+ Biologic Behavior
- Smooth muscle tumors are the most common intestinal mesenchymal tumor
- Mean age 9 years (range, 4-14 years)
- Sites: small intestine and cecum
- 50% have localized peritonitis as a result of tumor rupture
- Intestinal leiomyosarcoma has been reported as a cause of nephrogenic diabetes insipidus in 1 dog
- 38%-54% metastatic rate with metastatic sites including the liver, spleen, lungs, kidneys, and diaphragm
+ 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
- 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
- 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
+ Prognosis
- MST 13.0-21.3 months after surgical resection
- 1-year survival rate 75% and 2-year survival rate 66%
- 54% metastatic rate, but metastasis is not a poor prognostic factor with a MST 21.7 months