Dr. Alia Al-IbrahimConsultant Pediatric Nephrology

Clinical assistant professor

CONTENTS: 1- Anatomy of urinary system2- Function of urinary system3- Normal development4- Congenital anomalies of urinary system:-Dysgenesis of the kidney -Agenesis - Hypo plastic - Dysplastic - A plastic-Abnormalities in shape & position - Ectopic Kidney - Horse shoe Kidney - Crossed fused Ectopia-Abnormalities of collecting system - Hydronephrosis - Bladder extrophy - PUV - Patent Urachus-Clinical presentation- Antenatal screening- Postnatal Evaluation

Development of Urinary system:

The Urinary system goes through three phases on its way to becoming fully functioning :

1- Pronephros2- Mesonephros3- Metanephros

Starting from 4th wk & end on 36 wk of intra uterine life

Normal Anatomy of the Urinary system

-4 wks gestation : kidney start development- 9 wks : first glomeruli , Bladder-36 wks : nephrogenesis ceases ( 1 million glomeruli in each kidney).

- Postnatal increase in the size of the kidney is due to enlargement of the Glomerular diameter & significant increase in tubular volume & length

Active period of nephrogenesis between 20-36wks, cease around 36 wks

Nephron: Glomerulus, Bowman's capsule, convoluted tubule, loop of Henle Formation begin at 8th wk. Postnatal increase in the size of the kidney is due to enlargement of the Glomerular diameter & significant increase in tubular volume & length.

Nephron

Ascent of kidneys:

A: 5th -6th wk the mature kidneys lie in the pelvis with their hila pointed anteriorlyB: 7th wk the hilum points medially , kidneys in the abdomen.

C: 9th wk kidneys in the retroperitoneal position at level of L1 , complete rotation , anteromedially.

Normal Function of the Urinary system:

Kidney :1- Filters blood- remove and eliminate soluble waste ( urine).2- Regulates blood volume and composition.3- Maintains water and electrolyte balance.4- Hormonal production; Erythropoietin, Renin.5- Metabolizes vitamin D to active form.

Ureters: convey urine from kidneys to bladder.

Urinary bladder: Temporary urine storage.Urethra: Conveys urine from bladder to outside.

Abnormalities during development:

1- Dysgenesis of the Kidney

a- Renal Agenesis(absent Kidney) : Failure of the ureteral bud to communicate with the metanephric blastema 1:500 – 1: 3200 live births

AGENISIS

UNILATERAL BILATERAL

1- Unilateral : absent kidney, no symptoms. Avoid contact sport, other kidney hypertrophy , check for abnormality ( 50% ) Incidence increase with single umbilical artery absent ureter & hemitrigone. Hypertrophy, VUR in contra lateral kidney

2- Bilateral: Incompatible with extra uterine life Oligohyddramnios , no kidneys , non visualized bladder in antenatal US Death shortly after birth from pulmonary Hypoplasia ( Potter’s syn)Detected by US 12th wk of gestation

higher in boys.5% recurrent risk in subsequent pregnancy

Associated anomalies include: Anorectal, CVS, Skeletal.

b- Renal Hypoplasia : Small size, non dysplastic, less than normal # of calyces & nephron . 1- Unilateral: Incident diagnosis ( another urinary tract problem or HTN).

2- Bilateral: CRF manifestations.

3- Segmental Hypoplasia: ( Ask-Upmark Kidney).

C-Aplasia : rudimentary kidney

d-Renal dysplasia: Abnormality in the structure cartilages, cyst ( Abnormal metanephric differentiation) May affect all or part of the kidney.

1- Cystic 2- cartilelages

Hereditary : ARPKD ADPKD

Congenital: MCDK

Multicystic dysplastic kidney (MCDK):

-Non- functioning kidney replaced by large non-communicating cysts of varying sizes, no renal cortex, atretic ureter.

-Unilateral , 2 times more in male.

-Detected during antenatal US.

Investigations & diagnosis:1- US.2- DMSA ( no function in the affected side) , hypertrophy of contra-lateral kidney.3- MCUG : contra-lateral VUR (20%).

Complications:

1- Malignancy: Wilm's’ tumor, adenocarcinoma& embryonic carcinoma.2- HTN: cured by nephrectomy.3- Infection, bleeding into, or rupture of cysts if large.

Management:

Conservative:1- cysts < 5cm , high chance of involution, or cause no problems.2- reviewed annually for: - BP - urinary protein. - US for cysts involution, of MCDK. growth of contra-lateral kidney. Up to 2yrs of age then at 5yrs of age if normal.

Nephrectomy: 1- no involution by 2 yrs of age. 2- HTN 3- infections

11- Abnormalities in shape & position:

a- Ectopic Kidney: Failure of ascent of the kidney during embryogenesis. Incidence 1;900Associated anomalies: VUR, undesended testis in , hypospadius, Genital abnormalities in girls

Blood supply from internal, external iliac artery ,& or aorta

Ectopic in contra lateral side 90% fusion

b- Fusion Anomalies 1- horseshoe Kidney: 1:500-Commonest form of fusion (95%).

