[Comparison of echograms by a microscanner and histological findings of the common bile duct, in vitro study]

To confirm the relationship between the layer structure of the common bile duct by a microscanner (MS) and its histological features, we performed a study using the pinning method with needles and catgut. The locations of 67 needles inserted at random depths in 29 slices of the resected common bile duct from 18 patients were confirmed both by a MS and a microscope. The wall of the common bile duct was delineated as a two- (42 points) or three-layer structure (25 points); "low and high" or "high, low, and high echoic layers" from the mucosal side. A fibrotic layer (ss 1) was often (56/67 points, 16/18 patients) seen in the subserosa (ss) containing nerves and vessels larger than 100 mu in diameter. Among the 51 needle echoes demonstrated in the inner hypoechoic layer, 2 were located in the mucosa (m), 12 in the fm, 19 in the af, 17 in the ss 1, and 1 in the fatty layer of the ss (ss 2). Five of the 6 needles in the outer hyperechoic layer were in the ss 2, and 1 was in the pancreatic parenchyma (pa). Four of the 8 needles at the border between the inner hypoechoic layer and the outer hyperechoic layer histologically corresponded to fm, af, ss 1, and pa, respectively, and the other four corresponded to ss 2. From these results, we conclude that the inner hypoechoic layer contains not only m, fm, and af, but also ss 1. Therefore, this should be kept in mind for the preoperative assessment of the depth of bile duct carcinoma by MS.