Renal Doppler Indices for Predicting Acute Kidney Injury After Isolated CABG

Role of Renal Augmented Velocity Index and Resistive Index in Predicting Postoperative Acute Kidney Injury After Isolated Coronary Artery Bypass Grafting

Acute kidney injury can occur after coronary artery bypass grafting (CABG). This prospective, single-center observational study will evaluate whether two measurements obtained from renal Doppler ultrasound-the renal augmented velocity index (AVI) and renal resistive index (RRI)-can help predict postoperative acute kidney injury. About 200 adults undergoing elective isolated CABG with cardiopulmonary bypass will have bilateral renal Doppler examinations one day before surgery, within 60 minutes after admission to the intensive care unit, and 6 hours after intensive care unit admission. The primary outcome is acute kidney injury within the first 7 days after surgery, defined according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Ultrasound measurements will be analyzed offline and will not influence clinical care.

Study Overview

• Status: Not yet recruiting
• Conditions: Coronary Artery Disease; Acute Kidney Injury
• Intervention / Treatment: Diagnostic test: Renal Doppler Ultrasonography

Detailed Description

This is an academic, prospective observational cohort study at Bursa Yuksek Ihtisas Training and Research Hospital. Adults scheduled for elective isolated on-pump CABG who provide informed consent will be enrolled consecutively.

Bilateral renal Doppler waveforms will be obtained at three time points: T0, one day before surgery after at least 10 minutes of rest; T1, within the first 60 minutes after postoperative intensive care unit admission; and T2, 6 hours after intensive care unit admission. AVI and RRI will be calculated from stored waveforms by investigators blinded to clinical outcomes. No treatment decisions will be based on these study measurements. No additional blood or urine samples will be collected for research, and no biospecimens will be retained.

The primary analysis will assess the association and predictive performance of perioperative AVI and RRI measurements for KDIGO-defined acute kidney injury within 7 postoperative days. Secondary analyses will evaluate severe acute kidney injury, renal replacement therapy, mechanical ventilation duration, intensive care unit and hospital length of stay, major postoperative complications, 30-day mortality, renal function and renal recovery at day 30, and perioperative changes in AVI and RRI.

• Study Type: Observational
• Enrollment (Estimated): 200

Contacts and Locations

• Study Contact: Name: Nuri Burkay Soylu, MD; Phone Number: +90 538 248 4728; Email: drburkaysoylu@gmail.com

Study Locations

• Turkey (Türkiye)
  • Bursa
    • Bursa, Bursa, Turkey (Türkiye)
      • Bursa Yuksek Ihtisas Training and Research Hospital
      • Contact: Nuri Burkay Soylu, MD; Phone Number: +90 538 248 4728; Email: drburkaysoylu@gmail.com
      • Principal Investigator: Nuri Burkay Soylu, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adults scheduled for elective isolated on-pump coronary artery bypass grafting at Bursa Yuksek Ihtisas Training and Research Hospital who meet all eligibility criteria. Consecutive eligible patients will be approached before surgery.

Description

Inclusion Criteria:

• Age 18 years or older.
• Scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass (on-pump).
• Able and willing to provide written informed consent.
• Both kidneys present.
• Adequate bilateral preoperative renal Doppler signal for study measurements.

Exclusion Criteria:

• Preoperative chronic dialysis or renal replacement therapy.
• Urgent or emergency surgery.
• Combined cardiac surgery, including valve, aortic, or another major additional procedure.
• Off-pump coronary artery bypass grafting or conversion of the planned surgical technique.
• Clinically significant rhythm disturbance preventing acquisition of three interpretable cardiac cycles.
• Renal transplant, solitary kidney, significant renal artery stenosis, previous renal artery intervention, hydronephrosis, or other relevant renal vascular or structural disease.
• Inadequate bilateral preoperative renal Doppler examination.
• Withdrawal of consent.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Elective Isolated On-Pump CABG Cohort; Adults scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass. Bilateral renal Doppler ultrasonography is performed one day before surgery and at 0 and 6 hours after ICU admission. Renal augmented velocity index and renal resistive index measurements are analyzed offline and are not used to guide clinical care.

