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Echogenic Kidneys

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KEY POINTS
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Key Points

  • Echogenic kidneys can be a normal variant but are also seen in association with renal dysplasia, chromosomal abnormality, adult and fetal polycystic disease, Pearlman syndrome, Beckwith–Wiedemann syndrome, and CMV infection.

  • The incidence of echogenic kidneys has been estimated at 1.6 cases per 1000 sonograms.

  • Kidneys are considered echogenic if the reflectivity of the renal parenchyma is greater than the reflectivity of the liver.

  • Once diagnosed, other sonographic features of aneuploidy, renal anomalies, and CMC infection should be sought.

  • Consider genetic amniocentesis, TORCH titers, and fetal MRI to better evaluate the genitourinary tract and renal parenchyma.

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CONDITION
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There are some conditions that render the renal parenchyma echogenic on ultrasound examination. While increased renal echogenicity can be a normal variant in children, it has been associated with nephrotic syndrome, glomerulonephritis, and renal dysplasia (Krensky et al., 1983; Brenbridge et al., 1986; Cramer et al., 1986; Kraus et al., 1990). Premature infants also have an increased incidence of increased renal echogenicity (Benacerraf, 1998). While increased echogenicity is a subjective assessment, kidneys that are brighter than liver are considered to be echogenic. This becomes a potential indicator of fetal disease because of the association of this finding with chromosomal abnormality, adult and infantile polycystic kidney disease, Pearlman syndrome, Beckwith–Wiedemann syndrome, and cytomegalovirus infection. The cause of the increased echogenicity of the kidney in these conditions is unknown.

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INCIDENCE
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Little data are available to estimate a true incidence of echogenic kidneys in the fetus, in either normal fetuses or those with underlying pathology. However, De La Vega and Torres (2005) in a retrospective review of prenatally diagnosed renal disease found 13 cases among 7714 sonographic studies for an incidence of 0.16% or 1.6 cases per 1000 sonograms (Han et al., 2003).

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SONOGRAPHIC FINDINGS
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The kidneys should be considered to be echogenic if the reflectivity of the renal parenchyma is greater than the reflectivity of the liver (Figure 77-1). Once identified, it is important to note other possible associated findings that would aid in the differential diagnosis. It is important to look for other sonographic features that are associated with aneuploidy, especially trisomy 13, including ventriculomegaly, holoprosencephaly, agenesis of the corpus callosum, cleft lip or palate, cyclasia, or microphthalmia. Because of the association of echogenic kidneys with cytomegalovirus infection, attention should be paid to the presence of intracranial calcifications, echogenic bowel, ascites, hydrops, or cardiomegaly (Choong et al., 1993). If the possible renal abnormalities seen with echogenic kidneys (including severe obstructive uropathy at any level from the bladder outlet to the ureteropelvic junction) occur during the second trimester, they can result in increased echogenicity from renal dysplasia. The kidneys in adult and infantile polycystic kidney disease can also be echogenic, but they are usually much ...

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