Diagnostic accuracy of transabdominal ultrasonography for gallbladder polyps: systematic review

Previous research has shown variable but generally poor accuracy of transabdominal ultrasonography in the diagnosis of gallbladder polyps. We performed a systematic review of the literature with the aim of helping surgeons interpret and apply these findings in the preoperative assessment and counselling of their patients.

We searched PubMed, MEDLINE and the Cochrane database using the keywords "gallbladder," "polyp," "ultrasound," "pathology" and "diagnosis" for English-language articles published after 1990 with the full-text article available through our institutional subscriptions. Polyps were defined as immobile features that on transabdominal ultrasonography appear to arise from the mucosa and that lack an acoustic shadow, and pseudopolyps were defined as features such as inflammation, hyperplasia, cholesterolosis and adenomyomatosis that convey no risk of malignant transformation.

The search returned 1816 articles, which were narrowed down to 14 primary sources involving 15 497 (range 23-13 703) patients who had preoperative transabdominal ultrasonography, underwent cholecystectomy and had postoperative pathology results available. Among the 1259 patients in whom a gallbladder polyp was diagnosed on ultrasonography, 188 polyps were confirmed as true polyps on pathologic examination, and 81 of these were found to be malignant. Of the 14 238 patients for whom a polyp was not seen on ultrasonography, 38 had a true polyp on pathologic examination, none of which were malignant. For true gallbladder polyps, transabdominal ultrasonography had a sensitivity of 83.1%, specificity of 96.3%, positive predictive value of 14.9% (7.0% for malignant polyps) and negative predictive value of 99.7%.

Transabdominal ultrasonography has a high false-positive rate (85.1%) for the diagnosis of gallbladder polyps. Further study of alternative imaging modalities and reevaluation of existing management guidelines are warranted.