Rank in chronological order the phases of acute renal failure. Use all the options.

• A. Initial insult; Oliguric Phase; Diuretic Phase; Recovery Phase
• B. Oliguric Phase; Initial insult; Diuretic Phase; Recovery Phase
• C. Initial insult; Diuretic Phase; Oliguric Phase; Recovery Phase
• D. Recovery Phase; Initial insult; Oliguric Phase; Diuretic Phase

Answer: (A)

The sequence of acute kidney injury reflects how the kidney injury begins and then gradually recovers. It starts with the initiating insult to the kidneys (such as ischemia or nephrotoxicity). After that, kidney function declines further and urine output falls, producing the oliguric phase, which is characterized by low urine output, fluid accumulation, electrolyte imbalances, and rising BUN and creatinine. As tubular cells recover, urine production begins to rise again in the diuretic phase, but kidney function may still be impaired and electrolyte losses and dehydration are common. Finally, the recovery phase follows, with gradual improvement in glomerular filtration and normalization of renal function over weeks to months.

So the chronological order is initial insult → oliguric phase → diuretic phase → recovery. Placing diuresis or recovery before oliguria doesn’t fit the underlying progression, since reduced urine output marks the period of established injury before the kidneys resume higher-volume urine production and eventual recovery.