Using Canadian population-linked databases including 565,073 people with COPD aged 66 or older, Stephenson et al identified cases of acute urinary retention in 9,432 men and 1,806 women. The episodes were serious enough to result in an ED visit, hospitalization, or same-day surgery. Cross-matching against a drug claims benefit database, the odds ratio for AUR in those who had just started anticholinergic therapy (short- or long-acting) was only 1.42. Using both ipratropium and tiotropium together, or having benign prostatic hypertrophy, increased the odds ratio.