Diagnosis of Kidney Diseases

The old saying “A stitch in time saves nine” holds true for the treatment of kidney diseases. Chronic kidney disease (CKD) is not curable and if not treated can lead to end stage kidney disease (ESKD). As discussed in the previous chapter, a person with CKD can be asymptomatic, i.e. no symptoms of the disease may be apparent. However if diagnosis of kidney disease is made early, appropriate medical treatment can be rendered and progression to ESKD can be delayed or slowed. So whenever a kidney problem is even suspected, it is advisable to go for immediate check up and early diagnosis.

Who should get their kidneys checked? Who is at high risk for developing kidney problems?

Anyone can develop a kidney problem, but the risk is higher in the presence of :

• Symptoms of kidney disease
• Diabetes
• Difficult to control hypertension
• Family history of kidney disease, diabetes and hypertension
• Chronic tobacco consumption, obesity and/or elderly (above 60 years)
• Chronic intake of pain relievers, e.g., nonsteroidal anti-inflammatory drugs such as ibuprofen, naproxen
• Congenital defect of urinary tract

Screening in such high risk individuals helps in early detection and diagnosis of kidney disease.

How to diagnose kidney problems? What tests are normally performed?

To diagnose different kidney problems the doctor takes a detailed history, thoroughly examines the person, check the blood pressure and then advises appropriate tests. Routinely performed and most useful tests include urine tests, blood tests and radiological tests.

Urine Tests

Different urine tests provide useful clues for the diagnosis of various types of kidney disease.

Routine urinalysis

• It is a simple, inexpensive and very useful diagnostic test.
• Abnormality seen in a routine urinalysis provides important diagnostic clues but a normal urinalysis does not necessarily rule out underlying kidney diseases.
• Presence of protein in urine (proteinuria) is seen in various kidney diseases. It should never be neglected. Presence of protein in urine can be the first, the earliest and the only warning sign of chronic kidney disease (and even of heart disease). For example proteinuria is the first sign of kidney involvement in diabetes.
• Presence of pus cells in urine may indicate the presence of urinary tract infection (UTI).
• Presence of protein and red blood cells (RBCs) provides diagnostic clues for inflammatory kidney disease (i.e. glomerulonephritis).

Microalbuminuria

Microalbuminuria means that a very small amount of protein is present in urine. This test provides the first and the earliest clue for the diagnosis of kidney involvement in diabetes. At this stage, the disease may be potentially reversible with proper and meticulous treatment.

Other urine tests

• 24 hour urine for protein: In patients with the presence of protein in urine, this test is necessary to determine the total actual amount of protein lost in 24 hours. This test is useful to assess the severity of the disease and also the effect of treatment on the loss of protein.
• Culture and sensitivity test: This test provides valuable information about the type of bacteria causing UTI, and the choice of antibiotic selection for its treatment.It may take 48-72 hours to get the final results of this test.
• Urine test for acid fast bacilli:This test is useful to diagnose tuberculosis of urinary tract.

Blood Tests

Various blood tests are necessary to establish appropriate diagnosis of different kidney diseases.

• Creatinine and Urea - Blood levels of creatinine and urea reflects the function of the kidneys. Creatinine and urea are two by- products which are normally removed from the blood by the kidney. When the kidney function slows down, the blood levels of creatinine and urea increase. Normal value of serum creatinine is 0.9 to 1.4 mg/dl and normal value of blood urea nitrogen (BUN) is 20 to 40 mg/dl. Higher values suggest damage to the kidneys. Creatinine level is a more reliable guide of kidney function as compared to BUN.
• Hemoglobin - Healthy kidneys help in the production of red blood cells which contain hemoglobin. When hemoglobin is low, it is called anemia. Anemia is a common and important sign of chronic kidney diseases. However anemia can occur quite frequently in other illnesses. So anemia is not a specific test for kidney diseases.
• Other blood tests - Different blood tests frequently performed in kidney patients include:blood sugar, serum albumin, cholesterol, electrolytes (sodium, potassium and chloride), calcium, phosphorous, bicarbonate, ASO titer, complement levels etc.

Radiological Tests

• Ultrasound of the kidneys - A kidney ultrasound is a simple, useful, quick and safe (no radiation exposure) test which provides valuable information such as the size of kidney and the presence of cysts, stones and tumors. An ultrasound can also detect blockage to urine flow in the urinary tract. In advanced stage of CKD or ESKD both kidneys may be found to be small in size.
• X-ray of abdomen - This test is useul for the diagnosis of calcium containg stones in the urinary system urinary tract.
• Intra venous urography (IVU) - IVU (also known as intra venous pyelography-IVP) is a specialized X- ray test. In this test, a radio opaque iodine containing dye (fluid which can be seen on X-ray films) is injected into a vein in the arm. This dye then passes through the kidney and gets excreted in to the urine. The urinary tract (kidneys, ureters and bladder) are rendered radio-opaque, and this allows visualization of the entire urinary tract. A series of X-ray pictures are taken at specific time intervals which give a comprehensive view of the anatomy of the urinary system. IVU can reveal problems such as stone, obstruction, tumor and abnormalities in structure and function of the kidneys.

