Surgery is the branch of medicine that treats diseases and disorders by operative intervention. Surgical procedures may be undertaken for a variety of reasons. For example, the goal of surgery might be to relieve the mechanical obstruction of a tubular organ, such as the intestine, or to repair or replace structures in the heart. Surgery might also be used to remove a diseased or injured organ that threatens a patient’s survival, such as a gangrenous appendix or inflamed gallbladder, or a malignant tumor that cannot be remedied by other medical treatment. See also: Critical care medicine; Disease; Emergency medicine; Medicine; Surgery

The broad field of surgery can be divided into numerous specialized areas of expertise. Primarily, these areas are categorized according to specific organ systems. For example, neurosurgery involves the surgery on the central nervous system, including the brain and spinal cord; and orthopedic surgery is the surgical treatment of bone and joint diseases. Certain specialties are not limited to a single organ system. One such example is surgical oncology (cancer surgery), which deals with the treatment of various forms of cancers that are amenable to surgical therapy. See also: Cancer (medicine); Central nervous system; Oncology

Transplantation is another important area of surgical expertise. Transplant surgery involves the surgical insertion of a live, donated organ into a recipient who is experiencing end-stage failure of the corresponding organ. The organ donors are often healthy individuals who are close relatives of the intended recipient because their genetic similarities reduce the odds that the recipient’s immune system will aggressively reject or attack the new organ as foreign tissue. (A related problem is graft-versus-host disease, in which immune system cells carried within the transplanted organ mount a potentially lethal attack on the patient’s body.) Such rejection problems and the frequent difficulty of finding a suitable organ for surgery continue to severely limit the number of transplantation surgeries performed. The emergence of efficacious immunosuppressant medications, however, has led to tremendous improvements, and the function and longevity of transplanted organs can now often be superb. See also: Acquired immunological tolerance; HIV and bone marrow transplantation; Immunosuppression; Transplantation biology

Orthopedic surgery is the surgical treatment and management of disorders of the musculoskeletal system, including the bones and joints. Orthopedic surgery must also deal with fractures, athletic injuries, and rehabilitation. Because of the invention of more durable and flexible prosthetic devices, progress in the field of bone and joint replacement surgery has been excellent. See also: Absorbable orthopedic implants; Prosthesis; Sports medicine

Robots are playing a growing role in surgery. Specially designed surgical robots in the operating room can assist human surgeons. Teleoperated robots remotely directed by surgeons can also perform procedures that once required the presence of an expert. Robotic surgery is thus one way to provide better care to needy patients in inaccessible locations, such as outposts in Antarctica or in space stations, or to make unusually specialized surgical expertise more available to larger numbers of patients around the world. See also: Robotic surgery; Robotics