The role of magnetic resonance imaging in refining the diagnosis of suspected fetal renal anomalies

Fetal body organ T2* relaxometry at low field strength (FOREST)

Fetal Magnetic Resonance Imaging (MRI) at low field strengths is an exciting new field in both clinical and research settings. Clinical low field (0.55T) scanners are beneficial for fetal imaging due to their reduced susceptibility-induced artifacts, increased T2* values, and wider bore (widening access for the increasingly obese pregnant population). However, the lack of standard automated image processing tools such as segmentation and reconstruction hampers wider clinical use. In this study, we present the Fetal body Organ T2* RElaxometry at low field STrength (FOREST) pipeline that analyzes ten major fetal body organs. Dynamic multi-echo multi-gradient sequences were acquired and automatically reoriented to a standard plane, reconstructed into a high-resolution volume using deformable slice-to-volume reconstruction, and then automatically segmented into ten major fetal organs. We extensively validated FOREST using an inter-rater quality analysis. We then present fetal T2* body organ growth curves made from 100 control subjects from a wide gestational age range (17-40 gestational weeks) in order to investigate the relationship of T2* with gestational age. The T2* values for all organs except the stomach and spleen were found to have a relationship with gestational age (p<0.05). FOREST is robust to fetal motion, and can be used for both normal and fetuses with pathologies. Low field fetal MRI can be used to perform advanced MRI analysis, and is a viable option for clinical scanning.

Ultrasound and magnetic resonance imaging features of fetal urogenital anomalies: A pictorial essay

This pictorial essay focuses on ultrasound (US) and magnetic resonance imaging (MRI) features of fetal urogenital anomalies. Fetal urogenital malformations account for 30%-50% of all anomalies discovered during pregnancy or at birth. They are usually detected by fetal ultrasound exams. However, when ultrasound data on their characteristics is insufficient, MRI is the best option for detecting other associated anomalies. The prognosis highly depends on their type and whether they are associated with other fetal abnormalities.

A new sonographic marker in the diagnosis of prenatal bilateral renal agenesis, segmental anterior deviation of the aorta

Objectives

Bilateral renal agenesis is a rare congenital anomaly that is associated with high neonatal mortality. Bilateral renal agenesis is most often present with anhydramniosis in the mid-trimester.

Case presentation

We report a case of bilateral renal agenesis diagnosed prenatally. We presented the ultrasound and pathology images of this fetus with a new sonographic sign, segmental anterior deviation in the abdominal aorta.

Conclusions

To our knowledge, this is the first reported case of a fetus with a segmental aortic anterior deviation.

Update on the Prenatal Diagnosis and Outcomes of Fetal Bilateral Renal Agenesis

Importance

Bilateral renal agenesis is a rare congenital anomaly associated with poor prognosis.

Objective

The aims of this article are to review and summarize evidence on prenatal diagnosis and outcomes of bilateral renal agenesis.

Evidence Acquisition

A search was undertaken using PubMed and ClinicalTrials.gov databases from January 1, 1998, to September 1, 2018. Search terms include "prenatal diagnosis" OR "outcomes" AND "bilateral renal agenesis." Search was limited to English language.

Results

Fetal ultrasonography is the primary imaging modality for prenatal diagnosis of fetal urogenital tract abnormalities. However, ultrasonography is limited by several factors; it is operator dependent and associated with small field of view, has limited soft-tissue acoustic contrast, and is also influenced by patient habitus and fetal position. Color Doppler ultrasonography can be used as an adjunct to exclude bilateral renal agenesis by visualizing renal arteries. In the literature, prenatal magnetic resonance imaging has been reported to be equal to or superior to prenatal ultrasonography. Bilateral renal agenesis with oligohydramnios/anhydramnios is associated with a poor prognosis; perinatal death occurs secondary to pulmonary hypoplasia in the majority of cases.

Conclusions

Ultrasonography in combination with color Doppler ultrasonography permits the fetal urinary tract to be assessed in the first and early second trimester of gestation. The magnetic resonance imaging can be used as a complementary adjunctive modality in equivocal or inconclusive ultrasonographic findings.