Comparison of Ultrasonography, Computed Tomography, and Single‐Photon Emission Computed Tomography for the Detection and Localization of Canine Insulinoma

Abstract

Accurate preoperative detection, localization, and staging of the primary tumor and metastases are essential for the selection of appropriate candidates for surgery. In dogs with insulinoma, preoperative assessment usually is performed with transabdominal ultrasonography (US). There are no reports on the use of computed tomography (CT) for this purpose. The preoperative use of somatostatin receptor scintigraphy (SRS) recently has been advocated for the identification of insulinoma and gastrinoma in dogs, but its accuracy remains to be established. In this report US, CT, and single-photon emission computed tomography (SPECT) with [ 111 In-DTPA-D-Phe 1 ]-octreotide (a specific form of SRS) were compared for their effectiveness in detecting and localizing primary and metastatic insulinoma in dogs. Findings at surgery or postmortem examination served as control. Of 14 primary insulinomas, 5, 10, and 6 were correctly identified by US, CT, and SPECT, respectively. No lymph node metastases were detected by US or SPECT. CT identified 2 of 5 lymph node metastases but also identified 28 false-positive lesions. Two of 4 livers were found to be positive for metastases by 1 of the imaging techniques. US can be used for the initial evaluation of dogs with hypoglycemia. Although CT identifies most primary tumors, intraoperative inspection and palpation of the pancreas is still superior. SPECT appears as effective as US and CT in detecting insulinomas. Future developments in preoperative imaging techniques might improve current methods of canine insulinoma detection.Key words: Abdominal ultrasonography; Computed tomography; Diagnostic imaging; Dog; Pancreatic endocrine tumor; Somatostatin receptor scintigraphy. Insulin-producing pancreatic endocrine tumor, or insulinoma, is the most common of the 3 types of pancreatic endocrine tumor (PET) described in the dog (insulinoma, gastrinoma, and glucagonoma).1-3 Over 95% of insulinomas in dogs are malignant, and 40-50% have visibly metastasized at the time of surgery.2,4,5 Insulinomas are identified and staged by means of preoperative transabdominal ultrasonography (US) and, to a lesser extent, by computed tomography (CT) and by inspection and palpation during exploratory laparotomy.Data on the effectiveness of preoperative imaging techniques in dogs with insulinoma are limited to uncontrolled studies of transabdominal US. [6][7][8] In human medicine, several imaging techniques have been described and evaluated for preoperative identification and staging of PETs. Somatostatin receptor scintigraphy (SRS) has become an important and often 1st-line imaging method in humans with malignant PETs. [9][10][11][12] This imaging modality has a high sensitivity and a high specificity. [13][14][15] Additional advantages of this technique are whole-body scanning for extra-abdominal metastases, gamma probing for intraoperative identification of tumor foci, and selection of subjects suitable for treatment with a radiolabeled somatostatin analogue. otide was described for identification of insulinoma...

Description of the use of contrast‐enhanced ultrasonography in four dogs with pancreatic tumours

“…Moreover, pancreatic disorders may not cause changes in US appearance (Hecht & Henry 2007). Although US is the most widely used technique in the diagnosis of pancreatic tumours, it has a poor sensitivity for the diagnosis of insulinomas in dogs (Lamb et al 1995;Robben et al 2005).…”

“…These tumours are diagnosed based on clinical signs and clinicopathological investigations, in combination with diagnostic imaging (Feldman & Nelson 2004). Several imaging techniques, including B-mode ultrasonography (US), Doppler US, computed tomography (CT), planar scintigraphy and single-photon emission CT, have been used to evaluate pancreatic tumours (Lamb et al 1995;Robben et al 2005;Iseri et al 2007). A definitive diagnosis typically requires cytological or histopathological evaluation of the suspected neoplastic tissue (Steiner & Bryette 1996;Bennett et al 2001).…”

“…A definitive diagnosis typically requires cytological or histopathological evaluation of the suspected neoplastic tissue (Steiner & Bryette 1996;Bennett et al 2001). The sensitivity of abdominal US in detecting pancreatic tumours varies from 28 to 75% (Lamb et al 1995;Robben et al 2005;Goutal et al 2012). With the availability of safe US contrast agents, contrastenhanced ultrasonography (CEUS) has become a reliable method for the differential diagnosis of pancreatic tumours in humans (D'Onofrio et al 2003;Rickes & Wermke 2004;Rickes et al 2006).…”

Feasibility for Using Dual‐phase Contrast‐enhanced Multi‐detector Helical Computed Tomography to Evaluate Awake and Sedated Dogs With Acute Abdominal Signs

“…3 Reports describing CT evaluation of the canine abdomen have increased during the past decade. Applications include suspected disease of the upper and lower urinary tract, [5][6][7][8][9][10][11] spleen, 12,13 hepatic/portal venous system, [14][15][16][17][18][19][20][21][22][23][24][25][26] pancreas, [27][28][29] mesenteric/intrapelvic regions, 30,31 adrenal gland, [32][33][34] and gastrointestinal tract. 35,36 These reports primarily describe the use of anesthesia or heavy sedation during scan procedures in order to minimize motion artifacts that could result in nondiagnostic scans.…”

Helical Computed Tomographic Angiography of the Normal Canine Pancreas

“…[2][3][4] Conventional imaging modalities such as radiography and ultrasonography have limitations in sensitivity and specificity for the diagnosis of canine pancreatitis and neoplasia. 5,6 In humans, helical computed tomography (CT) of the pancreas is the imaging modality of choice for the diagnosis, staging and as a prognostic indicator of multiple pancreatic inflammatory diseases and neoplasia. Dual-phase CT angiography is commonly used in humans for staging of pancreatic neoplasia by identifying degree of vessel invasion to determine surgical curability.…”