THICKENED INNER HYPOECHOIC LAYER OF THE GALLBLADDER WALL IN THE DIAGNOSIS OF ANOMALOUS PANCREATICOBILIARY DUCTAL UNION WITH ENDOSONOGRAPHY

Background: An anomalous pancreaticobiliary ductal union (APBD) is a h igh-risk factor for biliary tract carcinoma, which often is not diagno sed before overt malignancy. The early detection of APBD is therefore clinically important. We evaluated the gallbladder wall in APBD patien ts with endoscopic ultrasonography. Methods: Clinicopathologic feature s and ultrasonographic findings of the gallbladder in 33 consecutive p atients with APBD between 1986 and 1995 were studied in relation to tw o subtypes of APBD, that is, undilated (n = 17) and dilated (n = 16). The gallbladder wall was evaluated with conventional ultrasonography a nd/or endoscopic ultrasonography. Histologic examinations of 25 resect ed gallbladders were made. Results: Fourteen of the seventeen patients with undilated type APBD (82%) had diffuse thickened gallbladder wall of 4 mm or more, whereas 5 of the 16 with dilated type (31%) had this finding (p < 0.01). The thickened gallbladder wall consisted sonograp hically of two layers: diffuse thickened inner hypoechoic layer and ou ter hyperechoic layer. Mucosal hyperplasia was histologically found in 8 of 9 cases (89%) with thickened inner hypoechoic layer on endoscopi c ultrasonography. Mucosal hyperplasia was observed in 10 of 11 undila ted type APBD cases (91%) in which cholecystectomy was performed. In a ddition, the presence of anomalous union was shown by endoscopic ultra sonography in 9 of 11 patients with undilated type APBD (82%) and all 7 of those with dilated type. The characteristic ultrasonographic patt ern of diffuse thickened inner hypoechoic layer was observed exclusive ly in patients with mucosal hyperplasia of the gallbladder associated with APBD among 2085 endoscopic ultrasonography examinations performed during the study period. Conclusions: Diffuse thickened inner hypoech oic layer of the gallbladder wall was frequently observed in APBD pati ents, especially those with the undilated type, on ultrasonography and /or endoscopic ultrasonography. This finding corresponded histological ly to mucosal hyperplasia of the gallbladder mucosa. Thickened inner h ypoechoic layer is a useful ultrasonographic sign that indicates mucos al hyperplasia of the gallbladder and, particularly, the possible coex istence of undilated type APBD before the appearance of overt malignan cy.