Hepatic hydrothorax (HH) is defined as transudate in the pleural cavity in patients with decompensated liver cirrhosis (DC) without concomitant cardiopulmonary or pleural disease. It is associated with high short-term mortality. HH can evolve via translocation through diaphragmatic gaps. The aim of this study was to evaluate the feasibility and safety of injecting ultrasound contrast medium into the peritoneal cavity to detect HH. This study included patients with concomitant ascites and pleural effusion who were admitted to our hospital between March 2009 and February 2019. A peritoneal catheter was inserted and ultrasound contrast medium was injected into the peritoneal cavity. In parallel, the peritoneal and pleural cavities were monitored for up to 10 minutes. Overall, 43 patients were included. The median age was 60 years and the majority of patients were male (n = 32, 74 %). Most patients presented with right-sided pleural effusion (n = 32, 74 %), 3 (7 %) patients with left-sided and 8 (19 %) patients had bilateral pleural effusion. In 12 (28 %) patients ascites puncture was not safe due to low volume ascites. Thus, the procedure could be performed in 31 (72 %) patients. No adverse events occurred. In 16 of 31 (52 %) patients we could visualize a trans-diaphragmic flow of microbubbles. The median time until transition was 120 seconds. Our clinical real-world experience supports the safety and feasibility of intraperitoneal ultrasound contrast medium application to detect HH in patients with DC, as a non-radioactive real-time visualization of HH. Our study comprises the largest cohort and longest experience using this method to date.