How to Detect AKI?

Detecting AKI: Blood Tests, Urine Output & Imaging Explained

Acute kidney injury (AKI) is primarily diagnosed through blood tests that measure creatinine levels and urine output to assess kidney function. A significant rise in the creatinine level in the blood indicates that the kidneys are not functioning properly. Doctors may also consider other factors, such as the overall clinical picture and urine output, to determine the severity of AKI.

Diagnostic Tests to Detect AKI

Here are some of those diagnostic tests which can detect and determine AKI in patients:

Blood Tests

Common blood tests that are done to detect AKI are as follows:

1. Serum Creatinine: It measures the creatinine level in the blood, a common waste product that your kidneys filter frequently. Elevated levels of creatinine in your blood can indicate underlying kidney-related issues.
2. Blood Urea Nitrogen (BUN): This diagnostic test also measures urea and nitrogen levels in your blood, apart from creatinine. These two elements are also waste products filtered by your kidneys. Higher levels of urea or nitrogen in your blood may indicate reduced kidney function.
3. Estimated Glomerular Filtration Rate (EGFR): The following test calculates and determines the total filtration rate based on serum creatinine levels, age, and sex. If the average filtration rate is lower than the normal range, then it signifies serious kidney problems.   
4. Electrolytes: It checks the levels of potassium, sodium, and bicarbonate to detect imbalances. Abnormal levels of electrolytes in your body indicate kidney problems and require immediate medical attention.
    

Urine Output

Healthcare providers monitor urine production regularly to track kidney function. A decrease in the levels of urine output can be a sign of AKI. This test is essential for patients who are suffering from serious kidney-related problems for a prolonged period.  

Urinalysis

It is a general urine test that identifies potential causes, such as urinary tract infections. This test measures and calculates the albumin-creatinine ratio (ACR), which is the ratio of albumin levels and creatinine levels. A urine albumin-creatinine ratio above 30 mg/g exhibits a possible sign of potential kidney damage.

Ultrasound

Ultrasound can measure kidney sizes, and in cases of AKI patients, their kidneys are slightly larger than healthy individuals. Additionally, it also assesses the thickness of the renal parenchyma (cortex and medulla), which can be thinned in case of acute kidney diseases.

Kidney Biopsy

Doctors perform kidney biopsies to examine kidney tissue injuries, which can lead to complications like renal cancer. It detects the cause and effect of injuries in your kidney tissues. Doctors usually recommend this test if they fail to detect the cause of AKI from apparent blood tests.

Furosemide Stress Testing

In this diagnostic test, doctors infuse furosemide (a diuretic) into the patient's body and monitor urine output. A low output signifies a poor response to furosemide and may suggest a higher risk of AKI development. This test is a loop diuretic challenge and is done to prevent the possibility of renal replacement therapy (RRT).

Fractional Excretion of Sodium (FENa) and Urea (FEUrea)

The following urine test measures the percentage of filtered sodium excreted. Additionally, it provides insight into how well the kidneys reabsorb sodium. Apart from this, it primarily focuses on differentiating between intrinsic and prerenal kidney causes of acute kidney injury (AKI).

Early diagnosis and treatment are crucial to prevent complications and improve outcomes. Understanding the cause of AKI is important for appropriate treatment. AKI can range from mild to severe, depending on the assessment of the creatinine levels and urine outputs.