Radiology #8: UFO
- Jan 5
- 1 min read
The Patient
A 28 year old man presents complaining of back pain. He tells you he was stabbed in the back about 6 months earlier, and presented to hospital at that time, but it was in a different province and he has no records of that hospital visit. You obtain a chest x-ray:
The Pictures
What do you think?
click to reveal answer
The quality of the film is fairly poor - but underneath the left hemidiaphragm a retained foreign body is easily visible. On examination, he was found to have a draining sinus overlying the area where the knife blade can be seen. A CT was performed, and the blade was confirmed to be in the subcutaneous tissue and to not involve any deeper structures. The blade was then removed under local anaesthetic and the patient was discharged with a course of antibiotics.
Clearly there has been an Unidentified Foreign Object that has been missed during the index presentation. The lesson here is the importance of looking under the diaphragm when interpreting a chest x-ray. It's easy to get fixated looking at the apices for that small pneumothorax, but the diaphragm is a great check area -particularly when you're trying to identify subtle findings like pneumoperitoneum, diaphragmatic rupture, or in this case, a not-so-subtle retained foreign body.
Thanks to Dr Naeem Vallee for submitting this case.
References
click to see references
[1] Foreign body. Radiopaedia [internet]. 2025. Accessed 10 Dec 2025. Available from: https://radiopaedia.org/articles/foreign-body-1
