Subdiaphragmatic free gas secondary to anastomotic leak

Case contributed by Henry Knipe


Day 7 post colectomy with primary anastomosis. Dysponea ?infective changes. Decreased breath sounds at both bases.

Patient Data

Age: 65
Gender: Female

 There is a large volume of free subdiaphragmatic gas with air-fluid levels under both hemidiaphragms.

Bilateral pleural effusions and bibasal collapse/consolidation. Cardiomediastinal contour is within normal limits. Surgical clips project over the LUQ.

Abdomen/Pelvis - performed approximately 4 hours after the x-ray


 Marked amounts of free fluid (13HU) and gas are demonstrated within the abdomen. Surgical sutures in keeping with a recent subtotal colectomy are noted - ? discontinuous. The rectal contrast falls short of the site of anastomosis. However, the free gas locules are predominantly centered within the left upper quadrant corresponding to the region of anastomosis suggesting this is likely the site of perforation. The segment of bowel opacified by the rectal contrast demonstrates no extraluminal extravasation.

The small and large bowel loops are dilated without evidence of mechanical obstruction in keeping with an ileus. 

 Large bilateral pleural effusions are associated with almost complete bibasal collapse.

Acknowledgement: Dr Bhaveen Marne.

Case Discussion

The volume of free subdiaphragmatic gas is out of proportion with the length of time since the operation seven days ago. The presence of air-fluid levels also suggests free intraperitoneal fluid. Together, this may represent primary anastomotic breakdown or leak. The patient returned to theater where the anastomotic leak was confirmed. 

For patients without contrast at the anastomotic site the most significant CT feature of an anastomotic leak is loculated fluid containing gas adjacent to the anastomotic site 1.

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