Vani S. Menon, MD
Derek Matoka, MD
BASICS
DESCRIPTION
• Renal ectopia describes a kidney that is located outside of the normal orthotopic position within the renal fossa
• Positions for ectopia:
– Pelvic kidney: Below aortic bifurcation; this is the most common ectopic position
– Lumbar: Near sacral promontory
– Abdominal: Above iliac crest
– Cephalad: Seen in conjuncture with omphalocele when intra-abdominal organs herniate into the defect and cranial ascent of kidney is limited by the diaphragm
– Thoracic: Above the diaphragm with vasculature arising from a cranial source
• Crossed fused renal ectopia
– Fusion occurs in up to 90% of cases
– Left to right crossing and more common in males
– Solitary and bilateral crossed varieties less common
– Type of anomaly is descriptive of the fusion anomaly
(inferior, lump, S-shaped [aka sigmoid], L-shaped, disc, or pancake)
– Fused unit usually caudal to the orthotopic renal moiety
• Horseshoe kidney is a noncross-fused ectopia
EPIDEMIOLOGY
Incidence
• 1 in 500 to 1 in 1,290 in postmortem studies
– Incidence is higher in autopsy series than in clinical studies, suggesting many clinically insignificant and not recognized
– Left side favored over right
• Pelvic kidney 1 in 2,200 and 1 in 3,000
• Crossed renal ectopia: Extremely rare
Prevalence
N/A
RISK FACTORS
Potential relationship with maternal illnesses/teratogenic exposure
Genetics
N/A
PATHOPHYSIOLOGY
• Failure of ascent
– Anomalous vasculature impeding ascent; possibly and abnormally situated umbilical artery
– Thought to occur at the 4th–8th wk of gestation
– Normal kidney ascent to the level of L2 at the end of the 8th wk of gestation
• Abnormality of the ureteric bud or metanephric blastema
• Fusion abnormalities occur early in embryogenesis
– Horseshoe kidney is the most common fusion anomaly
– Two renal moieties joined at lower pole in 90% of cases
• Anatomic considerations:
– Orthotopically located adrenal gland
– Ureter inserts into bladder in orthotopic position
– Renal pelvis of ectopic kidney is usually anterior to the parenchyma secondary to malrotation
– Failure of development of fascial layers in the flanks on the side not occupied by renal tissue
• Malrotation of the ectopic kidney almost always occurs
ASSOCIATED CONDITIONS
• Vesicoureteral reflux: Estimated incidence between 20 and 30%
– Contralateral kidney demonstrates reflux in approximately 50% of cases
– Bilateral renal ectopia carries highest risk for reflux—>70% (1)[C]
• Hydronephrosis: Seen in over 50%
– Half of these cases are due to either ureteropelvic junction obstruction (UPJO) or ureterovesical junction obstruction (UVJO)
– 25% of the hydronephrotic cases are secondary to reflux and the remaining 25% due to malrotation (2)[C]
• Genital anomalies: Estimated incidence between 15 and 45%
– 10–20% of males will have cryptorchidism, hypospadias, or duplicated urethras
– 20–66% of females will have uterine or vaginal anomalies
• Cloacal anomalies: 14% of these patients will have an ectopic kidney
• Nephrolithiasis
• Recurrent urinary tract infections (UTIs)
GENERAL PREVENTION
N/A
DIAGNOSIS
HISTORY
• UTIs (30%), vague abdominal pain or renal colic
• Incidentally during pre- or postnatal screening
• Abdominal mass, hypertension, hematuria, incontinence, renal insufficiency
PHYSICAL EXAM
• Usually normal
• May find abdominal mass or flank tenderness
• Genitourinary abnormalities
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Urine analysis and culture
• BUN/Cr
Imaging
• If kidney absent on ultrasound (US), radionucleotide imaging should be performed to evaluate for an ectopic kidney
– Average differential function of ectopic kidney is 35% (1)[C]
• Diuretic renography if moderate-to-severe pelvicalyceal dilation or progressive dilation found to evaluate for obstructive process
• Voiding cystourethrogram for febrile UTI and/or pelvicalyceal dilation
• If kidney is nonfunctional, computed tomography scan or abdominal US for localization
• Recent use of magnetic resonance urogram for small, poorly functioning kidneys can be utilized
Diagnostic Procedures/Surgery
N/A
Pathologic Findings
N/A
DIFFERENTIAL DIAGNOSIS
• Horseshoe kidney
• Malrotated kidney
• Ptosis of orthotopically located kidney
• Supernumerary kidney:
– Usually caudad to orthotopic kidney
TREATMENT
GENERAL MEASURES
Specific treatment for renal ectopia itself is not indicated. However, special considerations for associated conditions may be necessary.
