Embryology - Urogenital I + II Flashcards
Pronephrosis
– forms from cervical nephrotomes; gives rise to pronephric duct
Mesonephrosis
– 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
Metanephros
– 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
Kidney Structures Derive from
Structures will derive from intermediate mesoderm –runs symmetrically the entire length of embryo along dorsal wall in urogenital ridge
Abnormalities of Rena/Ureter Development
volume and structure number form and fusion the ascent the rotation of the kidneys
Renal Agenesis - Bilateral
(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
Renal Agenesis - Unilateral
- 1 in 1100 births
- Problem with ureteral bud adrenal gland is still present in absence of kidney
- Compensatory hypertrophy of the lone kidney
Renal Form Anomalies
4-6th week
1 in 400
ureter, kidney tend to be normal
Horseshoe Kidney
– 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
Renal Ascent Anomalies
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
Multicystic Dysplastic Kidney
-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)
Antenatal Hydronephrosis
– 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
Uretopelvic Junction Obstruction
- 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
Primary Vesicouretic reflux
– 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
Primary megaureter
- ureter doesnt develop correctly
ectopic ureter
-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
Urinary Tract Infection
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
Ureterocoele
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
Duplication
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
Weigert-Meyer Law
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
Posterior Urethral Valves
– 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
Hypospadias
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)
Testicular Descent
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
Cryptorchidism
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
