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Objective:
Pancreatic cancer (PC) is recognized to be an important, albeit uncommon, cause of acute pancreatitis (AP). Conversely, AP may be the initial clinical presentation of PC, and may provide an index event to identify an underlying PC. However, only ~2% of AP is due to PC, with the majority being due to etiologies such as alcohol and gallstones, generally involving to some extent the entire gland. In our clinical practice, we’ve noted patients with AP confined to the body and tail of the pancreas with sparing of the head, suggesting that an element of ductal obstruction to be present upstream from the pancreatic head. We postulate that once identifiable causes of duct obstruction at the level of the body and tail such as prior acute necrotizing pancreatitis (resulting in ductal injury), background chronic pancreatitis (in the setting of a preexisting ductal stricture or stone) or a visible pancreatic mass have been excluded, the presence of a small PC causing duct obstruction should be entertained. Our objective was to assess the frequency of unexplained isolated distal pancreatitis in patients presenting with a first episode of AP and to evaluate the presence of underlying PC in these patients.

Materials and Methods:
This was a retrospective chart review study, in which all patients with newly diagnosed AP who had contrasted CT studies within 4 weeks from presentation during 2019 and 2020 were included. Patients with known PC, visible pancreatic mass, history of prior AP, sequela of necrotizing AP on CT, and prior pancreaticobiliary intervention were excluded. CT scans were evaluated for the presence of either generalized AP or isolated distal pancreatitis defined as AP confined to the body and tail (left of SMV) and peripancreatic soft tissues, with sparing of the head. Outcome was biopsy proven PC.

Results:
From a total of 256 patients identified as having AP, 111 (43%) were excluded as defined in the methods section above, leaving 145 (57%) patients as having a first episode of AP without an identifiable cause. 129 (89%) of these patients [68 men, 61 women; age 59 ±17 years] had generalized AP; none of these patients were subsequently diagnosed with PC with follow up between 18 and 42 months. Sixteen (11%) patients [10 men, 6 women; age 66 ±14 years] had isolated distal pancreatitis with 9 of those 16 (56%) patients subsequently diagnosed with PC. The rate of PC in patients with isolated distal pancreatitis (56%, 95% CI 30–80%) was significantly higher than the rate in other patients (0%), p < 0.0001. The median diagnostic delay of PC from initial presentation in these 9 patients were 267 days and patients had an average of 3 subsequent CT studies before the diagnosis of PC was suggested by the reporting radiologist.

Conclusion:
Isolated distal pancreatitis, in the absence of an identifiable cause, is an uncommon but unique imaging subtype of AP and could be a potential harbinger of early PC. We want to familiarize radiologists with this imaging manifestation of early PC and recommend that the presence of a small PC in this setting be actively pursued, to avoid diagnostic delay.