By Dr Ananya Mandal, MD
Nephrology deals with diseases of the kidneys. The steps taken to diagnose damage and diseases of the kidneys include:-
Some typical symptoms are associated with kidney damage. Since the kidneys are responsible for maintaining fluid balance and filter out the excess fluids and waste from blood, damage to the kidneys leads to fluid accumulation and imbalances in blood components excreted by the kidney.
Fluid overload leads to edema or swelling of the legs and face. This is a typical finding seen in kidney disease.
Long term kidney diseases also lead to symptoms of anemia. Blood pressure is normally regulated by kidneys to a great extent. Kidney damage often is accompanied with high blood pressure.
Blood tests reveal raised or altered levels of urea, creatinine and electrolytes including sodium, potassium, calcium, magnesium, phosphates, blood urea nitrogen etc.
Blood may also be tested for various organisms that may damage the kidneys including hepatitis B, hepatitis C, AIDS etc. Blood levels of antibodies to special antigens can also help detect lupus, amyloidosis and multiple myeloma.
Urine analysis may reveal excess proteins that are being excreted from the body in the urine. This is a sign of kidney damage that is especially seen in diabetic nephropathy or in long term kidney diseases.
24 hour urine samples or urine collected over a period of 24 hours helps detect total protein excretion in a day. This is an indicator of chronic kidney disease.
Kidney and urinary tract infections can also be detected in urine using microscopic analysis, culture and sensitivity studies. Microscopic examination of urine also shows red blood cells, white blood cells, pus, epithelial cells, casts or thin tubular structures that are cast images of the tiny tubules in the kidneys. Casts include hyaline casts, red cell casts, white blood cell casts, granular casts or broad casts.
Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR) is measured by studying the clearance of a substance which is freely filtered through the filtering units of the kidneys called glomerulus e.g. inulin.
In clinical practice creatinine clearance is used to calculate GFR. Clearance is a measure of volume of plasma cleared by the kidneys per time unit. Clearance is the product of urine concentration of creatinine and urine flow rate. Normal creatinine clearance in adult male is 90 -150 ml/minute.
Ultrasound scanning is one of the commonest and most used non-invasive imaging studies for kidneys diseases and damage. Ultrasound uses high frequency sound waves to create images of the abdominal organs.
Diseases such as hydronephrosis, polycystic kidney disease, kidney stones etc. are detected using ultrasound examination.
Other imaging studies
Other imaging studies that are used to detect structural or other abnormalities of the kidneys include Computed Tomography scan (CT scan) or Magnetic resonance imaging (MRI) scan. This can also help detect renal tumors and cancer.
To detect abnormalities in the blood vessels within the kidneys, MR angiography may be used. In this test a radio-contrast dye is injected into a vein in the arm and MRI images are taken as the dye passes through the kidneys. This gives a clear picture of the blood vessel network and their abnormalities within the kidneys.
If a lesion is detected on the kidney, a small amount of renal tissue may be taken from the kidney using long thin hollow needles under the guidance of ultrasound or other imaging studies. This is called renal biopsy and the tissues are then examined under the microscope for abnormal pathologies.
Intravenous urography (IVU)
Intravenous urography (IVU) is a test where an iodinated contrast dye is injected into the veins of the person. The dye is imaged using X rays or other imaging studies like CT scan to detect the flow of the blood and formation of urine in the kidneys as well as its outflow as it traverses through the kidneys.
Scintigraphy is another test using radioactive isotopes that helps detecting abnormal functions of the kidney.
Renal Arteriography is another test where a thin catheter is inserted into the femoral artery and under guidance through an imaging study.
A dye is injected into the aorta above the renal arteries and images of the blood vessels within the kidneys is obtained.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)