Kidney Week

Abstract: TH-PO1028

Serum Bicarbonate and Clinical Outcomes After Kidney Transplantation: A Systematic Review and Meta-Analysis

Session Information

• Transplantation: Clinical - Outcomes, Malignancy, and Pathology
  October 22, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Transplantation

• 2002 Transplantation: Clinical

Authors

• Hih, Nouraldin, Mansoura University, Mansoura, Dakahlia Governorate, Egypt

Nouraldin Hih, MBBS

• Soliman, Abdelsalam Karim, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Abdelsalam Karim Soliman

• Mohamed, Mohamed E., Newgiza University, Giza, Giza Governorate, Egypt

Mohamed E. Mohamed, MD

• Puttarajappa, Chethan M., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Chethan M. Puttarajappa, MD, MS

• Tevar, Amit D., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Amit D. Tevar, MD

• Randhawa, Parmjeet S., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Parmjeet S. Randhawa, MD, MBBS

• Soliman, Karim, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States

Karim Soliman, MBChB, MSc, PhD, FASN

Background

Metabolic acidosis is a common complication in kidney transplant recipients. Serum bicarbonate, a readily available laboratory surrogate, has been variably associated with allograft dysfunction and mortality, but the magnitude and consistency of these relationships remain unclear. We performed a systematic review and meta-analysis to assess the association between serum bicarbonate levels or metabolic acidosis and key post-transplant outcomes, and to explore dose–response and threshold effects.

Methods

PubMed and Scopus were searched for observational cohort studies evaluating serum bicarbonate or metabolic acidosis and post-transplant outcomes in kidney transplant recipients. Random-effects meta-analyses pooled hazard ratios (HRs) with 95% confidence intervals (CIs). Heterogeneity was assessed using the I2 statistic.

Results

Six cohort studies comprising 6,831 kidney transplant recipients were included. Metabolic acidosis (serum bicarbonate <22 mmol/L) was associated with higher risk of allograft dysfunction/failure (4 studies; n=5,145; pooled HR 1.76, 95% CI 1.46-2.13; I2=0%). Each 1 mmol/L increase in serum bicarbonate was associated with lower risk of allograft dysfunction/failure (pooled HR 0.90, 95% CI 0.88-0.92; I2=0%). Severe metabolic acidosis (<18 mmol/L) was associated with increased graft failure risk (pooled HR 2.15, 95% CI 1.36-3.41; I2=0%). Higher bicarbonate was associated with lower all-cause mortality (3 studies; n=4,473; pooled HR 0.86, 95% CI 0.79-0.95; I2=65%), with sensitivity analysis yielding HR 0.82 (95% CI 0.75-0.89; I2=0%). Higher bicarbonate was also associated with fewer cardiovascular events (pooled HR 0.95, 95% CI 0.91-0.98; n=3,538).

Conclusion

Metabolic acidosis and lower serum bicarbonate are significantly associated with allograft dysfunction/failure and all-cause mortality in kidney transplant recipients, with a consistent dose-response relationship. Severe acidosis confers particularly high risk, underscoring the importance of close monitoring. As all studies are observational, causality cannot be established. Randomized controlled trials are needed to determine whether bicarbonate supplementation targeting ≥22 mmol/L improves hard clinical outcomes and defines optimal therapeutic targets.

Acknowledgment

Non