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

Radiographic signs of acute pancreatitis in dogs include widening of the pyloroduodenal angle and a cranial abdominal mass effect/decreased serosal detail. In some dogs with acute pancreatitis, it has been anecdotally noted that the right renal silhouette could be well visualized on the ventrodorsal abdominal radiograph. The purpose of this study was to see whether increased right renal conspicuity (i.e., renal "halo" sign) is associated with pancreatitis, other causes of a right cranial abdominal mass effect, decreased abdominal serosal detail as with the presence of peritoneal effusion, or perhaps representing a normal variation. The medical records of 100 dogs were retrospectively collected and divided into four groups, including control dogs (n = 30), right-sided hepatic mass effect (n = 16), peritoneal effusion (n = 15), and acute pancreatitis (n = 39). Ventrodorsal radiographs from each case were randomized for evaluation by a radiologist blinded to the final diagnosis. A right renal halo sign was identified in 13/39 (33%) of dogs with acute pancreatitis, 2/16 (12.5%) dogs with a right cranial abdominal mass effect, and 1/30 (3%) control dog. This study supports that the renal halo signs on ventrodorsal radiographs is most prevalent in dogs with acute pancreatitis and may help support a clinical diagnosis of this medical disorder.