305 Flashcards
What is the first and rudimentary kidney to develop?
Pronephroi
What is the second and briefly functional kidney to develop?
Mesonephroi
What is the third and permanent kidney to develop?
Metanephroi
When does the pronephroi develop?
EARLY 4th week
What is the pronepheroi composed of?
clusters of cells and tubules
Where do the pronepheroi ducts run and open into?
Pronepheroi run caudally and open into the cloaca
What happens to the ducts of the pronepheroi?
remain and are utilized by the Mesonephroi
When does the Mesoneophroi develop?
LATE 4th week
What is the mesonephroi composed of?
the glomerulus and tubules
What is the purpose of the mesonephroi?
to function as the interim kidney for FOUR weeks until the permanent kidney develops
Where do the mesonephroi ducts open?
into the pronephroi ducts and into the cloaca
When does the mesonephroi degenerate?
At the end of the first trimester
What happens to the tubes of the mesonephroi?
become the efferent ducts of the testes
What is the metanephroi?
The primitive permanent kidney
When does the metaneprhoi develop and then become functional?
Develops in the 5th week; functional in the 9th week to produce urine that contributes to amniotic fluid
What does the nephron consist of?
glomeruli, collecting tubules and loop of Henle
From what end of the metanephric tubule does the glomeruli develop?
proximal
The metanephric diverticulum develops from the metanephric kidney and begins with the development of what?
ureteric bud
The ureteric bud develops into the permanent kidney and differentiates into what structure?
ureter and collecting tubules
What occurs during the 10th - 18th week in the metanephroi?
increase in number of glomeruli
When does the metanephric kidney reach full complement?
32 week GA
How many nephrons does the functional kidney have at term?
400k- 2million
The fetal kidney is divided into what?
lobes, will disappear in postnatal life as nephrons continue to grow
Initially, where are the kidneys positioned?
The kidneys are initially close together and with the growth of the abdomen, are elevated from the pelvis into the abdomen
When do the kidneys attain adult positioning?
by the 9th week GA
How much do the kidneys rotate to achieve correct positioning?
90 degrees
Where are the mature kidneys located in the body?
retroperitoneal; outside of the peritoneal cavity on the posterior wall of the abdomen
Where do the kidneys receive their blood supply when final position is achieved?
from the distal end of the aorta
In rudimentary stages, where do the kidneys receive their blood supply?
from nearby vessels
Where do the renal arteries initially branch off?
from the common iliac arteries
Which renal artery is longer and more superior?
right
When does glomerular filtration begin?
9 week GA
Accessory renal arteries occur in what percentage of the population?
25%
How many arteries will a kidney have if they have accessory arteries?
2-4; typically will only have 1 per kidney
From where do the accessory renal arteries arise?
the aorta
Where do the accessory renal arteries attach?
to the inferior or superior poles of the kidney
If an accessory renal arteries attaches to the right inferior pole it can cross what structures leading to what?
the anterior ureter and IVC; hydronephrosis
What is hydronephrosis?
the distension of the renal pelvis and renal calicies with urine
If the accessory renal arteries are damaged or ligated, what happens to the area of the kidney perfused by these vessels?
ischemia
What is the incidence of unilateral renal agenesis?
1:1k
Does unilateral renal agenesis affect more males or females?
males
In unilateral renal agenesis, which kidney is more likely to be affected?
the LEFT
In the presence of a single umbilical artery, what is the likely renal congenital implication?
unilateral renal agenesis
When is the diagnosis of unilateral renal agenesis typically made?
with the discovery of right renal hypertrophy; typically asymptomatic until that time
What is the incidence of bilateral renal agenesis?
1:3k
What is the prognosis of an infant with bilateral renal agenesis?
incompatiable with life
What is the cause of bilateral renal agenesis?
Failure of ureteric buds to develop
Bilateral renal agenesis is apart of what congenital syndrome?
Potter’s syndrome
What is a malrotated kidney?
the kidney fails to rotate therefore remaining in embryonic position; a/w ectopic kidney
What is an ectopic kidney?
Failure of one or both kidneys to ascend into the abdomen from the pelvis
What is a horseshoe kidney?
The poles of the kidney are fused become a U shaped organ
What is the incidence of a horseshoe kidney?
0.2% of general population; 7% of Turner’s syndrome patients
Why can’t a horseshoe kidney ascend into the abdomen?
