BackgroundDuring rectal cancer surgery the bowel may contain viable, exfoliated cancer cells, a potential source for local recurrence (LR). The amount and viability of these cells can be reduced using intraoperative rectal washout, a procedure that reduces the LR risk after anterior resection. The aim of this study was to analyse the impact of washout on oncological outcome when performed in Hartmann’s procedure (HP) for rectal cancer.MethodsA national cohort study on data for patients registered from 1995 to 2007 in the Swedish Colorectal Cancer Registry was carried out. The final analysis included patients belonging to TNM stages I–III who had undergone R0 HP with a registered 5-year follow-up. Multivariate analysis was performed.ResultsA total of 1188 patients were analysed (686 washout and 502 no washout). No differences were detected between the washout group and the no washout group concerning rates of LR [7% (49/686) vs. 10% (49/502); p = 0.13], distant metastasis (DM) [17% (119/686) vs. 18% (93/502); p = 0.65], and overall recurrence (OAR) [21% (145/686) vs. 24% (120/502); p = 0.29]. For both groups, the 5-year cancer-specific survival was below 50%. In multivariate analysis, washout neither decreased the risk of LR, DM, or OAR nor increased overall or the cancer-specific 5-year survival.ConclusionsThe oncological outcome did not improve when washout was performed in HP for rectal cancer.Electronic supplementary materialThe online version of this article (doi:10.1007/s10151-017-1637-5) contains supplementary material, which is available to authorized users.