<qa>  What is the purpose of this study?The purpose of this study is to compare the accuracy of ShuntCheck SC and ShuntCheck plus Micro-Pumper SCMP to radionuclide shunt patency testing SPS in evaluating shunt function in patients with adult hydrocephalus AH implanted with ventriculoperitoneal VP shunts when shunt obstruction is suspected and a diagnostic procedure such as radionuclide shunt patency testing SPS is required. 