Table of Contents
Overview – Congenital Kidney Abnormalities
Congenital kidney abnormalities affect up to 10% of the population and include a diverse range of malformations. While some are asymptomatic and discovered incidentally, others lead to serious complications such as urinary tract infections, hypertension, and renal failure. Early recognition—often antenatal—is crucial for appropriate monitoring and intervention. This page outlines common congenital abnormalities of the kidneys including agenesis, hypoplasia, ectopic kidneys, and horseshoe kidneys.
Renal Agenesis
Definition
- Agenesis refers to the complete absence of one or both kidneys at birth.
Risk Factors
- Intrauterine growth restriction (IUGR)
- Multiple gestation (e.g. twins/triplets)
Clinical Implications
- Bilateral renal agenesis:
- Incompatible with life
- Usually results in stillbirth
- Unilateral renal agenesis:
- Often asymptomatic
- Associated with compensatory hypertrophy of remaining kidney
- Increased risk of progressive glomerular sclerosis and chronic kidney disease later in life
- May be linked with other congenital defects (e.g. limb anomalies, hypoplastic lungs)
Diagnosis
- Typically diagnosed on antenatal ultrasound
- Confirmed by imaging postnatally
Prognosis
- Most individuals with unilateral agenesis live normal lives
- Long-term follow-up required to monitor for kidney function decline
Renal Hypoplasia
Definition
- Failure of one or both kidneys to develop to normal size
Risk Factors
- Family history
- Exposure to certain medications in pregnancy
Clinical Implications
- Usually unilateral
- Bilateral hypoplasia: may lead to early-onset renal failure
- Increased risk of:
- Hypertension in adulthood
- Recurrent urinary tract infections
Diagnosis
- Often detected on routine antenatal ultrasound
- Sometimes diagnosed later in childhood
Prognosis
- Depends on the degree of renal impairment
- Close follow-up required for blood pressure and renal function
Ectopic Kidney
Definition
- A kidney located in an abnormal position due to a birth defect
Clinical Implications
- Usually asymptomatic
- May be associated with:
- Obstruction
- Recurrent UTIs
- Nephrolithiasis
- Increased risk of trauma due to atypical positioning
Diagnosis
- Detected via ultrasound, X-ray, or CT
- Common locations:
- Just above the pelvic brim
- Fully within the pelvis
Prognosis
- Typically benign and requires no treatment unless complications arise
Horseshoe Kidney
Definition
- Fusion of the kidneys at the upper or lower poles, forming a continuous U-shape across the midline
- Crosses anterior to the great vessels
Risk Factors
- Genetic predisposition
- Associated with Turner syndrome and Edward syndrome
Prevalence
- Occurs in approximately 1 in 500–1000 births
- 90% involve fusion at the lower poles
Clinical Implications
- Often asymptomatic
- Increased risk of:
- Abdominal pain
- Kidney stones
- UTIs
- Vulnerable to trauma → patients advised to avoid contact sports
Diagnosis
- Renal ultrasound
Prognosis
- Usually does not affect life expectancy
- Monitoring is advised for urinary tract complications
Summary – Congenital Kidney Abnormalities
Congenital kidney abnormalities such as renal agenesis, hypoplasia, ectopic positioning, and horseshoe formation vary in clinical significance. While many individuals remain asymptomatic, some progress to chronic kidney disease or experience recurrent UTIs and hypertension. Prenatal imaging allows early detection and long-term monitoring can reduce complications. For a broader context, see our Renal Overview page.