Urine leukocyte count demonstrates limited diagnostic accuracy for complicated appendicitis in children: a retrospective cohort study.

Acute appendicitis remains a diagnostic challenge in children, and early identification of complicated disease is critical for timely management. While urinalysis is routinely obtained during emergency evaluation, its clinical value in assessing appendicitis severity remains unclear. This study aimed to evaluate the association between routine urinalysis findings and appendicitis severity, with particular emphasis on urine leukocyte count, and to compare its performance with systemic inflammatory markers. A retrospective cohort study was conducted at a tertiary pediatric referral center including 156 consecutive pediatric patients who underwent appendectomy for suspected acute appendicitis between January 2020 and October 2022. Patients were categorized into uncomplicated appendicitis, complicated appendicitis (frank perforation, gangrenous appendicitis, or periappendiceal abscess), and negative appendectomy based on operative and histopathological findings. Urinalysis parameters and systemic inflammatory markers were recorded at presentation. Receiver operating characteristic (ROC) curve analysis was performed to assess the discriminatory performance of urine leukocyte count for complicated appendicitis. Multivariable logistic regression was performed on 113 patients with complete data to identify independent predictors of complicated appendicitis. A total of 156 patients were included (uncomplicated appendicitis, n = 111; complicated appendicitis, n = 31; negative appendectomy, n = 14). Urine leukocyte counts were significantly higher in the complicated appendicitis group compared with other groups (p < 0.01). However, urine leukocyte count demonstrated limited diagnostic accuracy for complicated appendicitis (AUC 0.637), with low sensitivity (45.2%) and modest positive predictive value (46.7%). In contrast, C-reactive protein (CRP) levels increased stepwise with disease severity and showed marked separation between uncomplicated and complicated appendicitis (p < 0.001). In multivariable analysis, only CRP remained independently associated with complicated appendicitis (OR 1.04 per 1 mg/L increase, 95% CI 1.02-1.05; p < 0.001), whereas urine leukocyte count did not retain independent predictive value. Conclusion: Although urine leukocyte count is statistically associated with complicated appendicitis in children, it demonstrates poor discriminatory performance and limited clinical utility as a standalone marker. Systemic inflammatory markers, particularly CRP, provide superior and independent predictive value for appendicitis severity. In operated children with suspected appendicitis, routine urinalysis has limited value in separating complicated from uncomplicated disease and should not substitute for CRP measurement or appropriate imaging in the diagnostic workup.