NCC content Flashcards
non-excretory functions of renal system
- produces renin (regulates blood pressure)
- produces erythropoietin (initiated by hypoxia, hypovolemia, hypotension)
- metabolizes vitamin D
- degrades insulin
- produces prostaglandins (renal medulla does this)
define nephron
functional unit of the kidney
define GFR
the rate at which blood flows through capillaries in the nephron
-afferent and efferent arterioles dilate and constrict to control GFR (& BP)
when does nephrogenesis start and finish?
- starts at 7-8 weeks
- completed by 34 weeks
what are the three main functions of the nephron
- filtration
- reabsorption (occurs through remainder of tubules)
- secretion (active transport of substances back into the tubules)
what happens in the proximal tubule?
major site of reabsorption (Na, H20)
what happens in the descending loop of Henle?
reabsorption of H20
what happens in the ascending loop of Henle?
reabsorption of Cl, K, Na, Bicarb, Ca
what’s an important characteristic of the ascending loop of Henle?
IMPERMEABLE TO H2O
what happens in the distal tubule?
reabsorption of H20 & Na
-aldosterone acts on distal tubule to cause it to reabsorb more Na and H20 and to secrete K
what happens in the collecting ducts?
- presence of ADH allows for filtrate within ducts to become more concentrated by making ducts more permeable to H20
- H20 reabsorbed
How much Na do preterm babies have the ability reabsorb?
85-90% vs 95% in term infants
-can’t get rid of excess Na due to decreased GFR
How much of what is filtered by the kidneys (Bowman’s capsule) is reabsorbed by the body?
99%
what are the 2 clinical correlates associated with ADH?
- DI
- SIADH
when does GFR reach adult levels (120 ml/min)?
around 2 years of age
where is ADH made and stored?
- made in the hypothalamus
- stored in the posterior pituitary
what happens in DI?
- insufficient ADH
- collecting tubules become impermeable to H20 and body can’t reabsorb it
what happens in SIADH?
- too much ADH
- collecting tubules are very permeable to H20 so lots of it reabsorbed
which babies are prone to SIADH?
-CNS abnormality, midline defect, asphyxia, pneumothorax, post-operative babies
what does the RAAS system do?
regulates the extracellular fluid compartment
- helps body maintain fluid balance and blood pressure
- causes systemic vasoconstriction, body hangs on to more Na and H20, increase in intravascular volume
how is the RAAS system initiated?
release of renin
-produced by the juxtamedullary cells by afferent arterioles
How does renin function?
after release, it goes systemically to act on angiotensinogen, which is produced by the liver
how does angiotensinogen function?
it produces angiotensin I
how does angiotensin I function?
it goes through the pulmonary circulation where angiotensin-converting enzyme (ACE) changes it to angiotensin II
how does angiotensin II function?
causes vasoconstriction to increase blood pressure and acts on adrenal medulla to release aldosterone
how does aldosterone function?
causes distal tubule to reabsorb Na and H20
normal GFR in a term infant that can maintain homeostasis who isn’t stressed
30 ml/min
define anuria
define oliguria
normal urine output
3-5 ml/kg/h
define polyuria
> 5 ml/kg/h
what is acute renal injury/failure?
- loss of water and electrolyte homeostasis
- secondary to abrupt decrease in GFR
what causes acute renal injury?
- sepsis
- perinatal asphyxia
- hypotension not associated with sepsis
- just being premature
what is most common type of acute renal failure?
prerenal (80%)
what can happen if prerenal problems aren’t treated appropriately?
it can progress to intrinsic ARF
in postrenal ARF, where do the obstructions typically take place?
- ureter
- bladder
- urethra
what is the most common type of intrinsic ARF?
acute tubular necrosis
what is the most common cause of acute tubular necrosis?
untreated prerenal ARF
other causes of intrinsic ARF
- infection (fungal balls)
- aortic/renal artery thrombosis (UAC)
- renal vein thrombosis (dehydrated babies, babies with perinatal asphyxia, IDM)
- DIC
- congenital renal abnormalities
what rate of rise is abnormal for creatinine?
0.3-0.5 mg/d
what does a urinalysis tell you about the tubules?
reflects the structure of the tubules/glomerulus
what does FeNa tell us?
how well the tubules are functioning
- normally we should have low Na urine levels, so low FeNa levels
- can be used to differentiate prerenal from intrinsic failure
- elevated FeNa may indicate intrinsic failure (>2.5%)
- FeNa
