Kidney embryology

Question 1

Where do the male and female reproductive organs originate from?

Answer 1

Male - mesonephric (Wolffian ducts)

Female - paramesonephric (Mullerian ducts)

Question 2

How do the female reproductive organs form?

Answer 2

• mesonephric duct degenerates
• lower portion of mesonephric ducts remains to form ureteric bud
• paramesonephric duct remains - forms oviduct

Question 3

How do the male reproductive organs form?

Answer 3

• paramesonephric duct degenerates

- mesonephric duct remains to form the male reproductive organs and the ureteric bud

Question 4

Describe the embryonic kidneys.

Answer 4

3 embryonic kidneys

• all formed from the mesonephric duct
• 1 functional = metanephric
• 2 non-functional = pronephric + mesonephric (both degenerate)

Question 5

What is the metanephric kidney formed from?

Answer 5

• metanephric blastema or bud derived from the mesenchyme

- ureteric bud derived from the mesoheanephric duct

Question 6

What adult structures will form from the ureteric bud?

Answer 6

• ureter
• renal pelvis
• collecting tubules

Question 7

What adult structures will form from the metanephric bud?

Answer 7

• renal glomerulus and capillaries
• bowman’s capsule
• PCT
• loop of henle
• DCT

Question 8

Where is the metanephros (functional embryonic kidney) located?

Answer 8

Level of S1

Question 9

What is the final location of the metanephros?

Answer 9

Level of T12

Question 10

What is an ectopic kidney?

Answer 10

A kidney that fails to ascend

Question 11

What is usually the cause of a kidney/kidneys failing to form?

Answer 11

Defects in ureteric bud formation

Question 12

How common is unilateral kidney agenesis?

Answer 12

1:1,000 live births

Question 13

How common is bilateral kidney agenesis? What will happen to babies born with this condition?

Answer 13

1: 10,000 live births
- baby will not survive after birth - important in utero for the formation of amniotic fluid and therefore there will be oligohydramnios
- causes birth defects such as failure of lungs to develop and club foot

Question 14

What is a bifid ureter?

Answer 14

1. Ureter split into two - supply supernumerary (usually 2) kidneys on one side
   - -> kidneys smaller but still functional
2. ureter splits into to supply the same kidney (will be slightly larger)

Question 15

What is a pancake kidney? Is this type of kidney functional?

Answer 15

• when two poles of the kidney fuse
• usually occurs in ectopic kidneys that remain in the pelvis
• kidney should still be functional

Question 16

What is a horseshoe kidney? Is this type of kidney functional?

Answer 16

• kidneys fuse in the pelvic regions but only at one pole (usually bottom pole)
• forms a single U-shaped kidney
• cannot ascend past the inferior mesenteric artery
• kidney is still functional

Question 17

What is a polycystic kidney? Is this type of kidney functional?

Answer 17

• kidney that develops fluid-filled cysts
• autosomal dominant: 1:800-1,000 (mutation of polycystin)
• autosomal recessive: 1:20,000 (mutation in fibrocystin)
• functioning but 50% will have kidney failure by age 60

Question 18

What is the most common mutation in polycystic kidney disease? What type of pathology/”-opathy” does this result in?

Answer 18

• polycystin 1 (PKD-1) = 85-90%
• polycystin 2 (PKD-2) = 10-15%
• polycystin localised to primary cilia = ciliopathy
• involved in cell adhesion, Ca2+ transport and cell cycle