Ultrasonographic abdominal findings in patients with severe yellow fever and liver evaluation with elastosonography in convalescence

Abstract

Purpose To evaluate the abdominal ultrasound (US) findings in patients in the severe acute phase of YF, correlating with clinical and laboratory data, and to estimate the degree of hepatic fibrosis using shear-wave elastography with ultrasonography. Methods This is a combined retrospective description and follow-up study. First, bedside US examinations in all patients admitted with YF between January and April 2018. B-mode and Doppler were done, within 48h of patient admission. Liver and kidney echogenicity were compared to the spleen. All images were revised by a second radiologist. In a second stage, patients were submitted to a new US, 6 months after onset of symptoms, with the elastography technique (SWE). Exclusion criteria: patients with US features of previous chronic hepatic disease and/or portal hypertension. Results 46 patients were evaluated with bedside US. Six (13.0%) were female; median age was 44.8 (34.8-62.3). 26 (56.5%) patients died within 30 days of admission. The abdominal US findings were: gallbladder wall thickening (80.4%), increased renal cortex echogenicity (71.7%), increased liver parenchyma echogenicity (65.2%), perirrenal fluid (52.2%) and intraperitoneal free fluid (30.4%). Increased renal echogenicity was associated with higher median serum creatinine levels (5.1 (2.7-6.5) mg/dL versus 3.1 (1.0-2.4) mg/dL; p = 0.02) and higher rates of death within 30 days of admission (66.7% versus 30.8%; p = 0.03). There were no correlations between other clinical or laboratory data and US findings. Seventeen patients were evaluated with SWE 6 months after of onset of symptoms. Mean shear wave velocity was 1,4 ( ± 0,2) m/s; mean elasticity was 5,3 ( ± 1,7) kPa. Sixteen (94%) patients were classified in the F0/F1 Metavir category. One patient had mild increased stiffness and was classified as F2 Metavir. Conclusion This is the first study to describe the abdominal imaging findings in patients with YF using US. We found consistent findings related to direct effects of viral infection (pattern of diffuse liver fatty deposition and nephropathy) and secondary to inflammatory changes and/or hemorrhagic diathesis (gallbladder wall thickening and fluid collections). Increased renal echogenicity was associated with higher serum creatinine levels and death rates and thus should be considered a prognostic variable. After 6 months, 01 patient showed mild increased liver stiffness in the elastography evaluation. The results may shine a light upon the natural history of the infection, helping clarify the initial disease mechanisms and refute the hypothesis that fibrosis plays a role in the late phases of infection.