Metanephric adenoma of the kidney: clinical and radiological study of nine cases.

OBJECTIVE To analyse the clinical and radiological features of metanephric adenoma (MA, a rare benign renal tumour) in nine patients, and to review previous reports. PATIENTS AND METHODS From 1992 to 2007, we identified nine patients (eight women and one man) with MA at our institution. Four patients had a radical nephrectomy and five a partial nephrectomy. Preoperative imaging was reviewed by a senior radiologist. Renal colour Doppler ultrasonography (US), abdominal computed tomography and abdominal magnetic resonance imaging were used in seven, eight and four patients, respectively. RESULTS The mean (range) age of the patients was 46.8 (19-79) years. Six tumours were discovered incidentally. Three patients were symptomatic (two with haematuria and one with polycythaemia). There was no vascular flow on colour Doppler US within the tumours. There were peripheral and/or central calcifications in six of the tumours. All the tumours were well-circumscribed with minimal enhancement after injection with non-ionic intravenous contrast or gadolinium. CONCLUSIONS Renal MA is a benign tumour occurring mainly in young and middle-aged women. Polycythaemia is associated in approximately 10%. Generally, MA is solid, well-circumscribed and hypovascular, often with calcifications. Based on a combination of clinical and imaging features, it might be possible to suspect the diagnosis of MA and propose a preoperative diagnostic biopsy, a partial nephrectomy or active surveillance.