Results

In the 76 patients studied, the calibre of the common bile duct was found to be larger than normal, with a value of 4.74±2.3 mm, and a range of 1.6-13 mm. The results obtained by the 3 operators in the evaluation of the bile duct images showed high diagnostic accuracy of the harmonic image in the study of the distal third, bile duct content, and the relations between the bile duct and adjacent structures.

All of the three radiologists (A, B, C) rated the THI results better that those of conventional US (p>0.0001,Wilcoxon sign rank test).
The mean values and the standard deviation of the differences between THI and conventional US were respectively 1.25 (0.57), 1.22 (0.51), 1.09 (0.57) for radiologists A, B, C. There was no significant variation in the three observers’ evaluations of older patients (>74 years) and younger patients (p=0.35, Wilcoxon rank- sum test). Table II shows each operator’s ratings of the conventional US and THI images.

Fig. 1. - Mean values of the three radiologists’ evaluations of the common bile duct conventional US and THI.

Figure 1 shows the mean values of the three operators’ evaluations of the common bile duct using conventional US and harmonic imaging. It is clear that the use of harmonic imaging eliminates the 30% inadequate examinations found in conventional US. Moreover, the number of diagnoses of bile duct lithiasis (10 patients) was higher with harmonic imaging than conventional US (5 patients), with a diagnostic gain of 50%. The calculation of the agreement coefficient (weigthed Kappa: Cohen’s Kw test) showed an improvement in interobserver agreement (0.71 and 0.84 between A and B; 0.7 and 0.79 between A and C, 0.71 and 0.81 between B and C for conventional US and THI, respectively) (figs. 2, 3).