Renal (Kidney) Function Tests

kidney function test is done to access how the kidneys are functioning. Patients with acute renal failure i.e., symptoms such as decreased urine output, swelling in feet & ankles, shortness of breath, fatigue, confusion or patients with suspected chronic kidney disease i.e., swelling in feet & ankles, weight loss, shortness of breath, blood in urine, increased urination at night may be advised renal function test. 
It is also be undertaken as a general health screening test.
The test is done to adjust the dosing of drugs excreted by kidneys.
Tests are also done on patients of renal transplantation to monitor the functioning of the transplant.

The following parameters are measured blood urea nitrogen (BUN); serum electrolytes (sodium, potassium, chloride); proteins (total protein, albumin, globulin), uric acid, creatinine & estimated and urine routine examination.

kidney function test requires a blood sample and a urine sample. For the blood sample, a tourniquet (elastic) band is placed tightly on the upper arm. The patient is then asked to make a fist. This helps in the build-up of blood filling the veins. The skin is disinfected before needle insertion and the blood sample is collected in a vacutainer. For a urine sample, a container with a set of instructions on how to collect a sample will be shared by the phlebotomist.

• BUN: Urea is a degradation product of protein and amino acids. Increased blood urea nitrogen (BUN) may be due to prerenal causes (heart ailments, water depletion, and a high protein diet), kidney diseases, and postrenal causes (obstruction of the urinary tract, enlarged prostate gland, etc.).
• Creatinine: It is synthesized endogenously from creatine. It is removed from the plasma by glomerular filtration into the urine. It is used to calculate e GFR. Urine microalbumin to creatinine ratio >30 µg/mg indicates a renal disease Albumin/ microalbumin >30mg/L is associated with kidney disease

Patients need to fast (not eat or drink anything) for 8-12 hours before undergoing a kidney function test. However, they should drink water as usual because hydration levels affect the BUN readings.

It is advised not to eat a high-protein meal the night before the scheduled kidney function test, as it might give falsely elevated creatinine and blood urea levels.

Remember to inform the physician about all the medicines one takes, as some might affect the readings.

Midstream urine should be collected for kidney function tests so that the toxins and bacteria get flushed out at the start of the stream and decrease the probability of an erroneous result.

Abnormal blood tests done as part of a renal panel may indicate diseases such as diabetes, cancer, hypertension, renal infection, etc.

If the urinalysis done during the renal function test is negative. It may suggest renal stones, chronic kidney disease, or urinary tract infection.

Abnormal GFR values indicate impaired renal function and may suggest kidney failure.

If one or both kidneys' functioning falls 15% below normal, the patient is said to have kidney failure. Common symptoms include fatigue, water retention, change in urinary pattern, nausea, vomiting, etc. Elevated BUN and creatinine are found in such patients.

Dialysis is a procedure that mimics the functioning of kidneys. It filters out toxins, waste substances, and excess fluid from the blood. Also known as hemodialysis, it is recommended for patients with end-stage renal disease (ESRD), as their kidneys cannot perform their function. Dialysis needs to be performed at regular intervals. Kidney transplantation is often recommended in these patients. 

Renal (kidney) function test requires blood and urine samples.

The lab technician will tie a tourniquet (elastic) band tightly on the upper arm for the blood sample. The patient is then asked to make a fist. This helps in the build-up of blood in the veins. The skin is disinfected before needle insertion, and the blood sample is collected in a vacutainer.

A phlebotomist shares a container with collection instructions for a urine sample. The test reports can be expected within 24 hours.

The following parameters are measured in a kidney function test: 

• Blood urea nitrogen (BUN), serum electrolytes (sodium, potassium, chloride), proteins (total protein, albumin, globulin), uric acid, creatinine and estimated glomerular filtration rate (eGFR) and routine urine examination.
• GFR indicates the rate at which the kidneys filter waste. An eGFR of ≥ 90 is considered normal. Values lower than 90 are suggestive of kidney disease.
• Elevated BUN and creatinine levels indicate impaired kidney function. Urine microalbumin to creatinine ratio >30 µg/mg indicates renal disease.
• Albumin/ microalbumin >30mg/L also suggests abnormal kidney function.