What are the inclusion criteria for a longitudinal study of Endoscopic Ultrasonography (EUS)-guided Fine Needle Aspiration Cytology (FNAC) in diagnosing intraabdominal lesions?

Inclusion Criteria for a Longitudinal Study of EUS-Guided FNAC in Diagnosing Intraabdominal Lesions

Patient Population Criteria

Include patients aged 18 years or older with radiologically or clinically detected intraabdominal mass lesions requiring tissue diagnosis, as this population demonstrates the highest diagnostic yield and safety profile for EUS-guided FNAC. 1, 2

Primary Inclusion Criteria by Lesion Type

Solid Intraabdominal Masses

• Pancreatic solid masses of any size where tissue diagnosis is required, as diagnostic accuracy reaches 92-95% for these lesions 3, 4
• Subepithelial gastrointestinal lesions arising from the third or fourth echo layer (muscularis propria) to differentiate GISTs from leiomyomas and assess malignant potential 3, 4
• Intraabdominal lymphadenopathy of unknown origin with nodes accessible by EUS, as this modality achieves 89.7-92% sensitivity for malignant diagnosis 5, 6
• Extraintestinal mass lesions where previous tissue acquisition attempts have failed or are not feasible, given the 97% sensitivity and 98% accuracy in this setting 1

Pancreatic Cystic Lesions

• Cysts ≥3 cm in size regardless of other features, as this size alone confers 3-fold increased malignancy risk 3, 4
• Cysts ≥2.5 cm with at least one worrisome feature (thickened walls, mural nodules, main pancreatic duct dilation >5mm, abrupt caliber change with distal atrophy) 3, 4
• Cysts ≥1.7 cm with high-risk stigmata (obstructive jaundice, enhancing mural nodule ≥5mm, main pancreatic duct ≥10mm), as this size contains sufficient fluid for cytology and biomarker analysis 3, 4

Biliary Strictures with Extrinsic Compression

• Distal biliary lesions where EUS-FNA demonstrates 81% sensitivity compared to 59% for proximal lesions 3
• Pancreatic head lesions or lymphadenopathy causing extrahepatic bile duct compression, as EUS-FNA maintains diagnostic accuracy even with existing biliary stents 3

Technical Feasibility Criteria

Include only lesions accessible by the echoendoscope with the following specifications:

• Lesions within reach of standard linear echoendoscope (esophagus, stomach, duodenum, rectum) 1, 7
• Lesions where safe needle trajectory avoids intervening vessels as confirmed by color Doppler evaluation 7, 6
• Minimum lesion size ≥1.7 cm for cystic lesions to ensure adequate fluid volume for analysis 3, 4
• Solid lesions of any size, though diagnostic accuracy improves with size: 71% for <2 cm, 86% for 2-4 cm, and 95-100% for >4-5 cm 4

Clinical Scenario Criteria

Include patients where EUS-guided FNAC will alter management, specifically:

• High clinical suspicion for malignancy with non-diagnostic imaging or prior failed tissue acquisition attempts 3, 1
• Indeterminate subepithelial lesions where forceps biopsies are non-diagnostic 3, 4
• Potentially resectable lesions requiring preoperative tissue confirmation, particularly for pancreatic head masses where the needle tract will be included in surgical resection 3
• Patients who are surgical candidates but require definitive diagnosis before proceeding to resection 3

Exclusion Criteria to Avoid Complications

Exclude patients with the following contraindications:

• Uncorrectable coagulopathy (INR >1.5, platelets <50,000) to minimize bleeding risk 7
• Inability to safely access the lesion due to intervening vascular structures 7
• Mediastinal duplication cysts due to mediastinitis risk 3
• Potentially resectable proximal/hilar biliary malignancies where needle tract seeding could cause peritoneal metastases, unless the risk-benefit analysis strongly favors tissue diagnosis 3
• Active infection at the puncture site 7

Longitudinal Follow-Up Criteria

Include patients who can be followed for minimum 12-13 months to assess:

• Diagnostic accuracy through surgical pathology, repeat imaging, clinical follow-up, or disease progression 1, 2
• 30-day complication rates including infection, bleeding, pancreatitis, and perforation 1, 7
• Impact on management decisions, as EUS-FNA alters management in 72% of patients and reduces unnecessary surgeries by 91% 3, 4

Special Populations

Include patients with prior non-diagnostic EUS-FNA where repeat procedure is indicated:

• Pancreatic masses with initial negative cytology but persistent high clinical suspicion, as repeat EUS-FNA yields correct diagnosis in 61-84% of cases 3, 4
• Patients who are not surgical candidates or decline surgery, where repeat tissue sampling provides definitive diagnosis 3