The patient was referred for a CT scan by the gastroenterology team to rule out a pancreatic head tumor. 

Patient's serum IgG4 serum levels were performed after his initial CT, and were found to be markedly elevated.

The imaging findings of a bulky pancreatic head, with associated common bile duct and intrahepatic biliary tract dilatation can be misleading in this case. In pancreatic ductal adenocarcinomas, the tumor appears hypodense and poorly enhancing compared to the normal surrounding pancreatic tissue, appearing hypodense in the arterial phase in 75-90% cases, and may show delayed enhancement. In this particular case, the whole appearance of the pancreas is homogenous in all phases, with minor surrounding fat stranding, raising the possibility for other diagnoses. Please see: Pancreatic ductal adenocarcinoma

Looking at the imaging findings surrounding the abdominal aorta, with no aortic elevation, retroperitoneal fibrosis moves up in the list of differential diagnoses.

A correlation between retroperitoneal fibrosis, sclerosing cholangitis, and autoimmune pancreatitis can be found in medical literature. Please see: IgG4-related disease

This patient's condition significantly improved after the initiation of steroid therapy, with complete regression of his symptoms.