This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vascular surgery, Subject name: Surgery
Obstruction at the bifurcation of aoa leads to 
Select and explain. 
A. Rubor on putting leg in dependent position, B. Retrograde ejaculation, C. Gangrene of foot, D. Pallor of lower limb
C: Gangrene of foot
Answer: C: Gangrene of foot 
Explanation: . Obstruction at the bifurcation of aoa causes sudden,rapidly progressive ischemia in both the lower limbs,leads to gangrene of both lower limbs. Note:In aoic bifurcation thrombus,there is earlier history of claudication in the buttock often with LERICH'S SYNDROME.Symptoms are slow and gradual but not dramatic.Collaterals between aoa abd iliac aeries have wrll formed and so sudden.rapid developmet of gangrene will not occur. Refer page no 193 of SRB's manual of surgery 5 th edition.