kreatininclearance

Creatinine clearance is a measure of kidney function that estimates the rate at which the kidneys remove creatinine from the blood, reflecting the glomerular filtration rate (GFR). It can be measured directly with a 24-hour urine collection or estimated from serum creatinine using formulas.

In a measured approach, creatinine clearance is calculated as CrCl = (UCr × V) / Scr, where UCr is the urine creatinine concentration, V is the urine volume collected over a defined period (usually 24 hours), and Scr is the serum creatinine concentration. The value is typically expressed in milliliters per minute (mL/min) after adjusting for the collection period. The Cockcroft-Gault equation is the most widely used estimation in adults: CrCl ≈ [(140 − age) × weight (kg) × (0.85 if female)] / (72 × Scr in mg/dL). For pediatric patients, the Schwartz formula is commonly used: CrCl ≈ (k × height in cm) / Scr.

Creatinine clearance is used to assess renal function, guide dosing of renally excreted drugs, inform staging of kidney disease, and monitor progression. Normal values are typically around 90–120 mL/min in healthy young adults and decline with age; lower values indicate reduced kidney function.

Limitations include overestimation due to tubular secretion of creatinine, inaccuracies in 24-hour collections, and influences of muscle mass, diet, and hydration. Estimated GFR (eGFR) derived from MDRD or CKD-EPI equations is often preferred for ongoing assessment, as it does not require urine collection, though these estimates have their own limitations, particularly at higher GFR or in certain populations.