Renal function in children with cyanotic congenital heart disease: pre- and post-cardiac surgery evaluation

Cyanotic congenital heart diseases (CCHDs) are a series of cardiac anomalies that have long been recognized as a potential cause of nephropathy. There have been few reports on renal impairment in patients with CCHD before and after corrective cardiac surgery. The aim of this study was to evaluate the prevalence of renal dysfunction before and after cardiac surgery and the impact of some risk factors on final renal outcome.

Thirty children with CCHD who had done corrective cardiac surgery in the previous 6 months were enrolled in this study. All data prior to surgery were collected from the charts. Post-operation data including blood and spot urine samples were taken simultaneously for CBC, Cr, and uric acid and 24 hour urine was collected for microalbumin and Cr during the follow up visits. Pre- and post-operation parameters were compared to study the impact of cardiac surgery on renal function. Findings : Pre- and post-operative GFRs were not significantly different. Final GFR was significantly and inversely associated with pre- and post-operation age (P=0.008 r=-0.48, P=0.03 r=-0.38). Three (10%) patients had microalbuminuria. The prevalence of microalbuminuria in children older than 10 years was 30%. There was no link between microalbuminuria and age, GFR, and hematocrit (P=0.1, P=0.3, P=0.3, respectively). Patients with preoperation hematocrit >45 had a significantly lower final GFR compared to children with HCT <45 (83.7±6.5 vs 111.10.2, P=0.001). The mean uric acid fraction (FEua) excretion was 8.21±4.75. Pre-operative HCT was inversely associated to FEua (P=0.01, r=-0.44). There was no relationship between FEua and age, serum uric acid, and GFR (P=0.7, P=0.4, P=0.2).

Children with CCHD are at increased risk of renal injury which is related more to the duration of cyanosis and higher degree of hematocrit level. To lower the risk, corrective cardiac surgery is recommended to be done as soon as possible to improve renal function and stop more renal impairment.