Antenatal Hydronephrosis (Enlargement of Prenatal Renal Ducts)

The widespread use of prenatal ultrasonography (US) on the baby causes the early detection of many congenital anomalies in babies. One fifth of the anomalies detected prenatally by US are kidney-related problems. Anomalies detected before birth are roughly divided into 4 groups.

Size anomalies of the kidneys

Anomalies of the kidney tissue

Presence of cysts in the kidneys

Antenatal hydronephrosis

In this article, I will talk about antenatal hydronephrosis, as it is quite common and sometimes requires surgery, but requires careful follow-up.

Antenatal Hydronephrosis

Antenatal Hydronephrosis, It is the term that refers to the enlargement of the kidney, ureter or bladder and urethra, which is diagnosed by ultrasonography while the child is in the womb. If the event is unilateral, only the relevant kidney is affected and there is no risk for the child. In cases where it is bilaterally affected or in cases where only one kidney is affected, the fluid in which the child swims in the womb may decrease (oligohydramniosis). This is a serious condition and the child's lung and kidney development is affected and a condition that progresses to stillbirth may occur.

With the widespread use of US, hydronephrosis is frequently detected. Although every hydronephrosis does not indicate a serious disease, it should be carefully monitored and examined, situations requiring intervention should be identified and necessary treatment should be given.

Anterior-posterior diameter of the kidney at any period of pregnancy

• < 3mm. It is normal.

Between the 15th and 20th weeks of pregnancy

• If it is 4-7 mm, it is mild
• >If it is 7 mm, it is moderate. graded hydronephrosis

After the 30th week of pregnancy

• 5-8 mm mild
• 9-15 mm moderate
• >15 mm is considered as severe hydronephrosis.

What are the Causes of Antenatal Hydronephrosis?

The causes of antenatal hydronephrosis can be grouped under two main headings.

Causes related to obstruction (obstructive causes)

• Ureteropelvic stenosis (UPD)
• Ureterovesical stenosis (UVD)
• Posterior urethral valve (PUV)
• Double collecting system
• Ectopic ureter
• Ectopic ureterocele
• Urethral atresia
• Cloacal anomaly
• Mass compression (Sacrococcygeal teratoma, hydrocolpos, mesenteric masses, ovarian cysts, gastrointestinal tract duplications)

Causes not related to obstruction (nonobstructive causes)

• Vesicoureteral reflux (VUR)
• Multicystic dysplastic kidney
• Prune-Belly syndrome

In almost half of the unilateral cases, the cause is an insufficiency in the passage of urine at the uretero-pelvic junction. In this case, there is a problem in the passage of urine from the kidneys to the ureter, which is the channel that will transmit it to the bladder. In most such patients, the problem resolves on its own with close follow-up, but 1 in every 5 patients requires surgery.

Double kidney anomalies, ureteroceles (a ballooning of the part of the ureter, which is the urine-draining channel, inside the bladder). and inability of urine to pass completely to the bladder), uretero-vesical strictures (incomplete urine passage at the point where the ureter meets the bladder and the resulting enlargement of the ureter) are conditions that can be diagnosed in the prenatal period and usually have a unilateral course. Posterior-urethral valve refers to a stenosis right at the beginning of the channel called urethra, which discharges the urine from the bladder, and since the urine in the bladder cannot be completely discharged, both kidneys are affected by this condition. Since the urine in the bladder cannot come out sufficiently, this is reflected in the form of high pressure on the kidneys.

The following parameters are very important in a baby with hydronephrosis.

• General condition of the fetus
• Gestational age
• Unilateral or bilateral hydronephrosis
• Volume of amniotic fluid

Situations with Poor Prognosis

• Prolonged oligohydramniosis
• Presence of cortical cysts in the kidney
• Decreased lung volume
• In antenatal urine; If sodium>100 mEq/lt, chlorine>90 mEq/lt, Osmolarity>210 mOsm/lt; If β2 microglobulin, α1 microglobulin, alanine, valine, threonine are increased

Antenatal Hydronephrosis Ways to Follow in Diagnosed Patients

Termination of Pregnancy: More often in fetuses less than 24 weeks If there is no possibility, it is considered, the detected defect is of a nature that will not make life after birth possible.

Early Birth:Continuing the pregnancy endangers the life of the mother and/or the baby due to the pathology in the fetus or does not benefit both of them. .For example, premature rupture of membranes.

Antenatal Percutaneous Evacuation: The primary goal should be to save the life of the baby and the mother (such as causing hypertension or toxemia in the mother). Today, the aim is to prevent the negative impact on lung development caused by oligohydramniosis, which is a result of urinary obstruction, and thus to save the baby. It is considered especially in babies with bilateral hydronephrosis, if the renal cortex is very thin, the bladder wall is thickened and there is oligohydramniosis. However, the complication rate is 45%, and these are mainly; catheter blockage, insufficient evacuation and intestinal perforation in the fetus.

Open Fetal Surgery: Studies continue.

Follow-up after birth

Patients should be evaluated with a complete physical examination after birth and investigated with further tests. What needs to be done for unilateral cases is to start prophylactic antibiotics after the child is born, to have an ultrasound and, if necessary, a voiding cysto-urethrography (VCUG or MSUG) in the first week, and to have a renal scintigraphy (MAG-3) performed at the 6th week.

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