Further discussion with referrer this patient had an MVA as a child, and in this setting the peritoneal soft tissue nodules are likely focal deposits of splenic tissue in keeping with splenosis.
Abdominal splenosis is seen after abdominal trauma or surgery (e.g. splenectomy). It results from seeding of the peritoneal cavity with splenic tissue. Splenic nodules can sometimes be seen within the thoracic cavity if there is an associated diaphragmatic rupture.