1. Congenital Abnormalities of the Genitourinary System
Cohen et al.; Seminars in Roentgenology, Vol 39, No 2(April), 2004: pp

2. 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.

3. 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

4. Embryology of the GU System

5. 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

6. Antenatal US Assessment of the GU
Normal fetal kidney
GA 15 weeks

7. 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

8. 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

9. 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

10. Lying down adrenal sign
LK?
Lying down adrenal sign

11. 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

12. 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

13. Potter’s facies: Flattened and broad nose Recession of chin
Epicanthic folds
Low set ears
Hypertelorism

14. 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

15. 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)

16. 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)

17. Abnormalities of Kidney Form
Pelvic kidney
Short ureters (DDx with ptotic kidneys)
Blood supply from nearby iliac vessels
Dysrotation of renal pelvis

18. 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)

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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.

26. 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

27. 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.

28. 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.

29. 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

30. 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

31. 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

32. 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

33. 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

34. ~ The End ~