B5.070 Development of the Urinary System Flashcards
what forms much of the urogenital system
intermediate mesoderm
3 evolutionary stages of kidney development
pronephros- not functional
mesonephros
metanephros
develop in a craniocaudal sequence
describe the mesonephros
functional during embryonic development
mesonephric duct carries urine from mesonephros to fetal cloaca (sewer)…later becomes male reproductive system
paramesonephric duct becomes female reproductive system
ureteric bud
outgrowth from the mesonephric duct
will induce the formation of the metanephric kidney
forms within intermediate mesoderm towards caudal portion of embryo
length of nephrogenesis
continues throughout gestation until about 32-36 weeks
what forms the filtration units of the kidney
ureteric bud induced metanephric blastemal
endoderm (collecting tubules) fused with mesoderm (rest of nephron)
where do kidneys sit in a normal body
about T12
rise from S1 due to differential growth, no muscles pull them up
what is a wilms tumor
nephroblastoma
most common primary renal tumor affecting children and the 4th most common pediatric tumor
account for 9/10 kidney cancers in children
prevalence of wilms tumor
500 cases in US per year
pathophys of wilms tumor
mutation in WT-1 gene
mutations in or loss of WT1 or WT2 gene
tumor suppressor genes found on chromosome 11
hisopath presentation of wilms tumor
tightly packed cells fibrocytic or spindle shaped cells poorly-formed tubules classic triphasic combination of cells: 1. blastemic 2. stromal 3. epithelial
signs and symptoms of wilms tumor
painless, palpable abdominal mass loss of appetite abdominal pain fever nausea and vomiting blood in the urine high BP
diagnosis of wilms tumor
painless abdominal tumor felt by a doctor
US done first followed by CT or MRI
tumor biopsy NOT performed
why is a wilms tumor biopsy not performed
risk of creating fragments of cancer tissue and seeding the abdomen with malignant cells
treatment and prognosis of wilms tumor
surgical removal, plus radiation If tumor has spread
5 year survival is 90%
functions of amniotic fluid
cushioning the embryo
control of the body temperature
prevents adherence of amnion to the embryo
permits symmetrical external growth of the embryo
free movement of embryo
lung development
what is polyhydramnios
condition of having too much amniotic fluid
occurs in 1 in 100 pregnancies
causes of polyhydramnios
GI abnormalities: esophageal atresia, duodenal atresia, tracheoesophageal fistula fatal renal disorders (renal agenesis) Downs and Edwards syndromes anencephaly (impairs swallowing reflex) maternal DM
treatment of polyhydramnios
medications that reduce fluid production are as much ad 90% effective
indomethacin used for idiopathic or maternal DM polyhydramnios- cuts down on renal output of the fetus
if caused by a structural lesion, indomethacin doesn’t solve the issue but can decrease distention
what is amnio-reduction
procedure that can drain excess fluids
amniocentesis
2 types of renal agenesis
unilateral renal agenesis
bilateral renal agenesis
prevalence of unilateral renal agenesis
1/1000 births
slightly more common in males
not major unless other defects are present
effects of unilateral renal agenesis
remaining kidney undergoes slight hypertrophy
sometimes diagnosed during prenatal US, but usually unknown to affected individual
bilateral renal agenesis
1/8000-10000 births
65-80% males
due to oligohydramnios during gestation
incompatible with postnatal life
redundant kidney
more than 2 kidneys
very rare
rotational anomaly
kidney rotates as it ascends
typically unilateral
increases chances of hydronephrosis
what is the potter sequence?
characteristics exhibited by infants born with bilateral renal agenesis
typically die due to respiratory failure
may also be caused by chronic placental failure
potter sequence characteristics
flattened nose wide interpupillary space receding chin tapering fingers low set ears hip dislocation clubbed feet pulmonary hypoplasia males lack vas deferens and seminal vesicles females lack uterus and upper vagina
P O T T E R
pulmonary hypoplasia oligohydramnios twisted face twisted skin extremities defect (due to fetal compression caused by lack of fluid) renal agenesis (in utero)
horseshoe kidneys
thought to be due to fusion of right and left metanephric kidneys in the midline while in the pelvis
rise is limited by IMA
prevalence of horseshoe kidney
1/500 births
ectopic kidneys
pelvic kidney
often in a pancake shape
recessive polycystic kidney disease
1/20,000-40,000
cysts from collecting tubules
renal failure in infancy
dominant polycystic kidney disease
1/500-1000
cysts from anywhere
renal failure in adulthood
total prevalence of PKD
200,000 cases/ year in US
does the kidney drag its vascular supply when it ascends?
