Flashcards in Renal Deck (107):
How does the R kidney positioning differ from the L?
The R kidney is located slightly lower d/t displacement by the liver.
What are the three major functions of the kidney?
Differentiate between hydrostatic and oncotic pressures.
Hydrostatic pressure refers to the pushing of fluids against the vessel walls from within the vasculature and within the interstitial space.
Osmotic pressure refers to the pulling force exerted on the vessel walls from within the vasculature and within the interstitial space
What is thirst triggered by?
Increased concentration of extracellular fluid (increased osmolality)
Decreased circulating blood volume
The amount of fluid excreted in the urine is controlled primarily by which hormones?
Natriuretic Peptides (ANP and BNP)
Where is ADH synthesized and released?
Synthesized in the hypothalmus
Released by the posterior pituitary gland
What factors increase the release of ADH?
-Increased osmolality of the extracellular fluid
-Decreased circulating fluid volume
How does ADH impact the concentration of filtrate in the collecting duct (and DCT)?
ADH stimulates the epithelial cells in the collecting duct to produce aquaporins causing water to be reabsorbed from the filtrate to the capillaries.
This happens via osmosis d/t the increased concentration of solutes (increased osmolality) in the capillary vs. the decreased concentration (hypotonic solution) present in the renal tubules.
Where is aldosterone synthesized and released from?
What are the main stimuli for aldosterone release? (2)
1. Angiotensin II (AII)- from RAAS, activated by decreased circulating blood volume
2. Increased concentration of K ions in the plasma
How does aldosterone impact the concentration of the filtrate in the collecting duct? (3)
1. Stimulates the Na-K pump
2. Opens Na channels (increased Na in the blood pulls water into the vascular=increased blood volume)
3. Open K channels (K moves into filtrate)
What hormones opposed the action of aldosterone?
When are ANP and BNP release?
ANP is released with the atrial cells are overstretched signaling an excess of volume.
BNP is released by the ventricles when EDV is elevated indicating an excess of volume (HF)
How do natriuretic peptides oppose the action of aldosterone?
ANP opposes AII. Promote fluid excretion by nautriuresis (moving Na into the urine so that water follows=decreased blood volume)
How many nephrons are there per kidney?
Traces the flow of filtrate through the kidney.
Glomerulus to PCT to LoH to DCT to collecting duct
What are the general functions of the glomerulus?
The capillary net that filters plasma, making ultrafiltrate that is called tubular fluid once it enters the PCT
What are the general functions of the PCT?
Has cuboidal epithelial cells with brush border villus membrane to increase surface area and is the main site of reabsorption of water, lytes and nutrients (isotonic filtrate)
What is the general function of the thin descending Loop of Henle?
Impermeable to solutes but permeable to water. Concentrates fluid as well as diffuses water out. (hypertonic filtrate)
What is the general function of the thick ascending Loop of Henle?
Impermeable to water but has NaK2Cl active transporters that reabsorb more solutes and dilute the tubular fluid. (Hypotonic) Sets up and maintains interstitial concentration gradient
What is the general function of the DCT?
Electrolyte modifications. Sense concentraiton of Na and Cl via villi and signals juxtaglomerular cells via PGE to release renin. Aldosterone acts on late distal tubule principle cells.
What is the general function of the collecting ducts?
Site of free water reabsorption through water channels ( aquaporins)controlled by ADH.
Important to acid-base balance; allow H secretion and bicarb secretion when necessary
What are the functions of the kidney?(5)
1. Remove toxins/waste from the body
2. Maintain proper H2O and electrolyte balance of blood (excrete H20 and lytes, secrete renin)
3. Maintain proper pH of blood (usually excrete H and create bicarb)
4. Secrete EPO
5. Activate vit D (vital to Ca absorption)
What is filtration?
The movement of substances out of the blood into the filtrate. Glomerulus into the PCT.
What is reabsorption?
The return of substances from filtrate now present in the tubular fluid back into the blood.
What is secretion?
The movement of substances out of peritubular blood via kidney tubule cells in tubular fluid.
