Renal Flashcards
Kidney embryology
P S T
Pronephros: week 4, then degenerates
Mesonephros: functions as interim kidney for 1st trimester, later contributes to male genital system system
Metanephros: permanent, first appears in 5th week, nephrogenesis continues though weeks 32-36 of gestation
Ureteric bud (Metenephric diverticulum)- derived from caudal end of mesonephric duct, gives rise to ureter, pelvis, calyces, collecting ducts, fully canalized by 10th week
Metenephric mesenchyme (Metenephric blastema)- ureteric bud interacts with this tissue interaction induces differentiation and formation of glomerulus through to distal convoluted tubule Aberrent interaction between these 2 tissues results in several kidney malformations-- renal agenensis, multicystic dysplastic kidney)
Ureteropelvic junction- last to canalize–> congenital obstruction. Most common cause of prenatal hydronephrosis (detected by prenatal ultrasound
Potter sequence/syndrom
Oligohydramnios–> compression of developing fetus–> limb deformities, facial anomalies (low set ears and retrognathia, flattened nose), compression of chest and lack of amniotic fluid aspiration into fetal lungs–>pulmonary hypoplasia (cause of death)
Causes include ARPKD, obstructive uropathy (posterior urethral valve), bilateral renal agenesis, chronic placental insufficiency
Babies who cant pee- Pulmonary hypoplasia, oligohydramnios, twisted face, twisted skin, extremity defects, renal failure (in utero)
Horseshoe kidney
Inferior poles of both kidneys fuse abnormally, as they ascend from pelivis during fetal development they get caught on the IMA and remain low in the abdomen, kidneys function normally, associated with hydronephrosis (ureteropelvic junction obstruction), renal stones, infection increased risk of renal cancer
Higher incidence in chromosomal aneuploidy (turner syndrome (turner, 13 18 21)
Congenital solitary functioning kidney
only one functional kidney, asymptomatic, with hypertrophy of functioning, can be seen in utero
Unilateral renal ageneisis- utereteric bud fails to develop and induce differentiation of metanephric mesenchyme–> complete absence of kidney and ureter
Multicystic dysplastic kidney- Ureteric bud fails to nduce differentiation of metanephric mesenchyme–> nonfunctional kidney consisiting of cysts and CT, usually nongenentic and unilateral–> biat will be potter
Duplex collecting system
Bifurcation of ureteric bud before it enters the metanephric blastema creates a Y shaped bifid ureter,
Can also be 2 ureteric buds reaching and interacting with metanephric blastema
vesicoureteral reflux and/or ureteral obstruction, increased risk of UTIs
Posterior urethral valves
membrane remnant in posterior urethra in males
Urethral obstruction- bilat hydronephrosis, dilated/thickwalled bladder on US
oligohydramnios in severe obstruction
Kidney structure
Left kidney gets cut out, longer renal vein (with left gonal vein, the arteries both com from the aorta)
Renal blood flow: renal artery-> segmental artery-> interlobar artery-> arcuate artery-> interlobular artery-> aferrent arteriole-> glomerulus-> efferent arteriole-> vasa recta/ peritubular capillaries-> venous outflow
Left renal vein receives left suprarenal and left gonadal vein
Despite high renal blood flow, renal medulla recieves less blood flow–> very sensitive to hypoxia
Glomerulus
Filtration barier- Endothelial cells, Basement membrane-Podocytes (touch urine)
The afferent has the Juxtaglomerular cells that are connected to the macula dena near the distal convoluted tubules
Juxtaglomerular cells secrete renin in response to B1 receptors, decreased perfusion pressure, decrease NaCL (aka water) sensed by macula densa
Course of ureters
Renal pelvis, travels under gonadal arteries-> over common iliac artery-> underuterine artery/vas deferens (reteroperitoneal
Gynecologic procedures (ligating the uterine or ovarian vessels can damage the ureterpp> ureteral obstruction or leak
Bladder contraction compresses the intravesical ureter, prevening urine reflux
