216 lines
23 KiB
Markdown
216 lines
23 KiB
Markdown
---
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title: "Mass in Iliopsoas Compartment"
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docid: "e39c8918-27cb-4dd6-9166-2b265b777a35"
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authors:
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- key: "c1df94ab-4a9f-44c4-add7-1f174fb9ac45"
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value: "Siva P. Raman, MD"
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breadcrumbs:
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-
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name: "Gastrointestinal"
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slug: "gastrointestinal"
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treeNodeId: "b52263f7-5978-4a22-a17d-7260e0033943"
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-
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name: "Differential Diagnosis"
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slug: "differential-diagnosis"
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treeNodeId: "a0fd80ff-6231-49d3-94b8-ea083449979d"
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-
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name: "Abdominal Wall"
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slug: "abdominal-wall"
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treeNodeId: "08db01f7-2961-47f7-954d-2a5fca7e707d"
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-
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name: "Anatomically Based Differentials"
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slug: "anatomically-based-differentials"
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treeNodeId: "1525b44f-9d47-4ff4-8330-693211bd5eb5"
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-
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name: "Mass in Iliopsoas Compartment"
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slug: "mass-in-iliopsoas-compartment"
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treeNodeId: null
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category: "Gastrointestinal"
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documentVersionId: "b98553dd-1557-4132-99d5-3304036dd914"
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imageCount: 26
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lastUpdated: "07/01/22"
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pageDescription: "Mass in Iliopsoas Compartment"
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pageKeywords: "Gastrointestinal, Differential Diagnosis, Abdominal Wall, Anatomically Based Differentials, Mass in Iliopsoas Compartment"
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pageTitle: "Mass in Iliopsoas Compartment | STATdx"
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enhancedTitle: "Mass in Iliopsoas Compartment"
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type: "DDX"
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references: true
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breadcrumbs:
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- "Gastrointestinal"
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- "Differential Diagnosis"
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- "Abdominal Wall"
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- "Anatomically Based Differentials"
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- "Mass in Iliopsoas Compartment"
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---
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# ESSENTIAL INFORMATION
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- ## Key Differential Diagnosis Issues
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- Iliopsoas compartment masses are much more likely to result from infection or hemorrhage than from tumor
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- Iliopsoas pathology often due to spread from adjacent infection (such as spine) or adjacent tumor, rather than originating within iliopsoas itself
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- ## Helpful Clues for Common Diagnoses
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- **Iliopsoas****Hematoma**
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- Iliopsoas is most common site for spontaneous retroperitoneal hemorrhage (usually due to bleeding diathesis or anticoagulation)
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- Presence of multiple hematocrit levels within hematoma suggests coagulopathic hemorrhage
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- Other causes include surgery, trauma, or extension of bleeding from adjacent structures (e.g., bleeding renal AML, ruptured abdominal aortic aneurysm, etc.)
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- Appearance variable depending on age of hematoma
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- Acute bleeding may simply appear as homogeneous enlargement of muscle ± hematocrit levels
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- Chronic bleeds may appear hypodense and can be difficult to differentiate from abscess
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- **Asymmetric Musculature (Mimic)**
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- Iliopsoas muscles can be asymmetric in size, particularly in patients with unilateral leg amputation, paralysis, or lower extremity/spine arthritis
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- **Secondary Infection/Abscess**
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- Infection and abscess formation in iliopsoas typically due to spread of infection from contiguous structures
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- Most commonly infectious spread from bone, kidney, and bowel (including appendix)
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- Paraspinal psoas abscess should prompt careful search for infectious spondylitis (TB or pyogenic)
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- Renal sources of iliopsoas infection include renal/perirenal abscess or xanthogranulomatous pyelonephritis
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- Common bowel sources of iliopsoas infection include appendicitis, diverticulitis, or Crohn disease
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- Often associated with other features of infection (fat stranding, blurring of fat planes, ectopic gas)
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- ## Helpful Clues for Less Common Diagnoses
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- **Retroperitoneal Fibrosis**
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- Irregular soft tissue mass enveloping aorta, inferior vena cava, and ureters, which can involve adjacent psoas muscles
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- Variable enhancement depending on stage with hyperenhancement in early stages of disease and hypoenhancement in later stages
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- **Primary Infection**
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- Iliopsoas compartment is rarely primary site of infection, except in immunocompromised patients (including HIV) and intravenous drug abusers
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- Infection usually due to *Staphylococcus aureus*and mixed gram-negative organisms
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- **Primary Neoplasm**
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- Primary mesenchymal tumors (liposarcoma, fibrosarcoma, leiomyosarcoma, hemangiopericytoma, etc.) may rarely originate from iliopsoas compartment
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- **Secondary Neoplasm**
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- Hematogenous metastasis (e.g., lymphoma, melanoma) to iliopsoas very rare
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- More commonly directly invaded by adjacent tumors (e.g., retroperitoneal sarcoma, lymphoma, neurogenic tumors, adjacent bone tumor, etc.)
