Diagram showing a schematic nephron and its blood supply. The basic physiologic mechanisms of handling fluid and electrolytes by the nephron -<unk> , secretion, reabsorption, and excretion - are labelled. Renal functions include maintaining an acid–base balance; regulating fluid balance; regulating sodium, potassium, and other electrolytes; clearing toxins; absorption of glucose, amino acids, and other small molecules; regulation of blood pressure; production of various hormones, such as erythropoietin; and activation of vitamin D. One of the measures of kidney function is the<unk>  <unk> .<unk>  describes the flow<unk>  of filtered fluid through the kidney. Creatinine clearance<unk>  (CCr or CrCl) is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the<unk> . Creatinine clearance exceeds<unk>  due to creatinine secretion, which can be blocked by cimetidine. Both<unk>  and CCr may be accurately calculated by comparative measurements of substances in the blood and urine, or estimated by formulas using just a blood test result (eGFR and eCCr) The results of these tests are used to assess the excretory function of the kidneys. Staging of chronic kidney disease is based on categories of<unk>  as well as albuminuria and cause of kidney disease. The normal range of<unk> , adjusted for body surface area, is 100–130 average 125 mL/min/1.73m2 in men and 90–120 mL/min/1.73m2 in women younger than the age of 40. In children,<unk>  measured by inulin clearance is 110 mL/min/1.73 m2 until 2 years of age in both sexes, and then it progressively decreases. After age 40,<unk>  decreases progressively with age, by 0.4–1.2 mL/min per year. Estimated<unk>  (eGFR) is now recommended by clinical practice guidelines and regulatory agencies for routine evaluation of<unk>  whereas measured<unk>  (mGFR) is recommended as a confirmatory test when more accurate assessment is required.
Glomerular filtration rate
Effective renal plasma flow
Renal blood flow
Mean arterial pressure
Coronary perfusion pressure
Effective circulating volume
Renal threshold
Free water clearance