Adrenal lesions with heterogeneous suppression on chemical shift imaging: Clinical implications

Purpose: To investigate the frequency and significance of adrenal lesions that demonstrate heterogeneous suppression on chemical shift magnetic resonance imaging (MRI). Materials and Methods: A retrospective search of adrenal lesions identified on MR from November 1997-July 2001 was performed. The adrenal lesions were classified as having suppression typical for an adenoma, nonsuppression, or atypical heterogeneous suppression. Lesions with heterogeneous suppression were further reviewed. Follow-up for the heterogeneous lesions consisted of imaging studies or pathology from surgical excision. Results: Adrenal lesions were identified in 242 patients. Heterogeneously suppressing lesions were seen in 34 (14%) patients. Several different patterns of heterogeneous suppression were identified. Imaging or pathologic follow-up was available for 18 of the heterogeneously suppressing lesions (one patient had both). Fifteen patients with follow-up imaging showed stability of the lesion over a significant interval, suggesting a benign lesion. Pathology was available for four patients revealing two patients with adenomas and two patients with nodular hyperplasia. Thus, all 18 patients with heterogeneous suppression had a benign lesion. Conclusion: Adrenal lesions that have a heterogeneous pattern of suppression on out-of-phase chemical shift MR images are a common finding. Our small series suggest that these lesions are probably benign.