New Radiographic Clue for Diagnosing Canine Pancreatitis: The Right Renal Halo Sign

Right Renal Halo Sign in Dogs with Presumed Acute Pancreatitis on Radiographs: A Pilot Study

Elodie Huguet, Clifford R. Berry, Michael Schaer, Lenice McCoy, Yang Qu, Federico R. Vilaplana Grosso

Background

Acute pancreatitis in dogs is a common gastrointestinal disorder, with radiographic features often including loss of cranial abdominal detail and signs such as the "sentinel loop." Anecdotal observations suggested that the right renal silhouette might appear unusually conspicuous (a "renal halo sign") on ventrodorsal abdominal radiographs in affected dogs. The purpose of this study was to determine whether this radiographic sign correlates significantly with acute pancreatitis, compared to other abdominal pathologies or normal findings.

Methods

This retrospective study evaluated 100 dogs divided into four groups: acute pancreatitis (n=39), right cranial abdominal mass (n=16), peritoneal effusion (n=15), and normal controls (n=30). Inclusion required appropriate clinical and imaging criteria, including ventrodorsal abdominal radiographs. A board-certified radiologist, blinded to diagnoses, assessed the presence of a right renal halo sign—defined as ≥75% visibility of the right renal silhouette including the cranial pole. Statistical analysis used Fisher exact tests to assess significance between groups.

Results

The right renal halo sign was observed in 33% (13/39) of dogs with acute pancreatitis, 12.5% (2/16) with a right-sided abdominal mass, and only 3% (1/30) of normal controls. No dogs in the peritoneal effusion group showed the sign. Statistical analysis revealed significant differences between the pancreatitis group and both the effusion group (P=0.0333) and the control group (P=0.0127). The sign was thus more prevalent in dogs with acute pancreatitis compared to other groups.

Limitations

Limitations include the retrospective design, potential selection bias due to database search limitations, and uneven group sizes. The diagnosis of acute pancreatitis was based on clinical findings rather than histopathology, limiting diagnostic certainty. Additionally, ultrasonographic findings were not consistently available, and no correlation was made between the severity of pancreatitis and the presence of the halo sign.

Conclusions

The right renal halo sign was more frequently observed in dogs with presumed acute pancreatitis and may serve as a supportive radiographic indicator for diagnosis. While not specific, its presence—especially in conjunction with other radiographic features—could justify further diagnostic investigation, such as ultrasonography. Future studies with histopathological confirmation and cross-sectional imaging may clarify its diagnostic utility and underlying mechanisms.

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