Role of Endoscopic Ultrasonography (EUS) in Evaluating Fundal Lesions
EUS is the modality of choice for evaluating subepithelial lesions (SELs) in the gastric fundus, providing superior characterization of lesion origin, layer involvement, and tissue acquisition for definitive diagnosis. 1
Advantages of EUS for Fundal Lesions
EUS offers several key benefits when evaluating lesions in the gastric fundus:
- Layer identification: EUS can precisely determine which layer of the gastric wall contains the lesion, which is crucial for diagnosis and treatment planning 1
- Superior visualization: EUS is superior to cross-sectional imaging (CT/MRI) in delineating the layer of origin and narrowing the differential diagnosis 1
- Differentiation capability: EUS can reliably differentiate between intramural lesions and extrinsic compression with high sensitivity (89-98%) 1
- Tissue acquisition: Enables targeted sampling through EUS-guided fine-needle aspiration (FNA) or fine-needle biopsy (FNB) 1
Diagnostic Process for Fundal Lesions
1. Initial EUS Assessment
- Identify the layer of origin (5-layer pattern from lumen outward)
- Evaluate echogenicity (anechoic, hypoechoic, hyperechoic, or mixed)
- Assess lesion size, margins, and presence of vascular involvement 1
2. Layer-Based Differential Diagnosis
Based on the layer of origin, EUS helps narrow the differential diagnosis:
- Layer 2 (deep mucosa): Typically lipomas, carcinoids, or pancreatic rests
- Layer 3 (submucosa): Often lipomas or vascular lesions
- Layer 4 (muscularis propria): Commonly GISTs or leiomyomas
- Layer 5 (serosa): External compression or serosal-based lesions 1
3. Echogenicity-Based Differential Diagnosis
- Anechoic: Cysts, varices, or lymphangiomas
- Hypoechoic: GISTs, leiomyomas, neuroendocrine tumors, lymphoma
- Hyperechoic: Lipomas or fibrolipomas
- Mixed echogenicity: Pancreatic rest, malignant mesenchymal tumors 1
Tissue Acquisition Techniques
When tissue diagnosis is necessary for fundal lesions:
EUS-guided FNA/FNB
- Diagnostic accuracy: 46-93% for SELs 1
- Needle selection for fundal lesions: 22-gauge or 25-gauge needles are more maneuverable in the fundus compared to larger bore needles 1
- FNB vs. FNA: FNB needles generally provide better tissue acquisition than FNA needles for SELs (75-100% accuracy) 1
Special Considerations for Fundal Location
- Fundal lesions can be challenging to access due to scope positioning
- Smaller gauge needles (22G or 25G) are preferred due to better maneuverability in the fundus 1
- Cap-attached forward-viewing echoendoscope may be helpful for small SELs in difficult locations 2
Management Algorithm Based on EUS Findings
Characteristic benign lesions (lipomas, cysts, lymphangiomas):
- No need for EUS-FNA as EUS features are diagnostic 2
Indeterminate lesions <1-2 cm:
- Follow-up in 6 months, then yearly if stable 2
Lesions >1-2 cm or with concerning features:
Fourth layer (muscularis propria) lesions:
Limitations and Pitfalls
- Operator dependence: EUS interpretation is highly operator-dependent 1
- Technical challenges: The fundus can be a difficult location for EUS-FNA due to scope positioning 1
- Diagnostic limitations: Overall sensitivity and specificity of EUS in predicting malignant potential of SELs are only 64% and 80%, respectively 1
- Small lesion sampling: Diagnostic yield for small lesions may be insufficient, with accuracy of FNA being 71% for lesions <2 cm versus 95-100% for lesions >4-5 cm 1
Advanced EUS Techniques for Fundal Lesions
- Contrast-enhanced EUS: Can help distinguish GISTs (hyperenhancement) from leiomyomas (hypoenhancement) with >95% accuracy 1
- EUS elastography: May provide additional information about lesion characteristics 1
- Forward-viewing echoendoscopes: Particularly helpful for small SELs in difficult locations like the fundus 2
By following this systematic approach to EUS evaluation of fundal lesions, clinicians can optimize diagnosis and guide appropriate management decisions to improve patient outcomes.