Situs inversus. When you start looking at chest x-rays, get into the habit of quickly looking at what’s written on the film before you start, as this information can be very helpful. This patient has situs inversus – note the reversed position of the heart and aorta, and that the stomach is below the right hemidiaphragm and the liver below the left. The side marker (circled) is where it should be, which is what tells us that this is situs rather than the film being the wrong way around. Showing a dextrocardia case the wrong way round, so that it looks normal at first glance, has been a traditional method of embarrassing medical students for generations – if you don’t look at the side marker, you’ll be caught out.