John Thomas sign

The John Thomas Sign, also colloquially referred to as the Throckmorton Sign, is an informal and humorous term utilized within the domain of radiology. Named after the popular English euphemism for the penis, 'John Thomas,' this sign pertains to the orientation of the penis as visualized in pelvic X-ray imaging, in relation to pathology.^[1]

Description[edit | edit source]

When the penis casts a shadow on the X-ray image that points towards the side of a unilateral medical condition, such as a fractured bone in the pelvis or hip, this is referred to as a positive John Thomas sign. Conversely, if the shadow is directed away from the side of the pathology, it is defined as a negative John Thomas sign.^[2]

Clinical Relevance and Interpretation[edit | edit source]

The John Thomas Sign is essentially a piece of radiological humor rather than a clinically relevant finding. It has no known predictive value or meaningful clinical implications, and is predominantly shared as a lighthearted anecdote among radiologists and medical professionals.

Despite its humorous nature, the term highlights the importance of comprehensive image assessment in radiology. Radiologists must remain vigilant and detailed in their image analysis, as the position or appearance of one structure may indirectly hint towards the presence of underlying pathology elsewhere.^[3]

In Popular Culture[edit | edit source]

The John Thomas sign, while not commonly known outside of medical and radiological circles, occasionally surfaces in medical-themed popular culture. It serves as an example of the humor used by healthcare professionals to cope with the intense and demanding nature of their work.

John Thomas sign Resources
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