Acute Kidney Injury & Failure
The first step for assessing patients with acute kidney injury is urine analysis and renal ultrasound. Finding of small kidneys with ultrasound is consistent with chronic renal failure. Abnormal ultrasound further narrow down the diagnosis to pyelonephritis (with bacteria in urine) or glomerulonephritis (based on RBC casts), or renal artery/vein occlusion (based on visualization of whole RBC), or interstitial nephritis (based on eosinophils). Further if muddy brown cast are visualized and fractional excretion of sodium is > 1% the diagnosis of Acute Tubular Necrosis (ATN) is possible.