Semi-erect position for better visualization of subphrenic hepatocellular carcinoma during ultrasonography examination

PURPOSE To evaluate which body position is more useful for visualization of subphrenic hepatocellular carcinomas (HCCs) during ultrasonography (US) examination. METHODS This prospective study was approved by the institutional review board and written informed consents were obtained from all patients. A total of 20 consecutive patients with a single subphrenic HCC (treatment-naive, 1 to 3cm in size) underwent planning US examination for radiofrequency ablation. The examinations were done by one of three radiologists and the patients were examined under four different body positions: supine, right posterior oblique (RPO), left lateral decubitus (LLD) and semi-erect by being positioned on a tilted table. The visibility of the index tumor was prospectively assessed using a four-point scale. Needle insertion was considered to be technically-feasible if the visibility score was lower than 2. The visibility score and technical feasibility were compared by using Wilcoxon signed rank test and McNemar's test, respectively, for a pairwise comparison between different body positions. RESULTS The visibility score was statistically lower in semi-erect position (median, 2; [IQR, 1-2.75]) when compared to supine position (3, 2-4), RPO position (3, 2-4) and LLD position (4, 3.25-4) (P=0.007, P=0.005, and P=0.001, respectively). Technical feasibility of needle insertion was also statistically higher in semi-erect position (75%, 15/20) when compared to supine position (45%, 9/45), RPO position (35%, 7/20), and LLD position (20%, 4/20) (P=0.031, P=0.021, and P=0.001, respectively). CONCLUSION Semi-erect position is more useful for the visualization of subphrenic HCCs than supine, RPO or LLD positions.