Clinical, uropathogenic, and radiological profile of culture-positive urinary tract infections in children below 18 months of age

Sachin George; RV Deepthi; Georgie Mathew; Jude Antony Prakash; Dona Maria; Indira Agarwal

doi:10.4103/cmi.cmi_76_22

ORIGINAL ARTICLE

Year : 2023 | Volume : 21 | Issue : 2 | Page : 114-119

Clinical, uropathogenic, and radiological profile of culture-positive urinary tract infections in children below 18 months of age

Sachin George¹, RV Deepthi¹, Georgie Mathew¹, Jude Antony Prakash², Dona Maria³, Indira Agarwal¹
¹ Department of Child Health, Christian Medical College, Vellore, Tamil Nadu, India
² Department of Microbiology, Christian Medical College, Vellore, Tamil Nadu, India
³ Department of Biostatistics, Christian Medical College, Vellore, Tamil Nadu, India

Date of Submission	13-Jul-2022
Date of Decision	08-Nov-2022
Date of Acceptance	08-Nov-2022
Date of Web Publication	07-Apr-2023

Correspondence Address:
Dr. Indira Agarwal
Department of Child Health 2, Christian Medical College, Vellore - 632 004, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/cmi.cmi_76_22

Abstract

Background: Urinary tract infections (UTIs) are common in children and have the risk of renal scarring. To better identify this at risk group, the following study was carried out to analyze the clinical profile of children below 18 months of age with culture-positive UTI and the outcome of radiological investigations. The primary objective was to assess the clinical profile of culture-positive UTI children and diagnostic yield and correlation between radiological tests. The secondary objectives were to assess the prevalent uropathogens and their antibiogram. Materials and Methods: For this retrospective study, clinical details regarding radiological investigations, prevalent uropathogens and antibiograms, common antibiotics used in treatment, and uroprophylaxis were obtained through electronic medical records in children <18 months of age admitted with culture-positive UTI. Results: In 225 children seen over a period of 36 months, a slight male predominance (56%) was observed. Ultrasonography (USG) was done in nearly all children, micturating cystourethrography (MCU) was performed in only 40% of patients, dimercaptosuccinic acid (DMSA), performed after 6 months of the index UTI, in one-fifths of the patients. All three investigations were performed in one out of six children. USG and MCU used in combination detected the highest number of significant abnormalities (39%) compared to USG and DMSA (32%). Escherichia coli was the predominant uropathogen identified. Significant meropenem resistance (52%) was observed in the community-acquired UTI. Conclusion: The evaluation and follow-up of infants and young children with UTI show inadequate radiological evaluation, which could increase the risk of undetected and untreated renal sequelae.

Keywords: Dimercaptosuccinic acid renal scan, micturating cystourethrography, renal scars, ultrasonography, urinary tract infections

How to cite this article:
George S, Deepthi R V, Mathew G, Prakash JA, Maria D, Agarwal I. Clinical, uropathogenic, and radiological profile of culture-positive urinary tract infections in children below 18 months of age. Curr Med Issues 2023;21:114-9

How to cite this URL:
George S, Deepthi R V, Mathew G, Prakash JA, Maria D, Agarwal I. Clinical, uropathogenic, and radiological profile of culture-positive urinary tract infections in children below 18 months of age. Curr Med Issues [serial online] 2023 [cited 2023 Jun 4];21:114-9. Available from: https://www.cmijournal.org/text.asp?2023/21/2/114/373759

Introduction

Urinary tract infections (UTIs) are common in children and have the risk of renal scarring. Among febrile children, 6%–8% have UTIs.^[1] Most pediatric UTIs are caused by Gram-negative coliform fecal flora colonizing the perineum, which enters the urinary tract.^[2] Small children with UTI should have an evaluation with ultrasonography (USG), dimercaptosuccinic acid (DMSA) renal scan, and micturating cystourethrography (MCU), as per current guidelines.^[3] Appropriate radiological tests to be done after an initial episode of UTI are still debatable which is reflected in the differences in published guidelines. In spite of established guidelines, there are still variations in the management and treatment among individuals and institutions. The matter is further complicated by poor compliance among patients to follow-up and the rising cost of investigations. The aim of this retrospective study was to analyze the clinical profile of children below 18 months of age with culture-positive UTI and the adequacy of radiological evaluation thereafter.

Primary objective

The primary objective was to assess the clinical profile of culture-positive UTI children and diagnostic yield and correlation between radiological tests. The secondary objectives were to assess the prevalent uropathogens and their antibiogram.

