A procedure used to remove the contents of the stomach by washing it out; for example, after ingestion or swallowing a toxic (poisonous) substance: Gastric lavage is performed by placing the patient down with his or her head below the level of the stomach and turned to one side; then a lubricated tube is passed down the esophagus into the stomach and a funnel is attached to the top and water is poured into it until the stomach is filled.

The top of the tube is then lowered, allowing the fluid in the stomach to drain into a bucket and this gastric lavage is repeated until the water shows up clear and clean.