How is it Diagnosed?
Acute Renal Failure, now referred to as Acute Kidney Injury (AKI), is the sudden loss of
kidney function over hours to days. Diagnosis starts with identifying decreased urine
output (<0.5 mL/kg/hr) or a rapid rise in serum creatinine (≥0.3 mg/dL in 48 hours or
1.5× baseline in 7 days).
A comprehensive history looks for precipitating factors: dehydration, sepsis, drug
toxicity (e.g., aminoglycosides, contrast agents), or obstructive uropathy. Physical
examination focuses on signs of fluid overload (edema, hypertension) or hypovolemia
(dry mucous membranes, hypotension).
Blood tests including serum creatinine, BUN, and electrolytes confirm renal dysfunction
and help classify severity using KDIGO criteria. Urinalysis can reveal proteinuria,
hematuria, or cellular casts, aiding in distinguishing prerenal, intrinsic, or postrenal
causes.
Renal ultrasound is a non-invasive first-line imaging modality to detect hydronephrosis
or small shrunken kidneys. Fractional excretion of sodium (FeNa) helps differentiate
prerenal AKI (<1%) from intrinsic renal causes (>2%).
Other supportive tests may include urine electrolytes, osmolality, and a complete blood
count. In uncertain cases, renal biopsy may be indicated. Timely diagnosis allows for
appropriate management to reverse injury and avoid progression to chronic kidney
disease.