+ 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


+ 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


+ 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