Renal 1 Flashcards
what are the 9 major renal function
- excretion of metabolic waste products
- regulation of water and elctrolyte balance
- regulation of extracellular fluid volume
- regulation of plasma osmolality
- Regulation of RBC production (EPO)
- regulation of vascular resistance (renin)
- regulation of acid base balance
- regulation of vit D and bone mineral balance
- gluconeogenesis
what are the waste products excreted by the kidney
proteins - urea
nucleic acid - uric acid
muscle creatine - creatinine
hemoglobin - urobillin
also hormone metabolites, drugs and toxins
how does kidneys regulate vascular resistance
↓ renal BP causes juxtaglomerular cells in afferent arteriole to release renin
Renin → peripheral vasoconstriction → ↑ BP
describe a healthy kidney
- renal metabolism is equal to general BMR
- lower oxygen in body as a whole is correlates with lower oxygen in renal tissues
- low oxygen triggers EPO prodction by interstitial cells = inceased RBC production
describe a diseased kidney
- renal metabolism is LOWER than general BMR
- hypoxia in the body as a whole does not necessarily equate to renal hypoxia
- Slower local oxygen consumption of diseased renal tissue means oxygen levels do not drop at the same rate as the rest of the body and erythropoietin production is blunted
how do the kidneys regulate vitamin D and bone mineral balance
because active Vit D (calcitriol) is made in the kidneys
when are the kidneys used in gluconeogenesis
most occurs in the liver but kidneys contribute especially during FASTING
Describe the location of the kidneys
Just below rib cage, retroperitoneal, near posterior abdominal wall
what supplies the kidneys
Serviced by renal artery and vein, renal pelvis, nerves
what is the hilum
Curved side of kidney
what is the renal medulla
the collective terminology for the renal pyramids
what connects to the papillae
minor calyces
what surrounds the medulla
renal cortex, which is also covered by fibrous tissue capsule
what is the interstitium
fluid and cells that secrete ECM. some cells here also secrete EPO!
what are the working tissue masses of the kidneys
the tubules (nephrons and collecting tubules) and blood vessels
How are working tissues arranged
in the cortex
tubules and blood vessels are intertwined randomly
Cortex also contains scattered spherical renal corpuscles
looks like “speghetti and meatballs”
How are working tissues arranged in the medulla
tubules and blood vessels are arranged parallel
think medulla has two L’s and they are parrallel
looks like “bundles of pencils”
what is the term for the beginning of the nephron and what does it consist of
renal corpuscle
consists of glomerulus + glomerular capsule
describe the juxtamedullary nephron
- Loop of Henle is much longer, goes into the inner medulla
- Glomerulus located close to the boundary of the cortex and medulla
- Major role in urine concentration
describe the cortical nephron
- Relatively shorter
- Loop of Henle only goes into outer medulla
- Majority of nephron remains in the cortex
what is bowmans capsule
surrounds the glomerulus and is part of the renal corpuscle
what is the renal corpuscle
The glomerulus + the bowmans capsule!
what is the function of the afferent arteriole
carries blood into the corpuscle
describe the glomerulus
interconnected capillary loops where plasma is filtered.
fluids and substances to be extreted exit the capillaries and enter bowmans space.
capillaries are surrounded by podocytes
what are the functions of podocytes
surround the cappillaries in the glomerulus and function to:
1. remove material trapped in wall of capillaries
2. contract capillaries if needed.
what is the function of efferent arterioleis
carry blood OUT of the corpuscle
what are the two parts of the proximal tubule and where are they found
proximal convoluted tubule - found in cortex
proximal straight tubule - found decending into medulla
what are the four segments (in order) of the renal tubules
- proximal tubule
- loop of henle
- distal tubule
- collecting duct
what are the three parts of the loop of henle and their locations
descending limb - all begin at the same level, penetrate to different depths
Thin ascending limb - absent in “shallow” nephron loops
Thick ascending limb - distal portion - all begin at same level
All loops return to the same capsule they started from - cells in thick ascending limb closest to the capsule are specialized cells known as the macula densa
what is the other name for the distal tubule
distal convoluted tubule
what is the function of the collecting duct
joins tubules from nephrons
Collecting ducts merge to form successively larger ducts that eventually empty into a minor calyx
what is the etiology of horseshoe kidney (renal fusion)
thought to occur during
fetal organogenesis
2x more common in men
what is the pathophysiology of horseshoe kidney
- abnormal blood supply
- abnormal course of ureters
- often located lower than normal kidneys therefore NOT protected by ribs
What are the Symptoms of horseshoe kidney
- 1/3 asymptomatic
- UTI (MC complaint in children)
- abdominal pain/nausea
- increased incidence of complication
- other GU abnormalities/malformations
what are the complications of horseshoe kidney
- ureteropelvic junction obstruction (MC)
- renal lithiasis
- severe/upper UTI
- Vesicoureteral reflux
- Increased incidence of renal tumors/cancer
Diagnostic studies for horseshoe kidney
- CT with Intravenous Pyelogram
(May also do abdominal/pelvic CT or US) - Urinalysis/Urine Culture often performed
- Renal function labs
What is treatment for horseshoe kidney
- Medical - to manage disorders that
could predispose to complications - Surgical - to manage complications
as they arise
describe the contents of bowmans capsule
contains glomerular filtrate which is like plasma but with no proteins present.
this is the location which GFR is obtained
what is GFR?
