Angiomyolipoma

April 1, 2005

A 45-year-old man presented to the emergency department with severe left flank pain, tachycardia, and hypotension of about 48 hours’ duration. He had no significant medical history. His heart rate was 106 beats per minute; his blood pressure was 90/70 mm Hg. Laboratory results were notable for a hemoglobin level and a hematocrit in the lower end of the normal range.

A 45-year-old man presented to the emergency department with severe left flank pain, tachycardia, and hypotension of about 48 hours’ duration. He had no significant medical history. His heart rate was 106 beats per minute; his blood pressure was 90/70 mm Hg. Laboratory results were notable for a hemoglobin level and a hematocrit in the lower end of the normal range. The initial presumptive diagnosis was kidney stone disease. John Whyte, MD, of Washington, DC, and Anthony L. Filly, MD, of Palo Alto, Calif, report that a noncontrast CT scan showed left retroperitoneal/pararenal high-attenuation areas that were consistent with a hemorrhage. Interspersed in the hemorrhage were low-attenuation areas with negative Hounsfield units, consistent with fat (A). The clinical impression was hemorrhagic renal angiomyolipoma. A contrast-enhanced CT scan of the abdomen showed part of a mass in the mid- kidney posteriorly and fat attenuation consistent with an angiomyolipoma (B). No active arterial extravasation was noted. The incidence of angiomyolipomas in the general population is less than 3%. Typically, affected patients are older than 40 years and female. Angiomyolipomas have no malignant potential; however, the risk of hemorrhage increases as they enlarge. As the name implies, angiomyolipomas are composed of muscle, fat, and vascular tissue. The tumors most often involve the right kidney. They are frequently associated with tuberous sclerosis. Usually, angiomyolipomas are asymptomatic and the finding is incidental. However, an angiomyolipoma can cause flank pain and hematuria, which can be misdiagnosed as a kidney stone. This neoplasm can also cause abdominal pain and, as it grows, can result in a palpable abdominal mass. Fat attenuation in a renal mass is virtually diagnostic. Treatment usually consists of watchful waiting. In the event of hemorrhage, surgical resection or renal artery embolization is performed. This patient underwent surgical resection and had an uneventful recovery.