We investigated prevalence of and factors associated with acute kidney injury (AKI) in a group of patients hospitalized with viral bronchiolitis. We retrospectively enrolled 139 children (mean age = 3.2 ± 2.1 months; males = 58.9%) hospitalized for viral bronchiolitis in a non-pediatric intensive care unit (PICU) setting. The Kidney Disease/Improving Global Outcomes creatinine criterion was used to diagnose AKI. We estimated basal serum creatinine by back-calculating it by Hoste (age) equation assuming that basal eGFR were the median age-based eGFR normative values. Univariate and multivariate logistic regression models were used to explore associations with AKI. Out of 139 patients, AKI was found in 15 (10.8%). AKI was found in 13 out of 74 (17.6%) patients with and in 2 out of 65 (3.1%) without respiratory syncytial virus (RSV) infection (p = 0.006). No patient required renal replacement therapies, while 1 out of 15 (6.7%) developed AKI stage 3, 1 (6.7%) developed AKI stage 2, and 13 (86.6%) developed AKI stage 1. Among the 15 patients with AKI, 13 (86.6%) reached the maximum AKI stage at admission, 1 (6.7%) at 48 h, and 1 (6.7%) at 96 h. At multivariate analysis, birth weight < 10th percentile (odds ratio, OR = 34.1; 95% confidence interval, CI = 3.6–329.4; p = 0.002), preterm birth (OR = 20.3; 95% CI = 3.1–129.5; p = 0.002), RSV infection (OR = 27.0; 95% CI = 2.6–279.9; p = 0.006), and hematocrit levels > 2 standard deviation score (SDS) (OR = 22.4; 95% CI = 2.8–183.6; p = 0.001) were significantly associated with AKI.Conclusion: About 11% of patients hospitalized with viral bronchiolitis in a non-PICU setting develop an AKI (frequently mild in degree). Preterm birth, birth weight < 10th percentile, hematocrit levels > 2SDS, and RSV infection are significantly associated with AKI in the setting of viral bronchiolitis. What is Known:• Viral bronchiolitis affects children in the first months of life and in 7.5% of cases it can be complicated by acute kidney injury (AKI).• No studies investigated associations with AKI in infants hospitalized for viral bronchiolitis. What is New:• About 11% of patients hospitalized with viral bronchiolitis can develop an AKI (frequently mild in degree).• Preterm birth, birth weight <10th percentile, hematocrit levels > 2 standard deviation score, and respiratory syncytial virus infection are associated with AKI development in infants with viral bronchiolitis.

Case reportA 19-month-old girl with right fourth-degree vesicoureteral reflux and left small non-functional kidney was admitted with a 6-day 39°C fever. She was receiving antibiotic prophylaxis (amoxicillin-clavulanate) for urinary tract infections (UTIs). At admission, she had been taking ciprofloxacin for 2 days due to leucocyturia and nitrites shown by the urine dipstick without urine culture test being done. She appeared pale and in pain, although the clinical examination was unremarkable. Refill time was of 2–3 s. Urine and blood cultures (while assuming ciprofloxacin) were sterile. Procalcitonin and C reactive protein were 5.7 ng/mL and 10.55 mg/dL, respectively. Ceftazidime was started. After 2 days, we observed splenomegaly, haemoglobin level reduction from 95 g/L to 72 g/L, platelet level reduction from 195 000 to 89 000/µL, alanine aminotransferase (ALT) 466 U/L, aspartate aminotransferase (AST) 572 U/L, ferritin 553 ng/mL, triglycerides 434 mg/dL and d-dimer 2377 µg/L. Due to the persistence of fever after 48 hours of ceftazidime, it was replaced by meropenem because of suspected lobar nephritis sustained by multiresistant bacteria.Question 1Which of the following is the most likely diagnosis?Monocytic leukaemia.Hemophagocytic lymphohistiocytosis (HLH).Renal abscess/acute lobar nephritis.Macrophage activation syndrome (MAS).Question 2How would you manage this condition?Monitoring while continuing meropenem administration.Abdomen CT.Corticosteroid administration.Bone marrow aspirate.Question 3How would you confirm your diagnostic suspicions?Genetic testing.Immunological profile (soluble interleukin [IL-2] receptor alpha, tests of natural killer (NK) cell function, expression of perforin and granzyme).Neither A nor B.Both A and B.Answers can be found on page 2.