Torsion and Rupture of a Wandering Pelvic Accessory Spleen Associated with Essential Thrombocythemia: A Case Report

The pelvic accessory spleen is a rare anomaly, and its diagnosis is challenging. Essential thrombocythemia (ET) is a myeloproliferative neoplasm that can cause secondary myelofibrosis and splenomegaly. We report a case of torsion and rupture of a large wandering pelvic accessory spleen associated with ET.

A 62-year-old man with a history of ET presented with acute abdominal pain. Contrast-enhanced CT revealed a 9-cm pelvic mass with surrounding high-density fluid consistent with a hematoma, indicating its rupture. He was diagnosed with ET 8 years earlier, and disease control had gradually worsened. Splenomegaly and an 8-cm pelvic mass were detected 2 months before onset using CT and MRI. The signal-intensity pattern of the pelvic mass and the spleen on MRI was identical. Therefore, the mass was considered an accessory spleen rather than a tumor. Emergency laparotomy was performed. The pelvic mass was a wandering accessory spleen. There was no supportive tissue, except for a cord-like vascular pedicle. The mass was easily resected by ligating the pedicle. Splenomegaly was observed in the left lateral abdomen. In this case, both the native and pelvic accessory spleens were enlarged because of the progression of ET. The patient was discharged on POD 16.

Awareness of pelvic accessory spleen and its torsion is important in the differential diagnosis of pelvic masses and acute abdominal pain. When a large pelvic accessory spleen is identified, elective resection should be considered to prevent torsion or rupture. Although secondary enlargement of an accessory spleen after splenectomy has been reported, simultaneous enlargement of both the native and accessory spleens is exceptionally rare. To our knowledge, this is the first report describing the pathophysiology of simultaneous enlargement of the native and accessory spleens in association with a hematological disease.