Use of diffusion-weighted imaging in the noninvasive diagnostic of obstructed biliary ducts

This study sought to evaluate the role of diffusion-weighted imaging (DWI) in differentiation between obstructed and unobstructed bile ducts in patients undergoing magnetic resonance imaging (MRI).

Eighty-four patients, 40 males and 44 females (mean age: 56.4 ± 15.1 years), undergoing MRI with DWI (0-50-500-700) were evaluated and divided into two groups: 58 with abnormal laboratory tests (obstructed group) and 26 with normal laboratory values (unobstructed group). Laboratory tests were total bilirubin, alkaline phosphatase, and gamma-glutamyltransferase. Median ADC values were calculated and correlated with laboratory tests and degree of bile-duct dilatation (absent, moderate, or severe). The persistence of signal on DWI (b500 and b700) in the biliary tract was evaluated. Bilirubin values were tested for correlation with bile-duct ADC values and persistence of b700 signal. For statistical analysis, Student t test, chi-square test and Wilcoxon-Mann-Whitney test were used. ADC maps were plotted for three levels of the biliary tree, and a receiver operating characteristic (ROC) curve was calculated.

In the obstructed group, 15 patients had severe dilatation, 24 had moderate dilatation, and 19 had no appreciable dilatation; 38 patients had persistent signal on b700 images. In the unobstructed group, 23 patients had no dilatation and 3 had moderate dilatation; 4 patients had persistent signal on b700 images. Correlation was found between degree of bile-duct dilatation, bilirubin levels, persistence of b700 signal, and ADC map values. The calculated ADC map cutoff value (353 10^-6 mm²/s) was able to differentiate the obstructed and unobstructed groups with 92.3% sensitivity, 81% specificity, and 91.9% accuracy.

DWI is able to distinguish patients with obstructed versus unobstructed bile ducts, regardless of the degree of dilatation, correlating with clinical and laboratory findings.