Renal Embryology

Question 1

What are posterior urethral valves?

Answer 1

Membrane remnants in the posterior urethra (prostatic) in males that may lead to urethral obstruction

Question 2

What are the 6 findings associated with Potter sequence?

Answer 2

Pulmonary hypoplasia, Oligohydramnios, Twisted face, Twisted skin, Extremity deformities, Renal failure in utero (POTTER)

Question 3

When are the fetal kidneys fully developed?

Answer 3

At 36 weeks’ gestation

Question 4

How does a duplex collecting system often present?

Answer 4

Hydronephrosis

Question 5

What is the typical presentation for a patient with a congenital solitary functioning kidney?

Answer 5

The functioning kidney will be hypertrophied, but the patient typically has no symptoms

Question 6

An embryo’s ureteric bud fails to induce differentiation of the metanephric mesenchyme in utero. Is the kidney functional?

Answer 6

No; this results in a multicystic dysplastic kidney, a nonfunctional kidney

Question 7

What is a congenital solitary functioning kidney?

Answer 7

The presence of only 1 functioning kidney at birth

Question 8

What is the most common cause of bladder outlet obstruction in male infants?

Answer 8

Posterior urethral valves

Question 9

How are posterior urethral valves diagnosed?

Answer 9

By detection of bilateral hydronephrosis or thick/dilated bladder walls on prenatal ultrasonography

Question 10

What adult structures in the urinary tract are derived from the ureteric bud?

Answer 10

Collecting ducts, calyces, pelvises, and ureters

Question 11

What is the ureteric bud (metanephric diverticulum) derived from?

Answer 11

The caudal end of the mesonephric duct

Question 12

How is congenital solitary functioning kidney diagnosed?

Answer 12

Often prenatally by means of ultrasonography

Question 13

Is multicystic dysplastic kidney usually unilateral or bilateral?

Answer 13

Unilateral

Question 14

Why is the ureteropelvic junction the most common site of obstruction in the kidneys?

Answer 14

The ureteropelvic junction is the last structure to canalize (congenital obstruction)

Question 15

What is a patient with vesicoureteral reflux at increased risk for?

Answer 15

Recurrent urinary tract infections

Question 16

What are the 2 mechanisms by which a duplex collecting system may develop?

Answer 16

1) Bifurcation of the uteric bud before it enters the metanephric blastema results in a bifid ureter in the shape of a Y; 2) 2 ureteric buds interact with metanephric blastema

Question 17

A patient with bilateral multicystic dysplastic kidney has what condition?

Answer 17

Potter sequence

Question 18

What are 2 common causes of vesicoureteral reflux?

Answer 18

Insufficient/abnormal insertion of the ureter within the vesicular wall or ↑↑ pressure in the bladder leading to retrograde flow via the ureterovesical junction

Question 19

When does the pronephros degenerate during embryonic development?

Answer 19

Week 3

Question 20

What complications may arise in a patient born with a horseshoe kidney?

Answer 20

Infection, renal stones, hydronephrosis (eg, ureteropelvic junction obstruction), and rarely increased risk of renal cancer

Question 21

What 3 complications are associated with a duplex collecting system?

Answer 21

Urinary tract infections, ureteral obstruction, vesicoureteral reflux

Question 22

Posterior urethral valves are associated with what condition in the fetus?

Answer 22

Oligohydramnios in severe cases of obstruction

Question 23

Are multicystic dysplastic kidneys hereditary?

Answer 23

No; this is generally not a hereditary disorder

Question 24

Horseshoe kidney is associated with what genetic abnormalities?

Answer 24

Chromosomal aneuploidies, such as Turner syndrome and trisomies 13, 18, and 21

Question 25

What structure contributes to the development of male genitalia?

Answer 25

The mesonephros

Question 26

How is a prenatal hydronephrosis diagnosed?

Answer 26

It can be detected by prenatal ultrasonography; it may be unilateral or bilateral

Question 27

During which week of development is mesonephros present?

Answer 27

Week 4

Question 28

What permanent structure of the kidneys develops in the 5th week of gestation?

Answer 28

Metanephros

Question 29

What is the pathophysiology behind the horseshoe kidney?

Answer 29

Inferior poles of both kidneys fuse, which leads them to be trapped under the inferior mesenteric artery during ascension in fetal development

Question 30

The interaction of which 2 structures in the developing kidney induces differentiation and formation of the renal tubules?

Answer 30

The ureteric bud and the metanephric mesenchyme (metanephric blastema)

Question 31

What is the most common pathologic cause of prenatal hydronephrosis?

Answer 31

Congenital ureteropelvic junction obstruction (the obstruction leads to hydronephrosis)

Question 32

What is the definition of vesicoureteral reflux?

Answer 32

Retrograde flow of urine from the bladder to the upper urinary tract

Question 33

What fetal structure functions as the interim kidney for the 1st trimester?

Answer 33

The mesonephros

Question 34

What are 4 causes of Potter sequence?

Answer 34

Reduced renal output (eg, ARPKD), bilateral renal agenesis, chronic placental insufficiency, and obstructive uropathy (including posterior urethral valves)

Question 35

An abnormal interaction between an embryo's ureteric bud and the metanephric mesenchyme occurs in utero. What is the kidney made of?

Answer 35

Connective tissue and cysts; this is a multicystic dysplastic kidney, which is nonfunctional

Question 36

What may occur if there is an abnormal interaction between the ureteric bud and metanephric mesenchyme?

Answer 36

Severe congenital malformation of the kidneys, such as renal agenesis or multicystic dysplastic kidneys

Question 37

What would most likely lead to death in a newborn with Potter sequence?

Answer 37

Oligohydramnios → compression of chest → lack of amniotic fluid aspiration into fetal lungs → pulmonary hypoplasia (cause of death)

Question 38

What adult structures in the urinary tract are derived from the metanephric mesenchyme?

Answer 38

Structures in the kidney, from the glomerulus to the distal convoluted tubule

Question 39

What is the mechanism through which unilateral renal agenesis occurs?

Answer 39

Failure of development of the ureteric bud induces differentiation of the metanephric mesenchyme, resulting in a complete lack of kidney and ureter.

Question 40

In kidney development, at what week in embryonic development is full canalization of the metanephros complete?

Answer 40

Week 10

Question 41

A horseshoe kidney gets trapped beneath which artery?

Answer 41

Inferior mesenteric artery (and it remains low in the abdomen)

Question 42

In which trimester of pregnancy does the fetal mesonephros develop?

Answer 42

First trimester

Question 43

A newborn has a flattened nose, low-set ears, and retrognathia (see image). Diagnosis?

Answer 43

Potter sequence (syndrome)

Question 44

A newborn is diagnosed with Potter sequence. By what mechanism did this condition occur?

Answer 44

Oligohydramnios→ fetal compression → limb deformities and facial anomalies (babies who can't "Pee" in utero develop Potter sequence)