EXOPHYTIC NONINVASIVE GROWTH PATTERN OF RENAL ANGIOMYOLIPOMAS: : IMPLICATIONS FOR NEPHRON SPARING SURGERY

Abstract

Angiomyolipomas are rare, benign lesions of the kidney composed of mature adipose tissue, thick walled blood vessels and smooth muscle. The successful use of nephron sparing surgery for these lesions has been well documented. 1‐3 Angiomyolipomas as large as 26 cm. have been reported, and yet even such large tumors are amenable to a nephron sparing approach. 1 This possibility is due to the benign nature of the disease and a noninvasive, exophytic growth pattern unique to these renal tumors. CASE REPORTS Case 1. R. F., a 49-year-old woman, was diagnosed elsewhere 10 years earlier with multiple, bilateral angiomyolipomas. At the time of referral serum creatinine was 0.7 mg./dl. (normal less than 1.5). Computerized tomography (CT) demonstrated a 7.1 cm. tumor on the right side, a 9.4 cm. tumor on the left side and bilateral, satellite lesions (fig. 1), all of which were radiographically consistent with angiomyolipomas. The patient underwent staged partial nephrectomies on the right side first and the left side 8 months later. In both instances the largest angiomyolipoma demonstrated exuberant exophytic but noninvasive growth with a small parenchymal base/origination point. As a result an avascular plane could be developed sharply before clamping the renal vessels between the tumor and renal parenchyma, narrowing the area of parenchymal involvement to 1 small focus, which allowed almost 90% of the renal parenchyma to be spared on both sides (fig. 2). Followup studies demonstrated excellent renal function bilaterally and creatinine at last followup was 0.7 mg./dl. Case 2. K. K. a 38-year-old woman, had flank pain on the right side diagnosed as multiple bilateral angiomyolipomas. CT demonstrated 2 large (6.3 and 8.5 cm.) and multiple smaller lesions in the right kidney and 7 small lesions in the left kidney. The patient underwent right partial nephrectomy and both large lesions demonstrated an exophytic, noninvasive growth pattern such that an avascular plane could be developed sharply between the tumor and renal parenchyma before clamping the renal vessels. This approach allowed more than 75% of the renal parenchyma to be spared.