The necessity of shunt series

Abstract

This work assessed the value of shunt series in the evaluation of children with CSF shunts, a test that is frequently ordered as part of the assessment of shunt integrity. The medical records of all children who underwent shunt series at Children's Hospital of Eastern Ontario between 1975 and 2007 were reviewed. Ancillary studies that were performed within 2 days of the shunt series (brain CT, MR imaging, ultrasonography, and radionuclide shuntography) were noted, as well as the subsequent requirement for a shunt revision. Shunt series and ancillary studies were categorized as either positive (revealing an observable sign that a shunt-related problem was present, such as shunt discontinuity on the shunt series or enlargement of the ventricles on the brain CT scan) or negative (no clear sign of a shunt-related problem). Shunt series were further grouped into shunt series performed for diagnostic reasons, shunt series performed on a routine basis during follow-up in clinic, and shunt series performed postoperatively. The length of time between shunt insertion and shunt fracture was noted. Statistical analyses were performed, including the derivation of sensitivities and specificities. There were 3416 shunt series in 394 patients, of which 3004 were performed with ancillary studies. On average, patients underwent 9 shunt series, with a minimum of 1 and a maximum of 43, during the follow-up period (range 3 weeks to 19 years). A total of 2493 shunt series and ancillary studies (83%) yielded negative results and no surgery was performed. One hundred thirty shunts series were negative with a positive ancillary study (4.3%) and no surgery was required. In 8.7% (261 shunt series negative, ancillary studies positive) shunt revision surgery was necessary. The opposite trend was far less prevalent (17 shunt series positive, ancillary test negative; 0.6%) in which surgery was required. There were 87 patients with 96 shunt fractures (2.8% of shunt series). The average time between shunt insertion and shunt fracture was 7.9 years (range 3 months to 18 years). Shunt series had a sensitivity of 18% and a specificity of 97%. The ancillary studies had a sensitivity of 84% and a specificity of 85%. The routine utilization of shunt series in the evaluation of a child with a CSF shunt is not necessary. This study showed that a very small number (0.6%) of shunt series helped in surgical decision making. Shunt series can be performed in selected cases, especially preoperatively in the absence of a baseline study to obtain information necessary for surgical planning.