A 62-year-old woman underwent laparoscopic radical left nephroureterectomy for a high-grade urothelial carcinoma in the lower renal pole. The 4.6-cm lesion had infiltrated through the renal parenchyma and into peripelvic fat. Surgical margins and 23 lymph nodes were negative for malignancy. CT prior to the intervention revealed a 1-cm splenule (Figure 1, arrow) along the lateral border of the abdominal cavity positioned anterior to the inferior margin of the spleen.
CT repeated a month later revealed a 1-cm nodule left of the nephrectomy bed (Figure 2). It was interpreted as the same splenule seen earlier, though its position had changed substantially (arrow). Because of the tumor's aggressive nature, recurrent carcinoma had to be ruled out.
After injection of 4 mCi of technetium-99m–labeled denatured red blood cells, SPECT imaging revealed intense physiologic activity in the spleen and subtle separate activity along the medial margin of the spleen. SPECT/CT imaging localized the activity to the nodule in question (Figure 3), confirming the diagnosis of a splenule.
Splenules are incidental findings of little clinical significance in most patients, but they must be properly identified in situations such as torsion and infarction and to differentiate them from metastatic lesions. Proper identification guides patient treatment and may also prevent unnecessary surgery.
Splenules result from the failure of the splenic anlage to fuse during the fifth week of fetal life. Accessory splenic tissue is relatively common, having been identified in 16% of patients undergoing contrast abdominal CT, and is seen in 10% to 30% of patients at autopsy.
Splenules typically are rounded, well-marginated soft tissue structures measuring less than 2 cm. They can be ovoid or, very rarely, triangular. They are most commonly located in splenic hilum near the tail of the pancreas but may also be seen along the splenic vessels, gastrosplenic or splenorenal ligaments, or the pancreatic tail.
Differentials in diagnoses can use clinical history and the mass's radiological appearance. Splenosis is a heterotopic autotransplantation of splenic tissue, usually following a traumatic rupture of the splenic capsule. Nodules related to splenosis may be numerous, are usually sessile, and lack the elastic muscular capsule of a splenule.
Splenules are usually very few in number, pedunculated, and are contained within a capsule.
Splenogonadal syndrome is a rare malformation resulting from the fusion of splenic tissue with the nearby developing gonad during weeks five to eight of gestation. More than 98% of reported cases have involved the left gonad, mainly in male fetuses. A characteristic location and shape differentiates splenogonadal syndrome from splenules. Splenogonadal syndrome is associated with cryptorchidism and orofacial or limb developmental abnormalities.
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This case report was condensed from “SPECT/CT imaging of a retroperitoneal nodule in a patient with history of infiltrating renal urothelial carcinoma,” published in the Journal of Radiology Case Reports (Citation: Radiology Case 2009;3:18-21).
Contributing author Duane Schonlau is a medical student at Ohio State University. Dr. David Barker is an assistant professor and Dr. Nathan Hall is an assistant professor and section chief of nuclear medicine in the radiology department at OSU.