Background: Positive peritoneal cytology has impact on prognosis of several intra-abdominal malignancies. There was no consensus on whether we should routinely perform peritoneal cytology in operated-colorectal cancer patients because previous studies showed very low yield.

Objective: The present study was conducted to investigate the incidence of free cancer cells in the peritoneal lavage cytology of patients underwent curative resection for colorectal cancer.

Materials and Methods: Between January 2006 and December 2012, intraoperative peritoneal lavage cytology was performed in 275 patients underwent curative resection for colorectal cancer. Immediately after exploration of abdomen, 100 ml of normal saline solution was instilled into peritoneal cavity over the tumor site. Peritoneal lavage was then aspirated and sent for cytological examination.

Results: Six (2.18%) of the 275 specimens examined were found to have positive peritoneal lavage cytology. Demographic variables, site of tumor, degree of differentiation, mucinous component, perineural invasion, angiolymphatic invasion, depth of tumor penetration, staging, and level of serum CEA were found not to affect the incidence of free cancer cells. Positive nodal status was the only factor found to be associated with incidence of positive peritoneal cytology (p = 0.04).

Conclusion: Our study demonstrates low incidence of positive free colorectal cancer cell in lavage fluid obtained before resection in patients that underwent curative intent resection for colorectal cancer. The factor associated with positive peritoneal cytology is lymph node involvement.

Keywords: Free colorectal cancer cell, Peritoneal lavage cytology, Colorectal cancer