EUS-guided in vivo microdialysis of the pancreas: a novel technique with potential diagnostic and therapeutic application

BackgroundMicrodialysis has been used in vivo to measure dynamic temporal variations in extracellular or interstitial concentrations of non-protein–bound substances that are unstable in the systemic circulation.ObjectiveTo evaluate the technical feasibility and possible complications of EUS-guided in vivo microdialysis of the pancreas.Design and InterventionUnder the guidance of an echoendoscope inserted into the stomach of each dog, the pancreatic parenchyma was punctured by using a 19-gauge needle. A specially developed microdialysis probe threaded through the lumen of the 19-gauge needle was positioned in the pancreas. The probe was constantly perfused with saline solution at a flow rate of 1.0 μL/minute.SettingExperiments on 8 beagle dogs.Main Outcome MeasurementsThe concentration of 5-fluorouracil (5-FU) in the microdialysate was measured at 10-minute intervals, once before and for 8 times after a single (20 mg/kg) bolus intravenous infusion of 5-FU.ResultsFollowing the administration of 5-FU, the concentration of 5-FU in all macrodialysate samples exceeded the cut-off value by more than 100-fold. The 5-FU levels in the microdialysate increased rapidly, peaked by 10 minutes (13.9 μg/mL), and gradually declined thereafter. No local bleeding or accumulation of fluid around the pancreas was observed.LimitationSampling was unsuccessful in 2 of the 8 dogs because the probe broke while being inserted into the pancreatic parenchyma.ConclusionEUS-guided pancreatic microdialysis is feasible and has multiple potential clinical/therapeutic applications, including monitoring pharmacokinetics focally and detecting novel biomarkers that are unstable or undetectable in the plasma.