伊藤 寿樹, 新保 斉, 栗田 豊

Toshiki ITO, Hitoshi SHINBO, Yutaka KURITA

JA静岡厚生連遠州病院泌尿器科

Department of Urology, JA Shizuoka Kohseiren Enshu Hospital

キーワード : benign prostatic hyperplasia (BPH), transrectal ultrasonography (TRUS), bladder outlet obstruction (BOO), resistive index (RI), pressure-flow study (PFS)

近年，高齢化時代の到来に伴い前立腺肥大症（benign prostatic hyperplasia: BPH）の診療機会が増えている．BPHはクオリティ・オブ・ライフ（quality of life: QOL）疾患との位置付けがなされているが，主たる病態の一つである膀胱出口部閉塞（bladder outlet obstruction: BOO）は，急性尿閉，腎機能障害，尿路感染症などを引き起こし生命予後にも関与するため，適切な診断と積極的な治療が必要である．BPHの診断において経直腸的超音波検査（transrectal ultrasonography: TRUS）は前立腺の形態的な評価に優れており非常に有用である．TRUSにより得られる前立腺の推定体積や膀胱内前立腺突出度（intravesical prostatic protrusion: IPP）はBOOの重症度を予測するパラメーターして有用である．また近年，ドプラ法によって得られる前立腺動脈被膜枝のResistive index（RI）がBOOの重症度と相関することがわかってきた．現在では一般的に，BOOの評価には内圧尿流検査（pressure-flow study: PFS）が最も正確な検査法と考えられているが，PFSは侵襲的な検査のため適応が制限される．今回の我々の検討では，PFSでBOOなしと判定された症例でのRIが0.66と低値であったのに対して，BOOのある症例では0.75と高値であった．また，RIからのBOOの有無について受信者操作特性（receiver operating characteristic: ROC）解析を行った結果，0.80と高値であった．BPHに起因したBOOの重症度評価においては，TRUSにRIの測定を組み合わせることによりさらなる診断能力の向上が期待できる．

Facing an aging society, health care providers are seeing an increase in the number of patients with benign prostatic hyperplasia (BPH), a condition that adversely affects the quality of life (QOL). Since bladder outlet obstruction (BOO), one of the main symptoms of BPH, can lead to acute urinary retention, renal dysfunction, and urinary tract infection, and thereby influence life prognosis, BPH requires proper diagnosis and aggressive treatment. Transrectal ultrasonography (TRUS) has proven extremely useful in evaluating prostatic morphology for diagnosis of BPH. The estimated prostatic volume, presumed circle area ratio, and intravesical prostatic protrusion based on TRUS are useful parameters for predicting the severity of BOO, and recent evidence has further suggested that the resistive index (RI) in the capsular branches of the prostatic artery obtained using Doppler ultrasound correlates with the severity of BOO. While pressure-flow studies (PFS) are now generally considered the most accurate method for diagnosing BOO, their use is limited due to the invasiveness of the procedure. In the present study, RI was relatively low at 0.66 in patients diagnosed as not having BOO based on a PFS, while that in patients with BOO was relatively high at 0.75. Receiver operating characteristic analysis showed that RI was relatively high at 0.80 for the presence/absence of BOO. Consequently, in determining the severity of BOO resulting from BPH, diagnostic accuracy is expected to be further improved by combining TRUS with RI measurements.