A 34-year-old female (gravida 5, term 2, para 2, abortion 2,
living 2) presented to the ultrasound lab as measuring large for
gestational dates. She was normotensive and asymptomatic. Her
prenatal course had been unremarkable, and she reported no
incidences of bleeding or pain. She had no personal or family
history of birth defects. Images from a routine obstetrical
ultrasound are illustrated in figures 1-4. Following the
ultrasound, a fetal karyotype demonstrated a normal 46 XY male. Two
weeks later, she delivered a still-born male fetus. Autopsy results
confirmed the presence of an 8-cm unencapsulated neoplasm replacing
the normal right kidney and extending into the lateral abdominal
wall. The mass compressed the liver and inferior vena cava. There
was generalized body wall edema. Microscopic examination revealed
an infiltrative neoplasm composed of spindle cells with fine
chromatin along with residual renal parenchyma and areas of
necrosis and dystrophic calcifications.
Transverse image of the fetal abdomen demonstrating a large 5-cm
cystic and solid mass in the right abdomen. Abdominal ascites is
Ultrasound image of the fetal calvarium displays skin thickening
consistent with anasarca and hydrops.
Sonogram of the fetal scrotum shows large bilateral
Ultrasound image shows a large pocket of amniotic fluid. The
amniotic fluid index was calculated to be 25 cm, indicative of
Congenital mesoblastic nephroma in association with hydrops
The patient was scanned using a Toshiba SSH 140A and a 5 MHz
transducer. Obstetrical ultrasound revealed a large, complex cystic
mass measuring 8.5 × 6.3 × 6.1 cm within the upper fetal abdomen
centered just to the right of midline and extending into the
lateral abdominal wall. The mass distorted the fetal abdomen and
the thoracic cavity appeared compressed. Bilateral hydroceles,
ascites, and anasarca were noted consistent with fetal hydrops. The
amniotic fluid index (AFI) was 25 cm or >97.5 percentile
consistent with polyhydramnios. The biparietal diameter and the
femur length were compatible with a 27-week gestation. The
abdominal circumference measured >95th percentile for a 27-week
gestation. The placenta was slightly edematous, measuring 4.6 cm in
thickness. The right kidney could not be identified. Differential
diagnosis considerations included multidysplastic kidney,
congenital mesoblastic nephroma, and Wilm's tumor.
Mesoblastic nephroma is the most common neonatal renal neoplasm.
Mesoblastic nephroma is usually discovered within the first few
months of life, however, it may be diagnosed by obstetrical
sonography as a complex renal mass.
Occasionally the pregnancy may be complicated by hydramnios or
dystocia, but usually the prepartum history is unremarkable.
Mesoblastic nephroma may demonstrate gross cystic changes involving
the junction of the tumor and the normal kidney, thus mimicking a
multilocular cystic nephroma.
Congenital mesoblastic nephromas are usually a benign disease, but
in association with hydrops fetalis can result in fetal death as
was the situation in this case report. After a review of the
English literature, we could find only one other case of fetal
hydrops in association with congenital mesoblastic nephroma that
was diagnosed prenatally.
There were two other cases of fetal congenitalmesoblastic nephroma
associated with hydrops fetalis; however, these were both diagnosed
Most renal anomalies result in oligohydramnios and, therefore, a
renal anomaly in association with polyhydramnios should be concern
for a mesoblastic nephroma. The etiology of the polyhydramnios is
uncertain; however, some observations have included a relationship
to gastrointestinal compression by the tumor or that the tumor will
increase fetal urine production.
The outline of a mesoblastic nephroma may be difficult to ascertain
because it is not always encapsulated in contrast to a Wilm's
It is important that this anomaly is diagnosed prenatally in
order to ensure proper obstetrical management to avoid such
occurrences as premature birth and dystocia.
Prepared by Crosby L. Gernon, MD, Chairman of
Ultrasonography, and Bob Alston, BS, RDMS, RVT, Chief
Sonographer, Department of Ultrasound, at Sabetha Community
Hospital of Sabetha, KS.