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Congenital Abnormalities of the Genitourinary System
Cohen et al.; Seminars in Roentgenology, Vol 39, No 2(April), 2004: pp
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Introduction Genitourinary abnormality: 10% of infants
Antenatal US survelliance(and improved NICU) has much to do with the improvement in infants survival over the last 3 decades.
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Imaging Modalities Ultrasound CT MRI
2-D, 3-D reconstructed anatomy Require sedation Paucity of intrapelvic and intra-abdominal fat MRI Fetal motion and long scan times Half-Fourier single-shot acquisitions with relaxation enhancement Nuclear medicine scintigraphy (Tc99m) Diethylenetrianine pentaacetic acid(DTPA) Mercaptoacetyltriglyceride(MAG-3) Dimercaptosuccinic acid(DMSA) Ureteral jet
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Embryology of the GU System
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Antenatal US Assessment of the GU
Amniotic fluid Formation Dialysate of maternal serum (early in pregnancy) Fluid across fetal skin (before skin keratinization) Fetal urine production(12 wks, most since 16 wks) 120mL/d at 20 weeks 600~1200mL/d at term Mean amniotic fluid volume 500mL at 20 weeks 800mL from 22 to 39 weeks When oligohydramnios α mortality rate
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Antenatal US Assessment of the GU
Normal fetal kidney GA 15 weeks
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Antenatal US Assessment of the GU
Normal fetal ureters, bladder, and genitalia Ureters: not imaged normally Bladder: GA 13~15 wks (fetus voids every 30~60 minutes) Bladder wall thickening bladder outlet or distal obstruction Genitalia: GA 16 wks
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Congenital Abnormalitis of the Kidney
3~4% of newborn Approach (Filly and Goldstein) Non-hydronephrotic Number (eg, agenesis) Form (eg, size, shape) Position (eg, pelvic kidney) Hydronephrotic or dilatation of the pyelocalyceal system Most common kidney anomalies
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Abnormalities of Kidney Number
Unilateral Renal Agenesis Failure of the ipsilateral ureteric bud to contact the nephrogenic blastema 1 / 1,000; Male, left kidney No ureter, renal a., ipsilateral trigone / ureteral orifice of bladder Contralateral kidney compensatory hypertrophy Commonly associated genital abnormalities 8~10% absence of ipsilateral adrenal gland
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Lying down adrenal sign
LK? Lying down adrenal sign
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Abnormalities of Kidney Number
Unilateral Renal Agenesis Associated syndromes VACTERL associations, bronchio-oto-renal syndrome, Fanconi pancytopenia, Kallman syndrome, and Fraser syndrome 90 % abnormalities of the remaining kidney, most common with VU reflux. Others including renal ectopia and malrotation, UPJ obstruction, duplication, and mulicystic dysplasia Nuclear medicine
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Abnormalities of Kidney Number
Bilateral Renal Agenesis 1~3 / 10,000 live births; Male predominant 5% recurrence rate in affected families Nonvisualization of the kidneys and bladder Premature(30~60%), lung hypoplasia, spatial restriction Supernumerary kidney Extremely rare Division of the metanephric diverticulum
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Potter’s facies: Flattened and broad nose Recession of chin
Epicanthic folds Low set ears Hypertelorism
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Abnormalities of Kidney Form
True hypoplasia kidney Rare, more common due to long-term ischemia, reflux, or obstruction Have no function and distorted collecting system
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Abnormalities of Kidney Form
Ectopic kidney Abnormal ascent path of least resistance Abnormalities of ureteral bud or metanephric blastema, genetic or teratogenic, vascular anomalies (eg, umbilical artery) 85% crossed ectopic kidneys fuse with the contralateral kidney creating a cross fused ectopia. M:F=2:1 Left to right phenomenon (3:1)
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Abnormalities of Kidney Form
Horseshoe kidney Most common renal fusion abnormality (1 in 500) Male, 90% asymptomatic Trisomy 18, Turner syndrome, NTD Risk of obstruction(esp. UPJ), VU reflux, infection, urolithiasis, and malignancy(renal pelvis carcinoma, Wilm’s tumor in isthmus)
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Abnormalities of Kidney Form
Pelvic kidney Short ureters (DDx with ptotic kidneys) Blood supply from nearby iliac vessels Dysrotation of renal pelvis
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Abnormalities of Kidney Form
Congenital Cystic Dz of the Kidney Classification Type I: infantile or autosomal recessive polycystic kidney disease (RPKD) Type II: multicystic dysplastic kidney disease (MDK) Type III: Adult or autosomal dominant polycystic kidney disease (DPKD) Type IV: cystic renal dysplasia due to early urinary tract obstruction (at any level)
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Abnormalities of Kidney Form
RPKD Affects both kidneys 25% recurrence in a future pregnancy Saccular dilatations of the collecting tubules Hundreds of tiny 1~2mm cysts not imaged on US as separate cysts Solid apperance, often homogeneously echogenic bilateral enlarged kidneys; severe oligohydramnios
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Abnormalities of Kidney Form
MDK Most common of congenital renal cystic dysplasia Most unilateral. Lethal in bilateral or contralateral kidney agenesis. 3~5% familial recurrence The renal pelvis is usually obstructed (type IIa) and the proximal ureter is essentially always (type IIa and IIb) obstructed because of atresia. Typically decrease in size over time Variably sized cysts with intercystic connective tissue. DDx with hydronephrosis: central and peripheral cyst size, reniform
