S3917 Misdiagnosed Mass: A Case of Trauma and Hidden Parasites

Introduction: Parasitic infections leading to intra-abdominal abscesses are uncommon in developed countries and can be diagnostically challenging. We report a rare case of a parasitic abscess in the right upper quadrant of a patient with situs inversus and intestinal malrotation, highlighting the importance of a broad differential diagnosis in patients. Case Description/Methods: A 56-year-old man with colonic diverticulosis and situs inversus presented with abdominal pain following a physical altercation. His laboratory findings were only remarkable for a white blood cell count of 13.14. A computed tomography (CT) abdomen revealed a well-contained collection with minimal fat stranding in the right upper quadrant, adjacent to the gastric fundus and large bowel. These findings were initially interpreted as a possible result of a contained perforated gastric ulcer or diverticulitis. Elevated tumor markers also raised a suspicion of malignancy. A follow-up CT scan to evaluate the collection better revealed a 33 × 35 × 62 mm soft tissue density in the right upper quadrant, with a mildly enhancing rim, bordered by the spleen, stomach, colon, and diaphragm. A ruptured splenule due to recent trauma was considered in the differential diagnosis. An magnetic resonance imaging of the abdomen showed a walled-off abscess, likely originating from the adjacent colon. Interventional radiology drainage was offered, but the patient declined at the time. Given the unclear etiology, a workup for infectious diseases was pursued. Serologies were positive for Entamoeba histolytica and Echinococcus IgG. Infectious diseases recommend against draining the cyst to prevent an anaphylactic reaction. The patient was discharged with outpatient follow-up arranged with parasitology and a repeat CT scan of the abdomen to evaluate the size of the mass, which showed a decrease in mass size. Discussion: This case highlights the importance of a broad range of differential diagnoses for patients with non-specific symptoms and unexplained collections. Echinococcosis (hydatid disease) typically affects the liver and lungs, but can also involve the spleen, heart, kidney, or brain. Amebic abscesses are treated with metronidazole, while echinococcal cysts are not managed with percutaneous drainage due to the risk of dissemination. Antiparasitic therapy with albendazole is necessary. Preoperative treatment with benzimidazoles is recommended to lower intracystic pressure and reduce the risk of rupture during cyst removal.