For instance, it takes about 24 hours for the creatinine level to rise, even if both kidneys have ceased to function. A number of alternative markers have been proposed (such as NGAL, KIM-1, IL18 and cystatin C), but none of them are established enough as of 2018 to replace creatinine as a marker of kidney function.Once the diagnosis of AKI is made, further testing is often required to determine the underlying cause. It is useful to perform a bladder scan or a post void residual to rule out urinary retention. In post void residual, a catheter is inserted into the urinary tract immediately after urinating to measure fluid still in the bladder. 50–100 mL suggests neurogenic bladder dysfunction. These may include urine sediment analysis, renal ultrasound and/or kidney biopsy. Indications for kidney biopsy in the setting of AKI include the following:
Unexplained AKI, in a patient with two non-obstructed normal sized kidneys. AKI in the presence of the nephritic syndrome. Systemic disease associated with AKI. Kidney transplant dysfunction.In medical imaging, the acute changes in the kidney are often examined with renal ultrasonography as the first-line modality, where CT scan and magnetic resonance imaging (MRI) are used for the follow-up examinations and when US fails to demonstrate abnormalities. In evaluation of the acute changes in the kidney, the echogenicity of the renal structures, the delineation of the kidney, the renal vascularity, kidney size and focal abnormalities are observed.
Acute kidney injury (AKI), previously called acute renal failure (ARF), is a sudden decrease in kidney function that develops within 7 days, as shown by an increase in serum creatinine or a decrease in urine output, or both.Causes of AKI are classified as either prerenal (due to decreased blood flow to the kidney), intrinsic renal (due to damage to the kidney itself), or postrenal (due to blockage of urine flow). Prerenal causes of AKI include sepsis, dehydration, excessive blood loss, cardiogenic shock, heart failure, cirrhosis, and certain medications like ACE inhibitors or NSAIDs. Intrinsic renal causes of AKI include glomerulonephritis, lupus nephritis, acute tubular necrosis, certain antibiotics, and chemotherapeutic agents. Postrenal causes of AKI include kidney stones, bladder cancer, neurogenic bladder, enlargement of the prostate, narrowing of the urethra, and certain medications like anticholinergics.The diagnosis of AKI is made based on a persons signs and symptoms, along with lab tests for serum creatinine and measurement of urine output. Other tests include urine microscopy and urine electrolytes. Renal ultrasound can be obtained when a postrenal cause is suspected. A kidney biopsy may be obtained when intrinsic renal AKI is suspected and the cause is unclear.AKI is seen in 10-15% of people admitted to the hospital and in more than 50% of people admitted to the intensive care unit (ICU). AKI may lead to a number of complications, including metabolic acidosis, high potassium levels, uremia, changes in body fluid balance, effects on other organ systems, and death.