Creatinine Clearance Simplified MDRD Formula Calculator


Clearance : ml/mn

What is creatinine clearance?

Creatinine clearance is a measurement used to assess kidney function. It is a calculation that estimates the volume of blood plasma that is cleared of creatinine by the kidneys per unit of time. Creatinine is a waste product produced by the muscles and is filtered out of the blood by the kidneys.

The creatinine clearance test involves collecting a 24-hour urine sample and measuring the creatinine concentration in the urine, as well as obtaining a blood sample to measure the creatinine level in the blood. The creatinine clearance is then calculated using the following formula:

Creatinine Clearance = (Urine Creatinine Concentration × Urine Volume) / (Serum Creatinine Concentration × Time)

The creatinine clearance value is usually expressed in milliliters per minute (ml/min) and serves as an indicator of the kidneys' ability to filter waste products from the blood. A lower creatinine clearance may indicate impaired kidney function or reduced glomerular filtration rate (GFR), which can be a sign of kidney disease or dysfunction.

Creatinine clearance is often used alongside other clinical and laboratory assessments to evaluate kidney function, diagnose kidney disorders, monitor the progression of kidney disease, and determine the appropriate dosage of certain medications that are excreted through the kidneys. It provides valuable information for healthcare professionals in assessing and managing kidney health.

Why prescribe creatinine clearance?

Creatinine clearance is prescribed for several reasons related to assessing kidney function and monitoring the effectiveness of certain medications. Here are some common scenarios in which creatinine clearance may be prescribed:

  1. Kidney Function Assessment: Creatinine clearance is used to evaluate the overall kidney function. It helps determine the glomerular filtration rate (GFR), which is a measure of how well the kidneys are filtering waste products from the blood. By obtaining the creatinine clearance value, healthcare professionals can assess if the kidneys are functioning normally or if there is any impairment.

  2. Diagnosis and Monitoring of Kidney Disease: Creatinine clearance is valuable in diagnosing and monitoring kidney diseases such as chronic kidney disease (CKD). A decrease in creatinine clearance over time can indicate a decline in kidney function and the progression of kidney disease. It is used alongside other clinical and laboratory parameters to assess the severity and stage of kidney disease.

  3. Medication Dosage Adjustment: Certain medications, especially those cleared by the kidneys, require dosage adjustment based on kidney function. Creatinine clearance provides an estimate of the kidney's ability to clear medications from the body. If a patient has reduced kidney function, their creatinine clearance may be lower, indicating a need for a lower dosage of medications that are primarily eliminated through the kidneys.

  4. Preoperative Evaluation: Prior to undergoing surgery, particularly procedures that may impact kidney function, creatinine clearance may be prescribed to assess baseline kidney function. It helps identify patients who may be at a higher risk of developing kidney complications during or after surgery.

  5. Monitoring Medication Toxicity: Some medications, such as certain antibiotics or chemotherapy drugs, can be toxic to the kidneys. Regular monitoring of creatinine clearance helps detect any decline in kidney function that may be associated with medication toxicity. This allows healthcare professionals to adjust medication dosages or consider alternative treatments if needed.

It's important to note that the specific reasons for prescribing creatinine clearance may vary based on individual patient circumstances and the healthcare provider's clinical judgment. Creatinine clearance is just one of the tools used in the comprehensive assessment of kidney function and plays a significant role in the management of kidney health and related conditions.

MDRD formula (Modification of diet in renal disease)

The MDRD formula, also known as the Modification of Diet in Renal Disease formula, is a commonly used equation to estimate the glomerular filtration rate (GFR) based on serum creatinine levels. The MDRD formula is primarily used for assessing kidney function in patients with chronic kidney disease (CKD). The formula takes into account factors such as age, sex, race, and serum creatinine level to estimate the GFR.

The MDRD formula is as follows:

GFR = 175 × (serum creatinine)^(-1.154) × (age)^(-0.203) × (0.742 if female) × (1.212 if African American)

In the formula, the serum creatinine level is expressed in milligrams per deciliter (mg/dL), and the age is in years. The GFR estimated by the MDRD formula is reported in milliliters per minute per 1.73 square meters (mL/min/1.73 m²), which is a standardized unit for comparing kidney function.

It's important to note that the MDRD formula has limitations and may not accurately estimate GFR in certain populations, such as individuals with extremes of body weight, muscle mass, or nutritional status. Additionally, it may not be as accurate in individuals with near-normal or high GFR. In such cases, other equations or direct measurements of GFR, such as using radioactive tracers or inulin clearance, may be more appropriate.

The MDRD formula is widely used in clinical practice and research settings as a convenient tool for estimating kidney function in patients with CKD. However, it's important to interpret the results in conjunction with other clinical information and consider the limitations of the formula when assessing an individual's kidney function.