Chronic Kidney Disease (CKD)
Structural or functional abnormality of the kidneys lasting for more than three months is called Chronic Kidney Disease.
The structural abnormalities include small kidney size, single kidney, horse shoe kidney, obstruction to collecting system etc.
The functional abnormalities include excessive protein loss in urine, elevated creatinine in the blood etc.
Diagnosis of Chronic Kidney Disease
Creatinine level in the blood is a sensitive and specific marker of kidney function. Creatinine is released from the skeletal muscles and therefore its value in blood is higher in those who have larger muscle mass.
Creatinine is normally thrown out by the kidneys through urine. When kidneys are working abnormally low, creatinine level in the blood rises.
On repeated checks, when this rise remains sustained for at least three months, the person is said to have chronic kidney disease.
Normal values for men are 0.7 to 1.1 mg/dL and for women are 0.6 to 0.9 mg/dL. These values vary from laboratory to laboratory and the same sample tested in two different labs will often give significantly different values.
Symptoms of kidney disease do not appear till 90 % of the kidney function is lost and therefore screening of individuals at risk (see below) is of utmost importance.
If the kidney sizes on sonography are small (i.e. < 9.0 cm), that almost confirms the diagnosis of CKD.
Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate is a parameter of kidney functions. It is the amount of blood that is cleared of waste substances ( e.g. urea, creatinine) every minute by the kidneys. In an ideal setup, it can be calculated by a tedious test involving injection of a substance and collection of timed blood samples and urine samples.
GFR can be estimated in the clinic by simple formulae based on creatinine level, body weight, race and age. This value is called estimated GFR (eGFR).
Normal values vary with race and dietary habits. Western population have a normal GFR of 100 to 125 mL/min. In Indian population, where people are of much smaller stature, have lesser muscle mass and have predominantly vegetarian diet, the GFR is commonly less than 100 mL/min.
However, a value of less than 60 mL/min is abnormal irrespective of age, race and muscle mass.
Stages of Kidney Disease
Based on GFR, National Kidney Foundation has divided CKD into five stages.
|Stage of CKD||GFR ( mL/min)|
|Stage I||> 90 with structural or biochemical abnormalities|
|Stage II||60 to 89|
|Stage III||30 to 59|
|Stage IV||15 to 29|
Next : Causes & Symptoms Of CKD