Gallstone ileus obstructing within an incarcerated lumbar hernia: an unusual presentation of a rare diagnosis.

We describe an unusual case of a 74-year-old woman who presented with signs and symptoms of small-bowel obstruction and a clinically appreciable, irreducible, left-sided lumbar hernia associated with previous iliac crest bone graft harvesting. Palpation of the hernia demonstrated a small, firm mass within the loops of herniated bowel. CT scanning recognised an intraluminal gallstone at the transition point, establishing the diagnosis of gallstone ileus within an incarcerated lumbar hernia. The proposed explanatory mechanism is that of a gallstone migrating into an easily reducible hernia containing small bowel causing obstruction at the hernia neck by a ball-valve mechanism, resulting in proximal bowel dilation and thus hernia incarceration; it remains unclear when the stone entered the hernia, and whether it enlarged in situ or prior to entering the enteral tract. This is only the second reported instance in the literature of an intraluminal gallstone causing hernia incarceration.