Psoas hematoma

Last revised by Mostafa Elfeky on 17 Jul 2023

Psoas hematomas are located in the retrofascial space, rather than in the retroperitoneum, because the psoas muscles are located in the iliopsoas compartment posterior to the transversalis fascia, which is the posterior boundary of the retroperitoneum.

Presentation is often vague and non-specific and may include abdominal, pelvic, back or groin pain and/or swelling. There may be signs of hemorrhage including tachycardia, hypotension or fall in the measured hemoglobin level 4

Psoas hematomas can present with constipation, urinary frequency, or fever if they are large. They can even compress the femoral nerve and cause femoral neuropathy 3,4.

There are many causes for psoas hematomas 1,2:

  • acute hematoma - low echogenicity; may have a similar appearance to a cyst
  • chronic hematoma - septa formation, calcification or appearance as a solid mass are all features 3
  • may present simply as an enlarged psoas muscle
  • acute blood will present as an area of high density +/- fluid-fluid level
  • chronic hematomas may have a similar appearance to psoas abscess 1

Appearance on MRI depends on the age of the hematoma 2:

  • acute hematoma
    • T1WI - isointense or slightly hypointense to muscle
    • T2WI - may be hypointense or hyperintense
  • subacute hematoma
    • T1WI - high intensity rim, higher intensity peripheral zone and lower intensity core
    • T2WI - relatively higher signal from core to periphery when compared to T1WI
  • chronic hematoma
    • hypointense rim on both T1WI and T2WI

Psoas hematoma can be complicated by superimposed infection or abscess and sometimes percutaneous aspiration and culture can be the only way to differentiate between the two 1

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