Tag Archives: Hydronephrosis

Ultrasound – Polycystic Kidneys

© 2018, GENASSIST, Inc.     

By Keith S. Wexler, MBA, Maternal Fetal Medicine, Prenatal Diagnosis and Biotech/Life Sciences Consultant, GENASSIST, Inc.

Paul Wexler, M.D., F.A.C.O.G., Medical Director, GENASSIST, Inc.

Clinical Professor, Department of OB/GYN, University of Colorado Health Sciences Center

Clinical Professor, Division of Genetics/Dept. of Pediatrics, Univ. of Colorado/The Children’s Hospital

Background:  A patient seen by her healthcare provider for her 20 week Level II ultrasound was found to have bilateral hydronephrosis (accumulating fluid in the kidneys and or collecting systems for the kidneys) of 5 mm.  The healthcare provider referred her to us for a 2nd opinion and a diagnosis of possible Polycystic Kidneys was made by Dr. Wexler.

Patient was referred to Maternal Fetal Medicine for confirmation of kidney and liver cysts.

Polycystic Kidneys and/or Polycystic Kidney Disease (PKD) is inherited in an autosomal dominant (50% risk to first degree relatives) or autosomal recessive manner (25% if both parents are gene carriers).

One of the characteristics of a disease caused by inheritance of a single deleterious gene (autosomal dominant inheritance) is variable severity.  This means that any or all children who inherit the deleterious gene (50% of children) could have milder or more severe problems related to their kidney function. 

Polycystic Kidney Disease has an incidence of approximately1:400 to 1:1000.

Polycystic Kidney Disease  may be acquired.

Most case of PKD are due to one or more mutations in the PKD1 gene on the short arm on chromosome #16 (16p13.3) or the PKD2 gene on the long arm of chromosome #4 (4q21-13). 

If the mutation is identified in the patient then Preimplantation Genetic Diagnosis becomes a possibility.

PKD causes multiple cysts to form in the kidneys and occasionally the liver and rarely the pancreas. Heart valve problems, abdominal wall hernias and intracerebral aneurysms can occur. 

The kidney cysts diminish kidney function eventually resulting in kidney failure.

The condition may be asymptomatic early in the course of the disease but can cause abdominal or back pain, blood in the urine, kidney stones, kidney infection, fatigue, joint pain and skin or nail abnormalities.

At least 400 mutations have been identified in the PKD1 gene responsible for approximately 85% of cases of Polycystic Kidney Disease (Type I) and over 40 mutations have been identified in the PKD2 gene responsible for approximately 15% of cases of Polycystic Kidney Disease (Type II)

Rarely, mutations in a third gene – PKD3 also can result in autosomal dominant PKD.

PKD can affect both the liver and kidneys and can result in serious renal problems either shortening the individual’s lifespan or resulting in kidney transplantation.

Hydronephrosis & Pyelectasis in Pregnancy

Hydronephrosis & Pyelectasis in Pregnancy© 2016
By Keith S. Wexler, MBA,
Facilitator of Information, Maternal Fetal Medicine, Prenatal Diagnosis and Biotech Consultant, GENASSIST™, Inc.


Hydronephrosis: Distention of the portion of the kidney that collects urine.
Pyelectasis: Dilatation of renal pelvis.
Renal Pelvis: Expanded portion at the center of the kidney which collects urine and funnels it into the ureter duct which transfers urine from the kidney into the bladder.

Ultrasound Marker – Hydronephrosis and/or Pyelectasis:

A common “ultrasound marker” in pregnancy, Hydronephrosis and/or Pyelectasis (often used interchangeably) is usually defined as more than 3 mm of fluid in a kidney measured in the anterior-posterior direction of the fetus.

Mild Pyelectasis is dilatation of the renal pelvis of 4 to 7 mm measured in an anterior posterior direction.
Moderate Pyelectasis is dilatation of the renal pelvis of 7 to 10 mm measured in an anterior posterior direction.
Severe Pyelectasis is dilatation of the renal pelvis of greater than 10 mm measured in an anterior posterior direction.

The good news with ultrasound in pregnancy is that we are able to see “ultrasound markers” on the baby that we were not able to see before ultrasound. The bad news however is that we are able to see “ultrasound markers”, that may not be significant, that we were not able to see before ultrasound.

Babies with chromosomal abnormalities are more likely to have one or more ultrasound markers than babies with normal chromosomes. The risk for a child with a chromosomal abnormality increases with the number of ultrasound markers seen.

The finding of a baby with one or more “ultrasound marker(s)” does NOT mean that the baby has a chromosomal abnormality. Care must be taken to evaluate the “ultrasound marker(s)” detected in pregnancy and decide how to best manage the remainder of the pregnancy for the best outcome.

Prognosis Based Upon Degree of Pyelectasis:

Less than 10 mm: Approximately 94% to 97% of babies will be normal after birth.
10 to 15 mm: 40% to 60% of babies will be normal at birth, 40% required medical or surgical intervention.
Severe: Most of those babies required medical or surgical intervention.

Further Ultrasound Evaluation When Pyelectasis is Detected:

Careful evaluation of fetal ureters and fetal bladder looking for dilatation or distention
Bilateral evaluation of kidneys
Evaluation of Amniotic Fluid Volume
Evaluation for other “ultrasound markers” or fetal anomalies
Follow-up ultrasound of kidneys at regular intervals (e.g. 4 to 6 weeks) until delivery

Increased Risk(s) for Trisomy 21 (Down Syndrome):

A single ultrasound marker in pregnancy may increase the risk for a baby with a chromosomal abnormality to approximately 3-4% above the patient’s maternal age related risk with some ultrasound markers being more significant than others.

If Pyelectasis is the only abnormality identified, the risk for Trisomy 21 (Down Syndrome) is approximately 1 in 300 to 1 in 350 pregnancies. Up to 25% of babies with Trisomy 21 (Down Syndrome) have mild hydronephrosis compared with 2-3 % of normal fetuses.


Although several years ago unilateral or bilateral pyelectasis greater than 3 mm was considered an indication for amniocentesis, today the recommendation for invasive testing would depend upon the presence of other sonographic markers, maternal age and/or other abnormal prenatal tests (i.e. blood testing, DNA etc) suggesting an increased risk for a chromosomal abnormality.


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