An update on renal scarring after urinary tract infection in children: what are the risk factors?

Genetic determinants of renal scarring in children with febrile UTI

BACKGROUND

Febrile urinary tract infections (UTIs) are among the most severe bacterial infections in infants, in which a subset of patients develops complications. Identifying infants at risk of recurrent infections or kidney damage based on clinical signs is challenging. Previous observations suggest that genetic factors influence UTI outcomes and could serve as predictors of disease severity. In this study, we conducted a nationwide survey of infant genotypes to develop a strategy for infection management based on individual genetic risk. Our aims were to identify genetic susceptibility variants for renal scarring (RS) and genetic host factors predisposing to dilating vesicoureteral reflux (VUR) and recurrent UTIs.

METHODS

To assess genetic susceptibility, we collected and analyzed DNA from blood using exome genotyping. Disease-associated genetic variants were identified through bioinformatics analysis, including allelic frequency tests and odds ratio calculations. Kidney involvement was defined using dimercaptosuccinic acid (DMSA) scintigraphy.

RESULTS

In this investigation, a cohort comprising 1087 infants presenting with their first episode of febrile UTI was included. Among this cohort, a subset of 137 infants who underwent DMSA scanning was subjected to gene association analysis. Remarkable genetic distinctions were observed between patients with RS and those exhibiting resolved kidney involvement. Notably, the genetic signature indicative of renal scarring prominently featured mitochondrial genes.

CONCLUSIONS

In this nationwide study of genetic susceptibility to RS after febrile UTIs in infancy, we identified a profile dominated by mitochondrial polymorphisms. This profile can serve as a predictor of future complications, including RS and recurrent UTIs.

Infant urinary tract infection in Sweden - A national study of current diagnostic procedures, imaging and treatment

BACKGROUND

Urinary tract infection (UTI) in infants is a common, potentially life-threatening bacterial infection, and must be managed carefully through the entire chain of care from diagnosis, choice of treatment, follow-up and risk stratification of future complications. This Swedish nationwide study of infant UTI was conducted to evaluate the current management of infant UTI, yield of investigations and the Swedish UTI guidelines' ability to detect abnormalities of importance in the urinary tract.

METHODS

Infants < 1 year with a first episode of UTI were included in a prospective multicenter study. Treatment and follow-up were provided by local pediatricians. Clinical and laboratory findings and imaging results were reported to the coordinating center. The current management and results were compared with a previous Swedish study.

RESULTS

One thousand three hundred six infants were included. Urine sampling was performed with clean catch technique in 93% of patients. Initial oral antibiotic treatment was used in 63%, predominantly third generation cephalosporines. Permanent kidney abnormalities were found in 10% and dilating vesicoureteral reflux (VUR) in 8%. Higher rates of male gender, non-E. coli infection and ultrasound dilatation were seen in infants < 1 month. UTI recurrences were reported in 18%.

CONCLUSIONS

Infant UTI is still generating a considerable amount of follow-up examinations. There is a significant shift towards clean catch as the main urine sampling method. Voiding cystourethrography is performed less frequently reducing the findings of low grade VUR. The incidence of renal scarring is comparable with earlier studies which suggests that the Swedish guidelines are able to identify individuals with risk for long-term complications.

Obesity and febrile urinary tract infection in young children

BACKGROUND

Obesity is a risk factor for infectious diseases. However, the relationship between obesity and febrile urinary tract infection (fUTI) is controversial. This study aimed to determine the relationship between obesity and fUTI in young children.

METHODS

We analyzed the medical records of children aged <2 years who were admitted to our hospital because of fever between April 2013 to March 2018. The children were categorized into three groups of non-obese, overweight, and obese according to the World Health Organization weight-for-length curves for children aged <2 years.

RESULTS

A total of 600 patients were enrolled in this study, of whom 118 were diagnosed with first fUTI. Patients in the fUTI group were younger than those in the control group (patients who were diagnosed with other febrile diseases) (5 ± 5.11 vs 11 ± 6.53 months; P < 0.001). There were no significant differences in the populations of overweight and obese children between the fUTI and control groups. In the fUTI group, the duration of fever, types of pathogen, recurrent rate, the grades of vesicoureteral reflux, and renal scarring were not associated with obesity. The white blood cell count and C-reactive protein levels were not significantly different among the three weight-for-length categories. The same results were obtained when the fUTI group was compared with an age-matched control group (n = 192, 4 ± 2.55 months old; P = 0.261).

CONCLUSIONS

Obesity is not a significant risk factor for fUTI in febrile hospitalized young children. Our study suggests that conducting urinalysis for febrile young children without obvious sources, irrespective of obesity, should be considered.

The Spectrum of Parenchymal Changes in Kidneys Affected by Intrarenal Reflux, Diagnosed by Contrast-Enhanced Voiding Urosonography and DMSA Scan

PURPOSE

To describe the parenchymal defects in kidneys with intrarenal reflux (IRR) diagnosed using contrast-enhanced voiding urosonography (ceVUS) and ^99mTc-DMSA scintigraphy (DMSA scan).

MATERIALS AND METHODS

A group of 186 uretero-renal units (URUs) was analyzed using ceVUS and DMSA scans: 47 without vesicoureteral reflux (VUR) (group A) and 139 with VURs, comprising 73 VURs without (group B), and 66 with IRR (group C). VURs included non-dilating (grades I-II), mildly non-dilating (grade III), and non-dilating (grades IV-V) grades. The parenchymal changes were analyzed using a DMSA scan.