no
induces formation of new arteries (directly off abdominal aorta) and veins (draining into IVC)
supernumerary renal arteries
extra arteries/kidney (more than 1)
present in 25-50% of population
effects of supernumerary renal arteries
may block urine flow out of the ureter, causing hydronephrosis
esp when additional arteries are caudal to the renal pelvis
hydronephrotic kidney
caused by obstruction of the lower ends of the ureter
typically due to supernumerary renal arteries
prevalence of duplicated ureters
most common renal abnormality
1% of population
found in 8% of kids with UTIs
more common in Caucasians and females
cause of duplicated ureters
ureteric bud either splits or arises twice
in most case, kidney is divided into upper and lower lobe with some overlap due to intermingling of collecting tubules
bifid ureter
slips between bladder and kidney
3 typical sites of sites of urinary caliculi (kidney stones)
- junction of renal pelvis with ureter
- as ureters cross iliac blood vessels at pelvic rim
- junction of ureter with bladder wall
kidney stone pain in males
may extend caudally into scrotum
development of the bladder
division of the cloaca by the urorectal septum into a dorsal rectum and a ventral urogenital sinus
epithelium of the bladder forms from urogenital sinus while other layers form from splanchnopleuric mesenchyme
examples urorectal septal defects and formation of the anal pit
urorectal fistula
rectovaginal fistula
rectoperitoneal fistula
anal pit (anal atresia)
what is the urachus
allantois remnant
prevalence of urachus defects
present in 1.03-1.6% of the pediatric population
males slightly more frequent than females
normal urachus development
channel of urachus usually seals off and obliterates around the 12th week of gestation
all that is left is a small fibrous cord between the bladder and umbilicus called the median umbilical ligament
urachial fistula
20%
drains urine from umbilicus from birth
periumbilical inflammation
urachal sinus
35%
can be asymptomatic
may present with umbilican infections with abdominal pain and drainage of some fluid
urachial cysts
43%
present around 2-4 years old
urachial diverticulum
2%
often have no symptoms
consequences of persistant urachal anomalies
continuous bladder and urine drainage around the umbilicus (42%)
recurrent urinary tract infections (5-10%)
urachal carcinoma (0.01%)
treatment of urachal defects
typically surgically resected
small risk of recurrence
prevalence of bladder exstrophy
1/ 10,000-50,000 live births
more common in males
what is bladder exstrophy
abnormality of formation of the anterior bladder wall and the bony pelvis
bladder does not form in its normal round shape and is instead flattened and exposed on the abdominal wall
pelvic bones widely separated
other abnormalities associated with bladder exstrophy
first child has it, second child has 1/100 chance
1/70 for a child w a parent with it
associated with elevated AFP levels (diagnosed at routine US at 16 weeks)
male genitalia development with bladder exstrophy
penis may appear short and curved in an upward direction
testicles may not be in a normal position in the scrotum and a hernia may be seen
female genitalia development with bladder exstrophy
clitoris and labia minora are separated and spread apart
vagina and urethra are shorter
uterus, fallopian tubes, and ovaries are generally normal
treatment of bladder exstrophy
surgery initiated shortly after birth bladder closure closure of anterior abdominal wall pelvic osteotomy baby in hospital for 3-4 weeks
esispadias repair
reconstruction of male genitalia with bladder exstrophy
6-12 months in boys
bladder neck reconstruction
reconstruction of urinary sphincter muscles
typically at time of potty training (2-3 years)
AFP measurement
measured in pregnant women through the analysis of maternal blood or amniotic fluid, as a screening test for a subset of developmental abnormalities
performed during the 16-19 week mark of pregancy
some congenital conditions or diseases in which AFP will be elevated
omphalocele gastroschisis HCC neural tube defects nonseminomatous germ cell tumors yolk sac tumor exstrophy of the bladder
