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Gastric Pathology: Gastrocolic Fistula due to Adenocarcinoma of the Colon: Simulation of Primary Gastric Leiomyosarcoma on CT

Won Jae Lee, MD, Karen M. Horton, MD and Elliot K. Fishman, MD



A large exophytic ulcerating mass involving the stomach is the classic CT description of a gastric leiomyosarcoma (1). We have recently been referred two patients, each with a large necrotic ulcerating mass involving the stomach. The CT appearance in each case suggested the diagnosis of exophytic gastric leiomyosarcoma. However, at surgery, each patient was found to have a large ulcerating carcinoma of the colon near the splenic flexure which had eroded into the stomach creating a gastrocolic fistula. Gastrocolic fistula can rarely occur as a complication adenocarcinoma of the colon, but to our knowledge the CT appearance has only been reported once in the world's literature (2). We present these two cases of colon cancer with gastrocolic fistula simulating a gastric leiomyosarcoma and discuss the role of CT in the diagnosis of gastrocolic fistula.

Case One

A 41-year-old man was admitted to the hospital with cramping abdominal pain, diarrhea, and bloody stool. A contrast-enhanced spiral CT scan of the abdomen was performed with oral administration of water, and showed a 9 X 10 cm, exophytic mass in the left upper abdomen located between the greater curvature of the gastric body and the splenic flexure (Figure 1). This mass had central necrosis with tiny air bubbles and a connection between the stomach and colon. Enhancing gastric mucosa adjacent to the bulky mass appeared to be compressed, whereas the colonic wall adjacent to the mass was irregularly thickened. There was no definite evidence of lymphadenopathy or distant metastases. The CT appearance was most suggestive of an exophytic gastric leiomyosarcoma.
The patient underwent surgical treatment including subtotal gastrectomy and partial colectomy. Final pathologic findings showed an invasive, moderately differentiated adenocarcinoma of the splenic flexure which had invaded the stomach. Ulcerations at both the colonic and gastric mucosa were detected compatible with a fistula.
Case Two
A 73-year-old woman was transferred from an outside hospital with the diagnosis partial colon obstruction. A enhanced CT scan was performed and demonstrated a large necrotic mass in the left upper abdomen located between the stomach and splenic flexure (Figure2). A gastrocolic fistula was also demonstrated. The mass appeared to invade the adjacent body and tail of the pancreas and there was a paraaortic and retrocrural adenopathy. The CT appearance was most suggestive of an exophytic gastric leiomyosarcoma.
The patient subsequently underwent a partial gastrectomy, splenectomy, transverse colectomy, distal pancreatectomy, and left adrenalectomy. Pathologic examination revealed a 12 cm poorly differentiated mucinous adenocarcinoma of the splenic flexure with extensively involvement of the stomach. A gastrocolic fistula was present. The mass also involved the pancreas.


Gastrocolic fistula can occur in a variety of benign and malignant conditions. In the past, adenocarcinoma of the stomach and colon were reported to be the most common etiology of gastrocolic fistula(3). However, in recent years, due to earlier diagnosis of carcinomas and as a result of wide spread use of nonsteroidal anti-inflammatory drugs and aspirin, benign gastric ulcers are now the most common cause of gastrocolic fistula formation (4, 5). Other disorders which have been reported to cause gastrocolic fistula include: Crohn's disease, tuberculosis, diverticulitis, syphilis, appendicitis, percutaneous gastrostomy, trauma, pancreatic abscess/carcinoma, lymphoma, retroperitoneal sarcoma, and carcinoid tumor (3,6-8).
Clinical diagnosis of gastrocolic fistula may be difficult, since its classic clinical features (i.e., feculent vomiting, foul-smelling eructations, and diarrhea with undigested food particles in the stool) are present in less than 30% of these patients (3,9). Also, other symptoms associated with gastrocolic fistula such as abdominal pain, weight loss, fatigue, anemia, severe nutritional deficiencies, and gastrointestinal bleeding are nonspecific. Therefore, definite diagnosis of gastrocolic fistula can be made by radiologic demonstration of the abnormal communication between the stomach and colon. The most reliable radiologic examination is postulated to be a contrast enema because the higher intraluminal pressure in the colon at the time of this procedure leads to a better filling of the fistula, while upper gastrointestinal series may not demonstrate the fistula (5,7).
In a review of English literature for CT demonstration of gastrocolic fistula, only two case reports were found, describing a gastrocolic fistula due to Crohn's disease and lymphoma (7,8). There is only one report in the Japanese literature of the CT demonstration of a gastrocolic fistula due to a colon cancer. In our two patients, the CT features included a bulky, exophytic mass with extensive necrosis which simulated the CT appearance of a primary gastric leiomyosarcoma. However, in addition to the bulky necrotic mass, a gastrocolic fistula was demonstrated on the CT, which has not been reported to occur with gastric leiomyosarcoma. In this respect, we suggest that a bulky mass between the stomach and colon with a gastrocolic fistula should first suggest an adenocarcinoma of the stomach or colon.


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