OBJECTIVE: The association between preexisting ventriculoperitoneal (VP) shunt and the risk of new-onset acute appendicitis in patients with traumatic brain injury (TBI) is not well established. The aim of the present study was to determine the relationships between VP shunt and acute appendicitis in patients with TBI. METHODS: A longitudinal cohort study matched by a propensity score in patients with TBI with (4781 patients) or without (9562 patients) VP shunt was conducted using the National Health Insurance Research Database in Taiwan between January 1993 and December 2013. RESULTS: The main outcome studied was diagnosis of acute appendicitis. The cumulative probability of acute appendicitis was not different between these 2 groups (P = 0.6244). A Cox model showed central nervous system (CNS) infection to be an independent predictor of acute appendicitis with an adjusted hazard ratio of 2.98. Patients with TBIwith both a VP shunt and a CNS infection had a greater risk of developing new-onset acute appendicitis (hazard ratio 4.25; 95% confidence interval 1.84-9.81) compared patients with TBI without a VP shunt or CNS infection. CONCLUSIONS: We concluded that VP shunt is not a risk factor in the development of appendicitis in patients with TBI. Patients with TBI with a shunt and a CNS infection may have a greater risk of developing acute appendicitis. Therefore, care in avoiding CNS infection is a key for the prevention acute appendicitis in this patient population.