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Abnormalities of Kidney Form
DPKD Most common cystic kidney disease 10~12% of patients on chronic dialysis Autosomal dominant (Chromosomes 16p and 4q), high degree of penetrance > 30 y/o, US sensitivity 100% Lumbar, inguinal, abd. pain or palpable flank mass Hypertension (renin ↑) 50~70% hepatic cysts <10% pancreatic or splenic cyst
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Abnormalities of Kidney Form
Cystic renal dysplasia due to early urinary tract obstruction Usually caused by post. urethral valves. Others: urethral atresia, caudal regression syndrome with persistent cloaca, other obstructions Abnormal isotonic urine (normally hypotonic) Contralateral kidney compensatory hypertrophy
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Hydronephrotic or Pyelectasis
Pyelectasis: dilatation ≧10mm (AP) Differential diagnosis UPJ obstruction UVJ obstruction Posterior urethral valves (PUV) VU reflux Neonatal unilateral hydronephrosis Followed closely (relative benign condition) Surgery if worsening of hydronephrosis or renal dysfunction
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Hydronephrotic or Pyelectasis
Grading system for hydronephrosis in fetus ≧ GA 20 wks (Grignon et al, 1986) Grade I dilatations (AP pelvic diameter < 1cm) normal and physiologic, no surgery required Grade II (1.0~1.5 cm) and Grade III (> 1.5 cm with slight dilatation of calices) intermediate hydronephrosis, 50% required postnatal surgical intervention. Grade IV (> 1.5 cm with moderate caliceal dilatation, no cortical atrophy) and Grade V ((> 1.5 cm with severe caliceal dilatation, atrophic renal cortex) ALL required surgery
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Hydronephrotic or Pyelectasis
Langer et al, 1996 Consider abnormal pelvic dilatation if > 10mm after 28 weeks with concurrent bladder or ureteral dilatation US evaluations for neonate routine pelvic dilatation should be made at 2~3 days of life.
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Cause of Congenital Renal Obstruction and Its Simulators
UPJ obstruction Most common cause of congenital hydronephrosis 1:1258 births , M:F=2:1 More common in Left side, 30% bilateral Stricture, extrinsic compression(aberrant renal artery/vessel), high ureteral insertion, local valves, ischemia Functional obstruction: deficiency of proximal ureteric smooth muscle fibers with associated fibrosis 35% may show worsening that will prompt pyeloplasty
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Cause of Congenital Renal Obstruction and Its Simulators
UVJ obstruction Congenital primary megaureter UVJ stenosis, ectopic ureter as part of a duplication 3 types of primary megaureter Obstructed: functional obstruction, distal 0.5~4 cm) Refluxing: short or absent intravesicle ureter or paraureteric diverticulum Nonrefluxing unobstructed: excluding any secondary causes by VCUG or perfusion nulear medicine. >50% treat conservatively.
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Cause of Congenital Renal Obstruction and Its Simulators
Renal Duplication Obstruction usually due to an ectopic ureterocele. Weigert-Meyer rule Drooping lily sign Ectopic Ureter 70% ureteral duplication Ureteral bud fails to separate from mesonephric duct Weigert-Meyer rule inserts into the bladder in a position more inferior and medial than that of the lower moiety ureter and enters the bladder in an ectopic location and usually has a ureterocele. The lower pole moiety has its own ureter that enters the bladder in normal position but usually refluxes. Therefore, both moieties may appear fluid filled and hydronephrotic. The refluxing moiety, which the affected patient may outgrow just as they may outgrow reflux in a single system, will have dilatation that will usually show a classic dilated pelvis with outpouchings consistent with dilated calyces. The obstructed upper pole moiety usually looks like a single echoless circular structure without calyces.
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Cause of Congenital Renal Obstruction and Its Simulators
Ureterocele Ureteral meatal obstruction Incomplete muscularization of the distal ureter Incorporates embryologically into the bladder DDx: pseudoseptated bladder, ovarian cyst, anterior meningocele
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Congenital Abnormalities of the Bladder
Bladder Agenesis Often part of a complex anomaly in a stillborn fetus Cloacal development possibly disturbed by lack of a bladder distended by urine failure of incorporation of ducts and ureters into the trigone. Bladder Exstrophy Associated epispadius, pelvic skeletal abnormality, imperforate anus, separation of the penis and scrotum 700 times the incidence of carcinoma
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Bladder Obstruction Bladder wall thickening consider relative or complete distal obstruction. Others including infection, inflammation, or neoplasm Most common PUV Less common urethral atresia or other syndromes
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Bladder Obstruction PUV 1 in 5,000~8,000 boys
Redundant membranous folds within the posterior urethra Sig. dilatation of pelvis, perirenal urinoma, or urinary ascites VU reflux in 2/3 of affected patients Oligohydraminos and renal cystic dysplaisa may occur. “Keyhole” sign in US DDx: Prune Belly syndrome, Megacystic-microcolon-intestinal hyperperistalsis syndrome
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Urachal Anomalies Residual remnants of the epithelium lined urachus result in small urachal cysts that may develop anywhere along the line of the urachus between the bladder and umbilicus. Urachal fistula, urachal sinus, or vesicourachal diverticulum Infection later in life
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~ The End ~
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