Blood supply to ureter: Proximal (renal arteries), Middle (gonadal artery, aorta, common and internal iliacs) Distal (internal iliac and superior vesicle arteries)
3 common points of ureteral obstruction: ureteropelvic junction, pelvic inlet, ureterovesicle junction
Fluid compartments
60-40-20 rule (percents of body weight)
60% total body water
40% Intracellular fluid, mainly composed of K, Mg, organic phosphates (ATP)
20% Extracellular fluid, mainly Na, CL, HCO3, albumin
Plasma volume 25% of ECG, 75% is interstitial fluid
Plasma can be measured by radiolabeling albumin
ECF volume can be measured by inulin or mannitol
Serum osmolality= 285-295 mOsm/kg of H20
Plasma volume= total blood volume x (1-Hct)
Total blood volume 6L
Glomerular filtration barrier
filters plasma
Fenestrated capillary endothelium
Basement membrane with type 4 collagen chains and heparanated sulfte
Visceral epithelial layer consisting of podocyte foot processes
All 3 layers contain negative charged glycoproteins that prevent entry of negative charged molecules (AKA Albumin)
Size barrier- fenestrated capillary endothelium (prevents entry of >100 nm molecules/ blood cells
Podocytes interpose with glomerular basement membrane: slit diaphragm (prevents entry of molecules > 50-60 nm)
Renal clearance
Cx= clearance (mL/min) Ux= Urine concentration of X (mg/mL) Px= Plasma concentration of X (mg/mL) V= urine flow (Vlow) rate (mL/Min)
Cx= (Ux *Vx)/ Px (volume of plasma that a substance is completely cleared in urine /time)
If Cx < GFR (net Reabsorption or not completely freely filtered)
if Cx> GFR (net tubular secretion of X
if Cx = GFR (no secretion or REAB)
GFR
Inulin can be used to estimate GFR cause not REAB or secreted
Cinulin= (Uinulin * V)/ Plamsa inulin
Normal GFR= 100 mL/min
Creatinine clearance is an approximate measure of GFR (overestimates cause creatinine is a litttle secreted in renal tubules)
Effective renal plasma flow
eRPF can be estimated using para Aminohippuric acid clearacen
it is filtered and secreated bu no REAB, so 100% of it goes in urine
eRPF = (Upah * V)/ Ppah
RBF= RPF/ (1-Hct)
usually 20-25% of Cardiac output
eRPF underestimates true renal plasma flow
Filtration
Filtration fraction= GFR/RPF ( how good is the glomerulus at fitering out the plasma)
proportion to GFR
normal 20%
filtered load (mg/min) = GFR x Plasma conentration
Ureter constriction does not change renal plasma flow
Dehydration - decreases RPF by a lot comared to gfR decrease so elevated FF
REabsorption and secretion rate calculation
Filtered load: GFR x Px
Excretion rate: V x Ux
Reabsorption = filtered - excreted
Secretion rate= excreted - filtered
FeNA = fractional excretion of sodium
amount excreted/amount filtered
Glucose Clearance
Glucose is normally completely reabsorbed in proximal convoluted tubule (PCT) by Na/glucose co transport
In adults 200 mg/dl glucosuria starts, at 375 all na glucose co transportes are fully saturated
pregants is associated with increased GFR (glucose gets in urine at normal leverls
SGLT 2 inhibitors (Flozins –> glucosuria
Proximal convoluted tubule
Early PCT contains brush border. reabsorbs all glucose and Amino acids and most HCO3-, Na, Cl, PO4-, K, H20 and uric acid
Isotonic absorption, generates and secretes ammonia (NH3) which enables the kidney to secrete more H+
SGLT2 inhibitors prevent Na/Glut co transporters
Angiotensin 2 increases the action of NA/H+ transporter
CO2 +H20 –> H2CO3 via carbonic anhydrase which then spontaneously turns into H+ and HcO3- (HCO3- gets reabsorbed and H+ gets secreted with Na being reabsorbed
Carbonic anhydrase ALSO can convert H2CO3 into CO2 and H2O from HCO3 and H+
Acetazolamide inhibits carbonic anhydrase
PTH inhibits Na/PO4 cotranssport–> PO4 excretion
Angiotensin 2 stimulates Na/H exchange–> increased Na and H20 and HCO3- reabsorption (permitting contraction alkalosis)
65-80% Na and H20 reabsorption
Thin descending loop of henly
Its thin because theres no water in it
passively reabsorbes H20, via medullary hypertonicity impermeable to Na, concentrating segment makes urine hypertonic
The medullary interstitium (extremely hypertonic) is highly permeable to water but not ions