This case demonstrates pneumoperitoneum, which was missed by a staff radiologist. When I saw this study, the first thing to catch my eye was the large lucency over the liver (star), especially since this was a supine radiograph. On a supine radiograph, you have to look for gas rising non-dependently along the anterior abdominal wall resulting in a "lucent liver sign." Additionally, as most of the answers noted, there is free air revealing itself as a Rigler sign in the left hemiabdomen. There is a segment of small bowel where you can see both surfaces of the bowel wall - intraluminal and serosal surface (arrow). Turns out, this was a case of a perforated sigmoid cancer.
Radiopedia has a great list of all of the different signs of pneumoperitoneum and being familiar with them will help you in cases where you might not have a classic Rigler sign or an upright chest radiograph with subdiaphragmatic free air.
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| Sigmoid wall thickening with an abscess in the right anterior pelvis. |
