surgery surgery surgery is a medical specialty that uses manual and/or instrumental techniques to physically reach into a subject's body in order to investigate or treat pathological conditions such as a disease or injury, to alter bodily functions (e.g. bariatric surgery such as gastric bypass), to improve appearance (cosmetic surgery), or to remove/replace unwanted tissues (body fat, glands, scars or skin tags) or foreign bodies. the subject receiving the surgery is typically a person (i.e. a patient), but can also be a non-human animal (i.e. veterinary surgery). surgeons conducting operations the act of performing surgery may be called a surgical procedure or operation, or simply "surgery". in this context, the verb "operate" means to perform surgery. the adjective surgical means pertaining to surgery; e.g. surgical instruments, surgical facility or surgical nurse. most surgical procedures are performed by a pair of operators: a surgeon who is the main operator performing the surgery, and a surgical assistant who provides in-procedure manual assistance during surgery. modern surgical operations typically require a surgical team that typically consist of the surgeon, the surgical assistant, an anaesthetist (often also complemented by an anaesthetic nurse), a scrub nurse (who handles sterile equipment), a circulating nurse and a surgical technologist, while procedures that mandate cardiopulmonary bypass will also have a perfusionist. all surgical procedures are considered invasive and often require a period of postoperative care (sometimes intensive care) for the patient to recover from the iatrogenic trauma inflicted by the procedure. the duration of surgery can span from several minutes to tens of hours depending on the specialty, the nature of the condition, the target body parts involved and the circumstance of each procedure, but most surgeries are designed to be one-off interventions that are typically not intended as an ongoing or repeated type of treatment. in common colloquialism, the term "surgery" can also refer to the facility where surgery is performed, or, in british english, simply the office/clinic of a physician, dentist or veterinarian. definitions surgery underway at the red cross hospital in tampere, finland during the 1918 finnish civil war. as a general rule, a procedure is considered surgical when it involves cutting of a person's tissues or closure of a previously sustained wound. other procedures that do not necessarily fall under this rubric, such as angioplasty or endoscopy, may be considered surgery if they involve "common" surgical procedure or settings, such as use of antiseptic measures and sterile fields, sedation/anesthesia, proactive hemostasis, typical surgical instruments, suturing or stapling. all forms of surgery are considered invasive procedures; the so-called "noninvasive surgery"ought to be more appropriately called minimally invasive procedures, which usually refers to a procedure that utilize natural orifices (e.g. most urological procedures) or does not penetrate the structure being excised (e.g. endoscopic polyp excision, rubber band ligation, laser eye surgery) or to a radiosurgical procedure (e.g. irradiation of a tumor). types of surgery surgical procedures are commonly categorized by urgency, type of procedure, body system involved, the degree of invasiveness, and special instrumentation. based on timing: elective surgery is done to correct a non-life-threatening condition, and is carried out at the person's convenience, or to the surgeon's and the surgical facility's availability. semi-elective surgery is one that is better done early to avoid complications or potential deterioration of the patient's condition, but such risk are sufficiently low that the procedure can be postponed for a short period time. emergency surgery is surgery which must be done without any delay to prevent death or serious disabilities and/or loss of limbs and functions. based on purpose: exploratory surgery is performed to establish or aid a diagnosis. therapeutic surgery is performed to treat a previously diagnosed condition. curative surgery is a therapeutic procedure done to permanently remove a pathology. cosmetic surgery is done to subjectively improve the appearance of an otherwise normal structure. bariatric surgery is done to assist weight loss when dietary and pharmaceutical methods alone have failed. by type of procedure: amputation involves removing an entire body part, usually a limb or digit; castration is the amputation of testes; circumcision is the removal of foreskin from the penis or clitoris (see female circumcision). replantation involves reattaching a severed body part. resection is the removal of all or part of an internal organ and/or connective tissue. a segmental resection specifically removes an independent vascular region of an organ such as a hepatic segment, a bronchopulmonary segment or a renal lobe. excision is the resection of only part of an organ, tissue or other body part (e.g. skin) without discriminating specific vascular territories. exenteration is the complete removal of all organs and soft tissue content (especially lymphoid tissues) within a body cavity. extirpation is the complete excision or surgical destruction of a body part. ablation is destruction of tissue through the use of energy-transmitting devices such as electrocautery/fulguration, laser, focused ultrasound or freezing. repair involves the direct closure or restoration of an injured, mutilated or deformed organ or body part, usually by suturing or internal fixation. reconstruction is an extensive repair of a complex body part (such as joints), often with some degrees of structural/functional replacement and commonly involves grafting and/or use of implants. grafting is the relocation and establishment of a tissue from one part of the body to another. a flap is the relocation of a tissue without complete separation of its original attachment, and a free flap is a completely detached flap that carries an intact neurovascular structure ready for grafting onto a new location. bypass involves the relocation/grafting of a tubular structure onto another in order to reroute the content flow of that target structure from a specific segment directly to a more distal ("downstream") segment. implantation is insertion of artificial medical devices to replace or augment existing tissue. transplantation is the replacement of an organ or body part by insertion of another from a different human (or animal) into the person undergoing surgery. harvesting is the resection of an organ or body part from a live human or animal (known as the donor) for transplantation into another patient (known as the recipient). by organ system: surgical specialties are traditionally and academically categorized by the organ, organ system