EXPRESS: Ultrasonographic findings of feline large intestinal adenocarcinoma and high-grade lymphoma

OBJECTIVES: This retrospective study aims to describe the ultrasonographic findings of cats with large intestinal adenocarcinoma (ACA) and high-grade lymphoma (LSA). METHODS: Cats diagnosed with large intestinal neoplasia with a complete abdominal ultrasound were included in the study. Signalment, clinical history, physical examination, bloodwork, and outcome data were collected. Tumor location, length, wall thickness and layering, echogenicity, lymphadenopathy, effusion, ulceration, and obstruction were recorded. RESULTS: Forty-four cats had ACA primarily affecting the colon in 28/44 cats and the ileocolic junction (ICJ) in 16/44 cats. The ACA tumors measured a median length of 22.85mm and a median wall thickening of 9mm. Regional lymphadenopathy was noted in 29/44 cats with a median thickness of 6.7mm. Obstruction was observed in 30% of the cats with ACA. Thirty-eight cats were diagnosed with high-grade LSA primarily affecting the ICJ in 20/38 cats, the colon in 14/38 cats and multifocally in the gastrointestinal tract in 4 cats. Also, 7/38 cats had other organ involvement. The LSA tumors measured a median length of 48mm and a median wall thickening of 15mm. Regional lymphadenopathy was noted in 31/38 cats with a median thickness of 11mm. Obstruction was present in 11% of the cats with LSA. Both tumor types commonly appeared as transmural, hypoechoic thickening with loss of wall layering. The median survival time for cats with large intestinal ACA and LSA were 19 days and 23 days, respectively. CONCLUSION AND RELEVANCE: Cats with large intestinal ACA and LSA shared a similar clinical presentation. Both neoplasia share similar ultrasonographic features, but LSA lesions are usually thicker and longer, and are accompanied by more frequent and pronounced lymphadenopathy than ACA lesions. Adenocarcinomas are more likely to cause obstruction while lymphoma tumors tend to have a multicentric distribution. Because imaging findings overlap, cytologic or histologic sampling remains essential for definitive diagnosis.