Congenital Anomalies


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Bilateral Renal Agenesis

Bilateral Renal Agenesis in 4D Scan


Congenital absence of both kidneys.


It is  due to failure of the development of the ureteric bud or of any interaction with the metanephric blastema. The incidence is 1–2/1000 for the unilateral form and 1/3000–4000 for the bilateral form.

Ultrasound diagnosis:

  1. The impossibility of visualizing the kidneys and the bladder.
  2. Severe oligohydramnios after the 16th week of gestation.
    • In these cases, it is important not to mistake the adrenal glands for the kidneys.
      • The features that may help in differentiating the adrenals from the kidneys are as follows:
        • The adrenal glands are smaller and oblong.
        • In contrast to the renal medulla, the adrenal medulla is hyperechoic rather than hypoechoic.
        • The renal pelvis cannot be visualized.
        • Due to the absence of the kidneys, these glands sometimes appear merely rounder than normal and fill the renal fossa in what has been termed the “lying down” adrenal sign.
    • The lack of an acoustic window, due to the severe oligohydramnios, can make the diagnosis challenging in some cases.
    • Although amnioinfusion has been proposed as a diagnostic aid, it is generally sufficient to employ color or power Doppler to confirm the absence of the renal arteries, a feature consistent with the diagnosis of bilateral renal agenesis.
    • The course of the superior vesical arteries can also help to confirm the non visualuzation of the bladder.
    • Fetal biometry and Doppler evaluation of the umbilical artery velocity waveform rules out another cause of nonvisualization of the fetal bladder and oligohydramnios: fetal growth restriction (FGR).

Differential diagnosis:

Other conditions possibly responsible for severe oligohydramnios: severe FGR and rupture of the membranes. In the presence of severe FGR, umbilical artery velocimetry is usually abnormal, while the presence of a normal bladder can help orientating the diagnosis towards rupture of the membrane, testifying a normal renal function.

Association with other malformations:

The anomalies most frequently associated with unilateral renal agenesis  affect the contralateral kidney and the internal genital organs (which cannot be visualized in the prenatal period). Extra-renal anomalies often associated with bilateral renal agenesis include cardiac, cerebral, and skeletal malformations.

Risk of chromosomal anomalies:

This is relatively low in isolated bilateral forms (1%–5%) and even lower in unilateral forms (<1%).

Risk of non-chromosomal syndromes:

This is high (20%–25%). Renal agenesis can be the main sign of more than 40 different syndromes. The most common syndromes and associations are as follows:
Fraser syndrome: look for ► renal agenesis +laryngeal atresia + cryptophthalmos + syndactyly

VA(C)TER(L) association: look for ► renal agenesis + vertebral anomalies + anal atresia + congenital heart disease (CHD) + tracheoesophageal fistula + limb anomalies;
Caudal regression syndrome: look for ► renal agenesis + sacral agenesis + lumbar vertebral anomalies+ femoral hypoplasia;
Sirenomelia: look for ► renal agenesis + fusion of the lower limbs + anal atresia + vertebral anomalies + genital anomalies;
Cerebro-oculo-facial-skeletal syndrome: look for ► renal agenesis + microcephaly + micrognathia + joint contractures;
Otocephaly: look for ► renal agenesis +agnathia + microstomia + holoprosencephaly + cleft lip and palate.

If renal agenesis is isolated, the empiric risk of recurrence is 3.5%, whereas if it is one sign of a syndrome, the risk of recurrence is obviously the risk associated with the underlying syndrome.

Obstetric management:

Karyotyping is not mandatory for the unilateral form. Although the association with chromosomal anomalies is not considered to be high in the bilateral form, some authors advise karyotyping, especially in cases associated with other malformations, to help estimate the recurrence risk.

US investigation of the parents’ kidneys is necessary in cases of unilateral agenesis, in view of the autosomal dominant inheritance pattern of the condition.

Postnatally, scintigraphy, to gain confirmation of the renal agenesis and to assess the residual renal function.

Postnatal therapy:

No treatment is available for bilateral renal agenesis: one-third of fetuses die in utero, and the remaining two-thirds die immediately after birth due to severe pulmonary hypoplasia.

Prognosis, survival, and quality of life. Bilateral renal agenesis is always lethal, due to the associated severe pulmonary hypoplasia. In fact, apart from provoking the typical Potter sequence (Potter facies, deformation of hands and feet, etc.), severe oligohydramnios induces lethal pulmonary hypoplasia. In fact, the compression of the fetal chest by the uterine walls and the absence of amniotic fluid impairs pulmonary development.



Congenital Anomalies Ultrasound Course

How to Purchase This Online Ultrasound Course

In this online ultrasound course you will learn how to approach and diagnose common morphologic fetal congenital anomalies using 3D/4D ultrasound.

Head and Neck Anomalies

  1. Occipital Encephalocele.
  2. Congenital Hydrocephalus.
  3. Oropharyngeal Teratoma.
  4. Cystic Hygroma.

Thoracic Anomalies

  1. Congenital Diaphragmatic Hernia.
  2. Congenital Hydrothorax.

Fetal Abdominal Anomalies

  1. Hirschsprung Disease.
  2. Exomphalos Major.
  3. Gastroschisis.
  4. Duodenal Atresia.
  5. Small Intestinal Obstruction.

Fetal Renal Anomalies

  1. Congenital Hydronephrosis.
  2. ARPCKD (Potter Type I).
  • Fetal Back Anomalies
  1. Spina Bifida.
  2. Sacrococcygeal Teratoma.

Included Ultrasound Videos

  • Cystic Hygroma.
  • Congenital Hydrothorax (Pleural Effusion).
  • Pleural Effusion (Hydrothorax).
  • Congenital Cystic Adenomatoid Malformation (CCAM) of the Lung.
  • Exomphalos Major (Omphalocele).
  • Gastroschisis.
  • Hirschsprung Disease.
  • Congenital Hydronephrosis.
  • Congenital Hydronephrosis – Virtual Contrast Imaging (Omni View).
  • Autosomal Recessive Polycystic Kidney Disease (Potter Type I).
  • Bilateral Renal Agenesis.
  • TUI of Fetal Ovarian Cyst.
  • Sacrococcygeal Teratoma.
  • Conjoined Twins.

Click on Curriculum tab above to view included lectures and quizzes.


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