+ Biologic Behavior
- Age: mean 9 years (range, 1-14 years)
- Sites: large intestine and mid-to-distal rectum
- Pseudomyxoma peritonei has been reported in 1 dog with small intestinal ADC and is characterized by deposition of mucinous pools on serosal surfaces and gelatinous ascites
- 44% metastatic rate for small intestinal ADC with metastatic sites including the regional lymph nodes, mesentery, and liver ± spinal meninges and testes
CLINICAL FEATURES
+ Clinical Signs
- Anorexia, weight loss, intermittent vomiting, and diarrhea
- Severe, persistent vomiting is occasionally observed if proximal small intestinal tumor causes obstruction
DIAGNOSIS
+ Physical Examination
- Palpable abdominal mass and cachexia are common
- Other findings include dehydration and abdominal pain
+ Laboratory Tests
- Anemia and leukocytosis are common in dogs with non-lymphoid intestinal tumors
- Anemia and hypoglycemia are common in dogs with intestinal leiomyosarcoma
- Mesenchymal tumors are associated with microcytic hypochromic anemia, hypoproteinemia, and mild leukocytosis
+ Abdominal Radiographs
- Abdominal mass, obstruction, or persistent irregularity of bowel appearance are identified in 25% of small intestinal tumors and nearly 50% of non-lymphoid intestinal tumors
- Abdominal mass is detected in 60% of canine mesenchymal small intestinal tumors
+ Contrast Radiography
- Intestinal mass identified in 57% of dogs with non-lymphoid intestinal tumors
- Contrast radiographs: mural lesions include luminal filling defect, intestinal wall thickening, mucosal ulceration, abnormal positioning of intestinal loops, and constricting annular lesions
+ Ultrasonography
- Intestinal mass identified in 87% (13/15) dogs with non-lymphoid small intestinal tumors
- Intestinal ADC are transmural, poorly echogenic, and associated with complete loss of wall layering, increased intestinal wall thickness (median 12 mm), luminal fluid accumulation proximal to the lesion (81%), and regional lymphadenopathy (57%)
- Loss of wall layering is an excellent predictive factor for differentiating intestinal neoplasia from enteritis in dogs (99% v 12%) with intestinal tumors 50.9-times more likely to have loss of wall layering
- Intestinal tumors also have significant increases intestinal wall thickness (15 mm v 6 mm) and are significantly less likely to have diffuse intestinal involvement (2% v 72%)
+ Exploratory Celiotomy
- Definitive diagnosis with exploratory celiotomy and biopsy
- Majority of small intestinal ADC are associated with annular constrictions
- Leiomyomas and sarcomas are usually large solitary masses growing through serosa
TREATMENT
+ Surgery
- Debilitation and hypoproteinemia may complicate treatment
- Exploratory celiotomy with resection and end-to-end anastomosis with 4-8 cm margins and serosal patching
- Mesenteric and regional lymph nodes should be assessed ± aspirated
+ Chemotherapy
- No proven chemotherapy for ADC, but combination of 5-fluorouracil and cisplatin may be effective
- Second-look surgery recommended for evaluation of response to chemotherapy
+ Prognosis
- MST 272-300 days
- Sex is a prognostic factor with MST for male dogs 272 days v 28 days for female dogs