Exploring kidney biopsy findings in congenital heart diseases: Insights beyond cyanotic nephropathy.

Background: The association between congenital heart disease and chronic kidney disease is well known. Various mechanisms of kidney damage associated with congenital heart disease have been established. The etiology of kidneydisease has commonly been considered to be secondary to focal segmental glomerulosclerosis (FSGS), however, this has only been demonstrated in case reports and not in observational or clinical trials.

Aim: To identify baseline and clinical characteristics, as well as the findings in kidney biopsies of patients with congenital heart disease in our hospital.

Methods: This is a retrospective observational study conducted at the Nephrology Department of the National Institute of Cardiology "Ignacio Chávez". All patients over 16 years old who underwent percutaneous kidney biopsy from January 2000 to January 2023 with congenital heart disease were included in the study.

Results: Ten patients with congenital heart disease and kidney biopsy were found. The average age was 29.00 years ± 15.87 years with pre-biopsy proteinuria of 6193 mg/24 h ± 6165 mg/24 h. The most common congenital heart disease was Fallot's tetralogy with 2 cases (20%) and ventricular septal defect with 2 (20%) cases. Among the 10 cases, one case of IgA nephropathy and one case of membranoproliferative glomerulonephritis associated with immune complexes were found, receiving specific treatment after histopathological diagnosis, delaying the initiation of kidney replacement therapy. Among remaining 8 cases (80%), one case of FSGS with perihilar variety was found, while the other 7 cases were non-specific FSGS.

Conclusion: Determining the cause of chronic kidney disease can help in delaying the need for kidney replacement therapy. In 2 out of 10 patients in our study, interventions were performed, and initiation of kidney replacement therapy was delayed. Prospective studies are needed to determine the usefulness of kidney biopsy in patients with congenital heart disease.