In which procedure is a catheter often placed into the venous system for access?

In hemodialysis, a catheter is frequently placed into the venous system to provide access to the bloodstream. This access is crucial for the dialysis treatment because it allows blood to be drawn from the body, filtered through a dialysis machine to remove waste products and excess fluid, and then returned to the body. The venous access is typically achieved through the insertion of a central venous catheter or through a fistula or graft specifically designed for this purpose.

The use of venous access in hemodialysis is essential due to the volume of blood that needs to be processed for effective treatment, making it necessary to connect to larger blood vessels. This method ensures that dialysis can be performed efficiently and safely.

In contrast, the other procedures listed do not primarily involve placing a catheter into the venous system for access. Thoracentesis involves a needle being inserted into the chest to remove fluid from the pleural space, pulmonary angiography assesses blood vessels in the lungs usually via arterial access, and endovenous laser therapy is a minimally invasive procedure targeting varicose veins, which may involve catheterization but not specifically for typical venous access like hemodialysis does.