Low fetal urinary obstruction is a malformation typical of male fetuses that consists in the total obstruction of the urethra at the level of its exit from the bladder. Although it can occur for different reasons, the most common is the existence of a membrane that obstructs the urethral outlet, known as posterior urethral valves.
Symptoms and diagnosis of lower urinary obstruction
The diagnosis of this malformation should be made by a specialist in Gynecology and Obstetrics throughout gestation by means of control ultrasounds. Fetuses with this disorder usually have an enlarged bladder, which causes the pressure of the urinary system to increase and be transmitted to the kidneys. The renal pelvises may dilate and if the situation is maintained and worsens it could end in renal hydronephrosis in the fetus.
If this situation progresses, the kidneys may stop functioning properly and oligohydramnios may occur. Without the correct amount of amniotic fluid (oligohydramnios) the normal development of the lungs could be affected and lead to pulmonary hypoplasia. This situation would have important consequences on the life of the fetus.
Treatment of lower urinary obstruction
It is important to note that most fetuses with dilated renal pelvises do not present with severe obstruction, i.e. their kidneys are functioning properly, the dilatation is not very important and the amniotic fluid is normal. In these cases, most of them, it is not necessary to treat before birth. Sometimes, even at birth, the situation is normalized and the urinary system is normal.
When there is a severe obstruction problem (renal hydronephrosis) but renal function is still preserved (normal amniotic fluid) it makes sense to treat intrautero.
There are two types of intrauterine interventions:
1. fetal surgical ablation (rupture) of the valve leaflets (Fetal Cystoscopy): this is a treatment performed by fetal endoscopy. The introduction of a fine instrument into the bladder makes it possible to visualize the urethral valves and break them, thus allowing urine to pass.
2. Amniotic Vesicle Drainage: This is a small eight-shaped tube that directly connects the bladder to the uterine cavity and allows urine to exit through the abdomen. It is placed through the abdominal wall.
Both procedures are performed under local anesthesia, maternal sedation and fetal anesthesia. They are not very aggressive interventions for the mother, but are technically very difficult. In the case of performing them, it should be done in a center with extensive experience in fetal surgery. In expert hands, treatment success is around 80% of the cases.