Sub-diaphragmatic gas is present on the right above the liver, indicating pneumoperitoneum secondary to hollow-viscus perforation. This is favored to be located at the descending colon where there is a lumbar rib directed into the retroperitoneum.
Ribs are present throughout the lumbar spine bilaterally, which are slightly more developed on the right than the left. The most caudal rib on the left is directed anteriorly into the abdomen. On the right at this level, the rib has an abnormal articulation with the right iliac crest and sclerosis at the interface, indicating pseudoarthrosis. A pseudarthrosis is also present on the left between the ribs 4th and 5th cephalad from the last rib-bearing segment. A transitional-type vertebra is present at the lumbosacral junction, with bilateral spatulated transverse processes that articulate with the sacrum (Castellvi type 2b). This transitional segment also demonstrates non-union of the lamina (spina bifida occulta).