Embryology - Urogenital I + II

Question 1

Pronephrosis

Answer 1

– forms from cervical nephrotomes; gives rise to pronephric duct

Question 2

Mesonephrosis

Answer 2

– develops caudal to pronephrosis
 Pronephric duct induces nearby intermediate mesoderm to become mesonephric duct
 Urogenital sinus – begins to develop from hindgut to become bladder and part of urethra
 Glomeruli – develop from paired dorsal aorta

Question 3

Metanephros

Answer 3

– primitive kidney
 Metanephric blastema – forms at tail end of mesonephros from intermediate mesoderm
 Metanephric cap – develops from metanaphric blastema and will become adult kidney (glomerulus, capsules, PCT, and loop of Henle)
 Ureteric ducts – small outgrowths from mesonephric ducts extend to metanephric caps
• Eventually become collecting tubules, calyces, and ureter
 Produces urine and amniotic fluid
 Eventual kidney will ascend and rotate into “adult” position

Question 4

Kidney Structures Derive from

Answer 4

 Structures will derive from intermediate mesoderm –runs symmetrically the entire length of embryo along dorsal wall in urogenital ridge

Question 5

Abnormalities of Rena/Ureter Development

Answer 5

volume and structure
number
form and fusion
the ascent
the rotation of the kidneys

Question 6

Renal Agenesis - Bilateral

Answer 6

(no kidneys) – baby generally does not survive
• Fetus develops pulmonary hypoplasia-oligohydramnios (lack of amniotic fluid produced by kidneys)
• Amniotic fluid helps to develops the kidneys so without enough the baby will have underdeveloped/small lungs
• Baby develops Potter’s facies
• Limb abnormalities

Question 7

Renal Agenesis - Unilateral

Answer 7

• 1 in 1100 births
• Problem with ureteral bud  adrenal gland is still present in absence of kidney
• Compensatory hypertrophy of the lone kidney

Question 8

Renal Form Anomalies

Answer 8

4-6th week
1 in 400
ureter, kidney tend to be normal

Question 9

Horseshoe Kidney

Answer 9

– always facing upward
 The 2 kidneys are connected by an isthmus
 Kidney will stop in its ascent at the inferior mesenteric artery
 Often have skeletal, cardiovascular, neural tube, anorectal defects, uretopelvic junction obstruction, stones, UTIs, hypospadias, cryptorchidism, and ↑chance of Wilm’s tumors
 Normal function on either side of horseshoe but decreased/no activity in the middle

Question 10

Renal Ascent Anomalies

Answer 10

o Week 6 begin to ascend
o Horseshoe kidney, ipsilateral renal ectopia, crossed renal ectopia, cross-fused renal ectopia
 All have vascular anomalies
o Ectopia – something is in the wrong place
o A = crossed renal; B=supernumerary; C=crossed-fused; D=double-crossed
o Adrenal glands do not ascend with the kidney – therefore variations in kidney location will not affect the location of the adrenal glands

Question 11

Multicystic Dysplastic Kidney

Answer 11

-most common renal abdominal mass in infants
 Dysplastic – not formed correctly
 Looks like bundle of grapes in ultrasound
 Non-functional kidney with atretic (narrow small) ureter
 Higher risk of anomalies associated with the contralateral kidney (UPJO, vesico-ureteric reflux, Wilm’s tumor)

Question 12

Antenatal Hydronephrosis

Answer 12

– dilation in kidney observed with ultrasound
causes: uretopelvic junction, primary vesicouretic reflux, multicystic dysplacstic kidney, posterior urethral valves, uretovesicle junction obstruction, megaureter, ectopic ureter, transient hydronephrosis

Question 13

Uretopelvic Junction Obstruction

Answer 13

• result of narrowing of proximal ureter & fluid backs up
  • If not diagnosed prenatally – patient presents with abdominal pain, hematuria (blood in urine), UTIs
  • 1/3 deteriorate and/or develop complications requiring surgery
  • Surgical intervention if pain, infection, or affecting function of kidney
  o Pyeloplasty – remove nonfunctional part and connect functional remains

