Introduction: Ventriculoperitoneal (VP) shunts are used in the treatment in hydrocephalus, although they have a propensity to become obstructed. A radionucleotide shunt patency test is the gold standard used help determine whether a shunt is blocked or not. The goal of this study was to validate the use of ultrasound in the assessment of a suspected obstruction in a VP shunt.
Methods: This was a prospective cohort study at a single institution. 17 patients scheduled to undergo a radionucleotide shunt patency study underwent a prior blinded ultrasound shunt patency study. Ultrasound with Doppler technology was used to visualize the shunt tubing at the level of the neck and to detect flow through the tubing following a rapid and forceful manual compression of the shunt reservoir. A peak flow velocity was recorded and was used to determine whether the shunt was blocked.
Results: A receiver-operator curve was performed and used to determine the best cut-off value for peak flow velocity. Patients with a peak flow rate <11cm/s were deemed to have a blocked shunt. 6 patients were deemed to have an obstructed shunt according to the radionucleotide shunt patency test, and all of these patients were classified as obstructed by the ultrasound study. One patient was classified as having an obstructed shunt by the ultrasound study that was found to have a patent shunt according to the radionucleotide study. The specificity of the ultrasound test was 90% and the sensitivity was 100%.
Conclusions: Ultrasound with Doppler technology has the potential to be a safe, quick, available and cost/effective screening test for patients with an obstructed shunt. The high sensitivity of the test makes it an attractive option for use as a screening method that could potentially reduce the number of cases requiring radionucleotide shunt patency study. Further studies are required to substantiate its reliability.
Patient Care: By decreasing the need for a radionucleotide shunt patency study, patients will be able to be more quickly and more cheaply be evaluated for shunt obstruction in the emergency department or in the clinic.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Discuss the importance of the diagnosis of shunt blockage 2) Compare and contrast the use of ultrasound versus radionucleotides for evaluation of shunt patency 3) Discuss the strengths and weaknesses of ultrasound for use as a diagnostic tool for evaluating shunt patency