Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic from Euvolemic Hyponatremia

Background and Objectives: Differentiating between hypovolemic (HH) and euvolemic hyponatremia (EH) is crucial for correct diagnosis and therapy, but can be a challenge. We aim to ascertain whether changes in serum creatinine (SC) can be helpful in distinguishing HH from EH. Materials and Methods: Retrospective analysis of patients followed in a monographic hyponatremia outpatient clinic of a tertiary hospital during 1 January 2014-30 November 2019. SC changes during HH and EH from eunatremia were studied. The diagnostic accuracy of the SC change from eunatremia to hyponatremia ( increment SC) was analyzed. Results: A total of 122 hyponatremic patients, median age 79 years (70-85), 46.7% women. In total, 70/122 patients had EH, 52/122 HH. During hyponatremia, median SC levels increased in the HH group: +0.18 mg/dL [0.09-0.39, p < 0.001], but decreased in the EH group: -0.07 mg/dL (-0.15-0.02, p < 0.001), as compared to SC in eunatremia. HH subjects presented a higher rate of a positive increment SC than EH (90.4% vs. 25.7%, p < 0.001). EH subjects presented a higher rate of a negative/null increment SC than HH (74.3% vs. 9.6%, p < 0.001). ROC curve analysis found an AUC of 0.908 (95%CI: 0.853 to 0.962, p < 0.001) for increment SC%. A increment SC% >= 10% had an OR of 29.0 (95%CI: 10.3 to 81.7, p < 0.001) for HH. A increment SC% <= 3% had an OR of 68.3 (95%CI: 13.0 to 262.2, p < 0.001) for EH. Conclusions: The assessment of SC changes from eunatremia to hyponatremia can be useful in distinguishing between HH and EH.

Automated summary

This study aimed to determine whether changes in serum creatinine can be helpful in distinguishing hypovolemic hyponatremia from euvolemic hyponatremia. The results showed that during hyponatremia, serum creatinine levels increased in the hypovolemic hyponatremia group and decreased in the euvolemic hyponatremia group. By analyzing the increment of serum creatinine, it is possible to differentiate between the two types of hyponatremia.