Rapid computed tomography technique to measure ventricular volumes in the child with suspected ventriculoperitoneal shunt failure II. Clinical application.

Objectives: Assessment of ventricular volume change is critical in the child with suspected shunt failure. Minimal increases may represent high pressures in the child with reduced ventricular compliance but are difficult to detect subjectively. Objective techniques described limit anatomic sampling and are time intensive. The purpose of this study was to develop a rapid technique to measure ventricular volumes in children with suspected shunt failure.
Methods: Ventricular volumes were calculated in 12 children with baseline and emergent computed tomography scans performed for suspected shunt failure. Volumes and percent interval changes were correlated with clinical course. Two observers performed the volume analysis blinded to the clinical information; 1 observer performed the analysis twice. Time to perform the analysis was recorded for 5 studies.
Results: The intraobserver and interobserver correlation coefficients were 0.99 and 0.96/0.97, respectively. The mean time to perform the analysis was 2 minutes 42 seconds. Median percent change in patients with and without shunt obstruction was +50% (range: +24%-+367%) and +2% (range: -22%-+36%), respectively. Among patients subjectively read as having stable ventricular sizes, volume changes of -11% to +32% were calculated.
Conclusions: The technique has excellent intra- and interobserver correlation and is rapidly performed. The range of percent volume changes between patients with and without shunt malfunction overlaps. Subjective assessment of ventricular changes is significantly less sensitive than the volume calculation technique. The technique may be most useful in patients with decreased ventricular compliance in whom small interval changes may represent large pressure increases.