Thoracic, abdominal and pelvic CT and US imaging features in children with hemophagocytic lymphohistocytosis

Abstract

Background : Hemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS) is a life threatening condition characterized by uncontrolled autoimmune hyperinflammation based on various inherited or acquired immune deficiencies. Main symptoms and signs include fever, neurological symptoms, hepatosplenomegaly and cytopenia. This study aims to describe the chest, abdomen and pelvis CT findings as well as the US findings of the abdomen and pelvis, in a large series of patients diagnosed with HLH in a single institution. Methods: This is a retrospective case review of the US and CT imaging features of the chest, abdomen and pelvis in 39 bone marrow biopsy-proven patients diagnosed with HLH/MAS that has been approved by our institutional review board (IRB). The study was done at one institution, The Hospital for Sick Children, Toronto, Canada. The imaging data of the 39 patients were retrieved using the PAC system. Two patients lacked available studies in the hospital records. The chest CT (26 patients), abdominal and pelvic CT (25 patients) and abdominal and pelvic US (34 patients) examinations in 37 children at presentation were retrospectively reviewed blindly by 2 pediatric radiologists. Discrepancy was resolved by consensus. Statistical analysis utilizing logistic regression and odds ratio have been used to estimate the patient's outcome. Results: The major CT findings in the chest included pleural effusion in 16/26 patients (61.5%), lymphadenopathy in 15/26 patients (57.7%) and air space disease in 12/26 patients (46.2%). In the abdomen and pelvis, the major CT findings were as follows: ascites in 17/25 patients (68%), hepatomegaly in 16/25 patients (64%), splenomegaly in 14/25 patients (56%), abdominal wall edema and periportal edema in 13/25 patients (52%). Regarding ultrasound, hepatomegaly and splenomegaly were observed in 23/34 patients (67.6%), ascites and echogenic kidneys were seen in 19/34 patients (55.9%), and gall bladder wall thickening was found in 18/34 patients (52.9%). A logistic regression model and odds ratio was used. We found that abdominal wall edema detected on CT has 8 times the risk of having a severe clinical outcome. Conclusion: Large series of children with HLH/MAS demonstrated nonspecific imaging findings; however, in the appropriate clinical setting in acutely ill child, these findings should suggest the diagnosis of HLH/MAS to the radiologist. Early diagnosis and early management of this disorder can be life-saving.