Pitfalls of endoscopic ultrasound staging after application of electrocautery.

Patients may be referred for endosonography after endoscopic resection of polyps because of cancer identified in the histologic specimen. To assess the effects of electrocautery-induced tissue changes on tumor staging by endosonography, endosonography findings after endoscopic removal of large polyps were correlated with surgical and endoscopic pathology. Endosonography findings revealed irregular and thickened wall layers, especially in the muscularis propria with pseudopod extensions. Five of 7 patients had evidence of cancer in the endoscopic specimen. However, no residual tumor was found in the surgically resected bowel (2 patients) or in subsequent biopsies of the endoscopic resection site (3 patients). In 2 other patients, no cancer was present in the endoscopic specimen, and follow-up biopsies of the endoscopic resection site were all benign. Electrocautery-induced inflammatory changes create hypoechoic changes within the gut wall that may mimic tumor invasion. Irregularities in the muscularis propria layer cannot be relied upon to diagnose a T2 or T3 lesion by endosonography in this setting. Patients with large polyps greater than 2 cm and other mucosal lesions with malignant potential should undergo endosonography prior to endoscopic resection.