Gluteal injection site granuloma
Updates to Article Attributes
Gluteal injection site granulomas are a very common finding on CT and plain abdominal xraysradiographs. They occur as a result of subcutaneous (intralipomatous(i.e. intra-lipomatous) rather than intramuscular injection of drugs, which cause localised fat necrosis, scar formation and dystrophic calcification.
Once familiar with the entity they rarely pose any diagnostic confusion, although they have been reported to be metabolically active on FDG-PET.
Pathology
Fat necrosis, which can liquefy. This cavity is surrounded by fibrous tissue and reactive inflammatory cells (lymphocytes, foamy histiocytes, and giant cells). Capillary growth can be prominent. Dystrophic calcification can eventually occur.
Radiographic features
CT
Usually seen as well-defined small nodules that often contain calcification.
MRI
Typical signal characterisitcs include
- T1 - hypointense
-
T2
-- appearance depends on the temporal evolution of the granuloma
. - may be T2 hyperintense if the reaction is inflammatory
- may
beT2be T2 hypointense if the reaction is fibrous
- appearance depends on the temporal evolution of the granuloma
Differential diagnosis
The differential depends on whether or not the granuloma is calcified.
Non-calcified
- soft tissue sarcoma
- subcutanous metastases
Calcified
- infection
:- parasitic infestation - neoplasm
:- primary bone-forming tumour- osteosarcoma
- tumour necrosis
- autoimmune
- trauma
-<p><strong>Gluteal injection site granulomas</strong> are a very common finding on CT and plain abdominal xrays. They occur as a result of subcutaneous (intralipomatous) rather than intramuscular injection of drugs, which cause localised <a href="/articles/fat-necrosis-1">fat necrosis</a>, scar formation and <a href="/articles/dystrophic-calcification">dystrophic calcification</a>.</p><p>Once familiar with the entity they rarely pose any diagnostic confusion, although they have been reported to be metabolically active on <a href="/articles/fdg-pet">FDG-PET</a>.</p><h4>Pathology</h4><p>Fat necrosis, which can liquefy. This cavity is surrounded by fibrous tissue and reactive inflammatory cells (lymphocytes, foamy histiocytes, and giant cells). Capillary growth can be prominent. Dystrophic calcification can eventually occur.</p><h4>Radiographic features</h4><h5>CT</h5><p>Usually seen as well-defined small nodules that often contain calcification.</p><h5>MRI</h5><p>Typical signal characterisitcs include</p><ul>- +<p><strong>Gluteal injection site granulomas</strong> are a very common finding on CT and plain abdominal radiographs. They occur as a result of subcutaneous (i.e. intra-lipomatous) rather than intramuscular injection of drugs, which cause localised <a href="/articles/fat-necrosis-1">fat necrosis</a>, scar formation and <a href="/articles/dystrophic-calcification">dystrophic calcification</a>.</p><p>Once familiar with the entity they rarely pose any diagnostic confusion, although they have been reported to be metabolically active on <a href="/articles/fdg-pet">FDG-PET</a>.</p><h4>Pathology</h4><p><a title="Fat necrosis" href="/articles/fat-necrosis-1">Fat necrosis</a>, which can liquefy. This cavity is surrounded by fibrous tissue and reactive inflammatory cells (lymphocytes, foamy histiocytes, and giant cells). Capillary growth can be prominent. <a title="Dystrophic calcification" href="/articles/dystrophic-soft-tissue-calcification">Dystrophic calcification</a> can eventually occur.</p><h4>Radiographic features</h4><h5>CT</h5><p>Usually seen as well-defined small nodules that often contain calcification.</p><h5>MRI</h5><p>Typical signal characterisitcs include</p><ul>
-<strong>T2 </strong>-<ul>-<li>appearance depends on the temporal evolution of the granuloma.</li>- +<strong>T2</strong><ul>
- +<li>appearance depends on the temporal evolution of the granuloma</li>
-<li>may beT2 hypointense if the reaction is fibrous</li>- +<li>may be T2 hypointense if the reaction is fibrous</li>
-<li>infection : parasitic infestation<ul>- +<li>infection - parasitic infestation<ul>
-<li>neoplasm : primary bone-forming tumour<ul>- +<li>neoplasm - primary bone-forming tumour<ul>
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