Renal Angiomyolipoma

A 39-year-old woman who had a fever and episodes of nonbloody vomiting for 5 days presented to the emergency department after the sudden onset of severe, left-sided flank pain (10/10 severity) that was sharp, constant, and radiated to the front. She had no associated urinary symptoms, vaginal discharge, or bowel disturbances. Her last menses, 10 days earlier, was regular. Aside from a urinary tract infection 2 years earlier, her medical history was insignificant.

Blood pressure was 130/86 mm Hg; heart rate, 90 beats per minute; temperature, 37.1°C (98.8°F); and respiration rate, 18 breaths per minute. Severe left upper quadrant tenderness extended to the left costovertebral angle. No bruises, hematomas, or skin changes were noted. Other physical examination findings were unremarkable.

The basic metabolic profile and results of liver function tests and urinalysis were normal; a pregnancy test was negative. Complete blood cell (CBC) count showed a hemoglobin level of 9.1 g/dL; the hematocrit value was 29%. A chest radiograph was normal.

Pyelonephritis, renal adenocarcinoma, perinephric hamartoma or abscess, rib fracture, herpetic neuralgia, renal cyst (infected), adult polycystic kidney disease, caliceal diverticula, and angiomyolipoma were considered in the differential diagnosis. Because the patient’s symptoms were not consistent with pyelonephritis—the most common diagnosis for her age group—CT of the abdomen was performed. CT scans with contrast revealed a left perinephric mass of 7 cm and a large collection of intravenous contrast within the capsule, suggestive of angiomyolipoma with active bleeding (A and B).

A follow-up CBC count showed a drop in the hemoglobin level to 8.2 g/dL, which warranted a blood transfusion and urgent selective arterial embolization. A follow-up CT scan with (C) and without (D) contrast demonstrated successful embolization. The remaining left kidney was well enhanced with excellent left renal flow.

Renal angiomyolipoma is a rare, benign parenchymal renal hamartoma found in 1% to 3% of the general population¹; it accounts for 0.5% of all renal tumors.² It often occurs as part of a tuberous sclerosis complex (Bourneville disease) and is associated with seizures, mental retardation, and adenoma sebaceum in 20% to 50% of patients with the disease.³ Other manifestations of Bourneville disease include retinal phacoma and hamartomas of the brain and viscera.

Patients with renal angiomyolipoma often have flank pain, a palpable tender mass, abdominal discomfort, fever, and gross hematuria. Hemorrhage occurs in 15% of angiomyolipomas and in 50% to 60% of tumors larger than 4 cm.¹ Angiomyolipoma is the second most common renal cause of retroperitoneal hemorrhage after renal adenocarcinoma. Other associated signs and symptoms include nausea, vomiting, hypertension, anemia, elevated white blood cell count, and renal insufficiency. Characteristic histologic findings are proliferation of spindle cells, epithelial cells, and adipocytes in concert with many thick-walled blood vessels.

The diagnosis can usually be made based on imaging studies, such as CT or MRI, without the need for biopsy. The high fat content of an angiomyolipoma distinguishes it from renal adenocarcinoma.

Symptomatic angiomyolipomas are usually managed with transcatheter selective arterial embolization. Asymptomatic lesions of 4 cm or larger require frequent follow-up, with serial CT every 6 months. Prophylactic embolization of these lesions is recommended in select high-risk patients, including younger women who intend to become pregnant and patients in whom follow-up is difficult. Renal-sparing open surgery (partial nephrectomy) is reserved for patients with persistent hemorrhage or suspected malignancy and those in whom embolization fails. This patient recovered without surgical intervention and was discharged after 3 days. ■

REFERENCES:

1.Wallace MJ, Wallace S. Renal angiomyolipoma. In: Adam A, Dondelinger RF, Mueller PR, eds. Interventional Radiology in Cancer. New York: Springer-Verlag; 2004:204.

2.Geffin M, Oates RD. Evaluation of renal mass lesions. In: Siroky MB, Edelstein RA, Krane RJ, eds. Manual of Urology: Diagnosis and Therapy. 2nd ed. Hagertown, Md: Lippincott Williams & Wilkins; 1999:106.

3.Nelson CP, Sanda MG. Contemporary diagnosis and management of renal angiomyolipoma. J Urol. 2002;168:1315-1325.