It is held in place by the inferior mesenteric artery
Is a horseshoe kidney symptomatic?
No; the ureters, bladder and collecting systems all develop typically
What is the inheritance pattern in polycystic kidney disease?
autosomal recessive
What occurs in neonates with polycystic kidney disease?
bilateral accumulation of small cysts that lead to renal insufficiency
What is the prognosis of an infant with polycystic kidney disease?
incompatible with life unless treated with postnatal dialysis or kidney transplant
What is the prognosis of an infant with multicystic dysplastic kidney disease?
good outcome expected; typically unilateral
What is multicystic dysplastic kidney disease?
the formation of cysts (fewer and smaller than PKD) that cause dilation of parts of the nephron- typically the loop of Henle
What organs does the urogenital sinus give rise to?
bladder, urethra and penis/ clitoris
What type of tissue is the bladder derived from?
epithelial
The prenatal bladder is initially continuous with what embroyologic structure?
the allantois
As the allantois thickens into a fibrous cord, it becomes what structure?
the urachus
What contributes to the formation of the trigone and ureters?
the mesonephric ducts
What is the function of the trigone of the bladder?
is is a smooth, triangular region of the bladder that, as it stretches, will signal the brain of the need to void
The openings of the mesonephric ducts move close together to enter what structure?
the prostatic part of the urethra
The mesonephric ducts become what structures in the male and female child?
in the male, the ducts will become ejaculatory ducts; in the female, they will degenerate
What is the incidence of exstrophy of the bladder?
1:10k-1:40k
Is exstrophy of the bladder more likely to affect males or females?
males
Exstrophy of the bladder is likely to occur with what penile anomaly?
epispadias
What structures are exposed to the environment with exstrophy of the bladder?
the trigone and ureteric orficies
When does the fetal kidney achieve an adult number of nephrons?
34-35 wk GA
When does Na and H2O reabsorption begin in the loop of Henle and tubules?
12-14 wk GA
Amniotic fluid is primarily composed of what >18wk GA?
fetal urine
How frequently does the fetal bladder fill and empty?
Q20-30 min
Low renal blood flow and low GFR is related to what in the intrauterine environment?
high pulmonary vascular resistance, low systemic vascular resistance
Renal blood flow in both term and preterm infants is low in direct correlation to what?
high renal vascular resistance (transition is slower in preterm infants)
What causes a reduction in renal vascular resistance?
an increase in renal blood flow and GFR increase
What is the rate of effective renal perfusion in a postnatal infant at 30 week, 3 mo and 1-2 yrs?
30 week: 20cc/min
3 mo: 300cc/min
1-2 yr: 650cc/min
Increases in renal blood flow are directly related to what factors?
the formation of new glomeruli, vascular remodeling, a decrease in renal vascular resistance and the release of vasoactive substances (adenosine, angiotensin II, NO, and the RAAS system)
What is the fetal urine concentration abilities of an infant (compared to an adult)?
20-30%
What are the implication of fetal physiology on urine production?
impaired ability to conserve Na (loose a lot of Na) and fetal kidneys are less sensitive to ADH (tendency to diuresis)
What organ produces Renin and why?
Kidneys; in respones to decreased Na in distal tubules
What organ produces Angiotensinogen and why?
Liver; renal artery hypotension decreased Na in distal tubules
What does Renin convert?
Angiotensinogen into Angiotensin I
Angiotensin converting enzyme is produced by what organ?
Lungs
What does ACE convert?
Angiotensin I to Angiotensin II
Angiotensin II causes what physiological changes?
1) constriction of blood vessels (inc BP)
2) Stimulates adrenal cortex to secrete aldosterone
3) Aldosterone acts on kidneys to reabsorb Na Cl (therefore H2O) and excrete K- inc fluid vol/inc BP
4) stimulates posterior pituitary to secrete ADH (acts on distal tubule ducts to NOT reabsorb H2O)
4) inc sympathetic activity
What is the net outcome of the RAAS system?
cascade of events causing the retention of Na, H2O, inc effective circulating vol and inc perfusion of juxtaglomerular apparatus
Angiotensin in fetal life is produced by what?
yolk sac
When is AT II found in immature renal tubules
by 30d GA
What is the fetal response to aldosterone?
low, therefore infants are not retaining H2O
What is RAAS system activity in neonates?
higher than adults; gradually decreases over first few months of postnatal life
Angiotensinogen and plasma renin activity patterns are parallel, what are they and when do they change?
