Spider Nevus
The spider nevus, or spider angioma, is the most representative and classic vascular lesion of chronic liver disease. Clinically, it has a central arteriole from which numerous small, twisted vessels radiate . Spider nevi range in size from a pinhead to 2 cm. Larger lesions can be seen to pulsate when pressed with a glass slide. Pressure over the central arteriole causes blanching of the whole lesion. Spider nevi are characterized by the abnormal permanent dilatation of end vessels. Histologically, spider nevi consist of a central ascending arteriole ending in a thin-walled ampulla beneath the epidermis from which small arterial branches radiate outward into the papillary dermis.
Spider nevi are most common on the face, neck, and upper part of the chest . They may be seen in 15 percent of healthy adults and not infrequently in children, where they tend to affect the hands and fingers. They may appear in large numbers during pregnancy, but usually disappear after parturition. They may also be seen in thyrotoxicosis or due to oral contraceptives.
In liver disease, spider nevi can regress with improvement of the underlying condition, although they are more likely to persist. Spider nevi are more common in patients with alcoholic cirrhosis than in those with viral or idiopathic cirrhosis. In alcoholic cirrhosis, they are associated with the presence of esophageal varicosities, and their presence may be a useful predictive marker for the future risk of esophageal bleeds.
Traditionally, vascular spider nevi and palmar erythema (see Palms: Palmar Erythema) have been attributed to estrogen excess, particularly because they also occur during pregnancy and because estrogens have an enlarging, dilating effect on the spiral arterioles of the endometrium. This also explains the spider nevi seen in men receiving estrogen therapy for prostatic cancer. Patients with nonalcoholic cirrhosis have been shown to have higher plasma estradiol-testosterone ratios and substance P levels than healthy controls do, and levels of substance P or vascular endothelial growth factor may have an etiopathogenic role. In alcoholic cirrhosis, the presence of alcoholism and elevated serum bilirubin are both important predictors of the presence of spider nevi.