Fetal Diagnostic Imaging: Cincinnati Fetal Center

Fetuses with bladder outlet obstruction and oligohydramnios present with posterior placentas, hands and feet up in front of the face, compressed chest, difficult-to-visualize stomach, and bladder visible at the base with umbilical cord and hypogastric arteries bifurcating around it.

Amnioinfusion is needed if the patient is a candidate for shunt placement and is performed as the first step in evaluation at Cincinnati Fetal Center.

Karyotype can usually be obtained from a washing of the amniotic sac during amnioinfusion.

Amnioinfusion allows visualization of the uncompressed chest for size measurement and comparison to norms, which helps predict pulmonary hypoplasia.

Heart size ratios are very critical in prognosis for fetuses with bladder outlet obstruction.

Associated cardiac anomalies are not common in fetal genitourinary disease.

Posturing of hands and feet can be part of the diagnosis when looking for complex genetic syndromes.

Velamentous cord insertions could complicate shunt placement.

After intervention, if fluid volume drops off again due to end-stage fetal renal disease, repeat amnioinfusions can be performed through several different techniques.

Profound oligohydramnios makes diagnosis difficult in bladder outlet obstruction cases.

Fairly dilated and tortuous ureters can be confused with a big bladder by referring physicians.

Bladder outlet obstruction diagnosis has shifted from mid-trimester to early third trimester detection in the past to now being diagnosed just outside of the first trimester.

A keyhole configuration of the bladder is commonly seen with posterior urethral valves or other obstructive neuropathies.

When assessing kidneys for renal function prediction, echogenicity of the parenchyma and orientation of renal cysts should be evaluated.

Tortuous structures extending below the lower pole of the kidney are more likely dilated ureters than dilated kidneys.

Irregular configuration, inconsistent echogenicity, and wide distribution of cyst size are concerning findings in renal imaging.

Early in the disease process, renal cysts can be distributed around the outer pole of the kidney, then become more disoriented and distorted as the process progresses.

It is important to confirm the presence of two kidneys, as multicystic dysplastic kidney can be associated with absence of the contralateral kidney.

Bladder outlet obstruction is not just isolated to the genitourinary system; evaluation must include looking for a variety of other abnormalities.

With oligohydramnios, the problem comes back to pulmonary hypoplasia, and if pulmonary hypoplasia is in place, it is very difficult to correct.

A bell-shaped thorax with lower ribs being pushed out indicates the pulmonary circuit is not developing normally.

If kidneys are high enough or big enough to impair diaphragmatic excursion, there is a bigger problem and more likely diagnosis of pulmonary hypoplasia.

Loss of diaphragmatic movement from phrenic nerve dissection is a primary reason for pulmonary hypoplasia, and big kidneys can cause the diaphragm to stop moving and create the same crisis for pulmonary development.

MRI provides a visual image that parents can better understand and gives a big picture of the baby with clear images for parents to see when dealing with a renal abnormality.

For bladder outlet obstruction, ultrasound alone is not sufficient; MRI is a very important discriminator for comprehensive evaluation.