OBJECTIVES: ICD-10-PCS codes do not provide direct procedure codes for some complex surgeries, in which the root operation involves multiple body parts. This study describes an innovative process to define coding algorithms for complex surgeries in real-world data research.

METHODS: A two-step process was used to determine the ICD-10-PCS codes taking open low anterior resection (LAR) as example. First, we used a CPT-ICD crosswalk and reviewed the frequency of ICD codes in the same episode wherein a CPT code for open LAR (44145, 44146, 45111) in the IBM MarketScan database. Second, we conducted a trend analysis to compare the volume of LARs in different coding scenarios in ICD-10-PCS codes with ICD-9-CM code in the Premier Healthcare Database (PHD) in ICD-9 and ICD-10 data eras from the same hospitals.

RESULTS: In MarketScan database, there were 4,245 episodes with an open LAR CPT code. The frequent ICD-10-PCS codes recorded as primary code during the same episode were: 0DTN0ZZ-resection of sigmoid colon (23.5%), 0DBN0ZZ-excision of sigmoid colon (18.9%), 0DTP0ZZ-resection of rectum (1.5%), 0DBP0ZZ-excision of rectum (2.1%), and 0D1N0Z4-bypass sigmoid colon to cutaneous (0.9%). In PHD, the average number of open LARs per quarter was 1,269 in ICD-9-CM data (48.62, 48.63). In ICD-10-PCS data, the count of open LARs per quarter was 968 for Scenario 1 (resection of rectum), 2,778 for Scenario 2 (resection/excision of rectum), 2,727 for Scenario 3 (resection of rectum or bypass sigmoid colon to cutaneous), 1,207 for Scenario 4 (resection of rectum or excision of rectum with bypass sigmoid colon to cutaneous). Scenario 4 produced a consistent volume of open LARs to ICD-10-PCS eras; therefore, we recommended this definition for open LAR in ICD-10-PCS.

CONCLUSIONS: A combination of CPT-ICD crosswalk and procedure volume trend analysis can be used to inform ICD-10-PCS coding algorithms for complex surgeries when coding guidelines are not in place.