Renal Embryo-- Melissa

Question 1

From what layer of embryonic tissue are the kidneys derived?
When in development does this happen?

Answer 1

DAY 22:

INTERMEDIATE mesoderm–> Forms lateral and medial urogenital ridge around aorta

Question 2

What does the medial urogenital ridge ultimately become?

Answer 2

Genital system

Question 3

What does the lateral urogenital ridge ultimately become?

Answer 3

Lateral general ridge–> nephrogenic cords–> renal system

Question 4

What are the 3 tissue types that derive from the Nephrogenic cords and when in development do they from?

Answer 4

Pronephros (Week 4/ Day 28)
Mesonephros (Day 21-28)
Metanephros (Day 32)

Question 5

Describe the function of the pronephros.

Where is it located and what does it form?

Answer 5

Located in CERVICAL region

Pronephros–> Nephrotomes (vestigal excretory units from by WEEK 4)–> Complete regression by WEEK 5

Question 6

Where is the Mesonephros located?
What does it form?
Describe the timeline of development:

Answer 6

Located UPPER THORACIC–>L3
Mesonephros–>
FIRST EXCRETORY TUBULES (Week 4/Day 28)–>
Rudimentary GLOMERULUS w/ Bowman’s Capsule–>
Consumed by Mesonephric Duct–>
Forms URETERIC BUDS–> penetrate Metanephros

Question 7

What are the derivatives of the Ureteric Buds? (4)

Answer 7

• Collecting tubules
• Major/Minor Calyces
• Renal Pelvis
• Ureters
• *Forms the drainage system around Day 28; continues developing for 5 mos

Question 8

How does the Metanephros contribute to renal development? Describe the timeline:

Answer 8

(Day 32) METANEPHRIC BLASTEMA penetrated by ureteric buds (via mesonephros) –>
Structures form DEFINITIVE ADULT KIDNEY

Question 9

What are the derivatives of the Metanephric Blastema? (4)

Answer 9

• Glomeruli
• Bowman’s Space (parietal layer + capillary podocytes)
• Proximal and Distal Convoluted tubules
• Loop of hence

Question 10

Where are the mature kidneys located?

How did they get here?

Answer 10

Located at T12-L3; Right lower than left because of Liver

Sacral region grows faster than caudal region–> kidneys move up

Question 11

How does orientation of the kidney change on its ascent to T12-L3?

Answer 11

Hilum faces Ventral–> Rotates 90 degrees medially–> Hilum faces medial

Question 12

What would cause a transient hydronephros?

Answer 12

If the metanephros forms urine before complete canalization of ureteric bud

Question 13

When is the definitive functional kidney formed?

Answer 13

Week 12/ 4 mos!

Question 14

Describe how urine production and removal occur in the fetus:

Answer 14

Urine excreted into amniotic cavity–> Fetus drinks–> Goes into GI then CV system–> PLACENTA excretes waste

Question 15

What is happens if the inferior renal vessels fail to degenerate?

Answer 15

Arteries obstruct urine flow at pelvitoureteral junction–> Dilation of calyces–> Hydronephrosis
*Similar to aortic ring and trachea

*note that if any rudimentary arteries from aorta to kidney fail to degenerate, obstruction will cause ischemic injury to location it supplies in kidney

Question 16

What is a horseshoe kidney?

What are some potential complications?

Answer 16

Fused kidney (usually at lower poles)--> U Shaped Kidney   --> Isthmus lies anterior to aorta + IVC, Inferior to IMA*** (Stops Ascent)
**Patients have higher risk nephroblastoma (Wilms Tumor)

Question 17

What is a Multicystic Dysplastic Kidney?

Is it compatible with life?

Answer 17

Ducts surrounded by undifferentiated tissue–> No Nephron development/ Ureteric Bud formation–> NO COLLECTING DUCTS–> NONFUNCTIONING Kidney replaced by CYSTS

• Bilateral = NOT compatible with life
• # 1 cause of mass in newborn; most not palpable at birth

Question 18

ARPKD: Age, Gene, sequele

Answer 18

PKHD1, Chrom 6, Fibrocystin

• cysts in collecting ducts
• enlarged kidneys
• adult or childhood renal failure ensue

Question 19

ADPKD: Age, Gene, sequele

Answer 19

PKD1 (Chrom 16), PKD2 (Chrom 4) : Polycystin 1, 2

• cysts throughout nephron
• adulthood renal failure
• more common and less progressive than ARPKD

Question 20

Pelvic Kidney: What happens?

Answer 20

Caudal end of embryo grows too fast in proportion to sacral–> Kidneys stuck in pelvis

Question 21

Renal Agenesis: What Happens?

Answer 21

Ureteric Bud fails to form from Mesonepnric bud–> Kidney fails to develop bilaterally–> Potter’s syndrome/ Compression of developing fetus–> NOT COMPATIBLE WITH LIFE

**POTTER**
Pulmonary hypoplasia 
Oligohydraminos (low amniotic fluid)
Twisted face
Twisted skin 
Extremity defects 
Renal Failure

Question 22

What is a wilms tumor and when does it present?

What is the cause?

Answer 22

Mutation on WT1, 11p13–> Kidney cancer arising in fetus or kids under 5yoa

Question 23

What is WAGR syndrome?

Answer 23

• Wilms tumor
• Aniridia (no iris!)
• genital anomalies
• mental retardation
• Hemihypertrophy

Question 24

What is Denys Drash Syndrome?

Answer 24

• Wilms Tumor
• Renal Failure
• Pseudohermaphridism

Question 25

How does a bifid ureter form?

Answer 25

Early division of urogenic bud--> two distinct ureters--> fuse along courses or have two distinct entrances into bladder

Question 26

What is a double renal pelvis and how does it form?

Answer 26

Two renal pelvises from from renal hilum--> immediate fusion to form one ureter

Question 27

What is an ectopic ureteric orifice? How does it present?

Answer 27

Ureter aberrantly enters seminal vesicle/ prostatic urethra/ vagina--> patient has chronic incontinance

Question 28

What is the most common way a megaloureter forms?

Answer 28

Obstruction downstream--> Abnormally enlarged ureter upstream

Question 29

What is a postcaval ureter?

Answer 29

Ureter traverses behind IVC

Question 30

What are posterior urethral valves? What are the consequences (3)?

Answer 30

Obstructing membrane in posterior male urethra--> Bladder outlet obstruction, ~lung hypoplasia, ~respiratory failure

Question 31

What is a ureteropelvic junction obstruction? What are the consequences? How is it diagnosed and treated?

Answer 31

#1 SITE OF OBSTRUCTION at area between kidney and ureter (last segment of fetal ureter to canalize)--> Hydronephrosis, palpable abdominal mass Dx: Diuretic venography Tx: Pyeloplasty and reattachment of ureter