Teaching Case

An asymptomatic 45-year-old man with prior history of post-traumatic splenectomy many years previously in the childhood, performed an ultrasonography that showed the presence of abdominal nodules/masses. Besides the referred splenectomy, his past medical history was not significant, without family history of clinical relevance. The physical examination was unremarkable and routine blood tests were normal.

An US examination showed some well-defined round and oval intraperitoneal nodules scattered though the abdominal cavity that had a homogeneously hypoechoic echotexture.
A subsequent abdominopelvic CT examination showed multiple nodules in several places in the abdomen, isodense to the liver at unenhanced CT images that had attenuation identical to that of the normal spleen in all phases of intravenous contrast material enhancement.
Scintigraphy and SPECT scans with labelled heat-damaged erythrocytes showed multiple foci of increased uptake in the abdomen, consistent with abdominal splenosis.

Splenosis is a benign and rare acquired condition in which auto-transplantation of focal ectopic splenic tissue implants occurs following splenectomy, particularly in previous traumatic cases of rupture.
Splenosis is most frequently seen in abdominal and/or pelvic cavities, but it can be observed in other less typical locations, like thorax, cerebrum or subcutaneous tissues. The number of implants is usually correlated to the extent of the injury, in cases of trauma.
The nodules of splenic tissue are usually incidentally found in ultrasonography or computed tomography (CT), because splenosis is asymptomatic in the majority of cases and usually has no clinical consequences. However, in rare cases, splenosis can result in bowel obstruction and large lesions may undergo torsion and infarction or rupture. The median time interval between the traumatic episode and the emergence of abdominal/pelvic splenosis is approximately 10 years [1].
The most important issue about this disease is that it represents a diagnostic challenge because it can be misdiagnosis as neoplastic disease, especially when the presentation is multiple nodules scattered through the abdomen, easily mimicking peritoneal metastases (peritoneal carcinomatosis). The diagnosis can be even more difficult if the patient has a past medical history of neoplastic disease [2, 3, 4].
An abdominal CT can lead to the correct diagnosis, based on the fact that these lesions exhibit equivalent tomodensitometric characteristics as normal splenic tissue. Neither ultrasound nor CT reveals that lesions are definitely of splenic origin, but the similar attenuation of the expected appearance of normal spleen on unenhanced and contrast-enhanced CT suggests the final diagnosis [5].
Typically, the heterotopic splenic tissue is metabolically active and damaged erythrocytes are sequestered in the reticuloendothelial system of ectopic splenic tissue. For this reason, radioisotopic scintigraphy with labelled heat-damaged erythrocytes is the technique with the greatest specificity in demonstrating the presence of splenosis because ectopic splenic tissue shows uptake of radionuclide activity. Tc-99m single-photon emission computed tomography (SPECT) can also confirm the diagnosis, with the advantage of having more detailed anatomic information [6, 7].
In the presence of nodules and/or masses in the abdominal or pelvic cavity in patients with past history of splenic trauma and/or splenectomy, splenosis always needs to be excluded. Radiologists have to suggest or confirm the diagnosis in the appropriate clinical setting, helping to avoid unnecessary invasive procedures.