Incidence of Post-Pyelonephritic Renal Scarring: A Meta-Analysis of the Dimercapto-Succinic Acid Literature

Purpose: We investigated ethnic differences in the risk of post-pyelonephritic renal scarring in infants and children for possible genetic determinants. Materials and Methods: We searched all peer reviewed articles published from 1980 through 2006 in the PubMed (R), MEDLINE (R) (Ovid), Cochrane Central Register of Controlled Trials and EMBASE (R) databases for the keywords, "renal scarring and pyelonephritis," "renal fibrosis" and "kidney scarring." References were included only when they specified acute pyelonephritis defined by a fever, positive urine culture and areas of photopenia in the renal cortex on 99mtechnetium dimercapto-succinic acid renal scans, repeat dimercapto-succinic acid scans obtained at least 3 months after acute pyelonephritis to assess for renal cortical scar formation and absence of recurrent urinary tract infection during followup. When possible data were analyzed according to patients and renal units. Results: Among 23 references the overall rates of renal scarring in terms of patients and renal units were 41.6% and 37.0%, respectively. In terms of patients the incidence of renal scarring following acute pyelonephritis varied by region, from 26.5% (Australia) to 49.0% (Asia). In terms of renal units the incidence of acquired renal cortical scarring varied by region, from 16.7% (Middle East) to 58.4% (Asia). When combined by vesicoureteral reflux status children and renal units with refluxing ureters exhibited an increased risk of renal scarring (odds ratios 2.8 and 3.7, respectively). Conclusions: Although scarring was different across some regions, only scarring in Asian studies comparing patients displayed a statistically significant difference. A regional effect explained the heterogeneity observed in the overall estimate for patients and partly for renal units. The greatest risk of renal scarring may be imparted by the presence of vesicoureteral reflux.