Background

Timely preoperative recognition of children with complicated appendicitis allows for planning and effective management. The aim of this study was to evaluate hyponatremia, an objective biochemical marker, as a predictor of complicated appendicitis.

Methods

A retrospective review of 1283 paediatric patients (≤15 years) who underwent acute appendicectomy from January 2016 to December 2020 (5-year period) was performed. Complicated appendicitis was defined by intraoperative findings of; macroscopic perforation, free pus, gangrene, faecal contamination or intraabdominal abscess. Comparison groups consisted of patients with complicated appendicitis, patients with uncomplicated appendicitis and patients with presumed appendicitis who went on to have no appendicitis on histology (no appendicitis group). Preoperative hyponatremia was defined as serum sodium <135 mmol/L.

Results

Of the 1283 children; 35% (443/1283) had complicated appendicitis, 54% (690/1283) had uncomplicated appendicitis and 12% (150/1283) had no appendicitis. Rates of hyponatremia were much greater in the complicated group (31.4%; 139/443) than in the uncomplicated group (3.8%; 26/690) (p < 0.0001) or the no appendicitis group 10.7% (16/150) (p < 0.0001). The no appendicitis group had higher rates of hyponatremia than the uncomplicated group (p = 0.001), an unexpected finding.

The receiver operating characteristic curve for diagnosis of complicated appendicitis versus uncomplicated appendicitis, using a cut-off serum sodium of <135 mmol/L will identify complicated appendicitis with sensitivity 31.4% and specificity of 95.7% (area under the curve of 0.76).

Conclusion

Hyponatremia is a discriminating predictor of complicated appendicitis in a paediatric population.