What is the diagnostic workup for an incidental finding of gastric wall thickening on a Positron Emission Tomography/Computed Tomography (PET/CT) scan?

Diagnostic Workup for Incidental Gastric Wall Thickening on PET/CT Scan

Incidental gastric wall thickening on PET/CT scan requires prompt endoscopic evaluation with biopsy as the next step in workup, as this finding may represent malignancy, particularly in patients over 50 years of age.

Initial Assessment

When gastric wall thickening is identified incidentally on PET/CT scan, the following diagnostic algorithm should be followed:

Step 1: Endoscopy with Biopsy

• Upper endoscopy (esophagogastroduodenoscopy or EGD) with targeted biopsies is the gold standard for evaluation 1, 2
• This allows direct visualization and tissue sampling of the thickened area
• Should be performed regardless of whether the patient is symptomatic or asymptomatic

Step 2: CT Abdomen and Pelvis with IV Contrast (if not already performed)

• If the initial PET/CT was performed without IV contrast, a dedicated CT with IV contrast is recommended
• Use neutral oral contrast (water or dilute barium) to better delineate the gastric lumen 1
• Assess for specific features that suggest malignancy:
  • Nodular or irregular wall thickening
  • Soft tissue attenuation of wall thickening (rather than low attenuation due to edema)
  • Lymphadenopathy
  • Distant metastases 1, 2

Clinical Significance of Gastric Wall Thickening

The importance of thorough evaluation is supported by research showing:

• Up to 83% of patients with incidental gastric wall thickening have significant abnormalities on endoscopy 3
• While gastric wall thickening may represent benign conditions (gastritis, peptic ulcer disease), it can also indicate malignancy 4
• Gastric wall thickening may be the initial presentation of:
  • Adenocarcinoma
  • Lymphoma
  • Neuroendocrine tumors 5
  • Other rare tumors such as myofibroblastic sarcoma 6

Important Considerations

Age-Related Risk

• Patients over 50 years of age with incidental bowel wall thickening have a higher risk of malignancy
• In one study, 25% of patients over 50 with colonic wall thickening had cancer, while none under 50 did 4
• However, gastric wall thickening warrants investigation regardless of age

Pattern of Thickening

• Focal, irregular, or nodular thickening is more concerning for malignancy than diffuse thickening
• Soft tissue attenuation on CT is more concerning than low-attenuation thickening 1

Associated Findings

• Look for additional concerning features:
  • Lymphadenopathy
  • Liver lesions
  • Peritoneal nodules
  • Increased FDG uptake in the thickened area on PET 5, 6

Potential Pitfalls

1. Inadequate biopsy sampling: Multiple biopsies should be taken from different areas of the thickened wall, as some conditions (like scirrhous gastric carcinoma) may be missed with superficial biopsies 2

2. Overlooking distant metastases: Ensure the pelvis is included in imaging to avoid missing distant spread 2

3. False negatives on endoscopy: Some submucosal or infiltrative processes may not be apparent on endoscopy alone; correlation with imaging findings is essential 1, 2

4. Attributing findings to benign causes without adequate investigation: Even in patients with known conditions that could explain wall thickening (e.g., H. pylori gastritis), malignancy should still be excluded 4, 7

By following this systematic approach to incidental gastric wall thickening on PET/CT, clinicians can ensure timely diagnosis of potentially serious conditions and improve patient outcomes.