直腸pm癌の超音波内視鏡診断―直腸指診，注腸造影，CT，MRIとの比較検討

Endoscopic Ultrasonography of the Rectal Carcinoma Invading the Muscularis Propria

要旨　1990年6月から1992年9月までの間に，当院で超音波内視鏡が行われた直腸癌患者136例の壁深達度の正診率は，全体で84％，組織学的深達度別では，m：80％，sm：80％，pm：69％，ss，s，a₁，a₂：91％，si，ai：78％であり，pm癌の正診率が最も不良であった．リンパ節転移の正診率は，全体で74％，pm癌では65％であった．pm癌の26例で超音波内視鏡，直腸指診，注腸造影，CT，MRIの診断能を比較すると，壁深達度の正診率は，それぞれ69％，58％，40％，48％，50％であり，超音波内視鏡の成績が最も良好であった．リンパ節転移の正診率は，注腸造影を除き，それぞれ65％，73％，83％，86％であったが，sensitivityは，それぞれ43％，0％，33％，50％であり，MRIおよび超音波内視鏡の成績が最も良好であった．

　In the preoperative staging of rectal cancer the overall accuracy rate of endoscopic ultrasonography (EUS) is fairly good. However, the diagnosis of transmural invasion in the carcinoma invading the muscularis propria is sometimes difficult because of (1) difficulty in differentiating the echogenicity of the tumor and the muscularis propria, (2) modification of ultrasound image of border of the tumor by inflammatory cell infiltration, fibrosis, and tumor angiogenesis, and (3) difficulty in detecting microscopic invasion. The diagnosis of lymph node involvement in the carcinoma invading the muscularis propria is also difficult because of (1) smaller size and less number of involved lymph nodes, (2) presence of microscopic metastasis, and (3) presence of obturator lymph node involvement without pararectal lymph node involvement. However, EUS is more accurate than digital examination, double-contrast barium enema study, CT, and MRI in the diagnosis of rectal carcinoma invading the muscularis propria.