Question 14

Primary Vesicouretic reflux

Answer 14

– retrograde flow of urine from bladder into ureter or kidney
• Caused by shortened length of submucosal ureteric tunnel of the bladder
• Thickness of bladder wall compared to length of ureter
o Less than 5:1 length  possibility of reflux
o Greater than 5:1 length  possibility of obstruction
o Can lengthen during growth and no longer require surgery
• Causes UTIs and pyelonephritis if flow backs up into kidney

Question 15

Primary megaureter

Answer 15

• ureter doesnt develop correctly

Question 16

ectopic ureter

Answer 16

-when ureter empties somewhere other than the bladder
o Empty anywhere into WOlfian (mesonephric) duct
 Men - Prostate, seminal vesical, posterior urethra
 Women - Epoophroron, gartner’s duct, vagina, cervix
o Can cause obstruction of kidney, UTI
o Incontinence in girls

Question 17

Urinary Tract Infection

Answer 17

o 3% girls; 1% guys
o 30-40% of children with UTIs have vesicoureteral reflex
 17% of these cases will cause infection leading to renal scarring
• 10-20% with scarring will become hypertensive
- more common in girls due to shorter urethra

Question 18

Ureterocoele

Answer 18

o Chwalle’s membrane exists b/n ureteric bud and urogenital sinus (where ureter enters bladder)
 Should disappear day 37 but if it persists then there will be a film covering the bladder and cystic dilation of terminal ureter ensues
o Often associated with a duplicated collecting system

Question 19

Duplication

Answer 19

o Duplication of ureter can develop anywhere along the length of the ureter
o Partial duplication – ureters join back together before entering the bladder
o Complete duplication – multiple ureters enter the bladder
o Relatively common (1 in 125) and not problematic
o “drooping lily sign” on x-rays; lower pole will be displaced inferolaterally
- follows WEIGERT-MEYER LAW

Question 20

Weigert-Meyer Law

Answer 20

 Lower pole ureter empties into the bladder superiorly & laterally – associated with reflux
• associated with reflux due to less bladder tissue to pass through
 Upper pole ureter empties into bladder inferior & medially – associated with obstruction
• must traverse through more urogenital tissue since it inserts by the neck of the bladder and therefore has more chance of obstruction

Question 21

Posterior Urethral Valves

Answer 21

– aka seminal colliculus (where vas deferens enters)
 BOYS ONLY
 During development, should move inferiorly, involute, and eventually fade away
 If they persist , urine will not drain well out of the bladder and can lead to oligohydramnios, renal failure, reflux, bladder dysfunction (dilation) and UTIs
 If untreated can lead to obstructive renal failure and kill the infant
 Treatment: incision of valve

Question 22

Hypospadias

Answer 22

 1:300 BOYS ONLY  generally NO OTHER PROBLEMS
 Median raphe – where the urogenital sinus “zips” up
 Abnormal proximal ventral urethral meatus (opening of urethra on underside of penis rather than the tip), deficient foreskin ventrally, ventral bend to penis (chordee)
 Develops when urogenital sinus doesn’t “zip” up completely when forming the foreskin and head of penis  leads to urethra opening anywhere along urogenital sinus
• Most common place is to open on glans of penis  normal sphincter control but must urinate sitting down; ejaculation will occur through lower urethral opening
 Treatment: foreskin flaps – foreskin used to attach to urethra and bring to head of penis; done after baby is 1 year old; can also use grafts (bladder mucosal, buccal mucosal, skin)

Question 23

Testicular Descent

Answer 23

 Testicle develop and mature in abdomen  descend through retroperitoneum to inguinal canal  passes through the patent processus vaginalis (connection between abdominal cavity and scrotum)  gubernaculum guides descent  processus vaginalis closes
• Failure of processus vaginalis to close results in hydrocele (fluid) or hernia
• Causes the vas deferens to wrap around ureters as kidneys rise and testes fall

