[The echographic and computed tomographic assessment of "spontaneous" hematomas of the abdominal wall].

Hematomas of the abdominal and pelvic wall are frequent findings, particularly in the patients undergoing long-term anticoagulant therapy. We reviewed a series of 9 cases of "spontaneous" hematomas of the rectus abdominis muscle (7 cases), of the obliquus internus muscle (one case) and of the gluteus muscles (one case) studied with US and CT. During the last 4 years, 9 patients complaining of the recent onset of a painful muscular swelling were examined: 8 of them were on anticoagulant therapy, while one was on long-term hemodialysis. They were examined with US (3.5 MHz, integrated with 7.5 MHz in 7 cases) and CT (contiguous 10-mm slices before and after i.v. contrast agent injection). Color Doppler was used in 3 cases. US showed different signs depending on hematoma onset and extent: the muscle was swollen, with an inhomogeneous structure with both coalescing liquid and echogenic areas in 2 cases, while the hematomas were bigger and appeared with mostly liquid areas and internal inhomogeneity due to blood clots in the remaining 7 cases. The evidence of pseudocystic areas with fluid blood levels (the so-called pseudohematocrit effect) was particularly specific of diffuse hematomas (4 patients). CT helped make the final diagnosis by showing the typical hyperdensity of fresh blood (at least 50 HU) in 9 cases and by defining the typical pattern of the pseudocysts with the hematocrit effect, but was useless in characterizing "pseudotumoral" lesions (3 cases), which were better defined by B-mode and color Doppler US. US is the examination of choice, even though it may misdiagnose small hematomas as muscular tumors or large hematomas as other diseases; color Doppler can be useful in the former case. CT usually permits the correct diagnosis by detecting fresh blood, which can however be found also in some muscular neoplasms.