Vascular surgeons have been concerned with impotence since the classic paper of Lerichel in 1923 recognized erectile failure as one of the first symptoms of aortoiliac occlusion. It was then observed that operations on the aortoiliac segment often caused impotence or sexual dysfunction, such as ejaculatory failure,' further stimulating interest in vasculogenic impotence. Subsequently, techniques of aortoiliac reconstruction were developed that minimized postoperative sexual disabilities by avoiding genital nerve injury and ensuring perfusion of the internal iliac arteries.3 In addition to large vessel occlusive disease, pudendal or penile artery occlusion and cavernosal venous leakage also cause erectile failure, which can sometimes be treated by microvascular operations.4Vascular surgeons also encounter impotence related to cavernosal smooth muscle dysfunction, particularly in diabetics, in whom impaired neurogenic and endothelial-mediated relaxation dominate the clinical manifestation of erectile failure.5 This article outlines useful diagnostic approaches for vascular surgeons when impotence either accompanies vascular pathology or appears as a presenting complaint.
PHYSIOLOGY OF ERECTIONPenile erection is a unique hemodynamic process mediated by increased arterial inflow into the corporal bodies along with reduction or, at some stages, complete cessation of venous outflow These hemodynamic changes form the bases for both noninvasive and invasive tests that seek to define the underlying pathophysiology of erectile failure. Recent research shows that endothelial-derived relaxant factor is involved in noncholinergic neural transmission leading to cavernosal smooth muscle relaxation essential for normal erection.6 Histochemically, nerve fibers positive for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) and diaphorase have been identified in human penile tissue, indicating nitric oxide synthase activity. 7 Other neurotransmitters such as vasoactive intestinal polypeptide (VIP) and fibers positive for acetylcholinesterase are also present. A complex chemical mediator-receptor system thus forms the basis of the first important step of smooth muscle relaxation. Receptors present in penile smooth muscle include those responsive to VIP, prostaglandin, dopamine, histamine, and probably others The underlying physiology, hemodynamics, and stages of normal erection have been recently reviewed.9 In the flaccid state, corporal smooth muscle remains intensely contracted because of normally present overriding adrenat UNIV OF TENNESSEE on June 4, 2016 pvs.sagepub.com Downloaded from
