An additional surgery that requires a return to the OR (including complications) is billable with -78.
Per the
CMS recently updated Global Surgery Booklet:
Return to OR for Related Procedure During Post-Operative Period
When treatment for post-operative complications requires an OR return trip, bill the CPT code that describes the procedures during the return trip. If no such code exists, use the unspecified procedure code in the correct series, 47999 or 64999. Don’t use the procedure code for the original surgery unless you repeat the identical procedure.
Use the CPT code and report modifier –78 (Unplanned return to the operating or procedure room by the same physician following the initial related procedure during the post-operative period).
The physician may also perform another procedure during the initial procedure post-operative period. When this subsequent procedure relates to the first procedure and requires the operating room, bill it using modifier –78.
NOTE: The CPT modifier –78 definition doesn’t limit its complications treatment use.
Regarding the appropriate CPT code, your most likely candidates are either:
49002 Reopening of recent laparotomy
35840 Exploration for postoperative hemorrhage, thrombosis or infection; abdomen
These codes are rather similar. My interpretation of the difference is that I would use 35840 if the physician found active bleeding and treated it. I would use 49002 if the bleeding had now stopped.
Here is a similar post discussing:
Wiki - Exploratory laparotomy, hematoma evacuation and pelvic irrigation