ObjectiveIt has been reported that the deletion allele of the insertion/deletion polymorphism of the angiotensin I converting enzyme gene is associated with increased cardiovascular risk and progressive renal disease, including immunoglobulin A nephropathy. We therefore investigated the relationship between angiotensin converting enzyme polymorphism and intrarenal microvascular structure in 56 patients with nondiabetic renal disease.Methods and resultsWe determined various cardiovascular hormones of the renin–angiotensin system and angiotensin converting enzyme gene polymorphism in 56 patients with nondiabetic renal diseases who underwent a renal biopsy. The patients were divided into three groups by angiotensin converting enzyme genotype (insertion/insertion,n= 21; insertion/deletion,n= 23; deletion/deletion,n= 12) using polymerase chain reaction methods. The angiotensin converting enzyme insertion/ deletion and deletion/deletion genotypes were associated with a significantly higher interlobular artery wall: lumen ratio than the insertion/insertion genotype (insertion/ insertion 0.27 ± 0.01, insertion/deletion 0.32 ± 0.01, deletion/deletion 0.33 ± 0.02;P< 0.05). Afferent arteriolar and tubulo-interstitial injury scores were similar among the three genotypes. Although serum angiotensin converting enzyme activity was higher in the deletion/deletion than in the other two genotypes (insertion/insertion 9.7 ± 0.7, insertion/deletion 10.7 ± 0.9, deletion/deletion 14.0 ± 2.4 IU/l;P< 0.05), other factors of the renin–angiotensin system, including blood pressure and serum creatinine levels, were not different among the three groups.ConclusionsThe angiotensin converting enzyme deletion/deletion genotype may be considered a risk factor for the development of microvascular wall thickening in nondiabetic renal diseases.