An increase in serum creatinine level is the first indication that a person may be suffering from acute renal failure. The first test in the category is blood creatinine level test. This test shows how well the kidneys may be working. Blood and urine sample collected over a period of 24 hours are generally used in this test. During the test process, blood is drawn through a needle and the same is checked for any rise in creatinine level in a pathology lab. In case the blood creatinine level is high, the kidney may not be working properly. This test helps determine the quantity of creatinine in the blood stream. Serum creatinine test is mildly invasive and the patient is not required to stay in the hospital for long. However, the test may be repeated if so desired by the doctor. 

Increase in BUN (blood urea nitrogen) levels occur due to non removal of urea from blood. The BUN test is generally used to measure amount of nitrogen that comes from urea. This is an important test to understand the functioning of the kidneys and help analyze facts responsible behind acute renal failure. For conducting blood urea nitrogen levels, a blood sample from a vein in the arm is taken and analyzed to measure the amount of nitrogen that comes from urea. In case BUN levels are high, it means that kidneys are not able to remove urea from blood. BUN (blood urea nitrogen) is a mildly invasive procedure and the patient can leave for home soon after the test is conducted. 

A Complete Blood Count (CBC) test helps the doctor gain valuable information about red blood cells, white blood cells and platelets. This information is of particular significance while analyzing causes of acute renal failure. The Complete Blood Count (CBC) test is done by drawing blood from a vein of the patient. The number of cells in the body, especially red blood cells, white blood cells and platelets, are determined through a Complete Blood Count (CBC) test. Any abnormal decrease in number of these cells is linked to a number of reasons, including acute renal failure. A CBC procedure is mildly invasive and the patient is not required to make multiple visits to the hospital. 

This is a vital test for analyzing the presence of acute renal failure. In this test, urine output is essentially measured for a period of 24 hours. A small tube or catheter is inserted into the bladder to collect the urine. The urine is collected in a container provided by the medical practitioner. Reduction in urine output during 24 hours, if observed, is analyzed. This reduction in urine output is linked to acute renal failure. Being an invasive test, the patient is required to remain in the hospital for a minimum of 24 hours and the duration of hospitalization can be extended if required. 

Retrograde pyelogram is a diagnostic X-ray procedure that helps determine tumors and stones that obstruct the ureter and kidneys. In this test a dye is used to determine any blockage in the kidney. In retrograde pyelogram test, a thin tube known as cytoscope is inserted into the urethra. A catheter is then inserted into the ureter through the cytoscope. A dye is injected through catheter and X-ray imaging is conducted. This test helps analyze conditions associated with formation of kidney stones and the reason behind acute renal failure. The process is invasive and the patient may be put on local anesthesia. Multiple visits may be required on part of the patient in case acute renal failure is diagnosed. 

Magnetic resonance imaging, which is conducted for a wide variety of reasons, may be helpful in diagnosing acute renal failure also. In this procedure, the abdomen of the patient is placed in a strong magnetic field in a long tube type chamber. Changes in structure of kidney and urinary tract are diagnosed through MRI, helping doctors arrive at a conclusion about acute renal failure in the patient. Magnetic resonance imaging (MRI) is non-invasive and the patient can go home the same day. 

A kidney scan or renal scintigraphy helps check the blood flow to the kidney. In case a blockage is detected, the same may be related to acute renal failure. A radioactive tracer is injected into vein in the arm. This travels to the kidney through the bloodstream. This test checks the damage to the kidney that may be caused due to any injury or infection including acute renal failure. A mildly invasive procedure, the patient is discharged immediately in case the results are negative. 

X-ray process of the abdomen is known as abdominal X-ray. It is commonly referred to as KUB (kidneys, ureters and urinary bladder). This is usually conducted to check for the presence of kidney stones. Abdominal X-ray helps identify urethral and bladder stones that might be responsible for acute renal failure. An abdominal X-ray usually includes liver, spleen, pancreas, kidneys and bladder as a clear picture of the whole urinary system is essential in identifying conditions responsible for acute renal failure. An abdominal X-ray is taken with the patient lying in upright, lateral or supine position. An early diagnosis can help prevent acute renal failure as adequate precautionary measures can be taken. 

These also help in check for presence of kidney stones, blockades and other urinary diseases including acute renal failure. The patient is made to lie down for the test. A gel cream is applied over the abdomen and a probe is moved over the body. Abdominal ultrasound and computed tomography scan helps in diagnosing a number of diseases including stones in gallbladder. It also helps determine kidney infection including acute renal failure. Abdominal X-ray, ultrasound and computed tomography scan are non invasive procedures and do not require hospitalization on part of the patient.