RESUMEN
Multiple theories have been proposed about the pathophysiology of Fetus-in-fetu (FIF). The most widely accepted theory is abnormal embryogenesis in diamniotic monochorionic pregnancies, in which a malformed parasitic fetus is found within the body of a twin host. Hepatic FIF has been reported in almost 1% of FIF cases, with only 2 case reports being published in the literature. This article presents the third case report of intrahepatic FIF. Additionally, we review the role of radiology in diagnosing these cases and guiding their proper management. This case report supports the monozygotic twin theory of FIF and the diagnostic dilemma of FIF vs. teratoma can be solved through collaborative work between radiologists and pathologists.
RESUMEN
BACKGROUND: Ultrasound shear wave elastography (SWE) measures liver stiffness noninvasively, but few studies have defined cutoff values for detecting liver fibrosis in pediatric patients using 2-D ultrasound SWE. OBJECTIVE: To evaluate the diagnostic performance of 2-D ultrasound SWE and define cutoff values for liver fibrosis in pediatric patients, using Canon (Toshiba) Aplio ultrasound systems. MATERIALS AND METHODS: This was an institutional review board-approved retrospective study of patients (≤18 years old) who had undergone both liver 2-D ultrasound SWE and percutaneous liver biopsy within 6 months. Liver biopsies were staged using the METAVIR (fibrosis) scoring system. Continuous data were compared using the Mann-Whitney U test. Receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic performance. RESULTS: Forty-six patients, with a median age of 11.5 years (interquartile range: 8.0-14.3 years), were included. Twenty-three patients were male (50%). Twenty-seven patients had a METAVIR fibrosis score of F0-1, and 19 patients had a score of F2-4. For differentiating METAVIR F0-1 from F2--4, the area under the ROC (AuROC) was 0.75 (95% confidence interval [CI]: 0.60-0.90). A cutoff of >1.89 m/s yielded sensitivity of 73.7% (95% CI: 51.2-88.2) and specificity of 77.8% (95% CI: 59.2-89.4). For the subset of patients without histological hepatic steatosis (n=35), the AuROC was 0.86 (95% CI: 0.71-1.0). The same cutoff of >1.89 m/s yielded a sensitivity of 80.0% (95% CI: 54.8-93.0) and specificity of 95.0% (95% CI 76.4-99.7). CONCLUSION: Two-dimensional ultrasound SWE distinguishes patients with no/mild fibrosis from those with moderate/severe fibrosis with good sensitivity and specificity. Diagnostic performance is comparable to that published for magnetic resonance elastography and is likely adversely impacted by steatosis.