The study is planned to be a single-center study and includes patients who underwent major surgery within Istanbul University Istanbul Faculty of Medicine with an invasive arterial line. Our aim to define the incidence of acute renal injury in our setting and to investigate the risk factors listed in detailed description. After obtaining written informed consent from the patients, preoperative risk factors will be notes. Following standard anesthesia monitoring as well as routine anesthesia induction and maintenance, invasive arterial monitoring will be performed due to the major surgery and hemodynamic values will be recorded throughout the surgery. The primary outcome will be acute renal injury based on KDIGO's (Kidney Disease: Improving Global Outcomes) definition of acute renal damage. Postoperative data regarding this outcome as well as additional data listed in detailed description will be collected.

The study is a single-center study that observes patients who undergo major abdominal surgery within Istanbul University Istanbul Faculty of Medicine.

Standard anesthesia monitoring (NIBP, SPO2(oxygen saturation by pulse oximetry), ECG) will be applied to the patients taken to the operation room. Routine anesthesia induction and maintenance will be performed by the anesthetist responsible for the patients. After anesthesia induction, invasive arterial monitoring will be performed.

Our data collection and recording will be as follows: preoperative, intraoperative, postoperative.

In the preoperative section;

• Age, gender, height, weight, BMI of the patient
• ASA (American Society of Anesthesiologists) classification, additional diseases and functional capacity
• Drugs used (ACE-İ, ARB (angiotensin receptor blocker), Statin, B-blocker, NSAID)
• Entry creatinine and eGFR (estimated glomerular filtration rate) calculated with CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration)
• Entry hemoglobin, lymphocyte, CRP (C reactive protein)
• The presence of ascites in the abdomen

In the intraoperative section;

• Surgery (gynecological oncology surgery, gastrointestinal surgery, genitourinary surgery) and its duration
• Applied form of anesthesia (general-regional)
• Liquids given during the operation (Crystalloid (isotonic, isolyte, lactated ringer), colloid, albumin) and their amounts oNoradrenaline requirement
• Use of diuretic, NSAID
• Blood transfusion
• Total amount of bleeding during the operation
• First arterial blood gas electrolytes taken due to routine major surgery
• The lowest amount of hemoglobin seen during the operation
• Routine invasive artery monitorization due to major surgery, and mean arterial pressure In the postoperative section;
• Requirement of intensive care
• Blood transfusion requirement
• Noradrenaline requirement
• Use of diuretic and NSAID
• Electrolyte values in the first blood gas taken routinely
• Creatinine value immediately after the surgery and at 24th and 48th hours
• First 48-hour urine output The diagnosis of acute renal injury is based on KDIGO's definition of acute renal damage. By analyzing from this information, significant risk factors for acute renal damage are identified and measures are taken against them.

Inclusion Criteria:

• Age of ≥18 years
• Patients who are ASA I-III
• Patients who have undergone major noncardiac surgery
• Patients who need post-operative intensive care follow-up due to major surgery or long surgery
• Patients diagnosed with CKD but do not need routine hemodialysis

Exclusion Criteria:

• Age of <18 years
• Patients who have undergone minor surgery
• Surgeries which lasts <30 minutes
• Patients who will be hospitalized less than two days postoperatively
• Patients who need routine hemodialysis due to CKD
• Patients who had renal transplantation

Patients who have undergone non-cardiac major surgery in Istanbul University Faculty of Medicine will be included in the study.