Transmesocolon internal hernia masking as simple sigmoid volvulus.

Transmesocolon internal hernias are very rare causes of bowel obstruction. Transmesenteric internal hernias normally associated with small bowel. It can be challenging to diagnose transmesocolon internal hernia hence we present a 93-year-old patient who was misdiagnosed with simple sigmoid volvulus on CT abdomen. She underwent endoscopic colonic decompression. Patient continued to deteriorate in the ward, and CT abdomen was repeated; it revealed the cause of the sigmoid volvulus was due to a defect through transverse mesocolon resulting in internal hernia. Patient was diagnosed with transmesocolic internal hernia with sigmoid volvulus. Patient underwent emergency laparotomy and Hartmann procedure. Transmesocolic internal hernia can be easily missed and needs to be considered when diagnosing patients with large bowel volvulus or obstruction.