P0062 - Atypical Extensive Retroperitoneal Fat Necrosis, Sequel of Acute Pancreatitis Attack

Muhammad Gilani, MD¹, Tugce Akcan, MD¹, Meghan Peterson, BS², Ahmed Zahid, MD^1
1Marshfield Clinic, Marshfield, WI; ²Medical College of Wisconsin, Wausau, WI

Introduction: Retroperitoneal fat necrosis can result as a sequela of pancreatitis due to the release of lipolytic enzymes during inflammatory processes, and its presentation varies. On CECT scan, retroperitoneal fat necrosis generally appears as a low attenuation collection, with minimal heterogeneity which may imitate certain malignancies, such as carcinomatosis and liposarcoma, and may lead to further invasive studies for evaluation. We report a case of extensive retroperitoneal fat necrosis that developed in 9 days after an episode of acute pancreatitis.

Case Description/Methods: 23-year-old man who presented with lower back and groin pain. Patient was diagnosed with acute pancreatitis 8 days ago based on clinical features, elevated lipase and CT abdomen & pelvis findings. He was asymptomatic at time of discharge. Patient was readmitted. Labs showed WBC 18,500 µ/L,CRP 22.6 mg/dL and procalcitonin of 2.34 ng/mL. CMP and lipase were within the normal range. CT of the abdomen& pelvis with contrast revealed a new, large retroperitoneal process with dense infiltrative tissue extending along the aorta starting just below the origin of the superior mesenteric artery and extending to the bifurcation measuring about 10.8 x 9.3 x 5.2 cm. Wispy tissue extended up along the pancreas and down the anterior pararenal spaces as well as along the iliac vessels. The retroperitoneal tissue exerted mass effect narrowing the inferior vena cava (IVC) just inferior to left renal vein and uplifted the aorta anteriorly off the spine. The pancreas itself enhanced normally. Due to elevated inflammatory markers and atypical distribution on CT, GI and ID were consulted. Extensive infectious work up including bacterial, mycobacterial, fungal was negative and tissue biopsy showed fat necrosis. Conservative management was pursued and follow up CT images at 4 and 12 weeks showed significant improvement.

Discussion: The distribution of retroperitoneal fat necrosis is typically peripancreatic, with extensions to the origin of the mesentery of the small intestine, the transverse mesocolon, and the omentum. This atypical presentation along with normal appearing pancreas on CECCT in our patient in 9 days led to extensive noninvasive and invasive work up that came out negative and benign. Patient was managed conservatively and follow up CECT showed significant improvement in retroperitoneal fat necrosis.





References available upon request.




Figure: Fig: CECT abdomen pelvis; left image at time of presentation, right image at 4 weeks


Disclosures:
Muhammad Gilani indicated no relevant financial relationships.
Tugce Akcan indicated no relevant financial relationships.
Meghan Peterson indicated no relevant financial relationships.
Ahmed Zahid indicated no relevant financial relationships.


Muhammad Gilani, MD¹, Tugce Akcan, MD¹, Meghan Peterson, BS², Ahmed Zahid, MD¹. P0062 - Atypical Extensive Retroperitoneal Fat Necrosis, Sequel of Acute Pancreatitis Attack, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.