Ectopic Kidneys

Content of This Page

1- Definition

2-Aetiology & Embryology

3- Clinical Features

4- Associated Anomalies

5- Investigations

6- Management Principles

7- Complications

8- Clinical Concepts

Definition

An ectopic kidney is a congenital positional anomaly in which a kidney is located in an abnormal place, usually due to a failure of normal embryological ascent from the pelvis into the abdomen.

Most common types:

  • Pelvic kidney – located low in the pelvis

  • Thoracic kidney – herniates above the diaphragm (rare)

  • Crossed renal ectopia – kidney crosses over to the opposite side, may be fused to the other kidney

  • These are often detected antenatally on ultrasound, or later when investigating UTIs or abdominal pain.
© image from Wikimedia Commons

Aetiology & Embryology

  • In normal development, kidneys form in the pelvis and ascend to the lumbar region by the 9th week of gestation.

  • Failure of this ascent, or abnormal rotation during migration, results in:

    • Malposition (e.g. pelvic ectopia)

    • Malrotation

    • Abnormal vascular supply

  • May occur in isolation or as part of a syndromic anomaly (e.g. VACTERL, caudal regression)

Clinical Features

Often asymptomatic

  • Found incidentally during imaging (e.g. antenatal scan or abdominal CT)

-Symptomatic cases may present with:

  • Recurrent urinary tract infections (UTIs)

  • Abdominal or flank pain

  • Lower abdominal mass (esp. if pelvic)

  • Hypertension or proteinuria in some cases

  • Poor renal function if obstructed or dysplastic

Associated Anomalies

Ectopic kidneys may coexist with:

  • Vesico-ureteric reflux (VUR)

  • Pelvi-ureteric junction (PUJ) obstruction

  • Ureteric duplication

  • Genital tract malformations (especially in females)

  • Renal dysplasia (underdeveloped nephrons)

Investigations

Imaging:

  • Ultrasound: often the first modality

  • CT/MRI: confirms location, vascular supply, and checks for associated anomalies

  • DMSA scan: assesses split renal function and detects scarring

  • MCUG (Micturating cystourethrogram): used when reflux is suspected

  • MAG3 renogram: evaluates drainage and function over time

© image from Wikimedia Commons

Management Principles

-If asymptomatic and functioning:

  • No active treatment needed

  • Educate the patient

  • Long-term monitoring:

    • Renal function (eGFR)

    • Blood pressure

    • Urinalysis (for proteinuria)

-If symptomatic:

  • Treat UTIs promptly

  • If obstruction → Surgical correction

  • Poorly functioning or non-functioning ectopic kidney with symptoms → may require nephrectomy

Complications

  • Hydronephrosis: due to ureteral kinking or abnormal insertion

  • Stones: stagnant urine flow predisposes to calculi

  • Reflux nephropathy: especially if VUR is present

  • Recurrent UTIs

  • Hypertension (due to segmental ischemia or scarring)

  • Impaired renal function if bilateral anomalies

Clinical Concepts

  • Pelvic kidneys are the most common form of ectopia

  • Think of ectopic kidney in a child with:

    • Recurrent UTIs

    • Single palpable kidney

    • Absent kidney on ultrasound

  • Always check for associated abnormalities, especially PUJ obstruction and reflux

  • Even if asymptomatic, ectopic kidneys need long-term follow-up

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