[Surgical volume. An American perspective].

Due to an increasing interest in patient safety and quality health care, many studies attempt to show a relationship between procedural volume at the institutional and individual level and patient outcome. Despite the correlation between number of surgeons and institutional volume in major operative procedures such as coronary artery bypass graft, pancreatic resection, and esophagectomy, these parameters are likely to be proxy for individual factors such as experience and structural aspects. In general the relationship between case numbers and results is more convincing in cancer surgery than for cardiovascular procedures, and risk adjustment may play an important role for interpreting results of the various studies. Exact thresholds cannot be determined and thus remain speculative. It appears difficult to implement practical changes based on the observations, because the etiology and causality of the relationship between volume and outcome are still not understood. The simple focus on volume does not apply to measurements of quality but can be a starting point for further studies to identify more specific factors associated with surgical quality.