Yes Alex, the answer is "what is a light bulb in the rectum", I'll take manual disimpaction for 500 please.
Humm.. I see a creep taking a clandestine camera-phone pic of an upside down chest x-ray.
Hard to tell, being upside down and with all the glare, but I'll guess "free air under the lt hemi-diaphragm."
Or that could be fundus.