The disposable trochar in the form of a gas insufflation needle having a removable rod and needle portion within an outer sheath is provided. The rod has a blunt end and is retractable during insertion so that the needle edge cuts through the abdominal wall. Once passing through the wall the rod extends so as to protect the bowel from the sharp needle. A gas port provided for introducing gas through the rod and out a side passageway near the blunt end. After the abdomen is extended, the rod and needle can be removed as unit from the sheath and thrown away and a suitable instrument introduced through an instrument port having a separable diaphragm. The gas can continue to be introduced around the instrument and into the abdomen while the instrument is in place. After the required medical procedures are completed, the instrument is removed. Then the sheath and associated parts are removed and thrown away.