Characterization of triple-phase computed tomography in dogs with pancreatic insulinoma

Abstract

Little information is available regarding triple-phase computed tomography (CT) of canine pancreatic insulinoma. A few case reports with small numbers of cases have indicated that hyper-attenuation in the arterial phase was a common finding on multi-phasic CT in dogs with insulinoma. Our purpose was to clarify the characteristic findings of dogs with insulinoma on triple-phase CT. Nine dogs with insulinoma that underwent triple-phase CT were included in the present study. Attenuation patterns in the arterial phase indicated hypo-attenuation in 4 cases and hyper-attenuation in 2 cases. In the remaining 3 cases, 1 case showed hypo-attenuation and 1 case showed hyper-attenuation in the pancreatic phase, and 1 case presented hyper-attenuation in the later phase. Altogether, 5 cases showed hypo and 4 cases showed hyper-attenuation in at least one phase. The enhancement pattern was homogenous in 7 cases and heterogeneous in 2 cases. Tumor margins were well-defined in 5 cases and ill-defined in 4 cases. Capsule formation was present in 5 cases and absent in 4 cases. In conclusion, it is important to note that hypo-attenuation was as common as hyper-attenuation in dogs with insulinoma in triple-phase CT in at least one phase. Additionally, mass lesions were most conspicuous not only in the arterial phase but in the pancreatic and later phases in some cases. Therefore, it is important to perform triple-phase CT and notice about variable findings for the detection of canine pancreatic insulinoma.

Canine insulinomas appear hyperintense on MRI T2‐weighted images and isointense on T1‐weighted images

“…As described in humans and canine patients, insulinomas are strongly enhancing during the arterial phase, due to their hypervascular nature, and in humans can be differentiated from other more poorly vascularized pancreatic tumors, which often appear as hypoattenuating . However, hypoattenuating insulinomas have also been identified in both human and canine patients, complicating the enhancements patterns …”

“…Persistent hypoglycemia with normal or inappropriately high insulin levels is suggestive of an insulinoma, but confirmation requires the support of histopathology . As surgical intervention is often recommended for definitive diagnosis and treatment, preoperative imaging is generally indicated …”

“…Many imaging techniques have been explored in both human and canine insulinomas. Abdominal ultrasound, although widely available, has a sensitivity ranging between 28% and 75% for detecting insulinomas in dogs . Thoracic and abdominal radiographs are often unremarkable given the small size of insulinomas and rare incidence of pulmonary metastases .…”

“…Meanwhile, another study on contrast‐enhanced ultrasound suggested that this modality may help to increase the conspicuity of canine insulinomas; however, enhancement characteristics in the examined patients were variable . Computed tomography, including dynamic CT, dual‐phase CT angiography, and triple‐phase CT, has appeared promising for identification of pancreatic insulinomas and their metastases in both canines and humans, but the enhancement pattern of canine insulinomas on CT remains to some extent inconsistent . As described in humans and canine patients, insulinomas are strongly enhancing during the arterial phase, due to their hypervascular nature, and in humans can be differentiated from other more poorly vascularized pancreatic tumors, which often appear as hypoattenuating .…”

“…Computed tomography, including dynamic CT, dual‐phase CT angiography, and triple‐phase CT, has appeared promising for identification of pancreatic insulinomas and their metastases in both canines and humans, but the enhancement pattern of canine insulinomas on CT remains to some extent inconsistent . As described in humans and canine patients, insulinomas are strongly enhancing during the arterial phase, due to their hypervascular nature, and in humans can be differentiated from other more poorly vascularized pancreatic tumors, which often appear as hypoattenuating . However, hypoattenuating insulinomas have also been identified in both human and canine patients, complicating the enhancements patterns …”