Question 24

Cryptorchidism

Answer 24

 When one or more testes fail to descend into the scrotum
 3.5% of boys; more common in pre-term babies (may correct on its own)
 Warm temperatures in upper abdomen increase chance of testicular cancer 10x if uncorrected; the higher the testicle the higher the risk
• 1% lifetime risk of developing malignancy
• Seminoma - germ cell testicular cancer (most common tumor)
 Orchidopexy – surgical procedure that moves undescended testicle into scrotum; doesn’t reduce the risk of cancers but allows for surveillance
• Less prone to trauma in the scrotum due to more mobility
• Enhanced fertility when in scrotum

Question 25

Sexual Indifferent Stage

Answer 25

o Differentiation of internal/ducts and external genitalia start about 6 weeks
 Bipotential of gonadal ridge, gonads, internal ducts, and external genitalia
 Regulated hormonally

Question 26

Development of Internal Genitalia

Answer 26

o Mullerian duct (formed by paramesonephros) and Wolffian duct (formed by mesonephros) are present along with gonads during the indifferent stage
 XX:Mullerian duct gives rise to ovary, uterus, and fallopian tubes (wolffian disappears)
 XY:Wolffian duct gives rise to testes, epididymis, vas deferens (mullerian disappears)

Question 27

Development of External Genitalia

Answer 27

o Penis homologue of clitoris
o Scrotal folds give rise to scrotum in males and labia majora in females
o Genital folds give rise to urethra in males and labia minor in females

Question 28

Male Pseudohermaphroditism

Answer 28

– internally male; externally female
o Genetically XY with various degrees of feminization due to testosterone synthesis disorder
 5-alpha reductase deficiency that converts testosterone to dihydrotestosterone
 Androgen receptor insensitivity – complete or partial
• complete – testicular feminization; normal testicles but they never descent  externally appear female
o vagina will be blind-ended with no uterus, cervix, or ovaries
o present around 16 years of age due to lack of puberty and never acquire secondary female characteristics
o tend to be raised as females because that’s how they identified most of life

Question 29

Female Pseudohermaphroditism

Answer 29

– internally female; externally male
o Genetically XX with normal female internal genitalia but Male external genitalia
 Exogenous androgens in pregnancy
 Congenital Adrenal Hyperplasia
• 21 hydroxylase deficiency – cannot make aldosterone or cortisol; synthesis is shunted towards testosterone
 Salt wasting due to low steroid (aldosterone) hormones

Question 30

True Hermaphroditism

Answer 30

o Both testicular tissue with seminiferous tubules and ovarian tissue with follicles
o 2 ovotestes – combination of two with variable presentation of internal ducts & external genitalia

Question 31

Wilm’s Tumor

Answer 31

– most common, malignant, SOLID, abdominal childhood renal tumor
o Arises from metanephric/renal blastema
o Diagnosed between 2-5 years of age; 8/million
o Heritable (15-20%) and non-heritable forms
o Associated w/ other anomaliescryptorchidism, renal anomalies, hemi-hypertrophy, hypospadias
o Treatment: surgical excision (nephrectomy) plus chemo/radiotherapy  85% cure rate

Question 32

Mixed Gonadal Dysgenesis

Answer 32

o Genetically 45XO, 46XY mosaic

o Undescended testicles, undifferentiated gonads, and remnants of Mullerian duct

Question 33

Formation of Ureters

Answer 33

o Mesonephric duct (with the uretic duct branching off as an outgrowth) is slowly absorbed into urogenital canal and becomes urethra in both sexes
o Trigone of Bladder – where absorbing takes place; posterior wall of internal bladder
o Uretic bud/duct – 1st to be absorbed & therefore lies more superior and lateral in urogenital sinus
o Mesonephric duct – 2nd to be absorbed; lies inferior and more medially in urogenital sinus