[1] Akershus Cent Hosp, Dept Surg, N-1474 Nordbyhagen, Norway
[2] Akershus Univ Cent Hosp, Dept Surg, Nordbyhagen, Norway
[3] Akershus Univ Cent Hosp, Dept Infect Control, Nordbyhagen, Norway
[4] Univ Oslo, Norwegian Radium Hosp, Dept Pathol, Oslo, Norway