Volume of filtrate formed per unit of time (usually mL/min)
- Healthy young adult male - 180 L/d (125 mL/min)
- Entire plasma volume is filtered by the kidneys approx. 60 times/day
what is reabsorbed in the proximal tubule
- ~60% of NaCl and H2O
- ~90% of filtered HCO3-
- Almost all glucose, amino acids
- Most K, PO4, Ca, Mg, urea, uric acid
what is produced/created in the proximal tubule
Ammonia! major site of production
what is secreted by the proximal tubule
- organic anions (e.g., urate)
- organic cations (e.g., creatinine, dopamine, Ach, epinephrine, histamine)
- Urea
- Ammonia
- Protein-bound drugs, chemo rx, toxins
what is the function of the descending loop of henle
- Highly water-permeable
- Reabsorbs ~15% H2O
what is the function of the
thin ascending loop of henle
Impermeable to water and ions except Na+ and Cl-, which are reabsorbed by diffusion
what is the function of the thick ascending loop of henle
- Very low water permeability
- Reabsorbs…
-NaCl via Na+/K+/2 Cl- pump
-Some Calcium and Magnesium
-May HCO3- reabsorption - May see secretion of urea
What is the Target for loop diuretics
the thick ascending loop of henle (na/K/2 Cl pump)
what is reabsorbed by the distal tubule
- ~5% of NaCl
- little H2O (low permeability)
- May reabsorb urea
also regulates calcium and pH
how does the distal tubule regulate pH
by either of the following:
* reabsorbing HCO3- and secreting H+
* reabsorbing H+ and secreting HCO3-
what is secreted by the distal tubule
K+
what is the target site for thiazide diuretics
Distal tubule
what are the two types of cells in the cortical collecting duct
principal cells
intercalated cells
what is the function of principal cells
- reabsorb NaCl and H2O
- secrete K+
- Site of action for aldosterone, eplerenone, and other K+-sparing diuretics
what is the function of intercalated cells
mediate HCO3- and H+ secretion and reabsorption
what is the final site of urine modification
medullary collecting duct
what is the function of the medullary collecting duct
- Final modification of urine
- Reabsorb NaCl, water and urea
- Secretes ammonia and H+
- Secretes or reabsorbs K+
what can cause acute nephron damage ( sudden loss of renal function )
- Hypotension (blood loss, septic shock, dehydration, heart failure)
- Obstruction of urine flow (BPH, renal stone, tumor)
- Substances (medications, toxins, myoglobin)
what can cause chronic nephron damage (slow, gradual loss of renal function)
Diabetes Mellitus
HTN
Autoimmune diseases
Infection/Inflammation
Polycystic disease
Nephrotoxic Substances
why is nephron damage so detrimental
because nephrons can not be regenerated after loss!
what is compensatory renal hypertrophy
increased size of each cell in nephron
when is compensatory renal hypertrophy seen
Seen in situations of ongoing hyperfiltration
* Pts born with one kidney
* Loss or donation of a kidney
* Pregnancy
this produces no ill consequences and can aid kidneys in achieving 80% of prior function
what does end stage renal disease result from
- Resection of significant amount of renal mass (~80%)
- Destruction of a significant amount of nephrons
what occurs when nephrons cannot compensate?
maladaptive deterioration
describe the process of renal disease progression
progressive nephron loss after severe or persistent disease
- Persistent glomerular HTN →
- Damaged glomeruli →
- Protein leakage and proteinuria →
- Inflammatory immune response →
- Renal tissue responds to inflammation with fibroblasts →
- Fibroblasts lay matrix that disrupts capillaries and tubules →
- Matrix becomes an acellular scar
what is the GFR for people with early CKD
60-99 for 3+ months with kidney damage markers is indicative of early CKD
what is the GFR for people with CKD
GFR<60 for 3+ months
will people with kidney disease always have decreased GFR. Why or why not
NO! can have normal or increased GFR due to:
- hyperfiltration at the glomerulus
- disease affecting various kidney areas
beware that GFR may not mean what you think!
