Microcirculation of subepithelial gastric tumors using contrast-enhanced ultrasound.

Objectives: The evaluation of subepithelial tumors of the stomach is normally the domain of gastroscopy and endoscopic ultrasound. We investigated these rare tumors using transabdominal B-mode ultrasound and performed perfusion analysis of these tumors with contrast enhanced ultrasound. Methods: Patients with gastrointestinal stromal tumors (GIST, n = 3), leiomyoma (n = 1) and schwannoma (n = 1) were routinely examined using conventional B-mode-ultrasound, colour Doppler ultrasound and contrast-enhanced ultrasound (contrast media: Sonovue(R); ultrasound device: Siemens Acuson Sequoia 512). Gastroscopy, endosonography with puncture of the subepithelial tumor and computed tomography were also performed in all patients. After surgery, the resected stomach tumors were correlated with the preoperative imaging findings. Results: All calculated tumor sizes using any imaging modalities showed a good correlation with the macroscopic tumor sizes ex-vivo. Histologically increased tumor size of the GISTs was correlated with large, central avascular areas. The GISTs and the leiomyoma presented with mixed echogenicity in B-mode-ultrasound. Colour Doppler ultrasound was able to detect some vessels in the periphery of the tumor only. Using contrast-enhanced ultrasound the GISTs and the leiomyoma presented hypervascular. The contrast pattern of these lesions was from the periphery to the centre or diffuse or a progressive centrifugal fill in during the arterial phase. We also registered slowly progressive washout starting at the end of the arterial phase and increasing into the late phase. The contrast media behaviour in the schwannoma was different from that describt above within the GISTs: it was noted to have a diffuse intralesional pattern at the start of the arterial phase followed by an early, rapidly progressing washout-phenomenon. Conclusion: In our pilot study B-mode transabdominal ultrasound was able to visualise gastric subepithelial tumors larger than three centimetre. Contrast-enhanced ultrasound is a proven method in clinical practice for the perfusion analysis of gastric subepithelial tumors. It can also be used for the planning of ultrasound-guided biopsies to avoid punctures of necrotic tumor parts.