Background <p>Trehalase is a brush-border glycoprotein enzyme found in the small intestine and in renal proximal tubules, where it breaks down trehalose into glucose. We examined whether a non-invasive urine measurement of trehalase could help with earlier recognition of acute kidney injury (AKI) in children presenting with acute dehydration.</p> Methods <p>We included 80 children who were evaluated in the Pediatric Emergency Department for acute dehydration and 40 healthy controls from the general pediatric outpatient clinic. Baseline laboratory data were extracted from the hospital information system. At time of presentation, blood and urine specimens were collected from all participants. Urinary trehalase and urinary creatinine levels were analyzed, and the urinary trehalase/creatinine ratio was subsequently computed.</p> Results <p>Participants were analyzed in three groups: dehydrated with AKI (n = 40), dehydrated without AKI (n = 40), and healthy controls (n = 40). Baseline urea and creatinine and presentation creatinine values were similar between all groups (p &gt; 0.05). At presentation, however, urea, urinary trehalase, and the trehalase-to-creatinine ratio were higher in dehydrated children than in controls (p = 0.001, p = 0.001 and p = 0.026 respectively). Within the dehydrated cohort, children with AKI had higher urinary trehalase, a higher trehalase-to-creatinine ratio, and higher presentation urea than those without AKI (p = 0.023, p = 0.049, and p = 0.001, respectively). Urinary trehalase showed high diagnostic accuracy (AUC 0.925); at a cut-off &gt; 9.55&#xa0;mg/dL specificity reached 100%.</p> Conclusions <p>Urinary trehalase, particularly when adjusted for urinary creatinine may capture early tubular injury in dehydrated children before serum creatinine rises. Larger studies are needed to establish clinically useful cut-offs and to confirm diagnostic performance.</p> Graphical abstract <p></p>