High postnatally for 2-3 weeks, then decrease
Low aldosterone production, responsivness and few receptors put the VLBW infant at risk for what?
dehydration and hyponatremia
What is vasopressin and where is it made/stored?
the precursor to ADH; made in hypothalamus and stored in posterior pituitary gland
What is the response to inc ADH production at birth?
distal and collecting tubules have decreased response to circulating ADH levels
The postnatal decreased response to aldosterone puts the infant at risk for what?
hypovolemia, dehydration
What are the contributing factors for increased secretion of ADH?
perinatal asphyxia, IVH, RDS, MAS and pneumothorax
What are the effects of SIADH?
dilutional hyponatremia, inc excretion of Na, decreased UOP, increased urine osmolality
How do you treat SIADH?
fluid restric (40-60cc/kg/d), monitor serum Na and replete if necessary, monitor UOP and lasix
How is SIADH diagnosed?
evaluation of serum and electrolyte levels and serum and urine osmolality
What changes to kidney function occur with birth?
RAAS activity increases, BP inc, RVR dec, inc renal perfusion, dec Na re absorption and inc GFR
What is the typical UOP rate for a term infant?
15-60cc/kg/d
What is the typical UOP rate for a preterm infant?
24-48cc/kg/d (1-3cc/kg/h)
What is considered oliguria?
UOP < 0.5cc/kg/h AFTER 48 hours
What is the expected UOP after 2 days?
void 1 or more times with each feed
What is the bladder capacity of an infant at 32 weeks GA?
13cc
What is the bladder capacity of an infant at 36 weeks GA?
20cc
What is the affect of MgSO4 exposure to an infant’s voiding pattern?
may delay voiding r/t decreased GFR and urine retention
95% of infants will void within how long?
24 hours postnatal life
What is the GFR in a 28wk and 35wk GA neonate?
28 wk: 2cc/min
>35wk: 10-13cc/min (after full complement)
After this, GFR and renal perfusion increase 5 fold
What contributing factors cause GFR to inc in direct correlation to inc GA?
inc renal perfusion, dec RVR and inc systemis BP
What contributing factors cause the kidneys to be unable to handle large amounts of solutes?
dec renal perfusion and GFR, smaller tubular reabsorption surface area, fewer solute transporters, dec control of H ions, dec Na/K atpase pump activity
What is the Na requirement of an infant?
1-3MEq/kg/d
What is the Na balance of a term infant?
positive
What is the Na balance of a preterm infant?
negative
What are the effects of an immature Na/Katpase pump?
high extracellular volume, tubule insensitivity to aldosterone and inc fractional excretion of Na
Why are preterm infants at increased risk for Na retention?
preemies cannot readily excrete a high Na load. When fluid intake is inadequate, they are at risk for Na retention and hypernatremia (especially in the first week of postnatal life)
What does the FENa measure?
it is an indicator of tubular function
What is the FENa calculation?
FENa= (urine Na/serum Na) x (serum creatinine/ urine creatinine) x 100
FENa is inversely proportional to what?
gestational age
The higher a FENa value indicates what?
more Na lost in urine
Glucose reabsorption is related to what other electrolyte?
Na
Infants have a glucose fractional excretion rate that is…
high
VLBW infants should be monitored very closely for
hyperglycemia, glycosuria as well as fluid and electrolyte imbalances
Attempts to excrete a high glucose load in an neonate can lead to what?
hyponatremia and dehydration
What is the normal GIR in infants?
4-6mg/kg/min
What is the GIR calculation
GIR mg/kg/min= (%glucose x IV rate)/ (6 x wt in kg)
How are glomeruli formed?
they are produced on branches of arteries rising from the dorsal aorta
Blood from glomerular capillaries is filtered by what?
Bowman’s capsule and glomerulus
What affect does increasing GA have on body composition?
initially total body water and ECF are higher than ICF; with inc GA, balance shifts
At 16wk, 32 wk and term, what percentage of the fetus is composed of water?
16 wk: 94%
32 wk: 80%
term: 78%
What causes total body weight loss following birth?
the shift of fluid from extracellular to intracellular compartments (ECF vol peaks at dol 3 followed by diuresis)