In cases of advanced CKD, IVU is usually not recommended because the injected dye can damage the already poorly functioning kidneys. Inkidney failure, excretion of dye during test may be inadequate. This test is also not recommended during pregnancy. Because of availability of ultrasound and CT scan, this test is used much less frequently nowadays.

• Voiding cystourethrogram (VCUG) - VCUG (previously known as Micturating cystourethrogram - MCU) test is most commonly used in the evaluation of urinary tract infection in children. In this special X - ray test, under sterile conditions, the bladder is filled with contrast medium via the urinary catheter. After the bladder is filled, urinary catheter is removed and the patient is asked to urinate. X -rays taken at intervals during urination show the outline of the bladder and urethra. This test is helpful to diagnose backflow of urine into the ureters, and up to the kidneys (known as vesicoureteric reflux VUR) as well as identifying structural abnormalities of urinary bladder and urethra.
• Other radiological tests - In special circumstances for the diagnosis of certain kidney diseases, other tests such as CT scan of kidney and urinary tract, renal doppler, radionuclear study, renal angiography, antegrade and retrograde pyelography etc. can be useful.

Other Special Tests

Kidney biopsy, cystoscopy and urodynamics are special tests which are necessary for the exact diagnosis of certain kidney problems.

Kidney Biopsy

Kidney biopsy is an important test useful in the diagnosis of certain kidney diseases such as glomerulonephritis, certain tubulointerstitial diseases, etc.

What is kidney biopsy? - During a kidney biopsy, a small piece of kidney tissue is removed through a needle and examined under a microscope. Kidney biopsy is performed to diagnose the exact nature of certain kidney diseases, e.g. glomerulonephritis and certain tubulointerstitial diseases, etc.

When is kidney biopsy advised? - In certain kidney diseases even a detailed history, physical examination and routine tests are unable to establish proper diagnosis. In such patients, a kidney biopsy may provide additional information, which can establish the correct diagnosis.

How does the kidney biopsy help? - The kidney biopsy establishes specific diagnosis of certain unexplained kidney diseases, e.g. glomerulonephritis and certain tubulointerstitial diseases, etc. With this information, the nephrologist is able to plan effective treatment strategy and guide patients and their family about the severity and course of the disease.

By which technique is a kidney biopsy performed? - The most common method is via a percutaneous needle biopsy (usually performed in the radiology suite), in which a hollow needle is passed through the skin into the kidney. Another rarely used method is open biopsy which requires surgery (performed in the operating room).

How is a kidney biopsy performed?

• The patient is admitted in hospital and his consent is obtained.
• Prior to biopsy it is ensured that blood pressure and blood tests on blood clotting are within normal. Medications used for the prevention of blood clotting (e.g. aspirin and clopidrogel) is recommended to be discontinued for at least 1- 2 weeks prior to biopsy.
• Ultrasound or CT scan is done to know the position of kidneys and to determine exact biopsy site.
• The patient is asked to lie face down – on his/her stomach with the abdomen supported by a pillow or towel. The patient is fully awake during the procedure. In small children the kidney biopsy is done under general anesthesia, so the child is not awake.
• After proper cleaning of the skin, the biopsy site is numbed with local anesthesia to minimize discomfort and pain.
• With the use of a hollow biopsy needle, 2 or 3 small thread like pieces are obtained from the kidney. These specimens are then sent to the pathologist for histopathology examination.
• After the biopsy, pressure is applied to the biopsy site to prevent bleeding. The patient is put on complete bed rest for 6-12 hours and usually discharged the following day.
• The patient is advised to avoid heavy work or exercise for at least 2-4 weeks after the biopsy procedure.

Are there any risks to kidney biopsy? - Like any surgical procedure, complications can occur in a few patients after kidney biopsy. Mild pain or discomfort over the puncture site and passing of reddish urine once or twice is not uncommon, but it usually stops on its own. In rare cases where bleeding continues, blood transfusion may be required. In extreme and very rare circumstances where by intractable severe bleeding persists emergency removal of kidney by surgery may become necessary.

Sometimes kidney tissue obtained may not be adequate for diagnosis (about 1 in 20). Repeat biopsy may be needed in such cases.

Source: Kidney Education Foundation