Ultrasound has become a daily practice for anesthesiologists for central venous catheterization and regional anaesthesia, but also for the diagnosis of pleuro-pulmonary, cardiac, and vascular diseases; this is illustrated by our observation. We report a case of a cirrhotic patient who underwent emergency surgery for a Colle's fracture under ultrasound-guided supraclavicular block which was complicated by acute dyspnoea. The use of ultrasound in the operating theater has revealed hepatic hydrothorax which occurred during a diaphragmatic paralysis secondary to the blocking of phrenic nerve due to the regional anaesthesia.