Prognostic value of renal pathological findings in children with atypical hemolytic uremic syndrome.

INTRODUCTION: Atypical hemolytic uremic syndrome (HUS) is accompanied by a poor prognosis and high mortality rate. We investigated the predictive value of severity of renal involvement, as evaluated by pathologic examination, for long-term outcome of atypical HUS.

MATERIALS AND METHODS: Kidney biopsies of 29 children diagnosed with atypical HUS between 1992 and 2005 were reviewed. The severity of glomerular, vascular (arteriolar and arterial), interstitial, and tubular involvement were determined. Scores of renal involvement were determined by re-evaluating kidney specimens. The outcome measures were death, chronic kidney disease (CKD), hypertension, and proteinuria.

RESULTS: After a mean of 3.7 years of follow-up, 24.1% of the patients had normal kidney function and blood pressure, 24.1% showed proteinuria, and 41.4% had CKD, and 10.3% had unknown prognosis. Overall, 24.1% of the patients died due to emergent hypertension with or without CKD. The existence of arteriolar and arterial thrombosis attributed to severe CKD (risk ratio, 3.67; 95% confidence interval, 1.63 to 8.2). Presence of thrombosis in the vessels, and thickening of the arterial medial and intimal layers had brought about a significantly higher mortality rate. Chronic kidney disease was more frequent in the children with vascular scores higher than 0.14 and a final score of more than 0.2.

CONCLUSIONS: The severity of renal pathological involvement, especially the degree of vascular damage, is a good predictor of long-term outcome of patient with atypical HUS.