What are the staging criteria for acute kidney injury?

Aug 20, 2021 Source: Cainiu Health

Dr. Yuan Xiaoying

Introduction

Acute kidney injury (AKI) is divided into three phases: the initiating phase, the maintenance phase, and the recovery phase. 1. **Initiating phase**: Patients often experience etiologies that precipitate AKI, such as hypotension, ischemia, sepsis, or exposure to nephrotoxic agents. 2. **Maintenance phase**: Glomerular filtration rate (GFR) typically remains low, and patients may develop oliguria or anuria. 3. **Recovery phase**: GFR usually returns to normal levels.

Acute kidney injury (AKI) is divided into three phases: (1) the initiating phase, (2) the maintenance phase, and (3) the recovery phase. During the initiating phase, patients are often exposed to etiologies that predispose them to AKI—such as hypotension, ischemia, sepsis, or nephrotoxic agents—but significant parenchymal renal damage has not yet occurred.

As renal parenchymal injury progresses, the glomerular filtration rate (GFR) declines, leading to the maintenance phase. This phase typically lasts 7–14 days, although in some patients it may persist for 4–6 weeks. During this period, GFR remains persistently low. Patients may develop oliguria (urine output < 400 mL/day) or anuria (urine output < 100 mL/day).

Patients in this phase commonly exhibit multiple clinical manifestations, including nausea, vomiting, anorexia, and fluid overload—evidenced by lower-extremity edema, hypertension, dyspnea or shortness of breath—as well as metabolic acidosis, hyperkalemia, hyponatremia, hypocalcemia, hyperphosphatemia, and anemia. The recovery phase begins when GFR gradually increases. During this phase, GFR typically returns to normal levels; oliguric patients begin to produce more urine, progressing to polyuria before eventually returning to normal urine output. In contrast to the relatively rapid recovery of GFR, recovery of tubular epithelial cell function tends to be delayed and may require several months.

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What are the diagnostic criteria for acute kidney injury?

I. Serum creatinine increases by ≥0.3 mg/dL (≥26.5 µmol/L) within 48 hours. II. Serum creatinine increases by ≥50% from baseline, confirmed or presumed to have occurred within 7 days. III. Marked reduction in urine output: urine volume <0.5 mL/kg/hour for ≥6 consecutive hours.

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What Are the Symptoms of Kidney Failure?

Renal failure is a syndrome characterized by impaired kidney function, metabolic disturbances, and multisystem symptoms resulting from various causes. It is primarily classified into acute kidney injury (AKI) and chronic renal failure, with some cases representing chronic renal failure. Typical AKI can be divided into three phases: the initiation phase, the maintenance phase, and the recovery phase. Its main manifestations include changes in urine output, multisystem symptoms, and disturbances in water, electrolyte, and acid-base balance.