RESUMEN
Background Ultrasonographic evaluation of thyroid nodules is challenging due to their high frequency and low malignancy rate. The risk stratification system developed by the American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS) focuses on addressing the primary contemporary objectives for these lesions, aiming to decrease unnecessary biopsies while maintaining a similar specificity compared with other risk stratification systems. Generally, when indicative of malignancy by ultrasound findings, the next best step in management is an evaluation by fine needle aspiration biopsy (FNAB) and cytological analysis with The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) results that determine further evaluation requirements, actions that are based on the risk of malignancy (ROM) of the assigned category, which could include surgical intervention. Objectives To validate and analyze the individual impact of each ultrasonographic finding indicative of malignancy in the ACR TI-RADS guidelines based on their respective correlation with results obtained by TBSRTC. Materials and method Reports for 212 thyroid ultrasound-guided FNABs from 2018 to 2020 were assessed. Only 117 had both ACR TI-RADS and TBSRTC reports available and were analyzed. Nodules were divided into two groups: ROM < 5% (Bethesda 1, 2; n = 58), and ROM > 5% (Bethesda 3, 4, 5, 6; n = 59). Statistical analysis was performed using the x2 test and bivariate logistic regression model for each characteristic included in ACR TI-RADS. Results Individual ultrasound characteristics with a more pronounced distribution towards the Bethesda > 5% malignancy group were: solid or almost completely solid composition (n=53, 62.3%), very hypoechoic echogenicity (n=3, 75%), wider-than-tall shape (n=50, 50.5%), lobulated or irregular margin (n=23, 65.7%), punctate echogenic foci (n=18, 72%), and thyroid isthmus location (n=6, 75%). Statistically significant individual ultrasonographic characteristics indicative of malignancy included solid or almost completely solid (p = 0.005), very hypoechoic echogenicity (p = 0.046), margin lobulated or irregular (p = 0.031), and punctate echogenic foci (p = 0.015). No significant association was found in the taller-than-wide shape for differentiating malignant from benign lesions (p = 0.969). Conclusions Specific ultrasound characteristics identified in the ACR TI-RADS system demonstrate a stronger correlation with an increased risk of malignancy when compared with cytologic evaluation results. These characteristics include a solid composition, lobulated or irregular margins, punctate echogenic foci, and very hypoechoic echogenicity. Our findings revealed that the scale points for the taller-than-wide characteristic do not adequately represent its true influence on the risk of malignancy.
RESUMEN
Resumen ANTECEDENTES: En Obstetricia, las imágenes en espejo son artefactos ecográficos infrecuentes que, potencialmente, pueden confundirse con embarazos heterotópicos y propiciar errores diagnósticos e intervenciones iatrógenas. Estas imágenes ficticias se generan por la existencia de una superficie reflectora como, por ejemplo, el intestino distendido o la vejiga repleta. CASO CLÍNICO: Paciente de 39 años, con embarazo por fertilización in vitro, que asiste a evaluación ecográfica del primer trimestre. En la ecografía de rutina a las 11 semanas se observó una imagen en espejo y en la resonancia magnética: útero gestante con una estructura retrouterina hipoecoica, sin feto en el interior. La imagen ecográfica en espejo volvió a reproducirse en el tercer trimestre. El embarazo llegó a término y finalizó por vía abdominal, sin que pudieran demostrarse las estructuras que se advirtieron en la resonancia magnética. CONCLUSIONES: Las imágenes en espejo se han reportado en ultrasonidos de diversas localizaciones pero pocos en la Obstetricia. Todo hizo suponer que la superficie reflectora fue la estructura hipoecoica retrouterina observada, transitoriamente, en la resonancia magnética.
Abstract BACKGROUND: In obstetrics, ultrasonic artifactual mirror images are infrequent, but potentially dangerous since they can be mistakenly interpreted as heterotopic pregnancies, precluding diagnostic errors and iatrogenic interventions. These images require a reflection surface such as dilated bowl or plenty bladder to be generated. OBJECTIVE: We report a first trimester scan ghost twin, diagnosed since first trimester of pregnancy. CLINICAL CASE: 39-year-old patient, with pregnancy due to in vitro fertilization, who attends ultrasound evaluation of the first trimester. Routine ultrasound at 11 weeks showed a mirror image and magnetic resonance imaging: a pregnant uterus with a hypoechoic retrouterine structure, with no fetus inside. The ultrasound mirror image reproduced again in the third trimester. The pregnancy came to an end and ended by abdominal route, without being able to demonstrate the structures that were noticed on the MRI. CONCLUSION: Very few reports of obstetric ultrasound mirror images have been reported. We hypothesize that the transient retrouterine hypoecogenic structure observed by MRI was the reflective surface that create the ghost twin image.