Splenosis is most commonly attributable to penetrating or blunt-force trauma to the thoracoabdominal region. As imaging technology has improved, splenosis has been noted in up to two-thirds of patients after splenectomy for trauma.
5 Furthermore, after splenic rupture, splenosis is relatively common, with a rate of up to 65% according to a case study by Malik et al.
6 The majority of documented cases of splenosis after trauma have been noted in the intrabdominal space, most commonly in the peritoneum, omentum, and mesentery. For the 18% of patients who have splenosis localized to the thorax, the most common ectopic site is the pleural space of the left lung.
6,7
In cases of splenosis, splenic tissue can be transferred into the thoracic cavity by either hematogenous spread or by passing through a tear in the diaphragm.
7 The etiologic process of splenosis includes splenic trauma or splenectomy
8; splenosis occurs less commonly as a result of congenital malformations from incomplete fusion of the dorsal mesogastrium.
3
Imaging of thoracic splenosis can be made noninvasively by means of scintigraphy with technetium Tc 99m heat-damaged erythrocytes.
6 Noninvasive heat-damaged scintigraphy has the highest specificity of all nuclear imaging diagnostic modalities, and some observers regard it as the standard for splenosis.
9 If scintigraphy is unavailable or results are inconclusive, further diagnosis can be achieved with fine-needle aspiration. Unfortunately, the location of a lesion often precludes fine-needle aspiration; if a lesion is accessible, its pathologic presentation can be misleading, with lymphocytic infiltrate misdiagnosed as lymphoma.
6 Video-assisted thoracoscopic surgery is an option that can serve both diagnostic and therapeutic purposes. Pathologic analysis can rule out such causes as pulmonary metastases, non-Hodgkin lymphoma, or mesothelioma.
If the diagnosis can be confirmed preoperatively, surgery is not indicated unless the patient is symptomatic.
9 It is usually not necessary to remove the pulmonary nodules because the splenic tissue is slow growing, noninvasive, and nonmalignant. The splenic tissue that is found in the lungs resembles tissue that is found in the spleen—with areas of red pulp, white pulp, and lymphoid follicles—and is usually surrounded by a capsule and fibrosis resulting from thoracoabdominal trauma. As was shown in the present case, most cases of thoracic splenosis are found incidentally by means of CT or magnetic resonance imaging because the majority of patients are asymptomatic. To our knowledge to date, there have been 4 reported symptomatic cases of thoracic splenosis; 2 patients reported having hemoptysis, 1 patient complained of a productive cough, and 1 patient reported having pleuritic chest pain.
6
The most serious complication in patients who have undergone splenectomy are increased infection rates and sepsis with encapsulated organisms such as
Neisseria meningitidis,
Streptococcus pneumoniae, and
Haemophilus influenzae. Some physicians have postulated that maintaining even a small amount of splenic tissue after splenectomy may offer immunologic advantages.
10 In 2006, Backhus and Bremner
10 suggested normal immune function following splenectomy due to splenosis tissue leading to a lack of Howell-Jolly bodies, “pitted” erythrocytes, and siderocytes in the peripheral blood smear.
11 However, since 2006 many animal studies and human anecdotal data have shown that splenic nodules, when separated from the spleen itself, do not regain full immunologic capability.
12 Patients with sepsis and splenosis have an estimated 58 times increased mortality or higher as compared with individuals with normal spleen function.
12 Such differences may be attributed to splenic implants resulting from cellular growth rather than redistributed portions of disrupted spleen. Furthermore, ectopic splenic tissue has a decreased amount of white pulp.
12 The functionality of ectopic splenic tissue continues to be strongly debated.
Postoperative OMT as described by O-Yurvati et al
4 can be performed safely in patients with splenosis, and, with OMT, normal recovery may be expected.