Predictors of ventriculoperitoneal shunt pathology

Diagnosis of ventriculoperitoneal (VP) shunt pathology remains a dilemma in patients with nonspecific constitutional signs and symptoms. Eosinophilia has been described in association with shunt infection and malfunction. Our purpose was to further define the relationship of eosinophilia and shunt pathology and to determine other predictors of VP shunt infection and malfunction.

Records of all patients admitted with a suspected VP shunt infection or malfunction were reviewed. The following data were abstracted: age; reason for and age at initial shunt placement; number of revisions; date of last revision; history of fever or vomiting; ventricular fluid cell count; differential and culture; complete blood count and differential; need for shunt revision or replacement; and use of antibiotics. After exclusion of patients admitted for initial shunt placement, the remainder were divided into three groups: those with shunt infection; those with shunt malfunction; and those without documented infection or malfunction.

Of 12 patients with shunt infection and 69 with shunt malfunction, 2 and 11, respectively, had eosinophilia defined as > or =5%. The presence of eosinophilia had a 96% positive predictive value for shunt pathology and raised the pretest probability of pathology from 84% to a post test probability of 96%. The combination of fever history and ventricular fluid neutrophils >10% had a 99% specificity for shunt infection, had a 93 and 95% positive and negative predictive value, respectively, and raised the pretest probability of infection from 12% to a posttest probability of 92%.

In patients suspected of having a VP shunt malfunction, the presence of > or =5% eosinophils in the ventricular fluid indicates shunt pathology. The combination of fever and ventricular fluid neutrophils > 10% is predictive of shunt infection.