Extensive Hematoma of the Vastus Intermedius Showing Components of Subacute and Chronic Hemorrhage With Associated Myositis of the Vastus Intermedius and Medialis

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Extensive Hematoma of the Vastus Intermedius Showing Components of Subacute and Chronic Hemorrhage With Associated Myositis of the Vastus Intermedius and Medialis

Soft tissue hematomas are notorious for causing diagnostic confusion on magnetic resonance imaging (MRI) because of their heterogenous signal characteristics, distinct from simple fluid. The varied MRI appearance of a hematoma is the result of the age of its hemorrhagic components. On spin echo T1-weighted imaging, an acute hematoma demonstrates signal intensity roughly similar to skeletal muscle, while corresponding T2 signal is relatively hypointense. Acute hematomas often show significant edema in the surrounding tissues manifest by increased T2- and decreased T1-signal intensity. These imaging characteristics for acute hematomas correspond to a lesion age range of several hours to a few days.¹

Subacute hematomas tend to show homogeneously increased T1- and T2-signal intensity, and may begin to demonstrate a markedly hypointense peripheral rim (relative to skeletal muscle). This low-signal intensity rim is due to the accumulation of hemosiderin-laden macrophages.² The imaging characteristics for the subacute hematoma correspond to a lesion age range of several days to 3 months.¹ Our patient’s history, if reliable, dated the injury to approximately 4 weeks. Nevertheless, the presence and recognition of hemosiderin within the lesion suggests some chronicity. The increased signal on the coronal T1-weighted image would be consistent with methemoglobin (Figure 1A), and the surrounding rim of low signal on the T2-weighted sequence with hemosiderin (Figure 1B). These signal features represent subacute blood and older hemorrhage respectively.

Chronic hematomas also demonstrate homogenous increased T1 and T2 signal, however the surrounding hypointense rim usually becomes more prominent. As above, this is due largely to the accumulation of hemosiderin laden macrophages progressively within the periphery of the hematoma. The development of a peripheral fibrous capsule likely contributes to this markedly hypointense surrounding rim.² Chronic hematomas generally refer to a lesion age range of >3 months.

The above guidelines for identifying and dating hematomas based on MRI characteristics are useful but often are somewhat oversimplified. Soft tissue hematomas tend to be complex, multiloculated lesons, often with fluid-fluid levels (Figure 2).³ Varied rates of clot retraction and serum reabsorption result in lesions that are markedly heterogeneous.² Therefore they may not demonstrate imaging characteristics that exactly follow the above guidelines.

Discussion

Most soft tissue masses are iso- to hypointense to skeletal muscle on T1-weighted spin echo images, and are high signal on T2-weighted spin echo images; imaging characteristics that are entirely nonspecific. Soft tissue masses that are of increased signal on T1 are limited, with the differential diagnosis including fatty lesions, hemangioma, subacute hematoma or intralesional hemorrhage, within a sarcoma. The presence of a nodule or rim of tumor often is helpful to distinguish a hemorrhagic neoplasm from a simple hematoma.^4,5 This distinction may sometimes prove difficult because as hematomas organize over time, they can develop enhancing fibrovascular components. When imaging is inconclusive, it is important to obtain close follow-up to exclude an underlying solid neoplasm.¹ Figure 3 demonstrates rim enhancement following intravenous gadolinium contrast without any enhancing solid components. The lack of any solid elements within the mass, rim enhancement only and the presence of subacute blood and older hemorrhage (hemosiderin) suggested a large hematoma with its internal composition showing hemorrhage in different phases of evolution. The presence of rim enhancement with lack of a solid mass following intravenous gadolinium permitted exclusion of a hemorrhagic sarcoma.

Most simple soft tissue hematomas have a clear history of antecedent trauma and/or anticoagulation. The lack of high T1 signal in a pre-existing mass that has enlarged, or abrupt development of a mass without increased T1 signal may be used to effectively exclude hemorrhage within the mass, unless the suspected hemorrhage has occurred within the preceding few days where acute hemorrhage demonstrates hypo- to isointensity on T1-weighted images.⁴ Intratumoral hemorrhage can cause significant enlargement of a known tumor that may be mistaken for progression of disease and treatment failure.⁶

Summary

The MRI appearance of hematomas is variable and depends on the age of the hematoma. Subacute to chronic hematomas demonstrate increased signal on T1-weighted images, placing them on a short list of entities that may demonstrate this imaging characteristic, namely fatty lesions, hemangioma, hematoma and intralesional hemorrhage. Distinguishing a simple soft tissue hematoma from a hemorrhagic neoplasm is critical for proper patient management, but is often difficult. Our patient’s presenting history and imaging findings were characteristic of hematoma, and our patient was managed nonoperatively, and discharged after being observed in the hospital for 48 hours. When imaging is inconclusive, or clinical history equivocal, it is important to exclude an underlying hemorrhagic soft tissue sarcoma, by follow-up to resolution.

References

1. Kransdorf M, Murphey MD. Imaging of Soft Tissue Tumors. 2nd ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2006.
2. Rubin JI, Gomori JM, Grossman RI, et al. High-field MR imaging of extracrainial hematomas. AJR Am J Roentgenol. 1987; 148:813-817.
3. Kuklo TR, Murphey MD, Islinger RB, et al. Pseudotumors presenting in nonhemophiliacs. Orthopedics. 2001; 24:483-486.
4. Sundaram M, McGuire MH, Herbold DR, Beshany SE, Fletcher JW. High signal intensity soft tissue masses on T1 weighted pulsing sequences. Skeletal Radiology. 1987; 16:30-36.
5. Sundaram M, McLeod RA. MR imaging of tumor and tumor-likelesions of bone and soft tissue. AJR Am J Roentgenol. 1990; 155:817-824.
6. Panicek DM, Casper ES, Brennan MF, et al. Hemorrhage simulating tumor growth in malignant fibrous histiocytoma at MR imaging. Radiology. 1991; 181:398-400.

Authors

Drs Trecek and Sundaram are from The Cleveland Clinic Foundation, Cleveland, Ohio.

Correspondence should be addressed to: Murali Sundaram, MD, Diagnostic Radiology/A21, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195.