Week 4: Congenital Renal Abnormalities

Question 1

Oligohydramnios

Answer 1

• Oligohydramnios: small amount of amniotic fluid (normally 90% is produced by fetal urine)
• seen in bilateral renal a genesis, renal hypoplasia
• mechanical urinary tract obstruction
• If have it before 30 weeks: strong assoc. w/ pulmonary insufficiency
• if appears after 30 weeks: little correlation with pulmonary insufficiency

Question 2

Bilateral agenesis: Potters Syndrome

Answer 2

-severe oligohydramnios
-2x as common in males
-fetal or neonatal death due to pulmonary hypoplasia
-No effective treatment
CLINICAL
-floppy or malformed ears
-epicanthal folds prominent
-beak like nose with flattened tip
-small chin
-abnormal positioning of arms and feet
-1/6000 live births

Question 3

Unilateral renal agenesis

Answer 3

• 1/400 live births
• more common in males
• etiology: due to absent ureteric bud or misplaced ureteric bud
• asymptomatic
• compensatory hypertrophy of contralateral kidney
• normal renal function and life expectancy
• abnormality of development of normal pronephric-mesonephric-metanephric system
• possible association with glial cell line derived neurotrophic factor

Question 4

renal hypoplasia

Answer 4

• reduction in nephron number and size
• normal renal tissue
• Oligomeganephronia: few large nephrons
• remaining nephrons with very large long tubules
• hypoplasia and dysplasia are clinical significant, need to monitor renal insufficiency and growth

Question 5

Renal dysplasia

Answer 5

• misplaced ureteric bud results in abnormal nephrogenesis
• abnormal differentiation of metanephric tissue resulting in nonfunctional nephrons
• persistance of embryonic elements
• coexistence of dysplasia and hypoplasia
• assoc. with cysts

Question 6

Multicystic dysplastic kidney

Answer 6

• detected by ultrasound or as newborn abdominal mass
• extreme form of dysplasia: non functioning cystic mass
• usually unilateral
• end up with involution of MCDK and hypertrophy of contralateral kidney

Question 7

Hydronephrosis

Answer 7

distension and dilation of renal pelvis and calyces

1. unilateral
   - may be secondary to uteropelvic junction obstruction
   - follow with ultrasound
2. bilateral
   - males: consider posterior urethral valves
   - females: consider ectopic uteroceles
3. Pre-natal diagnosis
   - not evident until 16-18th week, usually caught in 23rd week
   - can be detected on prenatal ultrasound

Question 8

Signs of renal obstructive disorders

Answer 8

• abdominal mass or distension
• abnormal urinary stream
• UTI due to stasis
• palpable flank or suprapubic mass

Question 9

Ureteropelvic Junction Obstruction

Answer 9

• Leads to narrow ureter and dilated renal pelvis
• unilateral or bilateral
• 2:1 male to female
• etiology: ureteral muscle abnormality, aberrant blood vessels crossing the junction, abnormal angle of insertion of the ureter into renal pelvis

Question 10

Ureterovesico Junction Obstruction

Answer 10

• unilateral or bilateral
• abnormal insertion of ureter into bladder wall
• Uteroceles: cyst like enlargement of lower end of ureter. protrudes into bladder. Distal end of ureter is tiny and causes obstruction and ballooning
• vesicoureteral reflux: retrograde flow or urine into ureter and/or kidney. Defected flap valve. evaluated by voiding cystourethrogram. Grading system-grades I and II resolve on own (reflux in ureter and pelvis with no distension)

Question 11

Posterior urethral valves

Answer 11

• mucosal folds at distal prostatic urethra obstructs bladder outflow
• only in males
• presents in first year of life
• absent or dribbling urinary stream
• general–>renal failure

Question 12

Anomalies of form, location, rotation

Answer 12

1. horseshoe: fused at lower pole, asymptomatic
2. migration abnormality: 6-9th week kidneys normally ascend. If disrupted, may be lower in pelvic region. Asymptomatic
3. Ectopic kidneys
   - pelvic kidneys: 1 or both kidneys have abnormal ascent
   - crossed fused renal ectopia: fusion of two kidneys during ascent, and both kidneys on one side. asymptomatic
4. Duplicated collecting systems
   - abnormal branching of ureteric bud
   - early branching results in duplicated kidney, ureter, and vesicoureteral junction
   - late branching: single kidney with 2 ureters
   - few clinical consequences