In which of the following procedures would a T-tube be used?

A T-tube is primarily used in procedures involving the biliary system, particularly during operations that involve the common bile duct. The purpose of a T-tube is to maintain patency of the biliary tract and facilitate the drainage of bile postoperatively. After a common bile duct exploration, a T-tube is often placed to allow for the drainage of bile, preventing complications such as bile leakage and helping to assess the functionality of the bile duct as it heals.

During the gastrostomy, the procedure involves creating an opening in the stomach for feeding; a T-tube is not relevant in this context. An appendectomy, which involves the removal of the appendix, does not involve the biliary system and therefore would not require a T-tube. Cardiac bypass surgery focuses on the heart and blood vessels and has no association with bile duct management, making the use of a T-tube unnecessary.

Thus, the use of a T-tube is specifically associated with common bile duct exploration, where it serves an important role in postoperative care and monitoring of the bile drainage system.