History
A 13-year-old 24-kg (52.8-lb) castrated male mixed-breed dog with a 3-month history of anorexia and vomiting was evaluated. On physical examination, the dog was slightly lethargic, yet alert and responsive, with 5% dehydration. The heart rate, respiratory rate, and capillary refill time were within reference ranges, and mucous membrane color was normal. The body condition score was 4 or 5 on a scale from 1 to 9. A systolic heart murmur (grade III/VI) over the left cardiac apex was detected. No abnormalities were detected on auscultation of the lungs. Hematologic and serum biochemical analyses revealed liver enzyme activities and renal function measurements within reference ranges. The dog, however, had lymphocytosis (8,673 lymphocytes/μL; reference range, 900 to 4,800 lymphocytes/μL), hyponatremia (132 mEq/L; reference range, 142 to 153 mEq/L), and hypochloremia (89 mEq/L; reference range, 110 to 120 mEq/L). Abdominal radiographs were obtained (Figure 1).
Right lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 13-year-old neutered male mixed-breed dog with a 3-month history of anorexia and vomiting.
Citation: Journal of the American Veterinary Medical Association 247, 11; 10.2460/javma.247.11.1233
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
In the right lateral and ventrodorsal abdominal radiographic images (Figure 2), various degrees of spondylosis deformans along T11-L4 and L7-S1 and degenerative new bone formation in the articular process joints from L1 to L6 are observed. A small ossification center cranial to the os penis is present. A gas-filled dilated fundus of the stomach located in the right cranial aspect of the abdomen is apparent in the ventrodorsal radiographic image, and the body of the stomach is filled with fluid within the midabdomen. A small amount of gas is present in the pylorus in the left middle portion of the abdomen. In the right lateral radiographic image, the fundus of the stomach is dilated and filled with fluid and is observed as a round soft tissue structure in the cranial aspect of the abdomen. The pylorus with peristalsis is evident as a gas-filled bilobed structure within the midabdomen. A normal-positioned pylorus should be fluid filled in the cranioventral portion of the abdomen on a right lateral radiograph. These radiographic findings support a diagnosis of gastric dilatation-volvulus. Moreover, a focal convex soft tissue filling defect is identified at the cranial aspect of the gas-filled area. The triangular soft tissue structure ventral to the gas-filled pylorus is the spleen; the organ is normal in volume. The contour and location of each kidney are not clearly defined, and the left kidney is presumed to be located at the level of L4-L5. Multiple uroliths are present in the urinary bladder. The location, size, and margin of the liver appear normal. The caudal vena cava is not seen cranial to the diaphragm, and the esophagus is mildly distended, both of which can be associated with a malpositioned stomach. Differential diagnoses for the focal convex soft tissue filling defect include neoplasia, gastric intussusception, granuloma, mucosal antral hypertrophy, or foreign bodies.
Same radiographic images as in Figure 1. A—The pylorus can be observed as a gas-filled bilobed structure within the midabdomen (white arrows), and a homogeneous convex soft tissue filling defect at the cranial aspect of the gas-filled structure (white arrowheads) is apparent. The spleen (open arrows) is located ventral to the gas-filled bilobed structure but is not enlarged. The fluid-filled fundus can be observed in the cranial aspect of the abdomen (black arrowheads). Multiple uroliths can be seen in the urinary bladder. B—The dilated gas-filled fundus of the stomach is in the right cranial aspect of the abdomen (white arrowheads), and the fluid-filled body of the stomach is within the midabdomen (black arrowheads). A small amount of gas can be seen in the pylorus in the left middle portion of the abdomen (white arrows). The left kidney is in the left caudal aspect of the abdomen (open arrows).
Citation: Journal of the American Veterinary Medical Association 247, 11; 10.2460/javma.247.11.1233
Ultrasonography was performed to characterize the mass in the pylorus further (Figure 3). The pylorus was found in the left middle portion of the abdomen, and a hyperechoic, asymmetric, inhomogeneous mass with irregular margins was detected at the pyloric region. The wall layering of the pylorus was completely lost. The wall of the proximal portion of the duodenum was mildly thickened, but the layering definition was preserved. The stomach was filled with a large amount of fluid. The ultrasonographic findings were compatible with the radiographically visualized soft tissue filling defect at the cranial aspect of the gas-filled pylorus. The most likely differential diagnosis for the pyloric mass was neoplasia such as adenocarcinoma, leiomyosarcoma (ie, gastric stromal cell tumor), or lymphoma. Although the size and echogenicity of the spleen were normal, the splenic vein was dilated.
Longitudinal ultrasonographic image of the pylorus of the stomach obtained with a 6- to 10-MHz microconvex transducer placed on the left cranial aspect of the abdomen. A hyperechoic, asymmetric, and inhomogeneous mass with irregular margins (approx 2 cm) protrudes into the fluid-filled gastric lumen, where the wall layering is completely lost. The layering of the caudal portion of gastric wall appears to be normal.
