Abstract. Background: Peritoneal recovery after uncom- plicated serum manipulation usually lasts 7 days and high values of serical CA 125 are measured following abdominal surgery. The aim of this study was to assess a possible correlation between peritoneal manipulation and serical CA 125 levels following abdominal surgery for benign diseases. Patients and Methods: Twenty-eight patients with abdominal benign disease were operated on. They were pooled into three groups of low, intermediate and high peritoneal manipulation, according to the extent of laparotomy and length of surgical peritoneal manipulation. Venous blood samples (5 ml) were taken from each patient 24-48 hours before surgery, 12-24 hours after surgery and on the 4th and 7th postoperative day. CA 125 levels were quantified by microparticle enzyme immunoassay. Results: After surgery, patients having high peritoneal manipulation showed significantly higher levels of CA 125 compared to the preoperative levels. In particular, the length of peritoneal manipulation was correlated with increasing levels of the marker (p<0.0001). Conclusion: Peritoneal manipulation was significantly correlated to serum CA 125 levels; therefore its role as marker of peritoneal surgical injury should be considered. Cancer antigen 125 (CA 125), a high molecular-weight glycoprotein of 200,000 Da, is the antigenic determinant recognised by the murine monoclonal antibody OC-125 as described by Bast et al. (1) CA 125 neoplastic marker has been demonstrated to be useful in detecting and predicting primary neoplasms or recurrences of the female genital tract, and in particular this antigen is expressed in nearly 80% of patients with epithelial ovarian cancer (2-7). However, elevated CA 125 serum levels are also observed in other clinical conditions such as pleural and pericardial effusions, dialysis, cirrhosis of the liver with ascitic fluid, peritoneal tuberculosis, and in patients who undergo abdominal surgery for benign disease (8-15). Peritoneal cells have been demonstrated to be a valid source of CA 125 (16-17) and are very highly produced in areas of inflammation (18). In the context that peritoneal repair after uncomplicated surgery has been demonstrated to be complete approximately on the 7 th postoperative day (19), this study investigated whether the length of peritoneal manipulation is related to postoperative CA 125 blood levels in patients who have undergone abdominal surgery during the immediate postoperative period. Patients and Methods Eligibility criteria. Patients who had undergone surgery for abdominal diseases were enrolled in this prospective observational study. Other inclusion criteria were: no evidence of neoplastic disease, pleural effusion or ascitic fluid, normal preoperative liver and renal function. All patients gave informed consent for their participation in the study, which was approved by the local Ethics Committee. Patients and study design. Twenty-eight consecutive patients underwent surgery for benign abdominal disease. Patient characteristics are reported in Table I. Patients were analysed and stratified according to the extent of laparotomy (in centimetres) and length of surgical peritoneal manipulation (in minutes) as follows: patients submitted to <8 cm laparotomy extension and <30 minutes of peritoneal manipulation (group 1, low manipulation), patients submitted to <8 cm laparotomy extension and 30-90 minutes of peritoneal manipulation (group 2, intermediate mani-pulation) and patients with >8 cm laparotomy extension and >90 minutes of peritoneal manipulation (group 3, high manipulation). Manipulation of the peritoneum was calculated starting from the time of incision of peritoneal surface until finishing at the closure of abdominal fascia, which completes the procedure. Patients were operated on under general or spinal anaesthesia. Surgical procedures performed 105 Correspondence to: Enricomaria Pasqual, Department of Surgical Sciences, Faculty of Medicine and Surgery, University of Udine, P.le Santa Maria della Misericordia 15-33100 Udine, Italy. Tel: +39 0432559303, Fax: +39 0432545566, e-mail: enricomaria. pasqual@uniud.it Key Words: Peritoneal manipulation, abdominal surgery, CA 125. in vivo 25: 105-110 (2011) The Length of Peritoneal Surgical Manipulation Correlates with Serum CA 125 Levels ENRICOMARIA PASQUAL, STEFANO BACCHETTI, GIOVANNI MORABITO, SERENA BERTOZZI, PIER PAOLO CAGOL and DINO DE ANNA Department of Surgical Sciences, Faculty of Medicine and Surgery, University of Udine, 33100 Udine, Italy 0258-851X/2011 $2.00+.40