Usually chronic and often dependent on the site of the tumour within the gastrointestinal tract. Signs include:
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* For more proximal lesions:
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Dogs and cats present with a history of gastrointestinal signs. Tumours of the small intestine are associated with vomiting, weight loss, melaena, flatulence and borborygmus, and large intestinal adenocarcinoma can cause haematochezia with tenesmus and mucous. Constricting lesions in the distal tract may also change the shape of the faeces passed. Other signs reported in either form include anorexia, diarrhoea and signs associated with acute intestinal obstruction or perforation and peritonitis.
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** Vomiting
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* For lesions within the small intestine:
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Small intestinal adenocarcinomas may be palpable transabdominally as a mid-abdominal mass. Distended loops of small intestine may also be palpated, and rectal examination may reveal melaena. A mass may be palpated per rectum in large intestinal adenocarcinomas. This may present as a constriction or as nodular lesions protruding into the lumen. Bright red blood may be discovered on rectal examination.
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** Weight loss
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* For tumours in the more distal tract:
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Various paraneoplastic syndromes have been associated with intestinal adenocarcinoma, including cutaneous disease and hyperviscosity syndromes.
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** Tenesmus
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** Hematochezia
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** Faeces may be altered in shape with constricting lesions
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* Other signs reported include:
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** Anorexia
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** Diarrhoea
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** Signs associated with acute intestinal obstruction (usually when the tumour has grown in an annular form), perforation and peritonitis