Pyometra is a common disease in countries where elective spaying is not routinely performed. Hormonal and bacterial factors are fundamental in the pathogenesis of the disease, which manifests itself as a potentially life-threatening bacterial infection of the uterus. Surgical ovariohysterectomy is the safest and most effective treatment for pyometra, and it has recently been shown that laparoscopically assisted methods for surgical treatment are feasible to use in selected cases. New protocols for improved medical treatment alternatives have also been tested with promising results. To be able to predict outcome and presence of complications early would be valuable in clinical practice for optimizing therapy and increasing survival. Results of commonly investigated clinical and laboratory investigations have been shown to be useful as predictive markers, with leucopenia being associated with increased risk of peritonitis as well as prolonged post-operative hospitalization after surgical treatment. A cage-side rapid and cost-effective diagnostic test would be highly valuable in clinical practice, and detection of pyometra-specific upregulated genes in the uterus and the corresponding products is a potential start in identifying novel markers suitable for such as test. The focus of the present review is to highlight recent findings on pathogenesis, prediction of outcome, diagnosis and treatment. Additionally, central research questions and suggestions for future investigations about several aspects of canine pyometra will be addressed.