Medical Must-See: Pregnant patient’s diagnosis a rare pain in the butt 

A combination of psoas haematoma and infectious sacroiliitis made for a complicated diagnosis.
MRI of the sacroiliac joint showing inflammatory changes of the sacroiliac joint (arrow) and an adjacent abscess (star).

Identifying the rare cause of a pregnant patient’s back and buttock pain was, well, a pain in the butt for her doctors.

The woman, carrying twins, presented at 29 weeks’ gestation because of her short cervix and increased preterm delivery risk, but she also complained of pain in her lower back and right buttock that was radiating to her right thigh.