Urinary Strong Ion Difference as a Marker of Renal Dysfunction. A Retrospective Analysis

Area of Science:

• Nephrology
• Critical Care Medicine
• Clinical Chemistry

Background:

• The kidneys are vital for maintaining electrolyte and acid-base balance.
• Urinary Strong Ion Difference (SIDu) is a key indicator of renal acid-base regulation.
• Evaluating SIDu's role in critically ill patients with acute kidney injury (AKI) is important.

Purpose of the Study:

• To assess the utility of Urinary Strong Ion Difference (SIDu) as a marker for renal dysfunction in critically ill patients.
• To investigate the correlation between SIDu values and the severity and outcomes of AKI.

Main Methods:

• Retrospective review of 143 critically ill patients diagnosed with AKI, categorized by KDIGO criteria and recovery status (Recovered-AKI vs. Persistent-AKI).
• Prospective recruitment of 36 healthy controls to establish reference SIDu values.
• Calculation of SIDu (NaU + KU - ClU) using urinary samples and comparison across groups.

Main Results:

• Persistent-AKI patients exhibited more severe renal dysfunction (higher serum creatinine) and significantly higher 30-day mortality (39%) compared to Recovered-AKI patients (13%).
• SIDu values were significantly different across groups, increasing from controls (16.4 mEq/l) to Recovered-AKI (30 mEq/l) and Persistent-AKI (47.3 mEq/l) groups (p<0.001).

Conclusions:

• Urinary Strong Ion Difference (SIDu) shows potential as a simple, inexpensive tool for evaluating AKI in critically ill patients.
• Further research is warranted to explore SIDu's ability to detect renal dysfunction earlier than traditional markers like serum creatinine or urine output.