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Contrast-enhanced ultrasound features of focal pancreatic lesions in dogs

Silvia Burti 1, Alessandro Zotti 1, Giuseppe Rubini 2, Riccardo Orlandi 3, Paolo Bargellini 3, Federico Bonsembiante 1, Barbara Contiero 1, Tommaso Banzato 1

Background
Primary pancreatic neoplasia is uncommon in dogs, with adenocarcinoma being the most frequent exocrine tumor and insulinoma the most common endocrine tumor. Contrast-enhanced ultrasound (CEUS) has been increasingly used to characterize focal pancreatic lesions in human medicine, but its application in veterinary medicine remains limited. This study aimed to describe the B-mode and CEUS features of benign and malignant focal pancreatic lesions in dogs, assessing its potential for distinguishing between different lesion types.

Methods
Study Design: Retrospective analysis of 75 dogs with focal pancreatic lesions diagnosed via B-mode ultrasound, CEUS, and cytopathology.

Lesion Classification: Based on cytopathology, lesions were categorized as:
-Adenocarcinoma (n = 23)
-Insulinoma (n = 23)
-Nodular hyperplasia (NH) (n = 17)
-Cysts (n = 7)
-Abscesses (n = 5)

Imaging Techniques:
-B-mode ultrasound assessed echogenicity, homogeneity, and acoustic enhancement.
-CEUS analyzed enhancement degree (hyper-, iso-, hypo-, or non-enhancing), enhancement pattern (solid vs. cystic), and wash-in/wash-out dynamics.

Statistical Analysis:
-Chi-square and Kruskal-Wallis tests evaluated differences between lesion types.
-Logistic regression and ROC curve analysis determined diagnostic accuracy.

Results
B-mode Findings:
-Adenocarcinomas were mostly mixed echogenic (78%), with acoustic enhancement (73%).
-Insulinomas were primarily hypoechoic (60%) with some mixed echogenicity (39%).
-NH lesions were consistently hypoechoic (94%) and displayed a homogeneous structure.
-Cysts were all anechoic with strong acoustic enhancement.
-Abscesses had mixed echogenicity (80%), sometimes appearing anechoic.

CEUS Findings:
-Adenocarcinomas were hypoenhancing (81%) and showed a non-homogeneous, cystic enhancement pattern.
-Insulinomas were hyperenhancing (78%), with homogeneous and solid enhancement.
-Nodular hyperplasia was isoenhancing (94%), distinguishing it from malignant tumors.
-Cysts were completely non-enhancing, consistent with fluid-filled structures.
-Abscesses showed variable enhancement, with both non-enhancing and hyperenhancing areas.

Diagnostic Accuracy:
-Hypoenhancement (AUC = 0.82) and non-homogeneous appearance (AUC = 0.81) were the strongest predictors of adenocarcinoma.
-Hyperenhancement was only seen in malignant tumors (adenocarcinomas and insulinomas).
-Isoenhancing lesions were mostly benign (NH).

Limitations
Cytopathology, rather than histopathology, was used as the gold standard, which may introduce classification errors.
Uneven case distribution, with adenocarcinomas and insulinomas overrepresented.
Retrospective study design, potentially leading to selection bias.

Conclusions
CEUS is a valuable diagnostic tool for differentiating benign and malignant focal pancreatic lesions in dogs. Adenocarcinomas tend to be hypoenhancing and non-homogeneous, while insulinomas are hyperenhancing and solid. The ability of CEUS to distinguish insulinomas from adenocarcinomas suggests it may improve diagnostic accuracy and guide clinical decision-making. Future studies should explore its role in preoperative planning and prognostication.

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