GASTRIC NEOPLASIA
The incidence of gastric neoplasia in the dog and cat is low, and clinical signs are insidious in onset. Often the only signs observed are inappetence, which can be present for months before other symptoms develop, and subtle weight loss.
Partial obstruction of pyloric outflow and abnormal motility cause progressively worsening vomiting, anorexia, and weight loss. Ulceration and chronic blood loss causes hematemesis and melena. Gastric neoplasia is summarized here. A more detailed discussion is included in Chapter 11.Adenocarcinoma is the most common gastric malignancy in dogs, followed by lymphosarcoma, leiomyosarcoma, fibroma, squamous cell carcinoma, and plasmacytoma. Adenocarcinoma occurs more frequently in males, with an average age of 8 years at the time of diagnosis. Lymphosarcoma is the most common gastric tumor of cats but does not have breed or gender predisposition. Diagnosis of gastric tumors is based on radiographic, endoscopic, or surgical findings. Contrast radiographs may reveal a thickened and ulcerated gastric wall. Endoscopic findings often reveal discolored and thickened mucosa, raised plaques with large central ulceration and thick raised margins (Figure 5-9; see color plate), or polypoid lesions. Diffuse
Figure 5-9 Malignant gastric ulcer located on the incisura angularis (1 to 3 o’clock position in the field of view) in a 13-year-old weimaraner with a 2-month history of chronic vomiting and weight loss. The dog had hypochromic microcytic anemia. The raised edges and central crater of the ulcer were very firm and required that multiple biopsy specimens be obtained from each of several sites to ensure adequate depth of tissue was obtained. Histopathologic findings confirmed gastric adenocarcinoma. (See color plate.)
thickening of the gastric wall, referred to as scirrhous carcinoma, also occurs.
More than half of tumors occur in the pyloric antrum, often near the incisura. Lymphosarcomas can appear as raised nodular masses anywhere in the gastric wall (Figure 5-10; see color plate) or as diffuse mucosal thickening, often with erosion or ulceration. Leiomyoma is the most common benign tumor and the second most common gastric tumor in dogs but is rare in cats. Leiomyomas are often asymptomatic unless pyloric outflow is obstructed. Benign polyps appear as pedunculated or polypoid nodules that protrude from the mucosal surface. Their cause is unknown, and they seldom cause problems unless they are large enough to cause delayed gastric emptying.Focal gastric carcinomas are best treated by surgical resection, whereas diffuse or extensive lesions are not usually resectable. Metastasis of carcinomas to lymph nodes, liver, or lungs has often occurred by the time of diagnosis,and adjunctive chemotherapy is not effective in improving survival. Lymphosarcoma is treated with chemotherapy, although the prognosis is guarded. Benign tumors and adenomatous and hyperplastic polyps causing partial outflow
Figure 5-10 Diffuse nodular gastric lymphosarcoma in a 9-year-old beagle with intermittent vomiting of 2 weeks’ duration and weight loss. Clinical signs resolved with chemotherapy (Adriamycin and L-asparaginase). After 6 months of remission, clinical signs reoccurred and the dog was euthanized. (See color plate.)
obstruction can successfully be resected with a good long-term prognosis.
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Figure 5-4 Normal stomach. A, Endoscopic appearance of a normal stomach.The smooth, pale-pink rugal folds of the greater curvature of the gastric body gradually become more linear distally at the junction with the pyloric antrum.The incisura angularis appears as a curved fold located at the 12 to 3 o'clock position. B, Appearance of a normal pyloric antrum (foreground) and pylorus (upper left).The antral mucosa is smooth, pale pink, and without rugal folds.The closed pyloric orifice is located at the center of the converging mucosal folds.
Figure 5-5 NSAID-induced ulcerative gastritis. Diffuse ulcerative gastritis in a 9-year-old German shepherd-mix with degenerative joint disease.The dog was being treated with aspirin (325 mg 2 times a day). Treatment began 2 months before presentation, but clinical signs of weakness, vomiting, melena caused by acute gastrointestinal blood loss, and anemia did not occur until the day of presentation.
FIGURE 5-6 NSAID-induced gastric ulcer. A, Gastric ulcer in pyloric antrum of a 5-year-old Welsh corgi that had been treated for back pain with ibuprofen (325 mg every day for 5 days).The dog had an acute onset of vomiting and an episode of melena on the day of presentation. B, Healing gastric ulcer in the same patient after 7 days of treatment with omeprazole (0.3 mg/lb every day).
Figure 5-7 Helicobacter gastritis. A, Endoscopic view of the gastric body and incisura angularis in a 3-year-old English bulldog with chronic intermittent vomiting. Raised nodules, some with a central reddened craterlike appearance, were present throughout the body and antrum. B, Endoscopic view of the pyloric antrum from the same dog showing a diffusely nodular mucosa.The pylorus is seen distally in the center of the image. Biopsy revealed the nodules to be accumulations of lymphocytes. Urease-positive Helicobacter organisms were present on the surface musosa and extending into the gastric pits. Clinical signs resolved after treatment with omeprazole (0.3 mg/lb every day) in combination with amoxicillin (10 mg/lb 2 times a day) for 14 days.
FIGURE 5-8 Gastric retention of food particles and bile-colored fluid in a 12-year-old miniature poodle with clinical signs of intermittent vomiting, regurgitation, inappetence, and bloating.The dog had no food or water for 14 hours before endoscopy. Results of gastric mucosal biopsies were normal, and the dog was diagnosed with primary (idiopathic) gastric motility disorder. Clinical signs improved, but did not resolve, when the dog was treated with cisapride and dietary management (small meals, fat- restricted food).
FIGURE 5-9 Malignant gastric ulcer located on the incisura angularis (1 to 3 o'clock position in the field of view) in a 13-year-old Weimaraner with a 2-month history of chronic vomiting and weight loss.The dog had hypochromic microcytic anemia. The raised edges and central crater of the ulcer were very firm and required that multiple biopsy specimens be obtained from each of several sites to ensure adequate depth of tissue was obtained. Histopathologic findings confirmed gastric adenocarcinoma.
Figure 5-10 Diffuse nodular gastric lymphosarcoma in a 9-year-old beagle with intermittent vomiting of 2 weeks' duration and weight loss. Clinical signs resolved with chemotherapy (Adriamycin and L-Asparaginase). After 6 months of remission, clinical signs reoccurred and the dog was euthanized.