[1] The Second Department of Surgery,
[2] Hokkaido University School of Medicine,undefined
[3] Kita-15,undefined
[4] Nishi-7,undefined
[5] Kitaku,undefined
[6] Sapporo 060-8638,undefined
[7] Japan e-mail: n-sagawa@med.hokudai.ac.jp Tel.: +81-11-7470334 Fax: +81-11-7067158,undefined