RESULTS

The median age for VUR diagnosis was 16.5 months in girls, and 8.5 months in boys (Z = 3.9; p = 0.001). IRR occurred in 51.4% of boys and in 25.9% of girls (χ² = 12.4; p < 0.001). The non-dilating VUR occurred in 44% of boys and 24.1% of girls (χ² = 7.7; p = 0.005). IRRs characterized upper and lower renal segments (81.8 and 63.6%) and middle segments (33.3%). Both incidence and increase in IRR correlated with the grade of VUR (p < 0.001). The incidence of reduced DMSA signal was statistically different among groups A + B and C, but not between groups A and B (χ² = 32.2; p < 0.001). No statistically significant relationship existed between the reduced DMSA signal and the grade of VUR in group C. The reduced DMSA signal appeared in 9.9% positions in kidneys from group A, 14% from group B, and 32% from group C. Out of all 118 IRRs, 38.1% had reduced and 61.9% had normal DMSA signal. Among 11 parenchymal scars found in all three groups, 2 belonged to group B, 9 to group C, while group A had no scars.

CONCLUSION

The parenchymal changes are the most prominent in the group with IRR, but they do not significantly differ among kidneys with different grades of VUR. VURs of higher grades are associated with a higher incidence of IRR and early clinical presentation. Scars can also appear in lower-grade VURs accompanied by IRR. Boys with VUR have earlier clinical presentation than girls, as they have significantly higher grades of VUR with a higher proportion of IRRs. Therefore, we suggest a subdivision of VURs into those with IRR and abundant parenchymal damage, and those without IRR and less parenchymal damage.

MR-Proadrenomedullin as biomarker of renal damage in urinary tract infection in children

Background

Midregional-proadrenomedullin (MR-proADM) is a useful prognostic peptide in severe infectious pathologies in the adult population. However, there are no studies that analyze its utility in febrile urinary tract infection (fUTI) in children. An accurate biomarker would provide an early detection of patients with kidney damage, avoiding other invasive tests like renal scintigraphy scans. Our objective is to study the usefulness of MR-proADM as a biomarker of acute and chronic renal parenchymal damage in fUTI within the pediatric population.

Methods

A prospective cohort study was conducted in pediatric patients with fUTI between January 2015 and December 2018. Plasma and urine MR-proADM levels were measured at admission in addition to other laboratory parameters. After confirmation of fUTI, renal scintigraphy scans were performed during the acute and follow-up stages. A descriptive study has been carried out and sensitivity, specificity and ROC curves for MR-proADM, C-reactive protein, and procalcitonin were calculated.

Results

62 pediatric patients (34 female) were enrolled. Scintigraphy showed acute pyelonephritis in 35 patients (56.5%). Of those patients, the median of plasmatic MR-proADM (P-MR-proADM) showed no differences compared to patients without pyelonephritis. 7 patients (11.3%) developed renal scars (RS). Their median P-MR-proADM levels were 1.07 nmol/L (IQR 0.66–1.59), while in patients without RS were 0.48 nmol/L (0.43–0.63) (p < 0.01). The AUC in this case was 0.92 (95% CI 0.77–0.99). We established an optimal cut-off point at 0.66 nmol/L with sensitivity 83.3% and specificity 81.8%.

Conclusion

MR-ProADM has demonstrated a poor ability to diagnose pyelonephritis in pediatric patients with fUTI. However, P-MR-proADM proved to be a very reliable biomarker for RS prediction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02765-2.

Types of Parenchymal Changes Diagnosed on DMSA Scans of Kidneys Affected by Different Grades of Vesicoureteral Reflux

Background

Renal parenchymal damage and scarring usually is associated with urinary tract infection (UTI), whereas the impact of vesicoureteral reflux (VUR) on the kidneys is unclear. We aimed to compare kidneys with all grades of VUR (grades Io-V) and those without VUR by using direct radionuclide cystography, voiding cystourethrography, and findings from ^99mTc-DMSA scintigraphy (DMSA scan).

Material/Methods

The present analysis included 253 renal ureteral units (RUU) from 129 children with VUR and recurrent UTI and children with a single febrile UTI associated with abnormal ultrasonographic findings. The 6 grades of VUR (Io, I, II, III, IV, and V) and 35 RUUs without VUR were divided into 4 groups: 1. Non-dilated VUR (grades Io-II); 2. Mildly dilated VUR (grade III); 3. Dilated VUR (grades IV–V); and 4. The control group.

Results

DMSA scanning showed significant differences between the groups with non-dilated VUR, grade III VUR, grades IV–V VUR, and the control group in kidney width (χ²=30.5; P<0.001); position and shape (χ²=30.6; P<0.001); intensity of activity (χ²=38.1; P<0.001); distribution of activity (χ²=34.5; P<0.001); and existence of scars (χ²=16; P<0.001). The probability of abnormalities on DMSA scans increased with the VUR grade. However, inside the groups of dilated and non-dilated VUR we found no significant statistical differences between those characteristics.

Conclusions

Our results indicate that kidneys without VUR or with non-dilated lateral VUR and dilated VUR on the contralateral side represent 2 different categories of parenchymal changes.