To better understand the occurrence of splenic disease as a potential manifestation of babesiosis by retrospectively estimating the frequency of acute splenic injury on abdominal and pelvic CT in a cohort of patients with active babesia infection.

In a search of our single institution, suburban teaching community hospital database, 57 patients were found to have positive babesia infection between the years 2021–2023. 29 of these patients underwent abdominal and pelvic CT (22 with and 7 without intravenous contrast), and 3 underwent abdominal ultrasound without any CT. The imaging was reviewed for the presence or absence of splenic abnormalities, and for follow-up imaging. Parasitemia levels at the time of imaging were also reviewed; parasitemia levels < 4% are associated with mild to moderate disease, whereas parasitemia levels > 4% are associated with severe disease.

21/32 (66%) patients who underwent any type of abdominal imaging (ultrasound, MRI, and CT) had splenomegaly. Of the 22 patients who had IV contrast-enhanced CT scans, 6 were found to have splenic infarction (27%). One of these 22 patients had multiple rounded non-peripheral hypoenhancing foci on both CT and MRI which did not meet criteria for infarction, in association with splenomegaly, and which resolved after treatment. 0/6 patients in the splenic infarction group had parasitemia levels greater than 4%, while 4 of the 16 patients (4/16) without infarction had parasitemia levels of greater than 4%.

Our study showed that splenic disease in patients with babesiosis mostly took the form of splenomegaly, and in a substantial minority of patients as splenic infarction. There were no cases of splenic rupture and perisplenic hematoma in our case series, likely reflecting a limitation of the relatively small study size. Concordant with prior studies, we found no identifiable association between parasitemia levels and the presence of splenic infarction.