Retained surgical swabs: possible causes for errors in x-ray detection and an atlas to assist recognition.

A swab or pack left in a patient may not be recognised on a radiograph. This will usually be due to poor observation, but errors may result from unfamiliarity with the pattern of the markers. In addition, some markers may be difficult to detect, though this usually applies only to swabs which are very small or to those produced by some continental manufacturers. It should also be realised that, in a very few hospitals, swabs which do not have an opaque marker may occasionally be used in theatre. All the X-ray detectable swabs provided by the major suppliers in the U.K. are demonstrated.