or body region involved. examples include: cardiac surgery — the heart and mediastinal great vessels; thoracic surgery — the thoracic cavity including the lungs; gastrointestinal surgery — the digestive tract and its accessory organs; vascular surgery — the extra-mediastinal great vessels and peripheral circulatory system; urological surgery — the genitourinary system; ent surgery — ear, nose and throat, also known as head and neck surgery when including the neck region; oral and maxillofacial surgery — the oral cavity and midface; neurosurgery — the central nervous system, and; orthopedic surgery — the musculoskeletal system. by degree of invasiveness of surgical procedures: conventional open surgery (such as a laparotomy) requires a large incision to access the area of interest, and directly exposes the internal body cavity to the outside. minimally-invasive surgery involves much smaller surface incisions or even natural orifices (nostril, mouth, anus or urethra) to insert miniaturized instruments within a body cavity or structure, as in laparoscopic surgery or angioplasty. by equipment used: laser surgery involves use of laser ablation to divide tissue instead of a scalpel, scissors or similar sharp-edged instruments. cryosurgery uses low-temperature cryoablation to freeze and destroy a target tissue. electrosurgery involves use of electrocautery to cut and coagulate tissue. microsurgery involves the use of an operating microscope for the surgeon to see and manipulate small structures. endoscopic surgery uses optical instruments to relay the image from inside an enclosed body cavity to the outside, and the surgeon performs the procedure using specialized handheld instruments inserted through trocars placed through the body wall. most modern endoscopic procedures are video-assisted, meaning the images are viewed on a display screen rather than through the eyepiece on the endoscope. robotic surgery makes use of robotics such as the da vinci or the zeus robotic surgical systems, to remotely control manipulators under stereotactic endoscopy. terminology excision surgery names often start with a prefix for the target organ to be excised (cut out) and end in the suffix -ectomy. procedures involving cutting into an organ or tissue end in -otomy. a surgical procedure cutting through the abdominal wall to gain access to the abdominal cavity is a laparotomy. minimally invasive procedures, involving small incisions through which an endoscope is inserted, end in -oscopy. for example, such surgery in the abdominal cavity is called laparoscopy. procedures for formation of a permanent or semi-permanent opening called a stoma in the body end in -ostomy. reconstruction, plastic or cosmetic surgery of a body part starts with a name for the body part to be reconstructed and ends in -oplasty. for example, rhino- is a prefix meaning "nose", therefore a rhinoplasty is reconstructive or cosmetic surgery for the nose. repair of damaged or congenital abnormal structure ends in -rraphy. reoperation or "redo" refers to a return to the operating theater after an initial surgery is performed to surgically re-address an aspect of patient care. reasons for reoperation include postoperative complications such as persistent bleeding, development of seroma or abscess, tissue necrosis or colonization requiring debridement, or oncologically unclear resection margins that demand more extensive resection. description of surgical procedure location inpatient surgery is performed in a hospital, and the person undergoing surgery stays at least one night in the hospital after the surgery. outpatient surgery occurs in a hospital outpatient department or freestanding ambulatory surgery center, and the person who had surgery is discharged the same working day. office surgery occurs in a physician's office, and the person is discharged the same working day. at a hospital, modern surgery is often performed in an operating theater using surgical instruments, an operating table, and other equipment. among united states hospitalizations for non-maternal and non-neonatal conditions in 2012, more than one-fourth of stays and half of hospital costs involved stays that included operating room (or) procedures. the environment and procedures used in surgery are governed by the principles of aseptic technique: the strict separation of "sterile" (free of microorganisms) things from "unsterile" or "contaminated" things. all surgical instruments must be sterilized, and an instrument must be replaced or re-sterilized if it becomes contaminated (i.e. handled in an unsterile manner, or allowed to touch an unsterile surface). operating room staff must wear sterile attire (scrubs, a scrub cap, a sterile surgical gown, sterile latex or non-latex polymer gloves and a surgical mask), and they must scrub hands and arms with an approved disinfectant agent before each procedure. preoperative care main article: preoperative care prior to surgery, the person is given a medical examination, receives certain pre-operative tests, and their physical status is rated according to the asa physical status classification system. if these results are satisfactory, the person requiring surgery signs a consent form and is given a surgical clearance. if the procedure is expected to result in significant blood loss, an autologous blood donation may be made some weeks prior to surgery. if the surgery involves the digestive system, the person requiring surgery may be instructed to perform a bowel prep by drinking a solution of polyethylene glycol the night before the procedure. people preparing for surgery are also instructed to abstain from food or drink (an npo order after midnight on the night before the procedure), to minimize the effect of stomach contents on pre-operative medications and reduce the risk of aspiration if the person vomits during or after the procedure. some medical systems have a practice of routinely performing chest x-rays before surgery. the premise behind this practice is that the physician might discover some unknown medical condition which would complicate the surgery, and that upon discovering this with the chest x-ray, the physician would adapt the surgery practice accordingly. however, medical specialty professional organizations recommend against routine pre-operative chest x-rays for people who have an unremarkable medical history and presented with a physical exam which did not indicate a chest x-ray. routine x-ray examination is more likely to result in problems like misdiagnosis, overtreatment, or other negative outcomes than it is to result in a benefit to the person. likewise, other tests including complete blood count, prothrombin time, partial thromboplastin time, basic metabolic panel, and urinalysis should not be done unless the results of these tests can help evaluate surgical