Heart and kidney intertwined, representing the connection between cardiac surgery and kidney health.

Kidney Health After Heart Surgery: How Early Biomarkers Can Make a Difference

Mira Elwood in Health & Wellness November 2025 • 4 min read.

"New research identifies a simple blood test that could predict kidney problems after cardiac surgery, giving doctors a head start on protecting vulnerable patients."

Heart surgery, while often life-saving, can sometimes lead to complications, one of the most concerning being acute kidney injury (AKI). AKI occurs when the kidneys suddenly can't filter waste from the blood, leading to a buildup of toxins that can harm the body. Recognizing AKI early is critical, but traditional methods, like monitoring creatinine levels, often lag behind the actual damage.

Creatinine, a waste product measured in blood tests, is the standard marker for kidney function. However, it can take 48 hours or more for creatinine levels to rise after the kidneys are injured. This delay makes early intervention challenging, potentially leading to more severe kidney damage and other complications.

A groundbreaking study published in Nefrologia sheds light on a potential solution. Researchers have identified that the estimated glomerular filtration rate (eGFR), calculated using a common blood test, can serve as an early biomarker for AKI in patients undergoing cardiac surgery. This discovery could provide doctors with a crucial head start in protecting their patients' kidney health.

eGFR: A Timely Predictor of Kidney Issues

Heart and kidney intertwined, representing the connection between cardiac surgery and kidney health.

The study, led by Ángel Candela-Toha and colleagues, investigated the usefulness of routine postoperative kidney function tests in predicting AKI in patients undergoing cardiac surgery. The research team analyzed data from 3,962 patients who underwent major cardiac surgery between 2002 and 2013.

Patients were divided into two groups: an exploratory group to identify potential predictors and a validation group to confirm the findings. The researchers then assessed the ability of various kidney function parameters, measured after surgery, to predict AKI one or two days in advance. AKI was defined using the Acute Kidney Injury Network (AKIN) criteria, based on serum creatinine levels.

Large Sample Size: The study's large cohort of patients strengthens the reliability of the findings.
Time-Dependent Analysis: Using time-dependent ROC curves allowed researchers to assess the predictive ability of eGFR at different time points after surgery.
Validation Group: The use of a separate validation group confirms the robustness of the results.

The results revealed that eGFR, estimated using the MDRD-4 equation, was the strongest predictor of AKI. The area under the ROC curve (AUC), a measure of predictive accuracy, ranged from 0.700 to 0.946 for eGFR, indicating a high level of accuracy. Different eGFR cut-off values were also identified based on the severity of AKI and the time elapsed since surgery.

What This Means for Patients and Future Research

This study offers a promising step forward in protecting kidney health after cardiac surgery. By using eGFR as an early biomarker, doctors can potentially identify patients at risk of AKI sooner and implement preventive strategies. Further research is needed to validate these findings in other populations and to determine the most effective interventions based on eGFR levels. However, this study provides valuable insights that could lead to improved outcomes for patients undergoing cardiac surgery.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.nefro.2018.01.002, Alternate LINK

Title: La Tasa De Filtrado Glomerular Estimada Es Un Biomarcador Precoz De La Insuficiencia Renal Aguda Asociada A La Cirugía Cardíaca

Subject: Nephrology

Journal: Nefrología

Publisher: Elsevier BV

Authors: Ángel Candela-Toha, María Carmen Pardo, Teresa Pérez, Alfonso Muriel, Javier Zamora

Published: 2018-11-01

Everything You Need To Know

Why is Acute Kidney Injury (AKI) a concern after heart surgery, and what are the limitations of traditional detection methods like creatinine monitoring?

Acute Kidney Injury (AKI) after heart surgery occurs when the kidneys can't effectively filter waste, leading to a toxic buildup in the body. Traditional methods for detecting AKI, like monitoring creatinine levels, are often slow to reflect kidney damage. This delay makes early intervention challenging, potentially leading to more severe kidney damage and complications. The *Nefrologia* study suggests using estimated glomerular filtration rate (eGFR) as an early biomarker to proactively address this issue.

What key finding did the study published in Nefrologia reveal about predicting kidney problems after cardiac surgery?

The study found that the estimated glomerular filtration rate (eGFR), calculated using a standard blood test, can serve as an early biomarker for Acute Kidney Injury (AKI) in patients after cardiac surgery. This early detection allows doctors to potentially intervene sooner and prevent further kidney damage. The study, led by Ángel Candela-Toha, provides evidence for the usefulness of routine postoperative kidney function tests. Researchers analyzed data from 3,962 patients who underwent major cardiac surgery between 2002 and 2013.

How did the study assess the accuracy of estimated glomerular filtration rate (eGFR) in predicting Acute Kidney Injury (AKI), and what were the results of this assessment?

The study, led by Ángel Candela-Toha, used a time-dependent ROC (Receiver Operating Characteristic) curve analysis to assess the predictive ability of estimated glomerular filtration rate (eGFR) at different times after surgery. The area under the ROC curve (AUC) values for eGFR ranged from 0.700 to 0.946, demonstrating a high level of accuracy in predicting Acute Kidney Injury (AKI). Different eGFR cut-off values were also identified based on the severity of AKI and the time elapsed since surgery, providing specific guidelines for intervention.

What are the potential implications of using estimated glomerular filtration rate (eGFR) as an early biomarker for Acute Kidney Injury (AKI) after cardiac surgery?

This research offers a promising step forward in protecting kidney health after cardiac surgery. By using estimated glomerular filtration rate (eGFR) as an early biomarker, doctors can potentially identify patients at risk of Acute Kidney Injury (AKI) sooner and implement preventive strategies. While further research is needed to validate these findings in other populations and to determine the most effective interventions based on eGFR levels, this study provides valuable insights that could lead to improved outcomes for patients undergoing cardiac surgery.

How does estimated glomerular filtration rate (eGFR) compare to creatinine levels in terms of early detection of kidney problems following heart surgery?

Creatinine is a waste product measured in blood tests and has been the standard marker for kidney function. However, creatinine levels can take 48 hours or more to rise after the kidneys are injured. The estimated glomerular filtration rate (eGFR) offers a potentially faster indication of kidney distress, giving doctors a head start compared to waiting for creatinine levels to change. Thus, using eGFR helps to address a critical time gap in diagnosis.