IRB No:-14821, Dated: 31.08.2022.

Materials and Methods

Study design and settings

This retrospective study was conducted at the department of child health in a tertiary care teaching hospital in southern India. Retrospective chart review was performed on children <18 months admitted with a urinary infection between the periods January 2015 and December 2017. Clinical details of children younger than 18 months, admitted with culture-positive UTI along with details about bacterial growth and antibiogram were obtained through electronic medical records. Children with urine cultures showing multiple organisms, contaminants, and negative cultures were excluded from the study. Antibiotics were administered and the sensitivity patterns were recorded. The details of the USG of the kidneys, MCU, and DMSA were noted.

Definitions

A positive urine culture was defined as the growth of a single organism with ≥10⁵ colony-forming units/ml in a properly collected urine sample either through suprapubic aspiration or clean catheterization. Positive findings in radiological investigations were defined as hydronephrosis (HDN), bladder abnormalities (thickened wall or cystitis) on USG; vesicoureteric reflux (VUR), dilated posterior urethra or posterior urethral valves (PUVs) on MCU, and parenchymal scars with or without small kidneys on DMSA.^[4] Pelviureteric junction obstruction (PUJO) was diagnosed based on the finding of the dilated renal pelvis with ureteric collapse in USG and subsequently confirmed by a diethylenetriaminepentaacetic acid scan. MCU was the reference standard for VUR detection and classification.

Statistical analysis

Data were entered into Microsoft Excel (Redmond, Washington, USA), and statistical analysis was performed using STATA 16 software (College Station, Texas, USA). Categorical variables were described as frequency (percentage), and continuous variables were described as mean ± standard deviation or median (interquartile range) depending on the normality of distribution. Diagnostic accuracy was assessed by sensitivity, specificity, positive predictive value, negative predictive value (NPV), and diagnostic odds ratio (OR; with 95% confidence intervals).

Results

Among the 336 children with suspected UTI, 111 patients were excluded since urine cultures were negative or grew contaminants. The remaining 225 children with a diagnosis of culture-positive UTI were enrolled in the study [Figure 1]. The baseline parameters of the study group are depicted in [Table 1]. Out of the 225 children enrolled in the study, 127 (56%) were males. The mean age of presentation was 7 months (range: 1–18 months).

Figure 1: Flow of study.

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Table 1: Clinical characteristics of children admitted with culture-positive urinary tract infection

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USG, done in 213 (94.7%) patients, was positive in 96 (45%) patients with bladder anomalies noted in 60 (28.1%) and HDN in 36 (16.9%) [Table 2]. Among the 102 (45.3%) patients who underwent MCU, VUR was reported in 20 (19.6%) and dilated posterior urethra without reflux in 2 patients. Dilating VUR (grades: 3–5) was seen in 8 (40%).

Table 2: Findings of radiological investigations

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DMSA was performed in 44 (19.5%) patients with a mean time to DMSA being 5.8 months (range: 1–58 months). Of the 17 (38.6%) positive DMSA scans, 4 (23.5%) had renal scarring. The sensitivity, specificity, and NPV of DMSA demonstrating an abnormality were 47.1%, 72.8%, and 64.0%, respectively, with diagnostic OR 2.37 (0.62, 9.03). Repeat DMSA was performed in 16 (36.7%) patients.

Only 39 children (17.3%) underwent all three imaging techniques. A total of 103 (45.7%) children had done both USG and MCU. Nine children with VUR in MCU had normal USG. The diagnostic accuracy of USG for detecting VUR was 59.1% but with a specificity of 78.8%, NPV (87.5%), and diagnostic OR 5.30 (1.96, 14.62).

Uropathogens with their antibiogram are shown in [Table 3]. The predominant isolates isolated were E. coli (72%), Enterococci (14%), and Klebsiella spp. (10%). The most common antibiotics used were gentamicin (99.4%), cefotaxime (77.7%), and amikacin (46.6%). Cephalexin (78.5%), nitrofurantoin (16.6%), and trimethoprim (4.7%) were commonly used for uroprophylaxis. There were 7 (3.1%) children with fungal UTIs. Fungal infection was treated with fluconazole in 4 (57.1%) patients and amphotericin B in 3 (42.8%).

Table 3: Prevalent Uropathogens and antibiogram of children admitted with culture-positive urinary tract infection

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UTI recurred in 24 (10.6%) patients. Three children each with recurrent UTI had PUV and PUJO.

