NUM-score: A clinical-analytical model for personalised imaging after urinary tract infections.

AIM: To identify predictive variables and construct a predictive model along with a decision algorithm to identify nephrourological malformations (NUM) in children with febrile urinary tract infections (fUTI), enhancing the efficiency of imaging diagnostics. METHODS: We performed a retrospective study of patients aged <16 years with fUTI at the Emergency Department with subsequent microbiological confirmation between 2014 and 2020. The follow-up period was at least 2 years. Patients were categorised into two groups: 'NUM' with previously known nephrourological anomalies or those diagnosed during the follow-up and 'Non-NUM' group. RESULTS: Out of 836 eligible patients, 26.8% had underlying NUMs. The study identified six key risk factors: recurrent UTIs, non-Escherichia coli infection, moderate acute kidney injury, procalcitonin levels >2 µg/L, age <3 months at the first UTI and fUTIs beyond 24 months. These risk factors were used to develop a predictive model with an 80.7% accuracy rate and elaborate a NUM-score classifying patients into low, moderate and high-risk groups, with a 10%, 35% and 93% prevalence of NUM. We propose an algorithm for approaching imaging tests following a fUTI. CONCLUSION: Our predictive score may help physicians decide about imaging tests. However, prospective validation of the model will be necessary before its application in daily clinical practice.

Hyponatremia and other potential markers of ultrasound abnormalities after a first febrile urinary tract infection in children.

Urinary tract infections are the initial manifestation in 30% of urinary tract malformations. Identifying these patients, who could benefit from a specific treatment, is still challenging. Hyponatremia during urinary tract infection has been proposed as a urinary tract malformation marker. We evaluate the prevalence of hyponatremia during febrile urinary tract infections and its association with subjacent urinary tract malformations. We performed a retrospective study of healthy patients under 16 years, diagnosed with a first episode of febrile urinary tract infection, who had undergone blood testing in the acute episode and at least one renal ultrasound during follow-up (January 2014-November 2020). Hyponatremia was defined as (serum sodium ≤ 130 mEq/L). According to imaging findings, we classified patients into three groups: normal kidney ultrasound, mild pelviectasis, and significant urinary tract malformation. We performed logistic regression models to identify independent risk factors for urinary tract malformation and mild pelviectasis. We included 492 patients and 2.8% presented hyponatremia. We identified normal ultrasound in 77%, mild pelviectasis in 10.8%, and urinary tract malformation in 12% of patients. We found an association between mild pelviectasis and hyponatremia [OR 6.6 (CI95% 1.6-26.6)]. However, we found no association between hyponatremia and urinary tract malformation. The parameters that were associated with malformations were presenting a non-E. coli infection, C-reactive-protein levels over 80 mg/L, and bacteremia. CONCLUSION: Hyponatremia during the first episode of febrile urinary tract infection is present in 2.8% of patients and is associated with mild pelviectasis in imaging. However, hyponatremia does not indicate a greater need for complementary tests to screen for urinary tract malformations. WHAT IS KNOWN: • Urinary tract infection is the first manifestation in 30% of children with urinary tract malformation. • Hyponatremia could be a marker to identify these children and guide the imaging approach. WHAT IS NEW: • Around 12% of children with a first episode of febrile urinary tract infection have a urinary tract malformation. • Non-E. coli infection, C-reactive protein levels over 80 mg/L, and bacteremia are markers for malformations to guide diagnostic imaging tests, but hyponatremia (Na ≤ 130 mEq/l) is not a reliable marker.

Blood analysis for screening of electrolyte and kidney function alterations in patients with febrile urinary tract infection.

AIM: To describe the prevalence, severity, risk factors, and clinical relevance of electrolyte disturbances and acute kidney injury (AKI) during febrile urinary tract infection (fUTI). METHODS: Retrospective observational study of well/fair-appearing patients between 2 months and 16 years, with no previous relevant medical history, diagnosed with fUTI in the paediatric emergency department (PED) with subsequent microbiological confirmation. Analytical alteration (AA) data were considered: AKI (creatinine elevation × 1.5 the median for age), plasma sodium alteration (≤130 or ≥150 mEq/L), and potassium alteration (≤3 or ≥6 mEq/L). RESULTS: We included 590 patients, 17.8% presented AA (13 hyponatremia, 7 hyperkalaemia, and 87 AKI). No patient presented severe analytic alterations or a higher frequency of symptoms potentially attributable to these alterations (seizures, irritability, or lethargy). Risk factors associated with these AA were clinical dehydration (OR = 3.5 95% CI: 1.04-11.7; p = 0.044) and presenting a temperature >39°C (OR = 1.9 95% CI: 1.14-3.1; p = 0.013). CONCLUSIONS: Electrolyte and renal function disturbances are infrequent in the previously healthy paediatric population with a fUTI. If present, they are asymptomatic and not severe. Based on our results, performing systematic blood analysis to rule out AA appears no longer justified, especially in the absence of risk factors.