What are the staging criteria for acute kidney injury?
Jun 04, 2019
Source: Cainiu Health
Dr. Yuan Xiaoying
Introduction
Acute kidney injury (AKI) is divided into three phases: the initiation phase, the maintenance phase, and the recovery phase.
1. **Initiation phase**: Patients often experience an insult that triggers AKI, such as hypotension, ischemia, sepsis, or exposure to nephrotoxic agents.
2. **Maintenance phase**: Glomerular filtration rate (GFR) typically remains low; 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 have not yet developed overt parenchymal renal damage. As renal parenchymal injury progresses, the glomerular filtration rate (GFR) declines, marking the transition into 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 low; patients commonly develop oliguria (urine output <400 mL/day) or anuria (urine output <100 mL/day).
Patients in this phase frequently exhibit multiple clinical manifestations, including nausea, vomiting, decreased appetite, and fluid overload—manifesting as lower-limb edema, hypertension, dyspnea or shortness of breath—as well as metabolic acidosis, hyperkalemia, hyponatremia, hypocalcemia, hyperphosphatemia, and anemia.
Recovery begins when the GFR gradually increases. During the recovery phase, GFR typically returns to normal levels; oliguric patients first experience increased urine output, followed by polyuria, and eventually return to normal diuresis. In contrast to GFR recovery, restoration of tubular epithelial cell function takes considerably longer—often requiring several months.
