124
Perinatal Urology
Joseph G. Borer; Richard S. Lee
Questions
1.A 34-week-old female fetus has evidence of normal amniotic fluid and unilateral upper pole hydroureteronephrosis with no evidence of an intravesical ureterocele. What does this most likely represent?
a.Vesicoureteral reflux (VUR)
b.Ureteropelvic junction obstruction
c.Obstructed ectopic ureter
d.Cloacal malformation
e.None of the above
2.Which of the following statements is TRUE?
a.Intermittent or varying degrees of hydronephrosis or hydroureter is pathognomonic of VUR
b.VUR cannot be definitively diagnosed on prenatal ultrasound.
c.Increasing degrees of hydronephrosis increases the risk of VUR.
d.Decreasing degrees of hydronephrosis decreases the risk of VUR.
e.None are true.
3.A 37-week-old fetus with a previously normal-appearing ultrasound (US) has a newly diagnosed enlarged left kidney with loss of corticomedullary differentiation, echogenic streaks, branching hyperechoic vessels, and a calcified intramural inferior vena caval plaque. What is the most likely diagnosis?
a.Renal artery thrombosis
b.Renal vein thrombosis
c.Congenital mesoblastic nephroma
d.Autosomal recessive polycystic kidney disease (ARPKD)
e.Wilms tumor
4.A 31-week-old male fetus has a thick-walled dilated bladder, dilated posterior urethra, unilateral severe hydroureteronephrosis, and late-onset oligohydramnios (after 29 weeks). There are no other US findings. Serial bladder taps have been performed, with the latest indices Na 90 (previous 115), Cl 100 (previous 120), Osm 190 (previous 225). As the consulting urologist, you would recommend:
a.early delivery at 31 weeks.
b.early delivery after 32 weeks.
c.in utero urinary tract decompression with shunt.
d.amnioinfusion with concomitant in utero shunt placement.
e.observation with delivery at term.
5.In which scenario is in utero decompression by shunt reasonable?
a.Single male fetus with decreasing amniotic fluid after 28 weeks
b.Single male fetus with severe bilateral renal cystic disease at 24 weeks
c.Female fetus with bilateral echogenic kidneys, decompressed bladder volume, and oligohydramnios
d.Single male fetus with severe hydronephrosis and oligohydramnios at 21 weeks
e.A twin male fetus with severe hydronephrosis and oligohydramnios at 21 weeks and a normal twin
6.To best distinguish between severe unilateral hydronephrosis and a multicystic dysplastic kidney (MCDK), which of the following combination best represents a MCDK?
a.Minimal or absent renal parenchyma
b.Absence of a central large cyst
c.Appearance of multiple noncommunicating cysts
d.a, b, and c
e.a and c
7.A 28-week-old fetus has bilaterally enlarged echogenic kidneys without renal cysts, hepatobiliary dilatation, and severe oligohydramnios. These findings suggest which diagnosis?
a.ARPKD
b.Posterior urethral valves
c.Bilateral MCDK
d.Autosomal dominant polycystic kidney disease (ADPKD)
e.Bilateral multilocular cystic nephroma
8.A 2-month-old male infant with an antenatal history of left moderate to severe
hydronephrosis has a postnatal ultrasound at 24 hours of life demonstrating mild hydronephrosis. A follow-up US at 2 months demonstrates left severe hydronephrosis. This can be explained by:
a.intermittent changing hydronephrosis consistent with VUR.
b.physiologic oliguria in the newborn.
c.worsening obstruction.
d.ureterocele disproportion.
e.none of the above.
9.Prenatal imaging findings that are consistent with bladder exstrophy include all of the following EXCEPT:
a.Absence of bladder filling documented on repetitive fetal imaging
b.Volume of amniotic fluid appropriate for fetal gestational age
c.Lower abdominal wall mass
d.Spinal cord or spinal column abnormality
e.Low-set umbilicus and inability to clearly visualize genitalia
.Cloacal exstrophy is most likely in the differential diagnosis when fetal ultrasonography and/or magnetic resonance identify which of the following?
a.Normal number, location, and anatomy of the kidneys
b.Omphalocele
c.Lower abdominal wall mass, absence of bladder filling on serial imaging, ectopic kidney, and spinal cord tethering
d.46,XY karyotype on amniocentesis and diminutive genitalia
e.Renal agenesis and contralateral hydronephrosis
.46,XX karyotype, cystic pelvic mass, bilateral hydroureteronephrosis, and the presence of ascites in a fetus are findings and characteristics most consistent with which diagnosis?
a.Cloacal exstrophy
b.Cloaca
c.Bladder exstrophy
d.Imperforate anus
e.Prune-belly syndrome
.FALSE statement(s) regarding the identification of a solid renal mass on fetal imaging include which of the following?
a.When possible, delivery should be planned at a pediatric tertiary care center to avoid a potentially life-threatening condition in early neonatal life.
b.A solid renal mass identified in the fetus is most often consistent with a
malignant tumor.
c.Prenatal identification of a renal mass warrants careful immediate postnatal monitoring of the neonate.
d.A solid renal mass in the fetus is a relatively common finding.
e.Both b and d.
Answers
1.c. Obstructed ectopic ureter. A duplication anomaly with upper pole hydroureteronephrosis is typically associated with a ureterocele, an ectopic ureterocele, or an ectopic ureter causing obstruction. A dilated ureter is typically identified.
