Congenital renal disorders: Pathology review

Two people came to the Nephrology ward one day.

The first is 29 year old Dan, who presents with hypertension, gross hematuria, and flank pain.

Dan’s family history showed that his grandmother died of a berry aneurysm.

Next is 35 year old Heather.

She doesn’t present have any symptoms, but she has been referred to the nephrology clinic because her primary care doctor discovered that she her kidneys have a “weird shape” on an abdominal x-ray.

Both individuals underwent abdominal ultrasound.

Dan had many cysts of different sizes on both kidneys, while Heather’s kidneys are located lower than normal and appear fused together.

Both Dan and Heather have congenital renal disorders.

The renal system starts developing during week 4 of intrauterine life.

It comes from the mesoderm, which is one of the three primitive germinal layers.

More specifically, it develops from a portion of the mesoderm called the intermediate mesoderm.

The intermediate mesoderm on either side of the embryo condenses to form a cylindrical structure called the urogenital ridge, and a portion of the urogenital ridge called the nephrogenic cord gives rise to urinary structures.

During renal development, the nephrogenic cord gives rise to three sets of structures: the nonfunctional pronephros in the embryo’s head region which regresses by the end of week 4.

Then, the mesonephros forms, appears in the thoracic and upper lumbar region and acts as temporary kidneys until they regress in week 12.

Finally the metanephros develops in the pelvic region, and it forms the permanent kidneys.

Ok, the metanephros sprout small buds called the ureteric buds.

At the same time, the intermediate mesoderm gives rise to another tissue called the metanephric blastema.

The blastema release growth factors that stimulates the ureteric bud to become the ureter, the renal pelvis, the renal calyces, and the collecting ducts.

Meanwhile, the ureteric bud release growth factors that cause the metanephric blastema to develop into nephrons.

At around week 20, the metanephric kidneys take over urine production, this becomes the major source of amniotic fluid.