Agenesis of the Kidney

Content of This Page

1- Definition & Types

2- Causes & Pathogenesis

3- Pathophysiology 

4- Clinical Features & Examination

5- Investigations

6- Management

7- Complications

8- Core Concepts

Definition & Types

Renal agenesis refers to the congenital absence of one or both kidneys, due to a failure in embryological development of the ureteric bud.

Types:

  • Unilateral renal agenesis

    • ~1 in 500 births

    • Often asymptomatic

    • May be discovered incidentally

    • Usually associated with compensatory hypertrophy of the remaining kidney

  • Bilateral renal agenesis

    • Rare and incompatible with life

    • Associated with Potter sequence (oligohydramnios, limb deformities, pulmonary hypoplasia)

Causes & Pathogenesis

  • Congenital malformation of the ureteric bud or metanephric mesenchyme

  • Can occur sporadically or as part of genetic syndromes

  • May be associated with other genitourinary abnormalities:

    • Ectopic kidney

    • Horseshoe kidney

    • Vesicoureteric reflux (VUR)

    • Renal dysplasia

Pathophysiology

  • In unilateral agenesis, the remaining kidney typically undergoes compensatory hypertrophy and can maintain normal renal function.

  • In cases of associated abnormalities (e.g. reflux nephropathy), there may be long-term risk of:

    • Hypertension

    • Proteinuria

    • Chronic kidney disease (CKD)

Clinical Features & Examination

  • Most children are asymptomatic

  • Renal agenesis may be suspected on:

    • Antenatal ultrasound (missing kidney or oligohydramnios)

    • Postnatal imaging for UTI, hypertension, or single palpable kidney

  • In bilateral agenesis:

    • Presents as stillbirth or early neonatal death

    • Features of Potter sequence

Investigations

  • Ultrasound: confirms absence of renal tissue

  • DMSA renal scan: for differential renal function

  • MRI/CT: useful in confirming anatomy or detecting associated abnormalities

  • Blood pressure and urinalysis: monitor function of the single kidney

Management

  • Unilateral agenesis:

    • No treatment needed if remaining kidney is normal

    • Long-term monitoring of:

      • Renal function

      • Blood pressure

      • Proteinuria

    • Lifestyle guidance: avoid nephrotoxic drugs, monitor hydration

  • Bilateral agenesis:

    • Not compatible with postnatal survival

Complications

  • Unilateral agenesis:

    • No treatment needed if remaining kidney is normal

    • Long-term monitoring of:

      • Renal function

      • Blood pressure

      • Proteinuria

    • Lifestyle guidance: avoid nephrotoxic drugs, monitor hydration

  • Bilateral agenesis:

    • Not compatible with postnatal survival

Core Concepts

  • Unilateral renal agenesis is often benign—prognosis is good if the single kidney functions normally

  • Always investigate associated anomalies (urinary tract, reproductive tract)

  • Avoid nephrotoxins and monitor renal health long-term

  • DMSA scan helps assess renal function and scarring

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