大腸癌術後化学療法により画像上同定困難となった肝病変に対して，術中腹腔鏡下造影超音波検査を併用し腹腔鏡下肝部分切除を施行した1例

Laparoscopic partial hepatectomy for the liver lesion which disappeared on imaging after postoperative chemotherapy of colon cancer, using intraoperative contrast enhanced ultrasonography : a case report

◆要旨：患者は54歳，男性．S状結腸癌に対して腹腔鏡下低位前方切除術を施行（pSI, pN 1（1/47）, H 0, P 0, pStageIIIa）した．術後にCapecitabineを投与したが10か月後に吻合部再発，11か月後にプリモビスト造影MRIにて後区域に径7mm大の病変を認めた．腹腔鏡下直腸切断術を行い，術後にmFOLFOX 6を3コース施行し，肝の病変は画像上確認困難となった．腹腔鏡下に術中ソナゾイド造影超音波検査を併用し，肝後区域部分切除術を施行した．術後の造影MRIにて術前に病変を認めた領域は切除されていることが確認されたが，組織検査では腫瘍増生や壊死，瘢痕は認めなかった．微小肝転移巣の切除に際しては腹腔鏡下の低侵襲手術が望ましいが，確認困難な微小病変の検索方法についてはさらなる検討が必要と思われた．

　We reported a case of hepatectomy with intraoperative contrast enhanced ultrasonography using Sonazoid, for a liver lesion, which disappeared on preoperative imaging after chemotherapy. A 54-year old man underwent laparoscopic low anterior resection for StageIIIA（T 3 N 1 M 0）sigmoid colon cancer. He developed local recurrence 10 months after surgery and liver metastasis in the posterior segment 11 months after surgery. The lesion was detected by Gadolinium Ethoxybenzyl Diethylenetriaminepentaacetic Acid Enhancer Magnetic Resonance Imaging（Gd-EOB-DTPA-enhanced MRI）, but not detected by ultrasonography, Fluorine-18-2-fluoro-D-glucose positron emission tomography and computed tomograhy. He underwent laparoscopic abdominoperineal resection for local recurrence, followed by chemotherapy with mFOLFOX 6. After 3 courses of this regimen, the lesion disappeared on Gd-EOB-DTPA-enhanced MRI. On ground of microscopic residual tumor, he underwent laparoscopic partial resection of posterior segment, using contrast-enhanced intraoperative laparoscopic ultrasound. Postoperative MRI imaging showed that the target lesion was completely removed, but histopathological examination showed sinusoidal obstruction syndrome without any occult metastases on the resected specimen. It is preferable to perform minimally invasive laparoscopic surgery for the resection of small lesions. Meanwhile, we have often encountered difficulties in identifying lesions during surgery. Further investigations about intraoperative technique to identify small targets are needed.