Final answer:
Eyelid erythema and edema suggests a serious complication of acute bacterial rhinosinusitis.
Step-by-step explanation:
The finding that suggests a serious complication of acute bacterial rhinosinusitis (ABRS) is Eyelid erythema and edema. While tender preauricular lymph nodes, foul-tasting post nasal drip, and facial tenderness are common symptoms of ABRS, eyelid erythema and edema indicate the infection has spread beyond the sinuses and may be causing orbital cellulitis.