Question: What procedure code do we use for decortication of a retroperitoneal abscess? Washington Subscriber Answer: The current CPT® manual does not have a code specifically for decortication of a retroperitoneal abscess. Decortication is a medical procedure involving the surgical removal of the surface layer, membrane, or fibrous cover of an organ. Considering this definition, one possible coding for reporting the procedure you reference is 49060 (Drainage of retroperitoneal abscess, open). During this procedure, the provider opens the abdomen and incises and drains an abscess located in the area behind and outside of the back wall of the peritoneum, the membrane lining the abdominal cavity. Note: If your provider’s documentation does not meet the criteria for code 49060, you should submit 49999 (Unlisted procedure, abdomen, peritoneum and omentum) with information explaining what was done.