Pancreatic Abscess Leads to Rare Biliary Reflux in Dog—Imaging Saves the Diagnosis

Spontaneous Unusual Backflow from Duodenum to Biliary System in a Dog with Pancreatic Abscesses: A Case Study

Robert Cristian Purdoiu, Sorin Marian Marza, Radu Lacatus, Lucia Bel, Lea Carisch, Patrick Kircher

Background:
Duodenobiliary reflux—the retrograde flow of duodenal contents into the biliary system—is extremely rare in dogs, with only one prior case reported. This case study presents the second known occurrence in a dog, linking it to a novel etiology: abscessing pancreatitis. Unlike human cases where such reflux often causes complications like infections or gallstones, the dog in this study did not show immediate secondary effects.

Methods:
A 3-year-old neutered male Yorkshire Terrier presenting with vomiting, anorexia, and abdominal pain underwent multimodal imaging (barium contrast radiography, CT, and ultrasonography) to investigate the cause. Initial imaging revealed gas in the biliary tree, and sequential barium studies captured the retrograde movement of contrast into the biliary system. Further imaging confirmed abscessing pancreatitis. The dog was treated medically but eventually underwent exploratory laparotomy for diagnostic confirmation. No histopathological analysis was performed post-mortem.

Results:
Barium contrast imaging demonstrated gradual filling of the biliary system by reflux from the duodenum. CT confirmed pancreatic abscesses, biliary distension, and contrast material within the biliary tree. Ultrasonography revealed pancreatic enlargement, hyperechoic fat stranding, and a distended major duodenal papilla. Exploratory surgery verified multiple pancreatic abscesses and adhesions to the duodenum. Despite intervention, the dog deteriorated and was humanely euthanized. No direct sphincter of Oddi functional testing was performed, but inflammatory disruption of the sphincter was strongly suspected.

Limitations:
The lack of sphincter of Oddi functional studies, histopathologic confirmation, and longer-term follow-up limit the strength of conclusions. The diagnosis of reflux was inferential based on imaging rather than direct measurement, and causal associations remain speculative given the single case report.

Conclusions:
This report identifies abscessing pancreatitis as a new cause of spontaneous duodenobiliary reflux in dogs. Multimodal imaging was critical for diagnosis. Severe pancreatitis should be considered a potential cause of unexplained biliary gas or contrast filling on imaging. This case expands the differential diagnosis for biliary abnormalities and highlights the importance of considering species-specific differences in pathophysiology.

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