What is the vasa recta?
Capillaries located around the LoH; absorb interstitial fluid without excessive removal of interstitial solute.
What is the renal corpuscle?
Glomerulus and Bowman's space
What is the kidney's release of renin stimulated by (RAAS stimulation)?
Decreased fluid volume
What is the RAAS inhibited by?
Increased fluid volume
What are the steps of the RAAS?
In response to decreased BP or volume renin is released by the kidneys.
Renin acts on the liver which release Angiotensinogen that is cleaved by the renin resulting in Angiotensin I which is converted via the lungs by ACE to Angiotensin II which stimulates the adrenal cortex to release Aldosterone. Aldosterone acts on the distal portion of the nephron to increase Na K ATP pumps to increased the reabsorption of Na and H2O=increased blood volume and BP
In addition to stimulated the release of Aldosterone what does Angiotensin II do?
How are the capillaries of the glomerulus different from other capillary networks in the body?
Glomerular capillaries branch from and drain into arterioles
Why is there no oncotic pressure in Bowman's space?
This area should be protein free which is indicative of decreased oncotic pressure
Why is the NFP in the efferent arteriole=0?
No filtration happens here.
What is the purpose of the podocytes?
Surround the fenestrated epithelium and are negatively charged, so they provide a barrier to movement of negatively charged ions
What do mesangial cells do?
Provide structural support for glomerular capillaries, secrete matrix proteins, phagocytose and regulate GFR
How do mesangial cells regulate GFR?
SMC:Contraction and relaxation which alters the available surface are for filtration and affects GFR
How does each nephron regulate its own GFR?
What is the regulatory structure that controls tubuloglomerular feedback?
2. Macula densa
3. Juxtaglomerular cells
What does the macula densa do?
Located near the end of the ascending LoH in the DCT. Senses changes in the amount of NaCl. Increased NaCl inhibits renin release and a decreased load promotes renin release (decreased amount of tubular fluid moving by)
What do the juxtaglomerular cells do?
Surround afferent arteriole. Produce and release renin
How is bicarbonate reabsorbed?
Bicarb is converted to CO2 and H20 via carbonic anhydrase in the PCT. Carbonic anhydrase is then used to the catalyze the reverse reaction creating H and bicarb; bicarb is reabsorbed back into the blood via the Na HCO3 transporter and H is excreted in the urine
What does decreased reabsorption cause?
Dilution of urine and overall increase in fluid volume
How is sympathetic nerve activity related to the 'fight or flight' response in the kidneys?
Diverts blood from kidneys and GI tract. Increases fluid reabsorption to shut of ability to make urine (Na and H2O reabsorbed)
What affect does in an increase in pressure sensed by baroreceptors in the afferent arteriole cause?
Inhibits renin release
What are the 2 mechanisms of regulation of RBF and GFR?
1. Autoregulation- myogenic mechanisms and tubuloglomerular feedback
2. Neural regulation
3. Hormonal regulation- RAAS, ADH, Natriuretic peptides
How do osmotic diuretics work?
Increase osmolality of the filtrate causing more water to remain in the tubule which is excreted as urine
How do ACE inhibitors cause diuresis?
Inhibit AII and Aldosterone. Inhibits reabsorption of Na which keeps more water in the filtrate to be excreted
How do loop diuretics work?
Block the Na K 2Cl pumps on the ascending loop to keep solutes in the urine
How do thiazide-like diuretics work?
Block Na Cl co-transporter in the DCT blocking Na reaborption
How do aldosterone blocking agents work?
Decrease Na and H2O reabsorption and K excretion (potassium sparing)
What are the different casts that may be found in urine and what do they indicate? (3)
1. WBC- pylonephritis
2. RBC- glomerulonephritis
3. Epithelial casts- ATN
Where is kidney associated pain most often felt?
CVA/flank pain; transmitted from T10-T12 and L1 via sympathetic afferent neurons
What is agenesis?
Congenital abnormality. Kidneys don't develop in the fetus.
