Differential diagnosis between splenic nodules and peritoneal metastases with contrast-enhanced ultrasound based on signal-intensity characteristics during the late phase.

PURPOSE: This study was done to assess the enhancement characteristics of splenic implants and to evaluate whether contrast-enhanced ultrasound (CEUS) after SonoVue injection allows the differential diagnosis with peritoneal metastases.
MATERIAL AND METHODS: Thirteen consecutive patients with splenosis and 13 consecutive patients with peritoneal metastases were investigated with CEUS after injection of 2.4 ml of SonoVue. Lesion enhancement was evaluated in real time for 240 s. All examinations were recorded digitally and analysed retrospectively. Frames were selected at different time intervals ranging from 0 to 4 min after injection. Average signal intensity was evaluated by measuring the average grey level in a region of interest encompassing the entire nodule. Results were evaluated using the Mann-Whitney test and interobserver variability using the Bland and Altmann method.
RESULTS: Splenic grafts presented with intense enhancement and without significant washout. Metastases presented with variable enhancement and progressive washout. Signal intensity values were significantly higher for splenic grafts, starting from 40 s after microbubble administration. Starting from 90 s after injection, there was no overlapping between enhancement of splenic grafts and peritoneal metastases, and only splenic grafts showed a percent of enhancement higher than 60% of the maximum enhancement.
CONCLUSIONS: CEUS after SonoVue injection may be considered a valuable alternative to scintigraphy for characterising peritoneal splenic grafts without radiation.