Acute Kidney Injury III: Clinical Manifestations

During the oliguric phase, urine output drops below 400 mL daily, causing fluid retention that leads to edema, hypertension, and distended neck veins. Pulmonary edema and heart failure may develop from fluid overload. This phase typically lasts 10 to 14 days and represents the initial stage of acute kidney injury.

The kidneys cannot excrete hydrogen ions during acute kidney injury, causing metabolic acidosis. The body compensates through deep, rapid breathing called Kussmaul respiration to eliminate carbon dioxide and restore acid-base balance. This respiratory pattern is a key clinical sign during the oliguric phase.

During the diuretic phase, urine output increases to 1-3 liters daily, but the kidneys cannot concentrate urine effectively. This causes significant loss of electrolytes, particularly sodium and potassium, leading to hyponatremia and hypokalemia. Patients also face dehydration and hypotension from excessive fluid loss lasting 1 to 3 weeks.

Azotemia, elevated blood urea nitrogen and creatinine, occurs when kidneys cannot excrete metabolic wastes. These accumulating toxins cause neurological symptoms including confusion, lethargy, and seizures. Azotemia also increases hyperkalemia risk, which can trigger dangerous cardiac arrhythmias during the oliguric phase.

The recovery phase lasts 2 weeks to 12 months, during which the glomerular filtration rate gradually improves and blood urea nitrogen and creatinine normalize. Complete recovery may take up to 12 months, though some patients experience residual impairment. Older patients or those with pre-existing kidney disease face greater risk for incomplete recovery.

Common symptoms during the oliguric phase include nausea, flank pain, and confusion. These occur alongside fluid retention, edema, and hypertension. Elevated potassium levels increase cardiac arrhythmia risk, while metabolic acidosis triggers compensatory breathing patterns during this 10 to 14-day initial phase.

During the diuretic phase, elevated urea levels cause osmotic diuresis, increasing urine output to 1-3 liters daily. Although the kidneys begin recovering, they remain unable to concentrate urine effectively. This results in excessive fluid and electrolyte loss, requiring careful monitoring of fluid balance and electrolyte levels to prevent complications.