Bilateral = incompatible with life
Unilateral= compensatory hypertrophy of functional kidney
What is hypoplasia of the kidney?
Congenital abnormality. Some fetal kidney development. Could lead to pediatric ESRF.
What causes cystic kidney disease?
Autosomal recessive (often lethal and do not make it to reproductive age= less common)
Autosomal dominate (Chromosome 16 PKD1 most common and Chromosome 4 PKD2)
What is cystic kidney disease?
Characterized by fluid filled renal cysts, may expand and disrupt urine flow.
Decreased cilia formation of the epithelial cells in the nephron that should detect pressure and solute content passing through and stimulate Ca and cAMP. Decreased intracellular Ca and excessive intracellular cAMP causes reduction of normally function kidney tissue and development of cysts.
Decreased GFR and ability to concentrate urine
What are the clinical manifestation of cystic kidney disease?
1. Hypertension (decreased GFR=decreased urine=incr. volume)
2. Pain (common)
3. Concomitant cystic liver involvement
What are common causes of secondary glomerular disorders?
What type of urine is common of a patient with nephrotic syndrome?
Proteinuria d/t necrosis of the glomerulus
Usually no hematuria(?)
What type of urine is common of a patient with nephritic syndrome?
Mild to moderate proteinuria
*Hematuria and RBC casts present in sediment (RBCs are indicative of less severe injury because they are less negatively charged than protein)
How can proteinuria eventually result in hyperlipidemia and hypercoagulability?
Proteinuria leads to hypoalbuminemia which stimulates the liver to increased fat production (hyperlipidemia) and clotting factor production (hypercoagulability)
How can proteinuria cause generalized edema?
Proteinuria causes hypoalbumemia which decreases intravascular osmotic pressure allowing fluid to move into the interstitium causing generalized edema
What is minimal change disease or MCD?
-Initiated by allergic or immune condition causing decreased GFR
- Fusion of the glolmerular podocytes and decreased production of anions of the basement membrane =decreased barrier)
-Occurs in children
-Sudden onset of edema, nephrotic levels of proteinuria, and hypoalbuminemia
What is acute glomerulonephritis?
Acute inflammation of the glomerulus.
Related to antibody deposition leading to inflammation which results in lysosomal degradation of the basement membrane.
GFR may fall d/t contraction of mesangial cells
What are the clinical manifestations of acute glomerulonephritis?
Hematuria, proteinuria, oliguria, azotemia, edema and HTN
What does membranous nephropathy describe?
Diffuse thickening of the glomerular basement membrane. (Glomerulonephritis)
What is a common cause of postinfectious acute glomerulonephritis? (aka acute proliferative glomerulonephritis)
Follows skin (impetigo) and throat infections
*Group A beta-hemolytic streptococci
Developing countries, smoky/coffee-colored urine
What is Berger disease?
-IgA nephropathy (found in tracts)
-Upper resp or GI viral infections
-Complex deposition leading to mesangial injury
- Hematuria presents in 1-2days
-Proteinuria (but no HTN or edema)
-Variable prognosis, could lead to ESRD
What is indicative of chronic glomeruloneprhitis?
Sclerosis and fibrosis of the kidney
What type of urine do patients with chronic glomerulonephritis present with?
Proteinuria with or without hematuria
What does the sudden reduction of kidney function consistent with acute renal failure lead to?(4)
-Disruption in fluid, lyte, and acid-base balance
-Retention of nitrogenous waste
-Increased serum Cr
What are the three sites of disruption in acute renal failure?
Prerenal (decreased renal perfusion)
Intrarenal (parenchymal renal damage)
Postrenal (obstruction to urine flow)
What happens to the BUN:Cr ration with each respective cause of acute renal failure?
Postrenal 10-20 (equally affected)
What will a patient present with d/t decreased GFR secondary to pre-renal acute renal failure?
Oliguria, high urine specific gravity and osmolality, low urine Na, azotemia
What are the two possible pathological processes associated with intra-renal acute renal failure?
