Intraabdominal hematoma: the concentric-ring sign in MR imaging.

Extracranial hematomas have variable CT appearances and may be confused with other entities. MR imaging of 12 patients with intraabdominal or intrapelvic hemorrhages showed that intraabdominal hematomas develop a unique MR appearance after 3 weeks. Nine hematomas imaged after this time all showed a characteristic concentric-ring configuration, with a thin, dark peripheral rim on all pulse sequences and a bright inner ring most distinctive on T1-weighted images. Six hematomas imaged during the first 3 weeks failed to show this architecture. The concentric rings in MR images of chronic hematomas allowed a tissue-specific diagnosis.