Department of Radiology, Shuguang Hospital, Affiliated with Shanghai TCM University, Shanghai, P. R. China

Fig. 1:
Axial images of the arterial (Fig. 1a) and venous (Fig. 1b) phases. The descending duodenum appears to be narrowed with localized wall thickening and inhomogeneous enhancement, as well as unclear boundaries to the pancreatic head (arrows). These findings lead to the suspicion of a duodenal tumor invading the pancreatic head.

A partial encircling of the annulus, giving a ‘crocodile jaw’ appearance, without signs of significant duodenal narrowing or pancreatic duct obstruction.
Courtesy of Department of Radiology, Shuguang Hospital, Affiliated with Shanghai TCM University, Shanghai, P. R. China

Fig. 2:
Axial images show a partial encircling of the annulus, giving a ‘crocodile jaw’ appearance, without signs of significant duodenal narrowing or pancreatic duct obstruction (arrows). The contrast is significantly enhanced in the image displayed at Monoenergetic Plus 45 keV (Fig. 2b), in comparison to that of the mixed image (Fig. 2a), showing clearer boundaries of the duodenum wall to the pancreatic head. Note that both images are displayed in the same window setting.

A cVRT image shows an annular pancreas in 3D.
Courtesy of Department of Radiology, Shuguang Hospital, Affiliated with Shanghai TCM University, Shanghai, P. R. China

Fig. 3:
A cVRT image shows an annular pancreas in 3D.

An annular pancreas is a rare congenital anomaly, in which the pancreatic tissue forms a complete or partial ring around the descending duodenum. It can remain asymptomatic, or appear in variable clinical presentations, such as duodenal obstruction or pancreatitis. An annular pancreas can be overlooked or misdiagnosed, and radiologists should be aware of the imaging findings. Typical CT image findings include pancreatic tissue extending posterior to the second part of the duodenum, or a ‘crocodile jaw’ configuration, where the pancreatic head is found anterior and posterior to the second part of the duodenum, or the presence of pancreatic tissue posterolateral to the duodenum. These findings are highly suggestive of an annular pancreas. DE CT allows images to be displayed at 45 keV, significantly enhancing the contrast. This helps the physicians differentiate the tissues of the duodenal wall and the pancreatic head, ending the suspicion of a duodenal tumor invading the pancreatic head. Cinematic volume rendering technique (cVRT) improves depth and shape perceptions, allowing a life-like 3D demonstration.

Scanner

Scan area

Abdomen / Pelvis

Scan mode

Dual Source Dual Energy

Scan length

477 mm

Scan direction

Cranio-caudal

Scan time

10.2 s

Tube voltage

100 & Sn150 kV

Effective mAs

125 / 64 mAs

Dose modulation

CARE Dose4D

CTDIvol

7.3 mGy

DLP

371.2 mGy cm

Rotation time

0.5 s

Pitch

0.6

Slice collimation

128 x 0.6 mm

Slice width

1.5 mm

Reconstruction increment

1.0 mm

Reconstruction kernel

Qr40 (ADMIRE 3)

Contrast

320 mg/mL

Volume

80 mL + 40 mL saline

Flow rate

3 mL/s

Start delay

Bolus tracking in the abdominal aorta @ 100 HU + 10 s