Does oliguria (decreased urine output) occur before an increase in serum creatinine levels in acute kidney injury (AKI)?

From the Guidelines

In acute kidney injury (AKI), urine output typically decreases before serum creatinine rises, serving as an early warning sign of kidney dysfunction. This sequence occurs because the kidneys can initially compensate for reduced function by concentrating urine, maintaining a relatively normal creatinine level even when glomerular filtration rate (GFR) has already decreased by 30-50% 1. Reduced urine output (oliguria, defined as <0.5 mL/kg/hr for at least 6 hours) is a key criterion for diagnosing AKI, as stated in the KDIGO guidelines 1. The earlier detection of decreased urine output explains why modern AKI classification systems like RIFLE and KDIGO include both urine output and serum creatinine criteria, allowing for earlier recognition and intervention in kidney injury before significant creatinine elevation occurs. Some key points to consider in AKI diagnosis and management include:

• The KDIGO guidelines define AKI as an increase in serum creatinine by ≥0.3 mg/dL within 48 hours or a ≥50% increase from baseline, or a urine output of <0.5 mL/kg/h for >6 hours 1.
• The staging of AKI is based on the severity of the injury, with stage 1 being the least severe and stage 3 being the most severe 1.
• The use of both urine output and serum creatinine criteria allows for earlier detection and intervention in AKI, which can improve patient outcomes. It is essential to monitor urine output and serum creatinine levels closely in patients at risk of AKI, as early detection and intervention can significantly impact morbidity, mortality, and quality of life.

From the Research

Definition and Diagnosis of Acute Kidney Injury

• Acute kidney injury (AKI) is characterized by an abrupt decrease in renal function or the onset of frank renal failure 2.
• The Kidney Disease: Improving Global Outcomes (KDIGO) defines AKI as an increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours, an SCr level increase of 1.5 times or more of the baseline level within 7 days, or a decrease in urine output to less than 0.5 mL/kg/hour for 6 hours 2, 3.
• AKI can be diagnosed based on serum creatinine level increase and/or urine output decrease 3.

Urine Output and Creatinine Level in AKI

• The KDIGO definition of AKI refers to the time of AKI development and is based on serum creatinine level increase and/or urine output decrease 3.
• A decrease in urine output to less than 0.5 mL/kg/hour for 6 hours is one of the criteria for diagnosing AKI 2, 3.
• An increase in serum creatinine level of 0.3 mg/dL or more within 48 hours is another criterion for diagnosing AKI 2, 3.
• The sequence of events, whether urine output reduction or creatinine level increase occurs first, is not explicitly stated in the provided studies.

Management and Treatment of AKI

• Management of AKI includes control of the underlying cause, achievement and maintenance of euvolemia, nutritional optimization, blood glucose control, and pharmacotherapy 2.
• Treatment with fluid resuscitation or diuresis is guided by the volume status 2.
• Nephrology consultation should be considered when there is inadequate response to supportive treatment and for AKI without a clear cause, stage 3 or higher AKI, preexisting stage 4 or higher chronic kidney disease, renal replacement therapy, and other situations requiring subspecialist expertise 4.