Congenital renal abnormalities

Question 1

Oligohydramnios

Answer 1

• Small amount of amniotic fluid, presence indicates mechanical urinary tract obstruction, bilateral renal agenesis, or severe ARPKD
• If present <30 wks; highly correlated w/ pulmonary insufficiency
• If present after 30 wks, there is minimal pulm insufficiency
• Bilateral renal agenesis (potters syndrome): severe oligohydramnios w/ fetal death due to pulmonary hypoplasia (fetus has flat face, low ears, extremity deformities)
• Renal a genesis can be due to abnormalities of development of the pronephric-mesonephric-metanephric system or from failure of development of ureteric bud

Question 2

Hypoplasia/dysplasia

Answer 2

• Renal hypoplasia: reduction in nephron number and size of kidney w/ normal renal tissue
• Renal dysplasia: misplaced ureteric bud results in abnormal nephrogenesis w/ abnormal differentiation (non-functional nephrons)
• Non inherited cyst formation in renal parenchyma (cartilage cysts)
• Usually unilateral, but can be bilateral (then must be distinguished from PKD)
• Often clinically significant and account for majority of peds pts w/ ESRD

Question 3

Hydronephrosis

Answer 3

• May be secondary to ureteropelvic junction (UPJ) obstruction (UTI)
• Male: consider posterior urethral valves
• Female: consider ectopic ureteroceles
• Will not be evident until 16-18th week of gestation

Question 4

Obstructive d/o 1

Answer 4

• Chronic obstruction leads to loss of nephrons, may have dysplasia along w/ obstruction
• Signs of obstruction: ab mass or dissension, abnormal urinary stream, UTI, palpable flank or suprapubic mass
• Ureteropelvic junction obstruction: muscle abnormality, aberrant blood vessels, abnormal angle of insertion
• No dilated ureter (obstruction is upstream)

Question 5

Obstructive d/o 2

Answer 5

• Ureterovesico junction obstruction: ureteroceles (cyst-like enlargements of the lower end of the ureter), vesicoureteral reflux, abnormalities of ureter insertion into bladder
• Dilated ureter (obstruction is downstream)
• UVJ obstuction: will have dilated ureter (obstruction is distal to ureter)
• UPJ obstruction: will not have dilated ureter (obstruction is proximal to ureter)
• Posterior urethral valves (only in males): mucosal folds obstruct bladder outflow at the distal prostatic urethra
• Pts present w/ absent urinary stream or dribbling and generally leads to renal failure

Question 6

Other congenital anomalies

Answer 6

• Horseshoe kidney: kidneys are fused at lower pole located in lower abdomen b/c can’t ascend due to IMA
• Migration: disruption of ascent of kidneys (one or both)
• Ectopic kidneys: both kidneys may be on the same side, or other problems w/ migration
• Duplicated collecting systems: arise from abnormal branching of the ureteric bud
• Early branching results in a duplicated kidney, ureter, and visicoureteral junction
• Late branching results in a single kidney and 2 ureters