Diagnostic test: Renal Doppler Ultrasonography; Bilateral renal Doppler examinations are performed at T0 (one day before surgery after at least 10 minutes of rest), T1 (within the first 60 minutes after postoperative ICU admission), and T2 (6 hours after ICU admission). Renal augmented velocity index and renal resistive index are calculated offline from stored waveforms. Study measurements do not guide clinical care.; Other Names: Renal Doppler Ultrasound

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of Acute Kidney Injury According to KDIGO Criteria	Number and percentage of participants who develop acute kidney injury according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria, based on serum creatinine and/or urine output.	From surgery through postoperative day 7

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of KDIGO Stage 2 or 3 Acute Kidney Injury	Number and percentage of participants who develop KDIGO stage 2 or 3 acute kidney injury based on serum creatinine and/or urine output criteria.	From surgery through postoperative day 7
Need for Renal Replacement Therapy	Number and percentage of participants who require postoperative renal replacement therapy.	During the index hospitalization, up to 30 days after surgery
Duration of Mechanical Ventilation	Duration of invasive mechanical ventilation, measured in hours from postoperative intensive care unit admission until successful extubation.	During the index hospitalization, up to 30 days after surgery
Intensive Care Unit Length of Stay	Duration of postoperative intensive care unit stay, measured in days from intensive care unit admission to intensive care unit discharge.	During the index hospitalization, up to 30 days after surgery
Hospital Length of Stay	Duration of the index hospital stay, measured in days from surgery to hospital discharge.	During the index hospitalization, up to 30 days after surgery
Incidence of Major Postoperative Complications	Number and percentage of participants with one or more major postoperative complications, including low cardiac output syndrome, perioperative myocardial infarction, new atrial fibrillation or serious arrhythmia, stroke or transient ischemic attack, reoperation for bleeding, sepsis or serious infection, prolonged vasopressor requirement, or mechanical circulatory support.	During the index hospitalization, up to 30 days after surgery
All-Cause Mortality	Number and percentage of participants who die from any cause within 30 days after surgery.	Through 30 days after surgery
Renal Function and Renal Recovery at Day 30	Serum creatinine and estimated glomerular filtration rate at day 30 will be compared with preoperative baseline values to assess renal recovery.	30 days after surgery
Change in Renal Doppler Indices	Change in renal augmented velocity index and renal resistive index from the preoperative T0 measurement to T1 and T2 postoperative measurements.	From one day before surgery through 6 hours after intensive care unit admission

Collaborators and Investigators

• Sponsor: Bursa Yuksek Ihtisas Training and Research Hospital
• Investigators: Principal Investigator: Nuri Burkay Soylu, MD, Bursa Yuksek Ihtisas Training and Research Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): September 15, 2026
• Primary Completion (Estimated): September 1, 2027
• Study Completion (Estimated): September 1, 2027

Study Registration Dates

• First Submitted: September 10, 2026
• First Submitted That Met QC Criteria: September 10, 2026
• First Posted (Actual): September 16, 2026

Study Record Updates

• Last Update Posted (Actual): September 16, 2026
• Last Update Submitted That Met QC Criteria: September 10, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Keywords: cardiac surgery; acute kidney injury; coronary artery bypass grafting; renal resistive index; KDIGO; prognostic biomarker; renal augmented velocity index; renal Doppler ultrasonography
• Additional Relevant MeSH Terms: Urogenital Diseases; Vascular Diseases; Cardiovascular Diseases; Male Urogenital Diseases; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Heart Diseases; Renal Insufficiency; Arteriosclerosis; Arterial Occlusive Diseases; Coronary Disease; Myocardial Ischemia; Acute Kidney Injury; Coronary Artery Disease
• Other Study ID Numbers: 2024-TBEK 2026/09-20

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared outside the study team. Access will be limited to the investigators specified in the approved study protocol.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No