Postoperative acute kidney injury (AKI) is an important surgical complication that increases hospital stay and mortality when it occurs after kidney surgery. Studies investigating the effects of restrictive or liberal fluid regimen on postoperative AKI during radical/partial nephrectomy have given controversial results. It is important to recognize AKI early so that supportive treatments can be started early. Serum creatinine level, which is frequently used in the detection of AKI, increases late and causes a delay in diagnosis. It has been reported that cystatin C level increases earlier than creatinine in the diagnosis of AKI, so it can be used for early diagnosis.

Hypovolemia and organ dysfunction may occur as a result of giving too little fluid during the operation; Giving too much fluid can also cause edema and organ damage. AKI, which develops after kidney surgery, is an important surgical complication and its incidence varies between 5.5% and 34%. Kidney damage is initially subclinical, and its detection is delayed with current diagnostic tools. Due to increased microvascular permeability as a result of excessive fluid administration during the operation, edema in organ tissues and systems may increase infection rates and kidney damage. In a study in which restrictive and free fluid was applied during abdominal aortic aneurysm surgery, they showed that there was deterioration in renal endothelial function in the liberal group; They found that the urine albumin/creatinine ratio increased. In another study, they reported that serum creatinine levels decreased on the first day in patients who underwent colorectal surgery in the group where they applied a liberal fluid regimen; However, they reported that they could not find a significant difference between them and the restrictive group on the following days. It has been shown that restrictive and liberal fluid management applied during abdominal surgery have no effect on renal functions. Although there are few studies in the literature showing that restrictive and liberal fluid regimens applied during abdominal operations affect postoperative renal functions; There are no studies investigating the ideal intraoperative fluid replacement in nephrectomy patients.

It is known that the serum creatinine level, which is routinely used to monitor renal functions, increases late and has poor sensitivity. The reason for this is that it begins to increase 48-72 hours after kidney damage begins and when 50% of functional neurons are lost. Cystatin C, produced by all nucleated cells, is freely filtered by the glomerulus and reabsorbed in the proximal tubule. It is not secreted by renal tubules and does not vary depending on gender, race, weight, changes in muscle mass and nutrition. Serum cystatin C is a biomarker that reflects glomerular filtration rate (GFR) well and can diagnose AKI more accurately than creatinine.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) I-II-III,
• The opposite kidney is in normal function

Exclusion Criteria:

• Those who are planned for bilateral partial nephrectomy,
• Patients with preoperative chronic kidney disease,
• Those using preoperative medications known to cause renal toxicity such as aminoglycosides, aspirin and angiotensin converting enzyme inhibitors,
• Coronary artery disease
• Congestive heart failure

All data, except patient names, will be shared with the editor upon request after the article is accepted.

Patients and those evaluating blood samples will not know which group they are in the study.