1. Vascular- RBF decreased, hypoxia, vasoconstriction
2. Tubular- inflammation and reperfusion injury, causes casts, obstructs urine flow, tubular backleak
Two most common causes of ATN?
Three phase of ATN include:
-Prodromal phase- insult occurs
-Oliguric phase- 1-2 to 8wks; oliguria, progressive uremia, decreased GFR, hypervolemia, hyperkalemia (?dialysis)
-Postoliguric phase- recovery; diuresis, tubular function impaired and azotemia continues, fluid volume deficient until kidneys recover
Full recovery is defined as normal BUN/Cr, may take up to a year.
Most common causes of chronic renal failure?
Polycystic Kidney Disease
Family hx of CKD
Age over 65
What is chronic renal failure defined as?
-Decreased kidney function or kidney damage of 3 months duration based on blood tests, urinalysis, and imaging
-GFR <60ml/minute/1.73m2 for 3 months with or without indication of damage
What causes relaxation of the internal sphincter and contraction of the bladder to enable urination?
What role does the cerebral cortex play in urination?
Inhibits via conscious control of the external sphincter
What role to sympathetic and parasympathetic nerves play in bladder function?
Sympathetic (L1-2)- allow relaxation and filling
Parasympathetic (S2-4)- cause bladder contraction and relaxation of the internal sphincter to initiate emptying
The detrusor muscle of the bladder must contract and urethral sphincters must relax
What is acute pylonephritis?
Infection of the renal pelvis/parenchyma usually from an ascending UTI
What is chronic pylonephritis usually associated with?
Reflux or an obstructive process leading to persistent urine stasis
(chronic inflammation causes scarring and loss of functional nephrons)
Common causes of urinary tract obstruction include:
Strictures of the ureters or urethra
Why do renal calculi most often form?
Supersaturation of solutes (Ca and Phos), low urine volume, abnormal decreased urine pH
Symptoms of kidney stone migration include:
Intense renal colic pain, abrupt and may radiate
Hematuria may be present
What is cystitis and what could cause it?
Inflammation of the bladder lining (cystele)
Infection (most common, originates in urethra), chemical irritants, stones, trauma
Dietary Calcium ______ kidney stones.
Prevents by binding oxalate and preventing absorption
How can hyperparathyroidism lead to hypercalcemia and kidney stones?
PTH is release from the parathyroid gland and increases circulating Ca levels. If Ca is not bound it increases the risk for stone formation
Distention/dilation of the kidney with urine.
Marked dilation of the renal pelvis and calyces and thinning of the renal parenchyma=decreased function
What can an overactive detrusor muscle causes?
Stress incontinence is secondary to:
Increases in intra abdominal pressure d/t weakening of pelvic muscles or intrinsic urethral sphincter deficiency
Overactive bladder syndrome is associated with:
Increased daytime frequency and nocturia
When does neurogenic bladder occur?
Pathology that produces a disruption of nervous communication governing micturition
Overflow incontinence can be caused by:
Underactive/inactive detrusor muscle
Possible pathogenesis of enuresis:
Deficiency in ADH
Nocturnal overactivity of the detrusor muscle
Immature/abnormal arousal mechanisms (incr. symp, dec para)
Vesicoureteral Reflux is:
Reflux of urine from the ureter-bladder junction
(may manifest as HTN in children)
What is ureteral ectopy?
Single ureter implanted in an abnormal location or a duplicate ureter
Increased risk for infection and reduced renal function
What is ureterocele?
Cystic dilation at distal end of the ureter that feeds into the bladder
Causes ureteral and renal calyx dilation, reflux and infection
Surgical intervention necessary
(s/s- hydronephrosis, UTIs, voiding dysfxn, hematuria, urosepsis, FTT)
Systemic hypertension leading to glomeruli dysfunction can lead to what pathologic change:
Obstruction of the renal tubule
A mass of proliferating cells found in Bowman’s space is associated with what disease?
Crescentic glomerulonephritis/rapidly progressing glomerulonephritis
Acute renal failure due to liver failure (hepatorenal syndrome) is due to:
Diminished intrarenal blood flow