As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF AND DURING GEAR RETRACTION, THE A-SYSTEM HYDRAULICS FAILED. FLIGHT RETURNED TO DEN AND COMPLETED AN UNEVENTFUL LANDING. MAINTENANCE REPLACED LEFT GEAR RETRACT ACTUATOR FLEX LINE AND NR 1 ENGINE DRIVEN PUMP. LEAK AND OPERATIONAL CHECK OK.