Syndrome (Early urethral obstruction sequence)
urethral obstruction sequence
results most commonly from urethral valve formation, but it can be due to
urethral atresia or more distal urethral obstructions. The obstruction may
also be functional. Because the most
common etiology of the disorder is malformed development of the
urethra, it is most common in males
occurs most commonly as a sporadic event and is associated with a
recurrence risk for future pregnancies.
obstruction -> enlarged bladder and
of urine in the fetal bladder and urinary system beginning at about 8 weeks
of gestation, when urine formation begins.
dysplasia. Renal dysplasia
can range from mildly affected
kidneys with near normal function
to severely hypoplastic/dysplastic
kidneys. Hydronephrosis and massively dilated ureters are present. Often
have VUR, bladder dysfunction, and recurrent UTIs.
cryptorchidism due to failure of the testes to descend because of pressure
from the enlarged bladder.
of abdominal contents: +/- malrotation of colon
of iliac vessels: disrupt blood flow to the lower extremities, leading to
distension: excess of abdominal skin and a deficiency of abdominal
Oligohydramnios deformation complex
obstruction is fatal in fetal life unless the urinary bladder is decompressed.
This can occur in utero though rupture. In some centers, prenatal
decompression of the bladder by
vesicoamniotic shunt placement,
which also increases amniotic fluid volume to promote lung development, has
been attempted. Infants who are born
alive frequently have renal damage, although the abdominal musculature usually
correlates with extent of renal dysplasia. Severe dysplasia associated with
maternal oligohydraminios and pulmonary hypoplasia results in perinatal demise
in 20% of cases.
amniotic fluid leakage and renal agenesis result in the oligohydramnios
sequence, which causes pulmonary hypoplasia and fetal compression. However,
prune belly is not an associated feature because the bladder is not distended.
Extrophy of the bladder refers to exposure of the bladder due to failure of
the infra-umbilical mesoderm to invade the cloacal membrane. Polycystic
kidneys do not cause an obstructive uropathy, although in some cases they are
associated with oligohydramnios.
CHLA Board Review 2005
Freedman AL, Johnson MP, Smith CA, Gonzalez R, Evans MI. Long-term
outcome in children after antenatal intervention for obstructive
uropathies. Lancet. 1999;354:374-377
Jones KL. Smith's Recognizable Patterns of Human Malformation. 5th ed.
Philadelphia, Pa: WB Saunders Co; 1997:622-623