Contrast-enhanced CT features of pyloric lesions in 17 dogs: Case series

Toshiyuki Tanaka, Yusuke Wada, Shunsuke Noguchi, Hidetaka Nishida, Hideo Akiyoshi

Background
Pyloric outflow obstruction in dogs can arise from conditions such as chronic hypertrophic pyloric gastropathy, hyperplastic polyps, and various gastric neoplasias. While ultrasonography and endoscopy are commonly used for diagnosis, contrast-enhanced CT (computed tomography) offers detailed insights into gastric wall abnormalities. This study aimed to evaluate the CT characteristics of various pyloric lesions in dogs, focusing on identifying patterns that differentiate benign from malignant conditions.

Methods
This retrospective case series examined CT images of 17 dogs with histopathologically confirmed pyloric lesions evaluated between 2015 and 2021. Data collected included lesion shape, growth patterns, enhancement characteristics during early and delayed contrast phases, and the presence of lymphomegaly or pulmonary metastases. Lesions were classified as affecting the mucosal or outer layers, with measurements standardized using specific CT settings. All findings were cross-validated by two experienced veterinary radiologists.

Results
The dogs had various diagnoses, including hyperplasia (5), adenoma (5), adenocarcinoma (3), gastrointestinal stromal tumor (GIST, 2), polyposis (1), and pyogenic granuloma (1). Key findings include:
- Hyperplasia and adenoma formed heterogeneous, mucosal mass lesions.
- Adenocarcinomas showed asymmetric wall thickening involving outer layers, with lymph node metastases in all cases.
- GISTs presented as outer-layer masses, occasionally with necrosis indicated by heterogeneous enhancement.
- Polyposis and pyogenic granuloma affected both mucosal and outer layers but were distinguishable based on enhancement symmetry.
No pulmonary metastases were observed in any case.

Limitations
The small sample size and retrospective design limited the study's scope. Histopathological or genetic evaluations (e.g., APC mutations) were unavailable for some cases. The lack of lymph node biopsies in certain cases reduced the accuracy of lymphomegaly assessments. These limitations necessitate cautious interpretation of findings.

Conclusions
Contrast-enhanced CT effectively characterizes canine pyloric lesions by highlighting specific patterns in lesion shape, enhancement, and localization. While adenomas and hyperplasia commonly presented as benign mucosal lesions, adenocarcinomas and GISTs involved deeper layers and displayed more aggressive features. CT findings can support differential diagnosis but should be supplemented with histopathological evaluations for definitive diagnosis. Future studies with larger, geographically diverse populations are recommended.

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