痛風石之超音波影像

Sonographic Features of Tophi

痛風石（tophi）是痛風的表現之一，對於痛風石的診斷往往依據病史詢問及理學檢查、血液生化檢查。超音波對痛風石而言，並非常規檢查。然而，痛風石若出現於非好發部位，或以非典型的形式表現，例如以類似感染、風濕性疾病、或腫瘤（neoplasm）的形式表現，會使鑑別診斷不易，此時可能需要更進一步的影像學檢查。超音波檢查可在此種情況下對於鑑別診斷有所幫助，此篇研究主要探討痛風石在超音波影像的特殊表現。我們回溯9個病人11個部位經超音波診斷為痛風石的個案。其中有4位病人5個部位接受外科摘除手術並經病理檢驗證實為痛風石。這11個部位的痛風石在超音波影像的表現可分為三類：第一類痛風石呈現一低回音區（hypoechoic）；第二類痛風石於靠近皮膚側呈高回音（hyperechoic）表現，其後則有回音後陰影（acoustic shadow）；第三類為於低回音區域中夾雜有高回音的小點或結節而呈一異回音（heteroechoic）區，回音後陰影不明顯，可視為第一類及第二類間的過渡期。

Tophi are the pathognomonic hallmark of gout. They are formed by large aggregations of urate crystals surrounded by an intense inflammation reaction of cells. We examined nine patients with tophi by means of 10-MHz ultrasonography. The presentation of tophi on ultrasonogram can be divided into three different classifications. In type I, tophus presented as a hypoechoic lesion surrounded by swollen soft tissue. In type II, a prominent shelly hyperechoic region with a strong post-acoustic shadow can be observed. In type III, tophus appears as some spotted or nodule hyperechoic calcification scattered among a hypoechoic area, which represents a transitional stage between type I and type II. Ultrasonography can differentiate tophi from other tumor-like conditions of soft tissue including neoplasm or infection. Compared with other imaging techniques, ultrasonography is safe, inexpensive, dynamic, and non-radioactive. Therefore, we believe that it is a useful tool in the diagnosis and follow-up of tophi which showld also include history, physical findings and blood biochemistry examinations.