Intestinal Adenocarcinoma

Intestinal tumours account for less than 10% of all tumours in dogs and cats and 22% of gastrointestinal tumours in dogs and 35% in cats. Adenocardinoma/carcinoma is the most common malignant tumour in dogs and accounts for 17% of intestinal tumours in cats.

Signalment

• Dogs:
  • Mean age: 6-9 years
  • Minor male predisposition
  • Large breeds may predominate particularly collies and German Sheperds

• Cats:
  • Mean age: 10-12 years
  • There are conflicting reports of whether there is a minor male predisposition
  • Siamese may have a breed predisposition

Description

• No organism or chemical agent has been identified that will induce spontaneous intestinal adenocarcinoma.
• The gross appearance of colorectal adenocarcinomas vary from pedunculated, particularly in the distal rectum, cobblestone, in especially the middle rectum or annular, also usually in the middle recutum and may also have associations with tumour behaviour and prognosis.
• The most frequent sites of metastasis are the mesenteric lymph nodes.

Diagnosis

Clinical Signs

Often dependent on the site of the tumour within the gastrointestinal tract and include:

• For more proximal lesions:
  • vomiting
• For lesions within the small intestine:
  • Weight loss
• For tumours in the more distal tract:
  • Tenesmus
  • Hematochezia
• Other signs reported include:
  • Anorexia
  • Diarrhoea
  • Signs associated with intestinal obstruction, perforation and peritonitis

Associated paraneoplastic abnormalities include:

• Neutrophilic leukocytosis
• Monocytosis
• Eosinophilia
• Cutaneous disease
• Hyperviscosity syndromes

Physical Examination

• An abdominal mass may be palpable
• A mass may also be palpable via digital examination
• Cats may also be dehydrated

Haematology and Biochemistry

Abnormalities observed include:

• Anaemia
• Leukocytosis
• Left shift
• Monocytosis
• Hypoproteinemia
• Raised hepatic enzymes
• High cholesterol
• Raised BUN - may be due to concurrent renal insufficiency, dehydration or absorption following intestinal bleeding

Abdominal Radiography

• An abdominal mass may be visible with plain radiography
• Alternatively evidence of obstruction may be observed
• Poor serosal detail may be apparent
• Contrast radiography can be useful for localising masses, revealing obstructions and filling defects and for intestinal areas more difficult to visualise via ultrasonography due to the accumulation of air.