A 22 years-old-man was admitted to emergency after trauma. He suffered multiple deep cuts on his left leg. A lesion of the ischiatic nerve was suspected, and an ultrasound (US) evaluation was requested to confirm it. The study was conducted in the emergency room using a linear ultrasound transducer of 6-15 MHz and demonstrated the completely truncation of the ischiatic nerve (neurotmesis - Sunderland Grade V) with the proximal end retracted up to about 3cm from the edge of the wound. It was a very useful information for the neurosurgeon who after performed an end-to-end neurorrhaphy with suturation of perineurium. This short report underlines the importance of US, that thanks to its high spatial resolution and its time- and cost-effectiveness, can be considered a very important tool for the physician in emergency room to characterize peripheral nerve lesions.