Kidney Damage Markers in Nicaraguan Adolescents in a Region of an Epidemic of CKD of Unknown Etiology

Abstract

Background An epidemic of Chronic Kidney Disease (CKD) is occurring across Central America, affecting, mainly among younger men. Most studies have focused on occupational factors, but the large number of cases at a young age suggests that initial damage may begin in childhood. The goal of this pilot study was to assess markers of kidney damage among adolescents before they start working. Methods We studied markers of kidney damage in 200 students (age 12-18) with no prior work history from 4 schools in different regions of Nicaragua (Jinotega, Masaya, North Chichigalpa, and South Chichigalpa). Schools represent a range of risk based on regional adult CKD mortality data. Urine was tested by dipstick and analyzed for albumin, NGAL, NAG, and IL-18, all normalized to urine creatinine concentration. Results Dipstick proteinuria (3%) and glucosuria (1%) were rare. Only 8% had an albumin to creatinine ratio (ACR) >30 mg/g. The median IL-18 level was higher than in healthy controls identified from other studies [45 pg/ml (21-115) vs. 15 pg/ml (7-28)]. Boys had lower levels than girls for all markers, particularly NGAL and IL-18. The results by school were consistent with their a priori risk: among boys, the highest mean levels of NAG, NGAL, and IL-18 occurred at the highest risk school while girls at the two highest risk schools had higher levels of NAG. Normalization for urine creatinine did not affect results. Conclusions Non-glomerular kidney damage may be present among children in an area of epidemic CKD. If confirmed, factors in addition to occupational exposure should be studied as possible causes of CKD.