-The lower poles of both kidneys unit across the midline

-The isthmus of horse shoe kidney lie at the level of L4-L5, is more susceptible to trauma

-More common in male, Turner syndrome, trisomy 18

Complications:

-50% VUR, abnormal vascular supply.- Stone & hydronephrosis 2° PUJO.- Wilm’s tumor- HTN

Diagnosis: DMSA, MCUG ,DTPA . can be missed by us.

-2- Crossed fused Ectopia:

- one kidney cross the midline to the other side and lie in an abnormal rotate- position & fused upper pole fused to the normal kidney lower pole.- ureter inserted in normal position.- anomalies of uro-gent.system

III-Abnormalities of the collecting system:

A- Duplex kidney : 1% , Familial, more in girls , 70% unilateral.-Two pelvicalyceal system within the kidney, complete or partial.- Kidney larger than normal.

Complete:-Kidney has 2 moieties, each with its own ureter>-The upper pole ureter opens lowermost & medially into the bladder .- May be ectopic draining in vagina, posterior urethra.- Ureterocoele ( obstruction).

-The lower pole ureter cause reflux, , PUJO, dysplastic part.

Incomplete: -Uncomplicated divided pelvis, or 2 Ureters join before entering the bladder.

Hydronephrosis:

Dilatation of renal pelvis & collecting system.-0.6- 4.5% antenatal US.-Several grading system ( Renal pelvic diameter).-Antenatal US ( 18-20 WKS). - severity of antenatal US. - Unilateral vs. bilateral - Renal parenchyma thin or Echogenic. - Bladder - Amniotic fluid

Causes: 1- Transient 2- Physiological 3- UPJO 4- VUR 5- Megaureter 6- Ureterocoele 7- PUV

Postnatal evaluation: 1- Physical exam: Abdominal mass, palpable bladder.2- US 3- VCUG : detect VUR, PUV.4- Diuretic Renogram : detect urinary obstruction with persistent hydronephrosis

Ureteropelvic junction obstruction ( UPJ):Detected antenatal, frequent cause of hydronephrosisMore common in Left side, Ectopic, malrotation, horseshoe kidney

Bilateral 40%Present: mass, UTI, Pain, Hematuria

Bladder extrophy:Failure of abdominal wall to close during fetal development & results In protrusion of the posterior bladder wall through the lower abdominal wall.-Symphsis pubis diastasis.- Multiple abnormalities in pelvis, bladder, urethra, & external genitalia.- Common in males

Associated abnormalities: 1- VUR2- Incontinence3- Repeated UTI

Posterior urethral valve (PUV):Commonest obstructive Uropathy in boys , 1:5000- 8000

Congenital valve in the posterior urethra due to persistent urogenital membrane.

-Associated with renal dysplasia ( Back pressure, common developmental insult).

Risk of perinatal mortality & risk of chronic kidney disease: 1- US suggestive at < 24 wks gestation. 2- Severe bilateral hydronephrosis. 3- Oligohyddramnios. 4- Echogenic kidneys.

Postnatal presentations:1- pulmonary Hypoplasia.2- Poor urinary stream3- Voiding dysfunction.4- Urosepsis.5- FTT.

Renal & urological manifestation:

1- Chronic kidney diseases. 60% dysplastic kidney2- VUR3- Bladder dysfunction.

Management: 1- correction of electrolytes.2- Treatment of sepsis.3- Resp.distress4- Temporary relieve of pressure5- cystoscopy : valve ablation6- Vesicostomy

Prune belly syndrome ( Eagle-Barrett syndrome, Triad syndrome)

Triad of:1- Deficiency or absence of anterior abdominal wall musculature.2- Bilateral cryptorchidism3- Ureter ,bladder,& urethral abnormalities( megacystis, Megaureter 2° dysplasia.

-Other systemic abnormalities in 75%: 1- GI : malrotation, gastroschisis. 2- Heart: CHD 3- Skeletal: talipes equinovarus, CDH. 4- Pulmonary hypoplasia

Clinical presentation : Wide spectrum1- Antenatal screening 0.1- 0.7%.2- UTI3- Hypertension4- Proteinuria5- Renal impairment6- Hematuria7- Stones

Antenatal Screening US 1- Fetal kidney2- Collecting system3- Amniotic fluid

Postnatal Exam:Physical exam: Associated anomaliesUrgent evaluation : Bilateral involvement, solitary affected kidney, oligohyddramnios.Renal studies: Renal US, VCUG, MAG3

Take home messages:

1- Congenital anomalies of the kidney are significant causes of ESRF in children.2- These anomalies often do not exist in isolation.3- May present beyond the neonatal period.4- Bilateral involvement. Oligohyddramnios, solitary kidney require urgent evaluation.5- Long –term follow-up of renal & bladder function is important.