MEDICATION
First Line
Antibiotic prophylaxis for reflux based on clinical need
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Nephrolithiasis
– Shock-wave lithotripsy, ureteroscopy, percutaneous nephrolithotomy, laparoscopic nephrolithotomy (3)[C]
• UPJO
– <15% are due to an aberrant crossing vessel
– Goal of management is to achieve dependent pelvic drainage
– Dismembered pyeloplasty: Open and minimally invasive
– Ureterocalicostomy
– Endopylotomy could be a consideration for failed pyeloplasty but is rarely indicated as the initial surgical intervention
• Vesicoureteral reflux
– Open vs. endoscopic repair for clinically significant reflux
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
N/A
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Outcomes for treatment of nephrolithiasis and UPJO are comparable to management of these entities in the orthotopic-positioned kidney
• Current literature suggests no adverse effects on blood pressure or kidney function (4)[B]
• No evidence for increased risk of malignancy
COMPLICATIONS
• Vesicoureteral reflux
• Nephrolithiasis
– Most likely due to urinary stasis
• UPJO/UVJO
• UTIs
• Bowel laxity in the region of the empty renal fossa
• Traumatic injury to renal unit due to poor protection in ectopic location
FOLLOW-UP
Patient Monitoring
• Nephrolithiasis
– Imaging by renal US and/or CT scans
• Vesicoureteral reflux
– VCUG and/or DMSA
• Hydronephrosis
– Renal US and/or nuclear scans
• Yearly blood pressure measurements
• Yearly BUN/Cr measurements
Patient Resources
• Urology Care Foundation: Ectopic Kidneys
http://www.urologyhealth.org/urology/index.cfm?article=22
REFERENCES
1. Guarino N, Tadini B, Camardi P, et al. The incidence of associated urological abnormalities in children with renal ectopia. J Urol. 2004;172:1757–1759.
2. Shapiro E, Bauer S, Chow J. Anomalies of the upper urinary tract. In: Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Elsevier Saunders; 2012.
3. Gupta M, Lee MW. Treatment of stones associated with complex or anomalous renal anatomy. Urol Clinic N Am. 2007;34(3):431–441.
4. van den Bosch CM, van Wijk JA, Beckers GM, et al. Urological and nephrological findings of renal ectopia. J Urol. 2010;183:1574–1578.
ADDITIONAL READING
Cinman NM, Okeke Z, Smith AD. Pelvic kidney: Associated diseases and treatment. J Endourol. 2007;21(8):836–842.
See Also (Topic, Algorithm, Media)
• Horseshoe Kidney
• Malrotated Kidney/Renal Malrotation
• Renal Dysplasia, Hypodysplasia and Hypoplasia
• Renal Ectopia Image 
• Renal Fusion Anomalies
• UPJO
• UTI, Complicated, Pediatric
• Urolithiasis, Pediatric, General Considerations
CODES
ICD9
753.3 Other specified anomalies of kidney
ICD10
• Q63.2 Ectopic kidney
• Q63.1 Lobulated, fused and horseshoe kidney
CLINICAL/SURGICAL PEARLS
• Renal ectopia carries an increased risk of urologic abnormalities such as reflux, hydronephrosis, and genital abnormalities.
• Over half the cases of reflux occur in the orthotopic kidney.
• >80% of ectopic kidneys will have differential function of approximately 35%.
• An anterior renal pelvis and anomalous vasculature must be a consideration prior to surgical intervention.
• Surgical interventions for nephrolithiasis have similar success rates as for orthotopic kidneys.