Mạch sao (Spider naevi)

Mô tả: Skin lesion consisting of a central arteriole with thread-like vessels that resemble spider’s legs radiating outward. Blanching occurs when the spider naevus is compressed, and refilling occurs from the central arteriole outwards when released. Naevi can vary in size from pinhead to 5 mm in diameter.112

Nguyên nhân: More common • 10–15% of healthy adults and young children • Alcoholic liver disease • Hepatitis B and C • Pregnancy • Patients on oral contraceptive pill (OCP) and oestrogen products Less common • Thyrotoxicosis

Cơ chế: Evidence regarding the pathophysiology is severely lacking. Of the few studies in this area, increased plasma oestrogen and substance P have been implicated in vasodilatation and neovascularisation to form spider naevi.113 Furthermore, the ratio of serum oestradiol to free testosterone is raised in male cirrhotic patients compared to the general population.114

Ý nghĩa lâm sàng: The presence of spider naevi is an important tool in predicting the level of liver cirrhosis. A study by Romagnuolo et al used the presence of spider naevi, platelet count, the presence of splenomegaly and albumin level as variables to calculate the likelihood ratio of cirrhosisfibrosis.115 This study found: • The presence of spider naevi was significantly associated with moderate to severe inflammation, significant fibrosis and cirrhosis of the liver. • The presence of spider naevi and elevated ferritin was a good predictor of inflammation. • Spider naevi with either splenomegaly or thrombocytopenia were good predictors of fibrosis.