USMLE Guide: Acute Kidney Injury

Introduction

This USMLE guide provides important information about acute kidney injury (AKI), a common condition encountered in clinical practice. It covers the definition, etiology, clinical presentation, diagnosis, and management of AKI.

Definition

AKI, also known as acute renal failure, refers to a sudden decline in kidney function. It is characterized by an abrupt increase in serum creatinine and a decrease in urine output.

Etiology

AKI can be caused by various factors:

• Prerenal: Reduced renal blood flow due to dehydration, hypovolemia, or decreased cardiac output.
• Intrinsic renal: Direct damage to the kidneys due to conditions like acute tubular necrosis, glomerulonephritis, or interstitial nephritis.
• Postrenal: Obstruction of the urinary tract, hindering urine flow and causing increased pressure on the kidneys.

Clinical Presentation

Patients with AKI often present with:

• Decreased urine output
• Fluid overload symptoms (edema, pulmonary congestion)
• Electrolyte abnormalities (hyperkalemia, metabolic acidosis)
• uremic symptoms (nausea, fatigue, confusion)

Diagnosis

The diagnosis of AKI involves a combination of clinical evaluation and laboratory tests:

• History and physical examination: Assess for risk factors and signs of dehydration, hypovolemia, or obstruction.
• Serum creatinine: Elevated levels indicate impaired kidney function.
• Urinalysis: Presence of red or white blood cells, casts, or protein can help determine the cause of AKI.
• Renal ultrasound: Assesses for obstruction or structural abnormalities.

Management

The management of AKI focuses on the underlying cause and supportive care:

• Prerenal AKI: Fluid resuscitation, correction of hypovolemia, and optimization of cardiac output.
• Intrinsic renal AKI: Address the underlying cause (e.g., discontinuation of nephrotoxic medications) and supportive care (e.g., renal replacement therapy if necessary).
• Postrenal AKI: Relief of urinary tract obstruction through catheterization, stenting, or surgical intervention.

Complications and Prognosis

AKI can lead to several complications, such as electrolyte imbalances, metabolic acidosis, and fluid overload. The prognosis varies depending on the cause, with postrenal AKI having a better prognosis than intrinsic renal AKI.

Conclusion

Acute Kidney Injury is a significant medical condition that requires prompt recognition and appropriate management. Understanding the etiology, clinical presentation, diagnosis, and management of AKI is crucial for medical professionals preparing for the USMLE examination and for providing quality patient care.