Stable GFR ≠ stable disease
Improved GFR ≠ improved disease
Normal GFR ≠ no kidney disease
what are the methods of estimating GFR
using a freely filtered substance that is not secreted, reabsorbed or changed along the tubule (BUN, Cr, cystatin C)
or can use:
24 hr creatinine clearance (CrCl)
estimation equations
how does body surface area affect GFR estimation
kidney function is proportional to kidney size which is proportional to BSA
smaller body = lower metabolic demands = less muscle mass = smaller kidney size
how does age affect GFR estimation
GFR declines with age even in patients w no hx of CKD
declining GFR is an independent risk factor for adverse health outcomes
what are the four factors affecting GFR estimation
Body surface area
age
gender
race
how does gender affect GFR estimation
males tend to have higher muscle mass and creatinine generation which decreases GFR
how does race affect GFR estimation
african americans tend to have higher muscle mass and creatinine generations, some GFR calculators take this into account
how is creatine obtained in the body
50% manufactured by the liver
50% absorbed from food (meat)
how is creatine used and metabolized
- taken up by high metabolism tissues such as skeletal muscle and brian.
- metabolized by creatine kinase into creatine phosphate which can be used as fuel for ATP production
- creatinine is the waste product of creatine
how does creatinine affect GFR
increased creatinine = decreased GFR
decreased creatinine = increased GFR
what factors can increase serum creatinine
- higher muscle mass
- increased meat intake
- increased creatine supplements
what factors can decrease creatinine
vegetarian
antibiotics or cimetidine
liver disease
how does creatinine respond to early v late CKD
- Early CKD - creatinine secretion is enhanced, blunting the expected rise in serum Cr
- Late CKD - extrarenal creatinine elimination increases, blunting expected rise in Cr
How does creatinine clearance estimate renal function compared to true GFR
estimates a higher renal function than true GFR.
this means creatinine clearance estimates GFR at the upper limit for what the true GFR may be
what is required when using creatinine clearance for GFR
24 hours urine measurement
check this
how do you obtain a urine sample for 24 hr CrCl
void intial urine after waking up and then collect ALL urine for the next 24 hours.
finish with collecting the first urine of the next morning within 10 min of 24 hour mark
what are the limitations of 24 hour urine CrCl
- incomplete urine collection
- cumbersome = poor compliance
- increased ceratinine secretion as GFR falls (idk what this means)
- overestimation of GFR
what is urea
a waste product of protein created by the liver
where is urea obsorbed
30-70% reabsorbed in the renal tubules
how does volume depletion affect urea reabsorption in tubules
- Reabsorption decreased in volume replete pts
- Reabsorption increased in volume deplete pts
dont reallu understand this but ok
what is the normal BUN:Cr ratio
10:1 to 20:1
how does volume depletion effect BUN:Cr
ratio may increase (20:1 or higher)
what factors could cause an increased BUN
- Dehydration
- Catabolic (cell breakdown) states such as GI bleed, cell lysis, corticosteroids
- Increased dietary protein
- Decreased renal perfusion such as during HF, RAS
- Tetracycline
what causes decreased BUN
- Liver disease
- Malnutrition
- Sickle cell anemia
- SIADH
how does BUN correlate with GFR
they are inversely correlated but BUN can change independently of GFR:
Rate of urea production is not constant
40-50% of filtered urea is passively reabsorbed
increased in volume depletion
BUN rises out of proportion to change in GFR and Cr
what is a better calculation of GFR? BUN or Cr
Cr because BUN can change independently of GFR.
when is BUN most used?
CKD patients
what is cystatin C
a protein produced at a fairly steady rate by all nucleated cells in the body
pros and cons of Cystatin C
Pros
* Less directly affected by muscle mass and metabolism than creatinine
* Not as impacted by age, sex, gender, or race as creatinine
* varies less than other markers
Cons:
* expensive
when is Cystatin C mostly used for GFR
when creatinine is at high risk for not being accurate:
* elderly
* body builders
* acutely ill patients (esp w muscle mass change)
what is the cockcrault-Gault equation
estimation of CrCl based on serum Cr in a patient with stable Cr
accounts for advancing age and weight increase
what are the limitations to the cockrault-Gault equation
- it was developed when obesity was less common and therefore it does not account for BSA
- it is highly dependent on serum Cr
what is the conclusion on reliability of the cockrault-Gault equation
it overestimates CrCl and is considered to be low accuracy
what is the actual equation of the Cockcrault-Dault equation
Idk if we actually need to know this so if you know plz text me lmao
What is the MDRD study equation
an equation that estimates GFR that is adjusted for body surface area. It is based on data from adult patients
what is the conclusion on reliability of the MDRD equation
more accurate than cockroft-Gault formula but it has not been studied in different back grounds (elderly, obese, diverse ethnic/racial backgrounds)
what is the actual equation of the MDRD study equation
dont need to know this so 5 it
What is the CKD-EPI study
a more accurate estimation of GFR than MDRD or cockrault-gault equation in patients with normal or mildly reduced GFR.
what are the order of the equations in order of most to least reliability
- CKD-EPI study
- MDRD
- Cockrault-Gault equation
what is the preferred equation to use for GFR in the US
CKD-EPI 2021