2.b. VUR cannot be definitively diagnosed on prenatal ultrasound. Previous studies have demonstrated that the degree of hydronephrosis does not correlate with the incidence of VUR.
3.b. Renal vein thrombosis. The ultrasound appearance of the kidney during renal vein thrombosis can be renal enlargement, loss of the corticomedullary differentiation, echogenic streaks, lack of definition of renal sinus echoes, and loss of venous flow in the affected kidney evident on Doppler imaging.
4.e. Observation with delivery at term. Serial bladder sampling during 3 days has been used to help determine whether the fetus is a viable candidate. The serial nature of the procedure allows one to see the subsequent trend of urine osmolality and electrolyte composition as a reflection of fetal kidney response. This fetus has encouraging urine electrolytes and only unilateral hydroureteronephrosis.
5.d. Single male fetus with severe hydronephrosis and oligohydramnios at 21 weeks. In utero intervention is currently indicated when the fetus's life is at risk. In utero decompression by shunting is only indicated in instances of presumed bladder obstruction in the setting of oligohydramnios. In utero intervention in the case of a twin gestation may place the other fetus at risk and therefore is not recommended.
6.d. a, b, and c. The findings of multiple noncommunicating cysts, minimal or absent renal parenchyma, and the absence of a central large cyst are diagnostic of a multicystic dysplastic kidney.
7.a. ARPKD. Bilaterally enlarged echogenic kidneys without renal cystic disease, particularly if associated with hepatobiliary dilatation or
oligohydramnios, suggest autosomal recessive polycystic kidney disease.
8.b. Physiologic oliguria in the newborn. It is important to keep in mind that a postnatal ultrasound examination performed within the first 48 hours of life may not yet demonstrate hydronephrosis or may underestimate the degree of hydronephrosis secondary to physiologic oliguria.
9.d. Spinal cord or spinal column abnormality. Ultrasound findings in a fetus with bladder exstrophy include nonvisualization of the fetal bladder, lower abdominal wall mass immediately inferior to a low-lying umbilicus, and diminutive genitalia. Other findings that may be evident to the experienced observer include normal kidneys in orthotopic position, normal vertebrae and spinal cord, abnormal symphyseal
diastasis, and anteriorly displaced anus.
.c. Lower abdominal wall mass, absence of bladder filling on serial imaging, ectopic kidney, and spinal cord tethering. The prenatal diagnosis of cloacal exstrophy should be suspected with findings of nonvisualization of the bladder in association with a low-lying umbilicus, lower abdominal wall mass—typically omphalocele—and kidney (number, location, and/or appearance) and lumbosacral spine abnormalities.
.b. Cloaca. Persistent cloaca should be considered in any female fetus presenting with hydronephrosis and a large cystic mass arising from the pelvis.
.e. Both b and d. Congenital mesoblastic nephroma is a rare benign congenital renal tumor and is the most common solid renal tumor in the neonatal period. Malignant tumors are rare. Delivery at a pediatric tertiary care center should be planned to avoid a potentially life-threatening condition in early neonatal life.
Chapter review
1.Oligohydramnios after 18 to 20 weeks may be the result of urinary tract obstruction or poor renal function.
2.Inability to identify the bladder on repeat prenatal ultrasound studies should suggest the diagnosis of exstrophy.
3.Dilatation of the posterior urethra (keyhole sign) suggests posterior urethral valves.
4.Neural tube defects are diagnosed prenatally by α-fetoprotein and
screening with ultrasonography.
5.Adrenal hemorrhage may appear as eggshell calcifications in contrast to the fine stippled calcifications of neuroblastoma.
6.An indication that renal function is salvageable is suggested by a fetal urine specimen in which the urinary sodium value is less than
100 mEq/L, the chloride value is less than 110 mEq/L, and the osmolality is less than 200 mOsm/kg.
7.Postnatal ultrasonography performed within the first 48 hours of life may not demonstrate hydronephrosis owing to decreased urine formation.
8.A dimercaptosuccinic acid scan is recommended to confirm the diagnosis of multidysplastic kidney when the ultrasound findings are not classic to differentiate it from cystic nephroma.
9.The most common form of congenital adrenal hyperplasia (CAH) is 21hydroxylase deficiency. Genital ambiguity in females can be minimized in CAH patients with prenatal treatment with dexamethasone.
10.Congenital mesoblastic nephroma is the most common solid renal tumor in the newborn. Wilms tumors are rare in the neonate.
11.Oligohydramnios in the second trimester is often associated with a lethal postnatal outcome due to pulmonary hypoplasia.
12.Bilateral hydronephrosis suggestive of bladder outlet obstruction should be evaluated promptly after birth. In boys the etiology is usually posterior urethral valves; in girls it usually is an obstructing ectopic ureterocele.
13.The ultrasound appearance of the kidney following renal vein thrombosis includes renal enlargement, loss of the corticomedullary differentiation, echogenic streaks, lack of definition of renal sinus echoes, and loss of venous flow in the affected kidney evident on Doppler imaging.
14.In utero decompression by shunting is indicated only in instances of presumed bladder obstruction in the setting of oligohydramnios.
15.The findings of multiple noncommunicating cysts, minimal or absent renal parenchyma, and the absence of a central large cyst are diagnostic of a multicystic dysplastic kidney.
16.In bladder exstrophy, usually the vertebrae and spinal cord are normal, and there is an abnormal symphyseal diastasis and anteriorly displaced anus. In cloacal exstrophy, lumbosacral spine abnormalities may occur.
SECTION B
Basic Principles