To our knowledge, the risk of renal scarring in children with a urinary tract infection (UTI) has not been systematically studied.
To review the prevalence of acute and chronic renal imaging abnormalities in children after an initial UTI.
We searched Medline and Embase for English-, French-, and Spanish-language articles using the following terms: “Technetium 99mTc dimercaptosuccinic acid (DMSA),” “DMSA,” “dimercaptosuccinic,” “scintigra*,” “pyelonephritis,” and “urinary tract infection.” We included articles if they reported data on the prevalence of abnormalities on acute-phase (≤15 days) or follow-up (>5 months) DMSA renal scans in children aged 0 to 18 years after an initial UTI. Two evaluators independently reviewed data from each article.
Of 1533 articles found by the search strategy, 325 full-text articles were reviewed; 33 studies met all inclusion criteria. Among children with an initial episode of UTI, 57% (95% confidence interval [CI]: 50–64) had changes consistent with acute pyelonephritis on the acute-phase DMSA renal scan and 15% (95% CI: 11–18) had evidence of renal scarring on the follow-up DMSA scan. Children with vesicoureteral reflux (VUR) were significantly more likely to develop pyelonephritis (relative risk [RR]: 1.5 [95% CI: 1.1–1.9]) and renal scarring (RR: 2.6 [95% CI: 1.7–3.9]) compared with children with no VUR. Children with VUR grades III or higher were more likely to develop scarring than children with lower grades of VUR (RR: 2.1 [95% CI: 1.4–3.2]).
The pooled prevalence values provided from this study provide a basis for an evidence-based approach to the management of children with this frequently occurring condition.
Comments
Follow-up DMSA scan: when after the index UTI?
To the Editor
In their excellent review of the risk of renal scarring in children after a first urinary tract infection (UTI), Shaikh et al(1) find that approximately 15% of children with a first UTI showed evidence of renal scarring 5 to 24 months later. In their review they consider all the abnormalities noted at least 5 months beyond the index UTI to be persistent based on a previous report from Jakobsson et al(2). However, in a later publication by Agras et al(3), they studied 105 children with a first episode of UTI; a technetium-99m dimercaptosuccinic acid (DMSA) scan was performed in all within the first week; follow-up scans were performed at 6 months and 12 months in those with abnormal findings. They found that, of the 13 patients with abnormal findings in the 6-month scan, these defects had resolved in 7 children at the time of the 12-month scan. The rate of renal scarring at 12 months was only 5.7% (6 of 105 patients).
We previously reported a study of 158 children with a first episode of UTI(4). The acute DMSA scan was abnormal in 77 cases. We think that data on the follow-up of these children may contribute to the discussion on this question. A second DMSA scan was performed after a minimum interval of six months (mean: 8 months) in 69 children and the lesions had resolved in 49 of them. A third DMSA scan was performed at least six months after the second scan (that is, at least 12 months after the index UTI) in 12 of the 20 children with persistent abnormalities in the second scan. We found that the defects had resolved in 5 children (41.6%). Even assuming that all the eight children missed for follow-up has persistent abnormalities, the resolution rate beyond six months would still be 25%.
It is difficult to find an explanation for the differences between the results found by Jakobsson and those found by Agras and ourselves. The small number of children included in theses series may be one explanation. The date the study was performed may be another explanation: Jakobsson published their study in 1997 and Shaikh found that older studies reported a higher prevalence of renal scarring, rates being relatively stable since 2002.
In conclusion, 25 to 50 percent of DMSA scan abnormalities found at the 6-month scan have resolved 12 months after the index UTI. If follow-up scans were performed routinely at least 12 months after the index UTI the rate of permanent renal scars would be lower than 15% previously estimated.
1)Shaikh N, Ewing AL, Bhatnagar S, Hoberman A. Risk of renal scarring in children with a first urinary tract infection: a systematic review. Pediatrics 2010; 126: 1084-1091.
2)Jakobsson B, Svensson L. Transient pyelonephritic changes on 99mTechnetium-dimercaptosuccinic acid scan for at least five months after infection. Acta Paediatr 1997; 86: 803-7.
3)Agras K, Ortapamuk H, Nalkoken S, Tuncel A, Atan A. Resolution of cortical lesions on serial renal scans in children with acute pyelonephritis. Pediatr Radiol 2007; 37: 153-8.
4)Fernandez-Menendez JM, Malaga S, Matesanz JL, Solis G, Alonso S, Perez-Mendez C. Risk factors in the development of early technetium-99m dimercaptosuccinic acid renal scintigraphy lesions during first urinary tract infection in children. Acta Paediatr 2003; 92: 21-6.
Conflict of Interest:
None declared