鴨下 亨¹, 横倉 稔明²

Tohru KAMOSHITA¹, Toshiaki YOKOKURA²

¹東京簡易保険総合健診センター放射線科, ²やすらぎの丘温泉病院放射線科

¹Department of Radiology, Tokyo Kampo Multiphasic Health Testing Center, ²Yasuraginooka Onsen Hospital

キーワード : Ejaculatory duct, Prostatic cancer, Benign prostatic hypertrophy, Transrectal ultrasonography

Transrectal ultrasonographic (midsagittal scanning) features of the ejaculatory ducts of 46 patients with prostatic cancer, 135 patients with benign prostatic hypertrophy, and 37 normal subjects were examined. We also tried to determine whether or not the combination of midsagittal scanning features of the ejaculatory duct and four ultrasonographic (axial scanning) criteria for prostatic cancer (asymmetry of the seminal vesicles, continuity of the capsular echo, irregularity of the prostate internal echo, and asymmetry of prostate shape) based on the General Rules for Clinical and Pathological Studies on Prostatic Cancer in Japan would improve the diagnostic capability of ultrasound. The displacement pattern of the course of the ejaculatory duct in midsagittal scanning was classified as backward or forward, and the pattern representing it was classified as smooth, tortuous, or disappearing. The incidences of these patterns in the three groups were compared, and the backward displacement pattern was common in benign prostatic hypertrophy and in the normal subjects, suggesting that an enlarged transition zone may have compressed the ejaculatory duct backward. The forward displacement pattern, on the other hand, was frequent in cases of prostatic cancer, probably as a result of forward compression of the ejaculatory duct by cancer present in the peripheral zone. The tortuous pattern was the most common in benign prostatic hypertrophy, and the disappearing pattern was the most common in prostatic cancer. The former may be attributable to compression of the ejaculatory duct by hyperplastic nodules of various sizes, and the latter to stricture of an ejaculatory duct that had been compressed by both cancer invasion and hyperplastic nodules. Prostatic cancer was identified based on the combination of course and line in 8 of the 9 cases with the forward displacement and disappearing patterns, 5 of the 9 cases with the forward displacement and tortuous patterns, and 17 of the 35 cases with the backward displacement and disappearing patterns. Forty-three patients satisfied the four axial scanning criteria, and prostatic cancer was ultimately diagnosed in 30 of them and benign prostatic hypertrophy in the other 13. Because both the positive predictive value and sensitivity of axial scanning alone were low (69.8%), the course and the line patterns on midsagittal scanning were used to complement them in the diagnosis of prostatic cancer. All 11 patients who satisfied the four criteria on axial scanning and forward displacement pattern on midsagittal scanning were ultimately diagnosed as having prostatic cancer, yielding a positive predictive value of 100%, although sensitivity was very low (36.7%). Thirteen of the 16 patients who showed both the backward displacement and the disappearing patterns in addition to the four criteria were diagnosed as having prostatic cancer, yielding a positive predictive value of 81.3% and a sensitivity of 68.4%. The combined findings mentioned above were seen in a total of 27 patients, 24 (88.9%) of whom were found to have prostatic cancer. We thus conclude that ability to diagnose prostatic cancer can be improved by using both the midsagittal scanning features of the ejaculatory duct and the four axial scanning criteria in combination, because each compensates for the inadequacies of the other.