Escaped faecalith causing a persistent psoas abscess.

Faecaliths have been widely implicated in the aetiology of acute appendicitis. According to Shaw, stones are formed in the appendix with greater frequency than in either the gall bladder or the urinary tract. In spite of this, faecaliths appear to cause few complications outside the appendix. We report an unusual complication resulting from an escaped appendiceal faecalith.