Tests performed on samples of your blood and urine are the first step in the investigation of kidney problems. Tests of these types can show how well the kidneys are removing excess fluids and waste. When changes in the shape or size of the kidney, bladder or urinary tract are suspected, a variety of imaging tests can be used. A sample of kidney tissue, a biopsy, is sometimes helpful in diagnosing the specific cause of the problem.
Tests commonly used for screening and diagnosis –There are several tests commonly used to help the healthcare professional recognise if you have kidney or urinary disease. A blood sample can be analysed for creatinine (and estimated glomerular filtration rate [eGFR]) and urea. The amount of these waste products in the blood increases as kidney filtration declines. Abnormal results are usually the first sign that kidney disease is present. A urine sample is typically also examined and analysed (urinalysis) as part of routine screening. This set of tests looks for indicators of kidney and urinary disease such as red blood cells, white blood cells (WBCs or leukocytes), and protein in the urine. If you have diabetes or high blood pressure, the amount of protein in your urine should be checked at least yearly to detect kidney disease in its early stages. Often a particular protein called albumin is measured and together with creatinine produces an albumin/creatinine ratio also known as ACR. Increased amounts of albumin in the urine are referred to as microalbuminuria. When you have symptoms suggesting infection, a urine culture can confirm the presence of a bacterial infection.
Tests to monitor kidney function –If you have been diagnosed with a kidney disease, your health care provider will request laboratory tests to help monitor kidney function. Blood levels of urea and creatinine are measured from time to time to see if the kidney disease is getting worse. The amount of calcium and phosphate in the blood and the balance of serum and urine electrolytes can also be measured, as these are often affected by kidney disease. Haemoglobin, measured as part of a full blood count (FBC) may be measured (the kidneys make a hormone, erythropoietin, that controls red blood cell production). Urine total protein or albumin can be used to test the effects of treatment in diabetes and nephrotic syndrome (a condition where the kidneys leak large amounts of protein into the urine). Parathyroid hormone, which controls calcium levels, is often increased in kidney disease and it may be checked to see if bone damage is developing that requires treatment.
|Condition||Tests Used in Diagnosis||Tests Used to Follow|
|Chronic kidney disease (chronic renal failure)||Serum urea, creatinine, eGFR, urinalysis including ACR||Serum urea, creatinine, eGFR, electrolytes, calcium, phosphate, alkaline
phosphatase, parathyroid hormone, FBC, urine ACR
|Urinary tract infections||Urinalysis, urine culture||Urinalysis, urine culture|
|Kidney stones||Imaging (see below), urinalysis||Urine sodium, calcium, phosphate, citrate, oxalate, uric acid|
|Nephrotic syndrome||Urinalysis; serum albumin, total protein, cholesterol; urine total protein; antinuclear antibody (ANA) test, hepatitis B test, hepatitis C test; complement levels||Urine total protein, serum cholesterol, urea, creatinine, eGFR|
|Nephritis||Urinalysis, serum urea, creatinine, eGFR, serum albumin, urine total protein, antinuclear antibody (ANA) test, antistreptolysin O (ASO), antiglomerular basement membrane antibody (anti GBM Ab), antineutrophil cytoplasmic antibodies (ANCA)||Serum urea, creatinine, eGFR, urinalysis|
|Kidney disease due to diabetes or high blood pressure||Urine ACR||Urine ACR,
urine total protein, serum urea, creatinine, eGFR
|Acute Kidney Injury (AKI)||Rate of increase in serum creatinine.
Serum sodium, urea, eGFR, urine ACR
|Serum creatinine, sodium, urea, eGFR, urine ACR|
Imaging techniques –If blockage to the flow of urine or kidney damage which might alter the shape or size of the kidney or urinary tract is suspected, a picture of the kidneys can be helpful. Imaging techniques such as an ultrasound, CT scan (computed tomography), isotope scan, or intravenous pyelogram (IVP) may be used. Various x-ray procedures can also be employed, such as an intravenous urogram, micturating cystogram (picture whilst passing urine), or renal arteriogram (which looks af the flow of blood in the kidney.
Kidney biopsy –A biopsy can determine the cause of protein or blood in the urine. Analysing a small piece of kidney tissue can reveal the nature and extent of structural damage to a kidney. A biopsy, obtained using a biopsy needle and diagnostic imaging equipment, is often useful when disease of the glomerular filter is suspected.