Splenunculus
Updates to Article Attributes
Splenunculi (also known as supernumerary or accessory spleens or splenules) are small nodules of spleen that are detached from the rest of the organ. They are benign and asymptomatic, their importance mainly related to the need to distinguish them from more sinister pathology.
Epidemiology
They are common, seen in up to 16% of CTs of the abdomen and up to 30% of autopsies 2.
Pathology
Accessory spleens are congenital nodules, composed of normal splenic tissue. The spleen forms from multiple smaller components during embryogenesis, and failure of this fusion can lead to one or more nodules remaining separate 2. Each component is extraperitoneal, as are splenunculi. They should not be confused from splenosis (see below) which is acquired and intraperitoneal.
Radiographic features
Splenunculi are typically a few centimetres in diameter when identified, well circumscribed rounded or ovoid nodules. Although most are located near the spleen, they have been identified elsewhere in the abdominal cavity including 2,3:
- near the spleen (most common)
- gastrosplenic ligament
- splenorenal ligament
- pancreatic tail
- greater omentum
- small bowel mesentery
- stomach or bowel wall
- scrotum
CT
They have density and enhancing characteristics similar to the rest of the spleen. Small (<1cm;1 cm) may appear hypodense compared with the spleen, most likely as an artefact of partial voluming 2.
The converse of that is that if a mass is seen at the splenic hilum, which does not enhance in the same fashion as the adjacent spleen, then alternative diagnoses should be entertained.
Nuclear medicine
Tc99m sulphur colloid scan
In rare instances the diagnosis can be confirmed with Tc99m sulphur colloid scan which will demonstrate increased uptake as long as the splenunculus is at least 2 cm in diameter.
Tc99m heat-denatured red blood cell scan
Splenic tissue (spleen and accessory spleens) will demonstrate intense physiological uptake 5.
Differential diagnosis
General imaging differential considerations include:
- peritoneal metastases
- lymph node enlargement
- tail of pancreas tumour or metastases
- renal tumour recurrence post nephrectomy
- adrenal mass
- pancreatic neuroendocrine tumours 5
Other conditions with abnormal location or morphology of splenic tissue include:
- lobulations or clefts: represent incomplete but partial fusion and are very common 2
- polysplenia: rarely multiple splenules are seen without a 'parent' spleen; this is referred to as polysplenia and is seen associated with situs abnormalities.
- splenosis: splenic tissue deposits following abdominal trauma or surgery (e.g. splenectomy), and do not have splenic arterial supply
- wandering spleen: spleen located in an unusual position within the abdominal cavity
-<p><strong>Splenunculi</strong> (also known as <strong>supernumerary</strong> or <strong>accessory spleens</strong> or <strong>splenules</strong>) are small nodules of <a href="/articles/spleen-1">spleen</a> that are detached from the rest of the organ. They are benign and asymptomatic, their importance mainly related to the need to distinguish them from more sinister pathology. </p><h4>Epidemiology</h4><p>They are common, seen in up to 16% of CTs of the abdomen and up to 30% of autopsies <sup>2</sup>. </p><h4>Pathology</h4><p>Accessory spleens are congenital nodules, composed of normal splenic tissue. The <a href="/articles/spleen-1">spleen</a> forms from multiple smaller components during embryogenesis, and failure of this fusion can lead to one or more nodules remaining separate <sup>2</sup>. Each component is extraperitoneal, as are splenunculi. They should not be confused from <a href="/articles/splenosis">splenosis</a> (see below) which is acquired and intraperitoneal. </p><h4>Radiographic features</h4><p>Splenunculi are typically a few centimetres in diameter when identified, well circumscribed rounded or ovoid nodules. Although most are located near the spleen, they have been identified elsewhere in the abdominal cavity including <sup>2,3</sup>:</p><ul>- +<p><strong>Splenunculi</strong> (also known as <strong>supernumerary</strong> or <strong>accessory spleens</strong> or <strong>splenules</strong>) are small nodules of <a href="/articles/spleen-1">spleen</a> that are detached from the rest of the organ. They are benign and asymptomatic, their importance mainly related to the need to distinguish them from more sinister pathology. </p><h4>Epidemiology</h4><p>They are common, seen in up to 16% of CTs of the abdomen and up to 30% of autopsies <sup>2</sup>. </p><h4>Pathology</h4><p>Accessory spleens are congenital nodules, composed of normal splenic tissue. The <a href="/articles/spleen-1">spleen</a> forms from multiple smaller components during embryogenesis, and failure of this fusion can lead to one or more nodules remaining separate <sup>2</sup>. Each component is extraperitoneal, as are splenunculi. They should not be confused from <a href="/articles/splenosis">splenosis</a> (see below) which is acquired and intraperitoneal.</p><h4>Radiographic features</h4><p>Splenunculi are typically a few centimetres in diameter when identified, well circumscribed rounded or ovoid nodules. Although most are located near the spleen, they have been identified elsewhere in the abdominal cavity including <sup>2,3</sup>:</p><ul>
-</ul><h5>CT</h5><p>They have density and enhancing characteristics similar to the rest of the spleen. Small (<1cm) may appear hypodense compared with the spleen, most likely as an artefact of partial voluming <sup>2</sup>.</p><p>The converse of that is that if a mass is seen at the splenic hilum, which does not enhance in the same fashion as the adjacent spleen, then alternative diagnoses should be entertained.</p><h5>Nuclear medicine</h5><h6>Tc99m sulphur colloid scan</h6><p>In rare instances the diagnosis can be confirmed with Tc99m sulphur colloid scan which will demonstrate increased uptake as long as the splenunculus is at least 2 cm in diameter.</p><h6>Tc99m heat-denatured red blood cell scan</h6><p>Splenic tissue (spleen and accessory spleens) will demonstrate intense physiological uptake <sup>5</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>- +</ul><h5>CT</h5><p>They have density and enhancing characteristics similar to the rest of the spleen. Small (<1 cm) may appear hypodense compared with the spleen, most likely as an artefact of partial voluming <sup>2</sup>.</p><p>The converse of that is that if a mass is seen at the splenic hilum, which does not enhance in the same fashion as the adjacent spleen, then alternative diagnoses should be entertained.</p><h5>Nuclear medicine</h5><h6>Tc99m sulphur colloid scan</h6><p>In rare instances the diagnosis can be confirmed with Tc99m sulphur colloid scan which will demonstrate increased uptake as long as the splenunculus is at least 2 cm in diameter.</p><h6>Tc99m heat-denatured red blood cell scan</h6><p>Splenic tissue (spleen and accessory spleens) will demonstrate intense physiological uptake <sup>5</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>
-<li>renal tumour recurrence post nephrectomy </li>- +<li>renal tumour recurrence post nephrectomy</li>
-<a title="Pancreatic neuroendocrine tumours" href="/articles/endocrine-tumours-of-the-pancreas">pancreatic neuroendocrine tumours</a> <sup>5</sup>- +<a href="/articles/endocrine-tumours-of-the-pancreas">pancreatic neuroendocrine tumours</a> <sup>5</sup>
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