A field block for an inguinal hernia repair is ideal for high risk patients unsuited for general or spinal anaesthesia. The innervation of the inguinal region is through the ventral rami of T11 and T12 and the two upper branches of the lumbar plexus, the iliohypogastric and ilioinguinal nerves.

The anterior cutaneous branch of the iliohypogastric nerve supplies the skin above the pubis and medial end of the inguinal ligament. The ilioinguinal nerve supplies the skin over the root of the penis and scrotum.

The ventral ramus of the 12th thoracic or subcostal nerve sends a branch to join the first lumbar root and supplies the skin over the lower anterior abdominal wall. The genital branch of the genitofemoral nerve may supply skin in the medial part of the groin.

Prilocaine 0.5% with adrenaline is a suitable choice of agent, which allows a large volume of solution to be used safely.