Two cases are presented which emphasize the difficulty of differentiating between a sigmoid volvulus, where the 'liver overlap sign' is the only sign present, and perforation of a hollow viscus where the only sign on a supine abdominal radiograph may be the 'football sign' simulating a 'liver overlap sign'. In the case of sigmoid volvulus described in this report, the correct diagnosis established only with much difficulty and after further conventional radiographs and contrast studies.

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