What are Kidney Function Tests
Table of Contents
Kidney function tests are a series of blood and urine tests that are used to evaluate how well the kidneys are functioning. These tests help to assess the overall health of the kidneys, diagnose any kidney diseases or disorders, monitor the progress of a known kidney condition, and determine the effectiveness of treatment. Beyond the kidneys, these tests are important in accessing conditions that impact kidney function.
Other terms used for kidney (or renal) function tests include UEC (urea, electrolytes, creatinine). Urinalysis is plays an important role in evaluation the state of kidneys and is discussed here in detail.
Uses or Indications for kidney function tests
These panel of tests are used evaluate how well the kidneys are working or functioning.
The kidney’s main role is the excretion of waste by forming urine, maintenance of body fluid levels, regulating blood pressure, and secretion of important hormones eg erythropoietin.
Kidney function tests are ordered when:
- Compromise of kidney function is suspected, either acute or chronic kidney failure
- Metabolic disorders eg diabetes mellitus, cardiovascular conditions eg hypertension, crushing’s disease among others
- Acute conditions eg blood loss, poisoning, infections, sepsis
- Part of workup in preparation for surgical operations, imaging studies etc
- Drug dosage calculation
- Evaluate the impact of drugs known to have an effect on kidneys
- As part of wellness check up
Preparing for Kidney Function Tests
No special preparations are necessary before collection of blood sample for the test. However its important to notify the clinician or laboratory staff of any medication s you may be taking. For urine, special instructions may be necessary and those are covered under urinalysis test (see above)
Specimen and collection
In most situations, whole blood(serum) from the forearm is adequate. In cases of shock, it may be necessary to get sample from larger veins such as femoral vein. The blood should be collected in (EDTA) red topped vacutainer and mixed gently. It should be taken to the lab within 4 hours or longer if kept in the fridge at 4-7c.
Analysis
Automated chemistry analyzers have replaced manual methods. Most analyzers in routine use utilize ion-selective electrodes and nephelometry in the measurements. Each of these is covered individually in detail, click on any to open the detail page.
Parameters of Kidney function tests
As mentioned, levels of several distinct substances are measured in blood to give an indication of health of the kidneys. These are either excretory products 9which will increase) or reabsorbed products (which decrease). For routine kidney function tests the parameters include:-
- Urea
- Creatinine
- Blood Electrolytes
- Sodium (Na)
- Potassium
- Chloride
- Calcium
- Magnesium
- PH
- Osmolality
Reporting
A report will typically include all the measured analytes, reference values, and a flag. Some laboratories will include some comments especially on abnormal values.
Reference Ranges
It’s important to note the reference levels of these analytes vary with age, and physiological situations eg pregnancy. Interpretation also takes into account the overall clinical picture, underlying cause(s), and clinical course among other factors.
Serum Reference Values
| Analyte | Pediatric | Adult | Units (SI) |
|---|---|---|---|
| Urea/BUN | 8-21 | 8-21 | mmol/L |
| Creatinine | 62-106 | ummol/l | |
| Sodium (Na) | 135-155 | 80-92 | mmol/l |
| Potassium (K) | 3.4-4.7 | 3.5-5.0 | mmol/L |
| Chloride (Cl) | 80-92 | 80-92 | mmol/l |
| Calcium (Ca) | 2.2-2.8 | 2.2-2.8 | mmol/L |
| Magnesium (Mg) | 0.65-1.05 | 0.65-1.05 | mmol/L |
| pH | 7.35-7.45 | 7.35-7.45 | |
| Osmolality | 283-292 | 283-292 | mosm/kg |
Interpretation
Interpretation also takes into account the overall clinical picture, underlying cause(s), and clinical course among other factors. Some of the more common findings are as follows
- Renal Insufficiency: Elevated levels of urea, creatinine, and electrolytes. Creatinine is the analyte mostly correlated with renal function. Click here to read a more detailed description of creatinine.
- Elevated electrolytes, particularly K constitute a medical emergency.
- Plasma and renal osmolality are important in determining pre-renal, renal, or post-renal causes of deficient renal function.
Some Calculated parameters such as estimated glomerular filtration (eGFR) rate are reported as well. The formular uses the level of creatinine and a handy calculator is available on our site here uses
Cost of renal function tests in Kenya
The cost of renal function tests in Kenya is dependent on the number of parameters included in the panel, the type, and the location of the lab. Typical cost range from KES 1200 – 3500. It’s common for clinicians to order the analytes individually based on the clinical condition. If you have a medical insurance cover from private insurance or NHIF, the cost of this test is routinely covered.
Note: You can check the average cost of laboratory tests in Kenya here
Where to get tested
Most level 4-6 private and public health facilities offer the test. However some components especially electrolytes such as calcium and magnesium are available in specialized facilities and laboratories like Metropolis, Lancet and Pathcare.
Follow-up testing for Kidney Function
Repeated serial measurements over time is be required to monitor the condition or monitor response to treatment. Its recommended to stick to one good laboratory for comparability and trend analysis.
Other diagnostic modalities eg imaging, and biopsy may be deployed to help in the diagnostic process.
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Disclaimer: The information provided on this medical blog is for general informational purposes only and should not be considered as a substitute for professional medical advice. Always consult with a qualified healthcare provider before making any healthcare decisions or taking any actions based on the information provided on this blog. The authors and publishers of this blog are not liable for any errors or omissions in the content or for any actions taken based on the information provided.