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- Plexiform neurofibroma (in neurofibromatosis) may involve psoas compartment
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## References
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# Selected References
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1. [Mondie C et al: Retroperitoneal hematoma. StatPearls, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=32644354%5Bpmid%5D)
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1. [Improta L et al: Overview of primary adult retroperitoneal tumours. Eur J Surg Oncol. 46(9):1573-9, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32600897%5Bpmid%5D)
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1. [Peisen F et al: Retroperitoneal fibrosis and its differential diagnoses: the role of radiological imaging. Rofo. 192(10):929-36, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32698236%5Bpmid%5D)
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1. [Babic M et al: Infections of the spine. Infect Dis Clin North Am. 31(2):279-97, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28366222%5Bpmid%5D)
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1. [Messiou C et al: Primary retroperitoneal soft tissue sarcoma: imaging appearances, pitfalls and diagnostic algorithm. Eur J Surg Oncol. 43(7):1191-8, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28057392%5Bpmid%5D)
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1. [Sunga KL et al: Spontaneous retroperitoneal hematoma: etiology, characteristics, management, and outcome. J Emerg Med. 43(2):e157-61, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=21911282%5Bpmid%5D)
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1. [Singh AK et al: Neoplastic iliopsoas masses in oncology patients: CT findings. Abdom Imaging. 33(4):493-7, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=17639377%5Bpmid%5D)
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## Images
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### Selected Images
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**Iliopsoas Hematoma**
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*Axial NECT shows enlargement of both psoas muscles due to coagulopathic hemorrhage. Although the hematoma is partly isodense to the muscle, the presence of hematocrit levels <img src='img/arrows/WC.png'/> makes the hematomas more apparent. Hematocrit levels suggest coagulopathy as the underlying cause of the bleed.*
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**Iliopsoas Hematoma**
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*Axial NECT shows enlargement of both psoas muscles due to coagulopathic hemorrhage. Although the hematoma is partly isodense to the muscle, the presence of hematocrit levels <img src='img/arrows/WC.png'/> makes the hematomas more apparent. Hematocrit levels suggest coagulopathy as the underlying cause of the bleed.*
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**Asymmetric Musculature (Mimic)**
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*Axial CECT shows marked asymmetry of the psoas muscles. In this case, the left psoas muscle <img src='img/arrows/WS.png'/> is atrophic due to a prior left leg amputation.*
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**Secondary Infection/Abscess**
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*Axial CECT shows lytic destruction of a vertebral body with an abscess <img src='img/arrows/WC.png'/> extending into the right psoas muscle. Note the presence of a large mycotic aneurysm <img src='img/arrows/WS.png'/> immediately anteriorly arising from the abdominal aorta.*
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**Secondary Infection/Abscess**
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*Axial T1 C+ MR shows an abscess <img src='img/arrows/WS.png'/> in the iliopsoas muscle directly contiguous with phlegmonous change <img src='img/arrows/WC.png'/> in the right lower quadrant due to the patient's fistulizing Crohn disease.*
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**Retroperitoneal Fibrosis**
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*Axial CECT shows a rind of mass-like soft tissue <img src='img/arrows/WC.png'/> encasing the aorta and inferior vena cava. While more mass-like than is typical, this was found to represent retroperitoneal fibrosis.*
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**Primary Neoplasm**
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*Axial T1 MR shows a large, fat-containing mass <img src='img/arrows/WS.png'/> occupying much of the right hemipelvis, with the right left psoas muscle <img src='img/arrows/WC.png'/> appearing stretched and distorted as a result of the retroperitoneal tumor. This was found to be a well-differentiated liposarcoma at resection.*
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**Secondary Neoplasm**
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*Axial CECT shows a large, homogeneous soft tissue mass <img src='img/arrows/WS.png'/> involving the right psoas and iliopsoas musculature. There were multiple enlarged lymph nodes elsewhere (not shown), and this was found to represent non-Hodgkin lymphoma.*
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**Secondary Neoplasm**
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*Coronal CECT shows an avidly enhancing mass <img src='img/arrows/WS.png'/> with central necrosis arising in the left iliopsoas muscle, representing a metastasis related to the patient's known renal cell carcinoma.*
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### Additional Images
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**Primary Neoplasm**
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*Axial CECT shows a huge retroperitoneal mass <img src='img/arrows/WO.png'/> abutting the psoas compartment. Some portions of the mass have well-differentiated fatty components, characteristic of liposarcoma.*
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**Primary Neoplasm**
