Congenital Renal Anomalies

Congenital Renal Anomalies Andrew Phan MS4 November 2005

Antenatal Ultrasonography
Antenatal ultrasonography is a routine procedure in the management of pregnant patients.
90% of fetal kidneys can be identified by 17 to 20 weeks of gestation, and 95% by 22 weeks
Antenatal detection of renal anomalies has changed approach to anatomic renal disease and has led to controversial therapies for obstructive uropathies
Allows for early diagnosis of congenital urine flow impairments.

Ultrasonography
Ultrasonography examines:
the dilatation of the urinary tract
the echostructure of the renal parenchyma
the volume of amniotic fluid
the visualization of the fetal bladder.

Accuracy of Screening
Study done by Livera et al. in 1998
6292 pregnant women reaching 28 weeks' gestation within the study period
Compared antenatal diagnosis to post-natal diagnosis
92 babies had abnormal antenatal scans
Of those 92, 42 had abnormalities confirmed on postnatal U/S. (4/42 died, 21/42 with surgery to correct at 18 months)
7 were missed on antenatal U/S.

Renal Anomalies
Renal dysplasia
Renal hypoplasia
Renal aplasia
Multicystic Dysplastic Kidney
Ureteropelvic Junction Obstruction
Vesicoureteral reflux
Ectopic ureters
Ureteroceles
Polycystic kidney disease
Posterior Urethral valves

Normal Kidney Development
Kidney derives from intermediate mesoderm
Pronephros is rudimentary kidney that appears in third week of gestation, regresses, and has no known function
Mesonephros is second transient kidney, from fifth to twelfth week of gestation. Degenerates in cephalocaudal direction. Mesonephric duct gives rise to portions of epididymis and ductus deferens in boys (forms vestigial structure in girls)
Metanephros (definitive kidney) appears during fifth week of gestation. Initiated by interaction between ureteric bud, a branch of mesonephric duct
Ureteric bud is responsible form formation of kidney and urinary collecting system.
Nephrogenesis involves differentiation of mesenchyme into tubular and glomerular epithelium

Normal Ultrasound Renal Anatomy Pyramid Collecting system Lower pole Cortex Capsule Upper pole

Normal Renal Measurements Han BK, Babcock DS. Sonographic measurements and appearance of normal kidneys in children. AJR 1985; 145(3):611-616.

Fusion of right and left kidneys

Horseshoe Kidney
Fusion of the lower poles of the kidneys midline
1/500 births. Seen in 7% of patients with Turner syndrome.
Wilms tumors are 4x more frequent than in general population. Other complications include obstructive uropathy, related to ureteropelvic junction obstruction, calculi and urinary tract infections.
Renal function is generally normal.

Dilation of renal pelvis, consistent with hydronephrosis

CT of separate patient with hydronephrosis. Note the diilation of the pelvis with substance that has similar echogenicity of water.

Hydronephrosis
Often a transient finding
Multiple etioligies, including urinary tract obstruction and vesicoureteral reflux. May result in abnormal renal development and injury.
If found antenatally, requires evaluation after birth.
Bilateral hydronephrosis seen in 20 to 40% of cases.
5% of individuals who have antenatal hydronephrosis will require surgical intervention

Etiologies of Hydronephrosis Woodward, M and Frank, D. Postnatal management of antenatal hydronephrosis. BJU International 2002; 89(2): 149-156. 1% Posterior urethral valves 2% Ureterocoele 8% Other ( ectopic ureter, prune belly, urachal cyst, and urethral atresia) 2% Multicystic dysplastic kidney 4% Megaureter (obstructed or unobstructed) 9% Vesicoureteral reflux (VUR) 11% Ureteropelvic junction (UPJ) obstruction 15% Physiologic 48% Transient

Reflux
An etiology in 9% of individuals with hydronephrosis. Predisposes individuals to chronic renal failure.
Best evaluated by voiding cysturethrogram (VCUG).
Grade I- Ureter only
Grade II - Ureter, renal pelvis, calyces without dilatation
Grade III - Dilatation or tortuosity of ureter and/or dilated pelvis
Grade IV - Shape of calyces maintained but dilated
Grade V - Gross dilation of collecting system
Management may include prophylactic antibiotics or surgical intervention

Cystic structures with no parenchymal development

Multicystic Dysplastic Kidneys
Kidney consists of groups of cysts with connective tissue. Minimal or no renal parenchyma.
1:2,400 live births
Multicystic dysplastic kidney is often unilateral.
Vesicoureteral reflux is common (20%) in the contralateral kidney
Current reccomendation is to evaluate for reflux with serial ultrasounds
Increased risk of hypertension.

Enlarged kidney with increased echogenicity. Poorly differentiated parenchyma with no evidence of macroscopic cysts.

Pulmonary hypoplasia secondary to enlarged kidneys

Autosomal Recessive Polycystic Kidney Disease
Kidneys increased in size with microcysts. Increased echogenicity with poor parenchymal differentiation.
Lungs may be hypoplastic secondary to kidney enlargement.
Liver may be involved with cysts, congenital hepatic fibrosis, and portal hypertension
~1:25,000
Wide spectrum of disease manifestation, even within families. Most severe manifestations die in utero. Most cases, however present by 1 year of age with renal impairment and hypertension.
Treatment at this time is symptomatic and aimed at managing complications of disease.

Enlarged kidney with macroscopic cystic structures in kidney. Kidney parenchyma is evident. The kidney has increased echogenicity.

Bilateral enlargement of both kidneys. Increased echogenicity with cystic structures seen. In 1/3 of cases hepatic cysts also seen.

Autosomal Dominant Polycystic Kidney Disease
Usually not clinically apparent in young children with onset usually during the fourth decade
Often bilateral involvement of kidneys with large cystic structures seen
Cysts may also be present in liver, pancreas, cerebral vessels and other organs
~1:700
Unlike ARPKD, congenital hepatic fibrosis is rare
Presents with gross or microscopic hematuria, hypertension, proteinuria, cyst infection and renal insufficiency
Progresses to end stage renal failure

Works Cited
Behrman: Nelson Textbook of Pediatrics, 17 th ed. 2004. Saunders, an Imprint of Elsevier.
Han BK, Babcock DS. Sonographic measurements and appearance of normal kidneys in children. AJR 1985; 145(3):611-616
Livera, LN, Brookfield, DS, Egginton, JA, Hawnaur, JM. Antenatal ultrasonography to detect fetal renal abnormalities: A prospective screening program. BMJ 1989; 298:1421.
Lonergan GJ , Rice RR , Suarez ES . Autosomal recessive polycystic kidney disease: radiologic-pathologic correlation. Radiographics. 2000. 20(3):837-55.
Mouriquand, PD, Wilcox, TD, and Troisfontaines, E. Antenatal and perinatal uro-nephrology:current questions and dilemmas. Pediatr Nephrol (1999) 13:938–944
Up To Date Online. www.utdol.com . 2005.
Woodward, M and Frank, D. Postnatal management of antenatal hydronephrosis. BJU International 2002; 89(2): 149-156.

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Congenital Renal Anomalies

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