Congenital kidney anomalies
- Lesion
Errors in kidney development or ascent produce missing, small, misplaced or fused kidneys.
What it is
About a tenth of people are born with some anomaly of the kidney or urinary tract. Bilateral agenesis is incompatible with life and causes the oligohydramnios (Potter) sequence; unilateral agenesis is compatible with normal life, with compensatory hypertrophy of the other kidney. Hypoplasia means a small kidney with fewer lobes. Ectopic kidneys usually lie in the pelvis; horseshoe kidneys, the commonest fusion anomaly, are joined at the lower poles. Many of these anomalies obstruct urine flow and favour infection and stones.
Structure
- Agenesis: no kidney and no ureter on that side.
- Hypoplasia: small kidney with normal architecture but fewer calyces and lobes.
- Ectopic kidney: normal or small, supplied by vessels from nearby arteries.
- Horseshoe kidney: an isthmus of renal tissue or fibrous band joins the poles in front of the aorta and vena cava.
Clinical notes
- Horseshoe kidneys are associated with Turner syndrome and trisomy 18 and carry higher risk of stones, hydronephrosis and Wilms tumour.
- Prenatal ultrasound detects most of these anomalies.
Test yourself
Think of the answer, then tap the question to see it.
What does bilateral renal agenesis cause in the fetus?
Oligohydramnios with the Potter sequence: pulmonary hypoplasia, facial and limb deformities.
Which poles are usually fused in a horseshoe kidney?
The lower poles.
What stops a horseshoe kidney from ascending?
The inferior mesenteric artery, which catches the isthmus.
Elsewhere in DurgiPedia
- Kidney: pronephros, mesonephros, metanephros and ascent
- Renal agenesis and the Potter sequence
- Horseshoe kidney and renal ectopia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Solitary or Single-functioning Kidney - NIDDK (NIDDK (National Institutes of Health), 2024); Ectopic Kidney - NIDDK (NIDDK (National Institutes of Health), 2024); Horseshoe Kidney - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.