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*Axial CECT shows a large, heterogeneous retroperitoneal mass <img src='img/arrows/WO.png'/>, which displaces the right kidney <img src='img/arrows/WC.png'/> anteriorly. Note medial displacement of the inferior vena cava (IVC) <img src='img/arrows/WS.png'/>. Malignant fibrous histiocytoma.*
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**Iliopsoas Hematoma**
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*Axial CECT shows hemorrhage into multiple sites, including iliopsoas, with active bleeding <img src='img/arrows/BC.png'/> and hematocrit sign <img src='img/arrows/BO.png'/>, indicating coagulopathic bleeding.*
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**Iliopsoas Hematoma**
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*Axial CECT shows a large abdominal aortic aneurysm <img src='img/arrows/WS.png'/> with extensive free hematoma <img src='img/arrows/WC.png'/> tracking laterally in the retroperitoneum, including immediately adjacent to the psoas muscle, compatible with aneurysm rupture.*
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**Iliopsoas Hematoma**
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*Axial CECT shows a large abdominal aortic aneurysm that has ruptured into the psoas compartment and retroperitoneum. Blood dissects along the left psoas and throughout the retroperitoneal planes.*
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**Iliopsoas Hematoma**
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*Axial CECT shows a large retroperitoneal mass arising from the iliopsoas compartment. A focus of active bleeding <img src='img/arrows/WS.png'/> and hematocrit levels <img src='img/arrows/WO.png'/> confirm coagulopathic hemorrhage.*
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**Retroperitoneal Fibrosis**
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*Axial CECT shows mantle of soft tissue encasing aorta, IVC, and ureter (with stent <img src='img/arrows/WC.png'/>).*
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**Secondary Infection/Abscess**
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*Axial CECT shows a small collection of gas and fluid <img src='img/arrows/WC.png'/> within the psoas muscle due to Crohn disease with a sinus tract from the terminal ileum.*
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**Primary Neoplasm**
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*Axial CECT shows a large, heterogeneous tumor <img src='img/arrows/WO.png'/>, which displaces the bladder <img src='img/arrows/WS.png'/> and external iliac artery <img src='img/arrows/WC.png'/>. This is a leiomyosarcoma arising from the psoas muscle.*
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**Secondary Neoplasm**
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*Axial CECT shows a soft tissue mass <img src='img/arrows/WO.png'/> that extends along the aorta, IVC, and right psoas. Biopsy showed ganglioneuroma arising from the sympathetic neural chain.*
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**Secondary Neoplasm**
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*Axial CECT shows retroperitoneal <img src='img/arrows/WS.png'/>, psoas compartment, and mesenteric <img src='img/arrows/WO.png'/> lymphadenopathy in non-Hodgkin lymphoma.*
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**Iliopsoas Hematoma**
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*Coronal NECT shows a large hematoma extending from the right psoas muscle <img src='img/arrows/WC.png'/> into the adjacent right iliopsoas muscle <img src='img/arrows/WO.png'/>.*
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**Primary Neoplasm**
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*Axial CECT shows a large, fat-containing mass <img src='img/arrows/WS.png'/> occupying much of the left abdomen with the left psoas muscle <img src='img/arrows/WC.png'/> appearing stretched and distorted as a result of the retroperitoneal tumor. This was found to be a well-differentiated liposarcoma at resection.*
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**Iliopsoas Hematoma**
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*Axial CECT shows a large hematoma <img src='img/arrows/WC.png'/> extending from the psoas muscle into the adjacent right abdomen. Note the presence of a tiny focus of active extravasation <img src='img/arrows/WS.png'/> within the hematoma.*
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**Secondary Infection/Abscess**
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*Axial T1 C+ FS MR at the level of the renal hilum shows predominantly right-sided enhancing paraspinal and epidural phlegmon <img src='img/arrows/WS.png'/>, associated with discitis and vertebral osteomyelitis. The presence of psoas infection should always prompt careful appraisal of the spine.*
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**Iliopsoas Hematoma**
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*Axial NECT shows enlargement of the right psoas muscle due to coagulopathic hemorrhage. Although the hematoma is partly isodense to the muscle, the presence of a hematocrit level <img src='img/arrows/WC.png'/> makes the bleed more apparent. Hematocrit levels suggest coagulopathy as the underlying cause of the bleed.*
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**Secondary Neoplasm**
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*Axial T1 C+ FS MR shows a heterogeneously enhancing mass <img src='img/arrows/WS.png'/> expanding the right psoas muscle, found to be a neurogenic tumor (ganglioneuroma) at resection.*
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**Primary Neoplasm**
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*Axial CECT shows a large mixed cystic and solid mass <img src='img/arrows/WC.png'/> involving the left psoas muscle <img src='img/arrows/WO.png'/>, representing a primary retroperitoneal leiomyosarcoma.*
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