Presentations

Abstract

Introduction:

An Indium-111 tagged white blood cell scan is an important adjunctive test in the evaluation of fever/sepsis of unknown origin. Indium scans-111 scans are highly sensitive and specific in the evaluation and localization of abscesses/infection. An indium-111 scan is a two-part nuclear medicine examination in which a patient's blood is withdrawn and the white blood cells (WBC) are isolated and tagged with radioactive indium 111 before being injected back into the patient. 24 hours following re-injection, allowing for the tagged WBC to migrate the area of infection, planar spot images to include full body and orthogonal spot projections are obtained. The second portion of the exam involves injection of radioactive sulfur colloid, to rule out a marrow replacing process which may also show increased WBC uptake. A positive indium WBC scan would show increased radiotracer accumulation on Indium-tagged WBC images with absence of radiotracer uptake on the sulfur colloid images.

Case Information:

Patient is a 38-year-old female with past medical history of chorioamnionitis presenting for LLQ pain and persistent fevers and chills. Several days prior, the patient was treated for presumed pyelonephritis with Ciprofloxacin. Initial laboratory evaluation revealed leukocytosis, negative urine pregnancy test and likely contaminated urine analysis. Initial imaging evaluation included CT abdomen and pelvis revealed a large, septated cystic mass within the midline pelvis without secondary findings suggestive of infection. Initial imaging suggested ovarian origin, with malignancy not ruled out. Findings were corroborated by Pelvic US. MRI was subsequently performed, suggesting likely ovarian carcinoma with peritoneal seeding. There was ongoing concern over the exact etiology of patient's leukocytosis, whether it was related to the ovarian lesion versus persistent pyelonephritis versus other occult infections. Indium tagged white blood cell was subsequently utilized for definitive evaluation. Indium-WBC scan displayed large, rounded region of discordant white cell uptake corresponding to the mass described in prior imaging. Patient subsequently underwent laparoscopic excision with Gynecological Oncology. Intraoperatively, a large cystic mass replacing the left ovary with dense adhesions to the adjacent intro-abdominal structures and surrounding inflammation. Pathology revealed that the large lesion was consistent with benign serous cystadenofibroma with hemorrhage and necrosis of the ovary compatible with torsion. Patient's leukocytosis was seen to be down trending at time of subsequent discharge.

Discussion:

The radiologic literature supports the overall accuracy of this scan in patient's with malignancy/known tumors, however, there are sporadic reports of false positive examinations secondary to tumor uptake mimicking abscess. In the case described above, initial imaging results were highly suggestive of ovarian malignancy, with pathological results revealing a relatively rare benign tumor, known to mimic malignancy on MRI and Ultrasound. Literature suggests that this tumor type accounts for approximately 1.7% of all benign ovarian tumors. A possible imaging characteristic which may differentiate from malignancy are dense fibrous stromal proliferation which may be seen on MRI. Focusing on the results of the indium white blood cell scan, there is obviously little literature regarding the expected appearance of a cystadenofibroma. There are several hypotheses as to why tumors may show increased/discordant indium-WBC uptake including increased blood pool from hypervascularity, intrinsic immunological activity, or a sequela of our innate immunological response to this perceived "foreign body".

Conclusion:

In conclusion, this is a case of both uncommon pathology and imaging findings, specifically the unusual Indium-WBC uptake by tumor. It has been suggested that the degree of uptake may be considered to differentiate between tumor and abscess, however other studies have shown little difference. Additionally, this case highlights some of the limitations and pitfalls of commonly utilized imaging modalities in the evaluation of complex ovarian pathology. Fortunately, the Indium- WBC scan was able to effectively rule out other sources of infection, focusing patient's care on this ovarian mass.