沼田 功

Isao NUMATA

古川市立病院泌尿器科

Department of Urology, Furukawa City Hospital

キーワード : ultrasonography, contrast enhancement, kidney , bladder, prostate

超音波造影剤は二酸化炭素を用いた自家製造影剤を動注して使用していたが, ガラクトースを用いた造影剤(Levovist®) が市販されるとともに静注による造影が主流となり, 肝臓を始め様々な分野で利用されている. 泌尿器科領域でも腎臓, 膀胱, 前立腺, と各臓器に利用され有用性が報告されている. 腎臓では細い正常血管を造影して腎機能の評価に利用し, 太い血管病変の診断にも利用されている. さらに腫瘍性病変の広がり, 良性・悪性の鑑別診断に応用され, 血液透析患者 への利用のしやすさと有用性も報告されている. 腎盂尿管腫瘍ではカラードプラのみでは血流状態を描出できなかったが, 造影剤を使用することで血流分布や腫瘍自体の造影も可能になっている. 膀胱癌では腫瘍の存在診断とともに腫瘍を造影 することで壁への浸潤度判定にも利用されている. また, 超音波造影剤による膀胱尿管逆流症の診断はヨード造影剤を用 いた排尿時膀胱尿道造影での判定と同等の感度, 特異度が見られる. 前立腺癌の造影超音波診断では腫瘍部位の明瞭化が 見られ, 感度の上昇が見られる. しかし, 早期前立腺癌には数mm の小さな腫瘍部位も多く, 特異度の上昇は得られて いない. 今後, 造影剤を有効に使用することで生検の部位を少なくして陽性率を高めることが期待される.

Before a galactose-based microbubble ultrasound contrast agent (Levovist®) became available, ultrasound contrast agents for enhancing tumors used carbon dioxide microbubbles. Now, Levovist® is used in various organs including kidney, urinary bladder, and prostate in the field of urology, and its usefulness has been reported. It is used for the diagnosis of renal function by enhancing small normal blood vessels. Also, pathological changes in blood vessels are diagnosed by enhancing abnormal vessels. Furthermore, it is applied to spread of neoplastic lesions and is used for the differential diagnosis between benign or malignant tumors. Moreover, its usefulness in hemodialysis patients has also been reported. The blood-flow distribution and tumor itself in the case of renal-pelvic or ureter tumors are also enhanced, although the blood-flow of these tumors is not revealed by color Doppler. It is used for judging the clinical stage of bladder cancers after these cancers are diagnosed by ultrasonography. Moreover, the vesicoureteral reflux is diagnosed easily by ultrasonography using the contrast agent. The sensitivity and specificity are the same as voiding-vesicourethrography using an iodine contrast agent. The ultrasound contrast agent will be used for the diagnosis and follow-up of vesicoureteral reflux patients. As the vessels in prostate cancer are enhanced, the tumor sites are seen clearly, and the sensitivity in the case of prostate cancer increases by using the ultrasound contrast agent at prostate biopsy. However, early prostate cancers also have many small tumor sites several mm in size. Therefore, an increase in specificity for cancer detection is not gained by using enhancement. It is expected that effective use of the ultrasound contrast agent will increase the positive rate of prostate biopsy and lessen the number of biopsy sites.