Role of Doppler Endoscopic Probe in the Diagnosis of Subepithelial Gastrointestinal Lesions.

RESEARCH PLAN I-TITLE Role of Doppler endoscopic probe in the diagnosis of subepithelial gastrointestinal lesions.

II-BACKGROUND Subepithelial lesions (SEL) are commonly encountered during routine endoscopies with an estimated prevalence of 3.5%. Most of the SELs are detected during upper gastrointestinal endoscopy. Subsequently, endoscopic ultrasound (EUS) is performed to better characterize the lesion and to rule out the presence of a vascular lesion before tissue sampling due to the high risk of severe bleeding with tissue acquisition in vascular injury. However, EUS can rarely establish a definitive diagnosis per se with limited accuracy.

In large lesions, it is possible to use cytology or histology needles via the EUS instrument to collect cells/tissue within the lesion. It can lead to accurate diagnosis and consistent management. However, EUS-guided tissue sampling can be technically challenging, with poor yield for small or mobile SELs. In addition, EUS is an expensive technique, high operator dependency and performed only in tertiary centers. It creates a time gap between endoscopic detection and the EUS examination and increases costs. That delay in diagnosis is a source of anxiety for the patient and for the caregivers.

Several methods were proposed to increase the diagnostic yield of tissue acquisition techniques, such as "bite-on-bite" biopsies which showed a limited diagnostic yield. Alternatively, the "unroofing" technique has also been advocated for histological diagnosis. In unroofing, a loop is used to remove the normal epithelium covering the subepithelial lesions and after epithelial removal, a biopsy forceps or loop is used to sample subepithelial lesions. Other techniques include endoscopic resection by snare or submucosal dissection. These enable a surgical specimen but are technically demanding and have been complicated by perforation and bleeding in most series.

There is a need for a method that enables rapid diagnosis in the same session as endoscopic detection of SEL regardless of their size. That method should ideally enable histological diagnosis with low risks of complications and should not require high technical expertise and should not be highly dependent on the operator. The ideal solution to address the diagnosis of gastrointestinal (GI) SEL would be one that would provide a tissue sampling after exclusion of a highly vascular lesion, in the same session as endoscopic detection.

Doppler endoscopic probe (DEP) is a Doppler endoscopic probe specially developed for the GI system, which enables blood flow detection during endoscopy.

DEP is CE and FDA approved and can be used through the working channel of the endoscope. Unlike standard EUS, which requires advanced endoscopic training, DEP is much easier to use. It allows the characterization of lesions as non-vascular, venous or arterial. Recent studies have demonstrated the safety and efficacy of DEP in vascular characterization in the gastrointestinal tract.

III PURPOSE

Primary objective:

• Proof of concept evaluation of the role of DEP in the characterization of GI SEL as non-vascular or vascular (arterial or venous)
• Relationship between findings on DEP versus findings on EUS (considered the gold standard) regarding SEL characterization as non-vascular or vascular (arterial or venous).

Secondary purposes:

• Accuracy in removing the histological characterization of subepithelial GI lesions.
• Complications in connection with tissue acquisition
• Inter-observer agreement of DEP and EUS results. IV METHODS This is a pilot projective feasibility study that will be run by Karolinska University Hospital in Stockholm Patients with subepithelial GI lesions were referred for EUS evaluation. The study will include 30 patients.

A conventional gastroscopy will be performed. After identification of the lesion, DEP is performed. The DEP probe is lubricated and deployed through the working channel of the endoscope. The probe will contact the mucosa slightly, covering the SEL. Then evaluate the lesion in 2 different angels. The results will be characterized and recorded qualitatively: no flow / arterial flow / venous flow and in terms of intensity: soft, medium or high.

After DEP, evaluation EUS will be performed by another endoscopist who will be tied to the DEP results. EUS will be considered the gold standard.

After both assessments, the lesion is characterized as no vessel / arterial / venous and as soft / medium / high flow intensity.

EUS will be followed by removal of SEL in patients where EUS excludes the presence of high vessel disease. "Unroofing" will be performed using a conventional endoscopic loop, through the working channel of the endoscope. After the surface of the lesion is disturbed, a biopsy forceps will be used for tissue acquisition. Tissue will be stored in formalin and processed and evaluated by the pathologist.