Citation: Journal of the American Veterinary Medical Association 247, 11; 10.2460/javma.247.11.1233
Outcome
Gastric decompression via an orogastric tube was performed, and a large amount of fluid was drained. Subsequent exploratory laparotomy revealed that the stomach was not dilated and that the pylorus had returned to the right side of the abdomen. An intramural mass was palpated at the pylorus. The pylorus, mass, and proximal portion of the duodenum were resected. Anastomosis of the stomach and duodenum (ie, Billroth I procedure) and cholecystoduodenostomy were performed. A biopsy specimen was obtained from an enlarged gastric lymph node. A histopathologic diagnosis of pyloric adenocarcinoma with lymph node metastasis was made.
Comments
Typically, gastric dilatation-volvulus is characterized by an acute onset, severely enlarged stomach filled primarily with gas but less fluid, a craniodorsal shift of the pylorus on the right lateral radiograph, and compartmentalization of the gas-filled stomach. Recognition of the pyloric location is essential for the diagnosis of gastric dilatation-volvulus. Splenomegaly may occur secondary to increased splenic portal vascular pressure. Other potential findings include radiographic evidence of functional ileus, megaesophagus, pneumatosis, and pneumoperitoneum.1 The dog described in the present report had a history of chronic gastrointestinal symptoms, a dilated but malpositioned stomach that predominantly contained fluid, and a spleen of normal size and shape. The history and imaging findings were not compatible with acute gastric dilatation-volvulus.
Chronic gastric dilatation-volvulus in dogs has been reported to involve incomplete volvulus and possibly has a dynamic nature. The malpositioned stomach has been observed to return to the normal anatomic position during endoscopy and surgery. Multiple imaging modalities, such as plain and contrast radiography, endoscopy, and ultrasonography, are valuable in the diagnosis of chronic gastric dilatation-volvulus.2 In the dog of the present report, the malpositioned stomach returned to its normal anatomic position after gastric decompression via an orogastric tube.
Stretching and laxity of the gastric ligaments that anchor the stomach is the primary etiology and is a common cause of gastric volvulus in humans.3 Similar to human chronic gastric volvulus, the cause of gastric dilatation-volvulus in the dog of the present report may have been associated with laxity of the gastric ligaments secondary to gastric content retention and chronic gastric distention. Gastric content retention, which is usually observed radiographically as fluid-filled gastric distention, is caused by partial pyloric obstruction secondary to pyloric adenocarcinoma.1 Chronic gastric dilatation-volvulus in dogs may be subclinical or associated with clinical signs (which may be intermittent) similar to those of partial pyloric obstruction, such as vomiting, weight loss, lethargy, or signs of abdominal pain.2 The history of the patient would also be consistent with partial pyloric obstruction. Although chronic gastric dilatation-volvulus associated with pyloric obstructive disease is proposed in this dog, an incidental finding of chronic gastric volvulus cannot be completely ruled out.
Ultrasonography is a useful modality for evaluating gastric wall thickness and layering definition in veterinary medicine. Gastrointestinal neoplasia commonly is associated with increased wall thickness and loss of layering definition.4 In the dog of the present report, increased wall thickness and loss of wall layering in the pyloric region were consistent with neoplasias such as adenocarcinoma, lymphoma, leiomyosarcoma, or gastrointestinal stromal tumor. Although adenocarcinoma, lymphoma, and leiomyosarcoma are usually hypoechoic, the former 2 tumors are predominantly sessile masses affecting all layers, and the latter is often a large mass restricted to the muscularis layer of the pyloric antrum.5 The pseudolayering pattern of the gastric wall is highly suggestive of gastric carcinoma.1 Gastrointestinal stromal tumor has been reported to have heterogeneous echotextures with possible hypoechoic or anechoic necrotic regions.6 A histopathologic diagnosis of gastric adenocarcinoma was made. Cytologic or histologic evaluation of a fine-needle aspirate or biopsy specimen is always necessary for a definitive diagnosis.
In conclusion, the dog of the present report had chronic gastric dilatation-volvulus, which was evident on radiographic evaluation. This condition was induced by a pyloric cancer that altered gastric outflow, resulting in gastric distention. The gastric distention caused stretching and laxity of the gastric ligaments with secondary gastric malposition.
1. Frank PM. The stomach. In: Thrall DE, ed. Textbook of veterinary diagnostic radiology. 6th ed. St Louis: Elsevier Saunders, 2013; 769–788.
2. Paris JK, Yool DA, Reed N, et al. Chronic gastric instability and presumed incomplete volvulus in dogs. J Small Anim Pract 2011; 52: 651–655.
3. Rashid F, Thangarajah T, Mulvey D, et al. A review article on gastric volvulus: a challenge to diagnosis and management. Int J Surg 2010; 8: 18–24.
4. Penninck D, Smyers B, Webster CR, et al. Diagnostic value of ultrasonography in differentiating enteritis from intestinal neoplasia in dogs. Vet Radiol Ultrasound 2003; 44: 570–575.
5. Lamb CR, Grierson J. Ultrasonographic appearance of primary gastric neoplasia in 21 dogs. J Small Anim Pract 1999; 40: 211–215.
6. Hanazono K, Fukumoto S, Hirayama K, et al. Predicting metastatic potential of gastrointestinal stromal tumors in dog by ultrasonography. J Vet Med Sci 2012; 74: 1477–1482.
