False diagnosis of renal agenesis on fetal MRI

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.

Complementary roles of sonography and magnetic resonance imaging in the assessment of fetal urinary tract anomalies

OBJECTIVE

The purpose of our study was to determine whether fetal magnetic resonance imaging (MRI) provides additional information that might affect the obstetric management of pregnancies complicated by sonographically diagnosed fetal urinary tract anomalies.

METHODS

Fetal MRI and sonography were used to study 39 women with suspected fetal urinary tract anomalies in the second and third trimesters of pregnancy.

RESULTS

In 24 of 39 cases (61%), fetal MRI confirmed the sonographic diagnosis. In 14 cases (36%), fetal MRI modified the initial sonographic diagnosis and counseling but did not change obstetric management. In 1 case (3%), the addition of fetal MRI resulted in a substantial change in the management of the pregnancy.

CONCLUSIONS

During the second and third trimesters of pregnancy, fetal MRI showed fetal urinary tract anomalies in excellent anatomic detail. Fetal MRI is a useful complementary tool in the assessment of sonographically diagnosed fetal urinary tract anomalies. In a small percentage of cases, it can have a substantial impact on obstetric management.

Magnetic resonance imaging diagnosis of severe fetal renal anomalies

OBJECTIVE

The purpose of this study was to describe magnetic resonance imaging (MRI) findings in fetuses with severe renal anomalies.

STUDY DESIGN

This was a case-control study that compared MRI findings in fetuses with suspected severe renal anomalies with gestational age-matched control fetuses. MRI was performed with T2-weighted single-shot fast-spin echo sequences. Each MRI was reviewed by an investigator who was blinded to clinical information.

RESULTS

There were 2 cases of bilateral renal agenesis, 2 cases if bilateral multicystic dysplastic kidney disease, 2 cases if unilateral renal agenesis and contralateral multicystic dysplastic kidney disease, 2 cases if polycystic kidney disease, and 2 cases of early membrane rupture/normal kidneys. Fetuses with lethal renal anomalies had a characteristic bladder appearance (signal void [dark]), whereas control fetuses had bright signal in both bladder and renal pelvis (P < .001). Both cases of early membrane rupture/normal kidneys had bright bladder signal, but 1 case did not have bright signal in the renal pelvis.

CONCLUSION

Fetuses with lethal renal anomalies had signal void in the bladder region on MRI.

MRI with diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) assessment in the evaluation of normal and abnormal fetal kidneys: preliminary experience

OBJECTIVE

To investigate apparent diffusion coefficient (ADC) mapping with the measurement of renal tissue ADC value of normal and pathological fetal kidneys at various gestational ages (GAs).

METHODS

Fifty pregnant women underwent magnetic resonance images (MRI) after ultrasound (US) for suspected fetal genitourinary disorders (16) or for suspected disorders in other organs (34). A multiplanar study of urinary system was obtained by using conventional T2-weighted sequences and echo planar imaging (EPI); Diffusion-weighted images and ADC maps were evaluated. The renal tissue ADC value was measured for all normal and abnormal fetuses and related to GA.

RESULTS

MRI confirmed urinary anomalies in 15 fetuses [2 renal developmental variants, 2 nephropathies, 4 multicystic dysplastic kidneys (MCDK), 7 renal tract dilatations] and detected normal kidneys in the remaining 35 fetuses. Normal renal parenchyma showed bright signal on diffusion-weighted images with ADC values ranging from 1,065 to 1,327 microm(2)/s with a tendency to decrease over GA. A pathological ADC was detected in cases of bilateral MCDK, huge dilatations and in cases of nephropathies.

CONCLUSION

Diffusion-weighted imaging (DWI) with ADC mapping can be used in the evaluation of fetal renal parenchyma and may become a tool of assessing function of the fetal kidney by means of measurement of renal tissue ADC values.