Utility of Follow-Up Computed Tomography (CT) and Fluorodeoxyglucose-Positron Emission Tomography/CT (FDG-PET/CT) in Diagnosing Gastrointestinal Stromal Tumor (GIST) Presenting as Spontaneous Hemoperitoneum: A Case Report.

Spontaneous hemoperitoneum is a rare and potentially life-threatening condition with a wide differential diagnosis. Gastrointestinal stromal tumors (GIST) can present with spontaneous hemoperitoneum, although diagnosing GIST as the cause of hemoperitoneum is challenging due to its rarity. A 76-year-old Japanese man presented with sudden epigastric pain and was found to have a 10 cm space-occupying lesion and ascites on ultrasonography. Despite stable vital signs, computed tomography (CT) findings showed a 10×15 cm mass with heterogeneously enhanced solid and cystic lesions, and the patient opted for conservative treatment. Two months later, a contrast-enhanced CT scan revealed a high-density area within the hematoma, prompting further investigation with fluorodeoxyglucose-positron emission tomography/CT (FDG-PET/CT), which showed FDG accumulation suggestive of malignancy. Exploratory laparotomy revealed a large encapsulated mass from the greater omentum, and histopathology confirmed a diagnosis of high-risk extraluminal gastric GIST. The patient was successfully treated with surgical resection. This case highlights two important clinical issues. First, follow-up CT and FDG-PET/CT are useful in detecting GIST when an unexplained intraperitoneal hematoma is identified. Second, surgical intervention is recommended in such cases to determine the cause. Contrast-enhanced follow-up CT and FDG-PET/CT are valuable in clarifying the presence of GIST, and surgical intervention is recommended to identify the causes of intraperitoneal hematoma. Further studies are needed to standardize the approach to spontaneous hematoma from GIST.