The diagnsotic accuracy of transabdominal ultrasonography needs to be considered when managing gallbladder polyps

Daniel French, Phil Allen, James Ellsmere

Division of General Surgery, QEII Health Sciences Centre, Dalhousie University, Halifax NS

Introduction: Transabdominal ultrasonography (US) is the most commonly used test to diagnosis gallbladder disease. Gallbladder (GB) polyps are reported in 1-5.6% of US studies. Histopathologic studies suggest there is a relationship between GB polyps and GB cancer. GB cancer has a 5-survival of less than 5% because patients are often asymptomatic until the cancer is at advanced stage. GB polyps reported on US do not correlate well with histological findings and the eventual development of GB cancer. The standard recommendation for GB polyps detected on US that are greater than 6-10 mm is cholecystectomy. Surveillance with US is recommended for smaller polyps. Recent advances in US technology may impact these recommendations. We hypothesize the recent advances in US technology has improved the accuracy of transabdominal US for diagnosing GB polyps.

Methods: Between January 1, 2000 and December 31, 2010, 102,740 transabdominal US were performed in our tertiary teaching hospital and there were 6,612 GB polyps reported. During the same time period, 13,703 cholecystectomies were performed. There were 229 patients who underwent cholecystectomy who also had a GB polyp identified on a preoperative US. Histopathologic correlation study was performed to assess the diagnostic accuracy for transabdominal US.

Results: GB polyps were found in 6.4% of transabdominal US reports. Polyps were found in 1.2% of cholecystectomy specimens. US detected only 50% of the polyps identified on histopathology. The table lists the histopathology for the 229 patients undergoing cholecystectomy with a preoperative diagnosis of a GB polyp.

Histopathology Number Incidence(%)
Normal GB83.4
Cholesterol Polyp177.4
Hyperplastic Polyp41.7
All Polyps2310.5

Of the polyps found on US, 89.5% were not found on histopathology. Of the 23 polypoid lesions correctly detected by ultrasound there were 17 cholesterol polyps, 4 hyperplastic polyps, and 2 adenomas.

The sensitivity and specificity of transabdominal US for diagnosing GB polyps were 50.0 and 98.3%, respectively. The positive and negative predictive values were 10.5 and 99.8%.

Conclusion: Despite improvement in US technology, the accuracy of transabdominal ultrasonography for GB polyps remains poor. This needs to be considered when managing patients with US detected GB polyps. We recommend that the decision to operate on US detected GB polyps be largely based on symptoms and following GB polyps with US should be discouraged.

Session: Podium Presentation

Program Number: S002

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