[1] UNIV ZURICH, KANTONSSPITAL,DEPT INNERE MED,GASTROENTEROL ABT, RAMI STR 100, CH-8006 ZURICH, SWITZERLAND
[2] UNIV ZURICH, CHIRURG KLIN & POLIKLIN, RAMI STR 100, CH-8006 ZURICH, WEST GERMANY
[3] UNIV ZURICH, RONTGEN DIAG ZENT INST, RAMI STR 100, CH-8006 ZURICH, SWITZERLAND
[4] STADTSPITAL WAID, CHIRURG KLIN, TIECHE STR 99, CH-8037 ZURICH, SWITZERLAND