Discussion

In this report from a tertiary care center in South India, we describe 225 children with bacteriological culture-proven UTIs, seen over a period of 36 months. A slight male predominance (56%) was observed with a median age of 7 months. USG was done in nearly all children, with HDN being reported in nearly a sixth of them. MCU was performed in only 40% of patients with any degree of VUR noted in one-fifth of patients. DMSA, performed after 6 months of the index UTI, in one-fifths of the patients, demonstrated scarring in a small proportion. All three investigations were performed in one out of six children. E. coli was the predominant uropathogen identified.

American Academy of Pediatrics guidelines states that renal and bladder ultrasound (RBUS) should be performed after initial febrile UTI in a young child, with voiding cystourethrogram performed only if RBUS showed abnormalities.^[5]

However, another article reported USG to be a poor screening test for genitourinary abnormalities with best reported sensitivity being 28%.^[6] The limitations of USG alone in detecting VUR have been acknowledged by several other studies also.^[7] Our study reported a sensitivity of 59% for USG as an initial screening tool. Ultrasound, being significantly dependent on the examiner, remains limited in demonstrating findings; however, its value cannot be underscored as it is feasible, noninvasive, avoid radiation, and easily available ubiquitously. Hence, it is imperative that RBUS in children, especially infants with UTI, be performed by experienced radiologists for the best results.

Recent studies which evaluated the diagnostic accuracy of DMSA scans for detecting reflux showed a sensitivity of 71%–84%, specificity of 56%–58%, and NPVs of 88%–94%.^[8],[9] In our study, sensitivity, specificity, and NPV of DMSA for VUR were 47.1%, 72.75, and 64% respectively. However, these values are significantly limited by the very small number of DMSA scans being done. Indian Society of Pediatric Nephrology recommends that a DMSA scan should not be done in the acute phase but 3 months after the UTI.^[3] The study reported a higher positivity of DMSA scans which could be explained by the fact that the majority of DMSA scans (61%) were done in the acute phase (<3 months).

USG and MCU used in combination detected the highest number of significant abnormalities in 39% while the combination of USG and DMSA detected 32%. If USG and DMSA would have been done as part of the initial work-up, our study would have missed 36% of cases of VUR which were diagnosed only by MCU [Table 4]. In a recent study, the maximum yield of radiological studies was obtained when USG was combined with DMSA and this combination missed only 25% of children with VUR which MCU could have detected. The authors also found the NPV of USG and DMSA for excluding MCU abnormality was 94% whereas it was a much lower 75.7% in our study. This may reinforce the claim to avoid unnecessary MCUs in children who have both normal USG and DMSA scans.^[4] Further data is required to validate this claim.

Table 4: Comparison of ultrasonography and dimercaptosuccinic acid with micturating cystourethrography

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The commonest uropathogens identified in our report were E. coli (72%), Enterococcus spp. (19%) and Klebsiella (10%) which is similar to published data.^{[10],[11],[12]} Significant meropenem resistance (52%) was observed in the community-acquired UTI in these children, signifying the prevalent use of meropenem in the community. Based on our susceptibility data, we were able to use 3^rd generation cephalosporin or amoxicillin–clavulanic acid with an aminoglycoside in our patients. Each center should decide on empirical therapy based on local antibiotic surveillance. Prophylactic antibiotic used was predominantly cephalexin in this group considering the age of the patients involved, with 10% of patients reporting breakthrough UTIs.

Our study is limited by its retrospective nature and the small number of MCU and DMSA scans performed. However, it carries an important message to practicing pediatricians that radiological investigations form an important role in the management of UTIs in children and should be judiciously used, improving diagnosis and prognosis. Identification of uropathogens in a large proportion of patients with antibiograms will be useful for pediatricians and general practitioners in the local geographic area. The reasons could be poor compliance, erratic follow-up, financial constraints, and inadequate guidance by the treating physicians.

Conclusion

It is advised that pediatricians and general practitioners must adhere to standard guidelines while managing UTIs. Adequate and appropriate radiological investigations to detect complications early on, play a key role in the identification of at-risk children. In those with complications, early referral to a pediatric nephrologist and long-term follow-up may help to mitigate further worsening of renal function. Important steps to be taken in this direction would include educating parents about the need for investigations, and repeated counseling including the risk versus benefit of investigations.

Research quality and ethics statement

All authors of this manuscript declare that this scientific study is in compliance with standard reporting guidelines set forth by the EQUATOR Network. The authors ratify that this study required Institutional Review Board/Ethics Committee review, and hence prior approval was obtained IRB Min. No. 14821 dated 31.08.2022. We also declare that we did not plagiarize the contents of this manuscript and have performed a Plagiarism check.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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