Endoscopic ultrasound (EUS) has evolved into a minimally invasive diagnostic and staging method. The addition of fine needle aspiration (FNA) increases the accuracy of EUS in the diagnosis and staging of pancreatic malignancies. An ultrasound probe attached to the end of the endoscope allows real-time direct visualization by means of ultrasound transmission. During the FNA process a needle is advanced through the biopsy channel of the endoscope and into the target lesion. In order to obtain a tissue specimen of a suspicious pancreatic lesion, an FNA needle must traverse either the stomach or duodenum to access the pancreatic mass. Once the needle has entered the target lesion a syringe is exchanged for the needle stylet and negative pressure is applied allowing acquisition of a cytology specimen. Negative pressure is released from the syringe and the stop cock is closed to the syringe. However, due to the relatively long length of the needle there is is significant remaining negative pressure at the needle tip. This leads to aspiration of surrounding material including GI mucosal contamination into the needle while removing it from the target lesion.
Contamination of the FNA specimen from gastric or duodenal epithelium can occur with continued negative pressure at the needle tip upon withdrawal of the needle out of the target lesion. While EUS-FNA has a high specificity (96%), sensitivity (87%), and accuracy (94%), gastrointestinal tract contamination can lead to misinterpretation of FNA specimens. Based on clinical experience, we propose a technique to eliminate any remaining negative pressure during EUS-FNA and therefore decreasing gastrointestinal tract contamination.
