Final answer:
The most common extracutaneous association with hypocomplementemic urticarial vasculitis is renal involvement.
Step-by-step explanation:
The most common extracutaneous association with hypocomplementemic urticarial vasculitis is renal involvement. Hypocomplementemic urticarial vasculitis is a rare condition characterized by urticarial skin lesions, systemic inflammation, and low levels of complement in the blood. Renal involvement can occur in the form of glomerulonephritis, which is inflammation of the glomeruli in the kidneys.