Embryology · Urogenital system
Renal agenesis and the Potter sequence !
- Malformation
One or both kidneys are missing. Without both, there is almost no amniotic fluid and the lungs fail to develop.
Updated 2026-11-01
See it in 3D: Kidneys · Ureters · Left adrenal gland · Right adrenal gland
What it is
Renal agenesis is absence of one or both kidneys because the ureteric bud fails to form or fails to induce the metanephric blastema. Unilateral agenesis often goes unnoticed because the other kidney grows to compensate. Bilateral agenesis leaves the fetus with almost no amniotic fluid and causes the Potter sequence, whose lethal problem is pulmonary hypoplasia.
Embryological cause
- Week 5: the ureteric bud fails to sprout from the mesonephric duct, or sprouts and fails to enter the metanephric blastema.
- Without the bud's signal the blastema forms no nephrons and disappears; without GDNF from the blastema the bud does not branch.
- Variants in genes of this pathway (RET, GDNF, PAX2 and others) have been described, but most cases have no identified cause.
- Without fetal urine after the first trimester, amniotic fluid almost vanishes: the uterus compresses the fetus and the lungs cannot expand.
Markers
- RET
- GDNF
- PAX2
- SALL1
How it presents
- Bilateral: oligohydramnios or anhydramnios from the second trimester; severe respiratory distress at birth from pulmonary hypoplasia.
- Potter facies: epicanthic folds, flattened nose, small chin, low-set flattened ears.
- Clubfoot, hip dislocation and contractures from compression.
- Unilateral: an incidental finding, sometimes with hypertension or proteinuria in adult life.
- It is reported more often on the left side and in males.
Diagnosis
- Prenatal ultrasound: anhydramnios, no visible kidneys or bladder.
- “Lying-down adrenal” sign: the adrenal gland looks long and flat in the empty renal fossa.
- Colour Doppler: no renal arteries are seen.
- Fetal MRI helps when oligohydramnios limits the ultrasound view.
Test yourself
Think of the answer, then tap the question to see it.
What is the embryological cause of renal agenesis?
The ureteric bud fails to form or to enter the metanephric blastema around week 5, so nephron formation is never induced.
What is the cause of death in bilateral renal agenesis?
Pulmonary hypoplasia, secondary to severe oligohydramnios: without amniotic fluid the fetal lung does not develop.
Why is Potter called a sequence rather than a syndrome?
Because one initial defect, the lack of fetal urine, sets off the other findings in a cascade through compression of the fetus.
What typical ultrasound finding is seen in the empty renal fossa?
A long, flat adrenal gland: the “lying-down adrenal” sign.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Kidney: pronephros, mesonephros, metanephros and ascent
- Amniotic fluid: polyhydramnios and oligohydramnios
- Pulmonary hypoplasia
- Malformation, disruption, deformation, sequence, syndrome, association
- Clubfoot (talipes equinovarus)
- Uterine anomalies: bicornuate, septate, didelphys, Müllerian agenesis
- Multicystic dysplastic kidney and polycystic kidney disease
- ACE inhibitors and ARBs: fetal kidney damage
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Potter Syndrome - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023); Embryology, Kidney, Bladder, and Ureter - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.