Kidney damage can mean any of the following:

• Albumin in Urine
• Red Blood cell in Urine
• Pathological abnormalities (such as an abnormal kidney biopsy result)
• Structural abnormalities (such as an abnormal kidney ultrasound result)

• GFR describes the flow rate of filtered fluid through the kidney. GFR gives a rough measure of the number of functioning nephrons. Nephrons are functional unit of kidney. There are total 1 billion nephrons in each kidney.
• The filtering units of the kidney, the glomeruli or nephrons, filter approximately 180 liters per day (125 mL/min) of plasma.
• The normal value for GFR depends upon age, sex, and body size, and is approximately 130 and 120 mL/min/1.73 m2 for men and women, respectively, with considerable variation even among normal individuals
• The most useful information to assess kidney function are estimation of the glomerular filtration rate (GFR) and examination of the urinary sediment.
• Estimation of the GFR is used clinically to assess the degree of kidney impairment and to follow the course of the disease
• However, the GFR provides no information on the cause of the kidney disease.This is achieved by the urinalysis, measurement of urinary protein excretion, and, if necessary, radiologic studies and/or kidney biopsy
• Significance of a declining GFR — In patients with kidney disease, a reduction in GFR implies either progression of the underlying disease or the development of a superimposed and often reversible problem, such as decreased renal perfusion due to volume depletion. In addition, the level of GFR has prognostic implications in patients with chronic kidney disease (CKD), and such patients are staged, in part, according to GFR. These issues are discussed in detail separately.
• However, there is not an exact correlation between the loss of kidney mass (ie, nephron loss) and the loss of GFR. The kidney adapts to the loss of some nephrons by compensatory hyperfiltration and/or increasing solute and water reabsorption in the remaining, normal nephrons . Thus, an individual who has lost one-half of total kidney mass will not necessarily have one-half the normal amount of GFR.

• These concepts have important consequences:
• A stable GFR does not necessarily imply stable disease. Signs of disease progression other than a change in GFR must be investigated, including increased activity of the urine sediment, a rise in protein excretion, or an elevation in blood pressure.
• Similarly, an increase in GFR may indicate improvement in the kidney disease or may imply a counterproductive increase in filtration (hyperfiltration) due to hemodynamic factors
• Some patients who have true underlying renal disease may go unrecognized because they have a normal GFR.

ASSESSMENT OF GFR:

• Clinical situations in which it is important to have more precise knowledge of the GFR include: prior to dose adjustment of medications, especially toxic medications with narrow therapeutic indices, such as chemotherapy; prior to kidney donation; and prior to determining the need for pre-emptive transplant.
• Estimation equations: The most common equations used in the United States are the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, the MDRD study equation, and the Cockcroft-Gault equation. These formulas are available on online. CKD-EPI equation is more suitable for the general population