Plasma sodium as a predictor of perforation in acute appendicitis: A prospective multi-centre study

BACKGROUND: Non-operative treatment for acute appendicitis (AA) in children has gained acceptance as an alternative to surgery in selected cases. Accurate preoperative differentiation between perforated and non-perforated AA is increasingly important, as the former requires emergency surgery while the latter may be managed conservatively. Previous research has suggested that low plasma sodium concentration (P-Na) may serve as a reliable predictor of perforation. This study aimed to evaluate the association between P-Na and appendiceal perforation in a prospective, multicentre paediatric cohort. METHODS: Previously healthy children, aged 1-15 years, presenting with suspected AA who subsequently underwent appendectomy were enrolled at five paediatric surgical centres (Stockholm, Oslo, Berlin, Odense and Cape Town). Blood sampling on admission included concentration of C-reactive protein, plasma sodium concentration, white blood cell count and neutrophil count. RESULTS: 451 children met the inclusion criteria. Mean plasma sodium concentration on admission was lower in children with perforated AA as compared to non-perforated AA, mean 133.6 (standard deviation (SD) 4.0) mmol/l and 138.2 (SD 2.7) mmol/l respectively. A cut-off value of P-Na > 136 mmol/l resulted in an odds ratio of 0.11 (95% CI 0.07-0.17) for perforation. In a multivariate logistic regression analysis CRP and P-Na, respectively, were the strongest predictors of perforation. Combining the two resulted in an area under the curve of (AUC) of 0.86 in discriminating perforated AA from non-perforated AA. CONCLUSIONS: In this large, prospective, multicentre study, low P-Na was independently associated with an increased risk of perforated AA in children. The predictive value improved when combined with CRP.