Cloaca (osteomyelitis)
Updates to Article Attributes
A cloaca (pl. cloacae/cloacas or cloacas) can be foundis a gap in the cortex of a bone affected by chronic osteomyelitis.
The cloaca is an opening in an involucrum which that allows the drainage of purulent and necroticpus or other material outfrom the bone into the adjacent tissues.
Terminology
The use of the deadterm cloaca should be reserved for cortical breaches that are the result of material draining from them, which should be distinguished from pathological fractures that occur as the result of force exerted on bone weakened by infection 1. Non-specific terms like "cortical breakthrough" may be used when there is doubt as to the aetiology. If the tract extends to the skin surface, the portion extending beyond the involucrum to the skin surface is called a sinus tract 1.
Pathology
Pus and other necrotic debris fills the medullary cavity of infected bone which weakens and then perforates through the cortex of the bone 2. The resulting opening then matures as pus flows through it out of the bone. Once the infection has resolved, there may be callus formation if the cloaca begins to heal.
Radiographic features
Plain radiograph
A cloaca may appear as a lucent gap in the cortex of a bone with other signs of osteomyelitis, such as periosteal thickening or involucrum formation.
CT
CT will more clearly identify a cloaca as a gap in the cortex, and can also identify associated features of chronic osteomyelitis such as the presence of a sequestrum. CT is more sensitive than MRI for the detection of cloacas 3.
MRI
On MRI, a cloaca will appear as a gap in the low signal cortex of bone, which may be easier to identify on T2 weighted or fluid-sensitive sequences by the high signal of pus or debris within the cloaca 1.
Treatment and prognosis
The resolution of a cloaca depends on the successful treatment of the causative infection. If this is successful, the cloaca may heal through callus formation, though some lucency may remain visible 1.
History and etymology
"Cloaca" derives fromis the Latin word for "sewer" or "drain".
Differential diagnosis
-
pathological fracture due to osteomyelitis
- presence of a fracture line through weakened bone, rather than a gap through which pus and debris is discharging
-<p>A <strong>cloaca</strong> (pl. cloacae/cloacas) can be found in chronic <a href="/articles/osteomyelitis">osteomyelitis</a>.</p><p>The cloaca is an opening in an <a href="/articles/involucrum">involucrum</a> which allows drainage of purulent and necrotic material out of the dead bone. If the tract extends to the skin surface, the portion extending beyond the involucrum to the skin surface is called a <a href="/articles/sinus-tract">sinus tract</a> <sup>1</sup>.</p><h4>History and etymology</h4><p>"Cloaca" derives from the Latin word for "sewer" or "drain".</p>- +<p>A <strong>cloaca</strong> (pl. cloacae or cloacas) is a gap in the cortex of a bone affected by <a title="Chronic osteomyelitis" href="/articles/chronic-osteomyelitis-1">chronic osteomyelitis</a> that allows the drainage of pus or other material from the bone into the adjacent tissues.</p><h4>Terminology</h4><p>The use of the term cloaca should be reserved for cortical breaches that are the result of material draining from them, which should be distinguished from <a title="Pathological fractures" href="/articles/pathological-fracture">pathological fractures</a> that occur as the result of force exerted on bone weakened by infection <sup>1</sup>. Non-specific terms like "cortical breakthrough" may be used when there is doubt as to the aetiology. If the tract extends to the skin surface, the portion extending beyond the involucrum to the skin surface is called a <a href="/articles/sinus-tract">sinus tract</a> <sup>1</sup>.</p><h4>Pathology</h4><p>Pus and other necrotic debris fills the medullary cavity of infected bone which weakens and then perforates through the cortex of the bone <sup>2</sup>. The resulting opening then matures as pus flows through it out of the bone. Once the infection has resolved, there may be callus formation if the cloaca begins to heal.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>A cloaca may appear as a lucent gap in the cortex of a bone with other signs of osteomyelitis, such as periosteal thickening or <a title="Involucrum" href="/articles/involucrum">involucrum</a> formation.</p><h5>CT</h5><p>CT will more clearly identify a cloaca as a gap in the cortex, and can also identify associated features of <a title="Chronic osteomyelitis" href="/articles/chronic-osteomyelitis-1">chronic osteomyelitis</a> such as the presence of a <a title="Bony sequestrum" href="/articles/bony-sequestrum">sequestrum</a>. CT is more sensitive than MRI for the detection of cloacas <sup>3</sup>.</p><h5>MRI</h5><p>On MRI, a cloaca will appear as a gap in the low signal cortex of bone, which may be easier to identify on T2 weighted or fluid-sensitive sequences by the high signal of pus or debris within the cloaca <sup>1</sup>.</p><h4>Treatment and prognosis</h4><p>The resolution of a cloaca depends on the successful treatment of the causative infection. If this is successful, the cloaca may heal through callus formation, though some lucency may remain visible <sup>1</sup>.</p><h4>History and etymology</h4><p>"Cloaca" is the Latin word for "sewer".</p><h4>Differential diagnosis</h4><ul><li>
- +<a title="Pathological fracture" href="/articles/pathological-fracture">pathological fracture</a> due to <a title="Osteomyelitis" href="/articles/osteomyelitis">osteomyelitis</a><ul><li>presence of a fracture line through weakened bone, rather than a gap through which pus and debris is discharging</li></ul>
- +</li></ul>
References changed:
- 1. Alaia E, Chhabra A, Simpfendorfer C et al. MRI Nomenclature for Musculoskeletal Infection. Skeletal Radiol. 2021;50(12):2319-47. <a href="https://doi.org/10.1007/s00256-021-03807-7">doi:10.1007/s00256-021-03807-7</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/34145466">Pubmed</a>
- 2. Lee Y, Sadigh S, Mankad K, Kapse N, Rajeswaran G. The Imaging of Osteomyelitis. Quant Imaging Med Surg. 2016;6(2):184-98. <a href="https://doi.org/10.21037/qims.2016.04.01">doi:10.21037/qims.2016.04.01</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/27190771">Pubmed</a>
- 3. Pineda C, Espinosa R, Pena A. Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy. Semin Plast Surg. 2009;23(2):80-9. <a href="https://doi.org/10.1055/s-0029-1214160">doi:10.1055/s-0029-1214160</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/20567730">Pubmed</a>
- 1. Pineda C, Espinosa R, Pena A. Radiographic imaging in osteomyelitis: the role of plain radiography, computed tomography, ultrasonography, magnetic resonance imaging, and scintigraphy. Semin Plast Surg. 2009;23 (02): 80-9. <a href="http://dx.doi.org/10.1055/s-0029-1214160">doi:10.1055/s-0029-1214160</a> - <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2884903">Free text at pubmed</a> - <a href="http://www.ncbi.nlm.nih.gov/pubmed/20567730">Pubmed citation</a><span class="ref_v3"></span>
- 2. Gold RH, Hawkins RA, Katz RD. Bacterial osteomyelitis: findings on plain radiography, CT, MR, and scintigraphy. AJR Am J Roentgenol. 1991;157 (2): 365-70. <a href="http://dx.doi.org/10.2214/ajr.157.2.1853823">doi:10.2214/ajr.157.2.1853823</a> - <a href="http://www.ncbi.nlm.nih.gov/pubmed/1853823">Pubmed citation</a><span class="auto"></span>
Image 1 MRI (STIR) ( update )
Image 3 Annotated image ( create )
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