On postoperative day 2 after a free anterolateral thigh flap transfer to the floor of mouth, the flap appears dark purple, swollen, with brisk capillary refill under 1 second and a positive Prickle sign (dark blood on needle prick). The arterial Doppler signal is present. These findings indicate:

• A Arterial insufficiency requiring immediate re-exploration for thrombectomy
• B Venous outflow obstruction requiring urgent exploration ✓
• C Normal postoperative hyperaemia requiring observation only
• D Partial flap loss requiring debridement of the distal third

Explanation

Venous congestion produces a dusky purple colour, swelling, rapid capillary refill, and dark readily flowing blood on needle prick, while the arterial signal remains audible until late. Arterial insufficiency instead gives a pale, cool, flat flap with absent refill and no bleeding on prick. A congested free flap is a surgical emergency because salvage rates fall sharply after 6 hours of venous thrombosis.

Reference: Grabb and Smith's Plastic Surgery, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.