Intro Flashcards
Complications from what 2 diseases commonly involve kidney dysfunction?
DM and CHF
The function of the kidney is to “maintain homeostasis”. What, exactly is it trying to regulate?
Trying to maintain
1) Sodium (140)
2) Potassium (4)
3) pH (7.4)
Where is the nephron located?
in the medullary pyramid of the kidney
After leaving the proximal convoluted tubule, where would I go next?
The strait proximal tubule (my point is, be able to draw the nephron)
Where are the macula densa cells?
They are in the distal convoluted tubule which is in contact (next to) the afferent arteriole
What do the macula densa cells do?
Sense the net amount of NaCl. If sodium concentration falls, it will
1) signal the JG cells
2) Vasodilate the afferent arteriole (increase GFR)
What do the JG cells do when stimulated?
They make and secrete renin
Besides getting a signal from the macula densa cells, what else triggers the release of renin from the JG cells?
stretch receptors detect drop in BP
Review: What is the order of the RAAS?
drop in BP–>renin release. Renin converts Angiotensinogen to AT1. ACE converts AT1 to AT2. AT2 vasoconstricts and releases aldosterone. sweeet
What happens in the kidneys in response to low concentrations of Na+?
Increased renin and increased GFR
MD cells shrink signaling JG cells/renin and signaling afferent arterial dilation
Within the glomerulus, the capillaries are arranged into lobular structures called _____________________
glomerular tufts
REVIEW: Capillaries are made up of ________ layer(s) of ______________ cells
one, endothelial
The capillary walls are fenestrated. Why?
the “windows” allow plasma to diffuse through, but retain formed elements like RBCs or proteins
What are the responsibilities of the fenestrated endothelial cells?
regulate coagulation, inflammation, vasomotor tone, make antigens, release NO.
(Capillaries: NOT CIA)
This layer is an important determinant of the glomerular protein filtration barrier.
Glomerular Basement Membrane (GBM)
What IS the GBM?
a gel made of glycoproteins and type IV collagen
What does the GBM do?
it’s part of the filtration system.
(The GBM helps to perform the filtration function of the glomerulus, separating the blood in the capillaries from the filtrate that forms in Bowman’s capsule)
What does a healthy basement membrane look like?
Thin and lacey
What happens when there’s damage to the GBM?
Sucks at filtering. Either it starts loosing important things in the urine like protein or RBC’s, or it becomes too thick and the GFR is decreased
This element of the glomerulus is also made from collagen and serves as a “cytoskeleton” providing support and protection of the capillary tufts.
Mesangium (mesangial cells and collagen)
Aside from support and protection, what other functions does the mesangium have? (3 more)
Contraction (help regulate GFR),
Phagocytic (clears big molecules),
Has growth factor receptors (when stimulated, they produce more matrix)
What happens to the nephron when a patient is given an ACEI or ARI?
dilation of the EFFERENT arteriole will decrease pressure in glomerulus
What glomerular structure wraps around the capillaries leaving “slits” between its interdigitations that allow for filtration of ultrafine filtrates (like water and monosaccharides)?
Podocytes
The “slit diaphragm” b/t the fingers of the podocytes are zig-zag shaped and ________ly charged to stop ________ from escaping with the ultrafiltrate.
negatively charged, proteins (albumin)
If there is damage to the podocytes, what is the main thing you will expect?
Protein being lost in the urine
What happens when you lose a bunch of plasma protein?
There are not many particles in the blood and so osmotic pressure will cause fluid to accumulate in the tissue
CASE: Young patient is brought in with sudden swelling following a resolved illness. There is lots of protein in the urine, but the BUN/creat is normal. Oddly you test his cholesterol and find that it’s high. There are “oval fat bodies” in his urine. What is your diagnosis?
Nephrotic syndrome
(leaky podocytes, leak albumin creating an oncotic pressure gradient that favors fluid retension. Loss of oncotic pressure in the plasma triggers VLDL and LDL secretion by the liver)
What are the hallmarks of Nephrotic syndrome?
1) peripheral edema
2) hypoalbuminemia (low in blood)
3) hyperlipidemia
4) Proteinuria (high albumin in urine)
5) Oval fat bodies in urine
6) “MINIMAL CHANGE” to glomerulus
How do you treat nephrotic syndrome?
Steroids, (maybe a little reassurance)
What indications necessitate a kidney bx?
1) Unexplained AKI or CKD
2) acute nephritic syndromes
3) Unexplained proteinuria/hematuria
4) Plan therapy for lesion
5) systemic dz a/w kidney dysfunction (SLE, goodpasture’s, etc)
6) suspected transplant rejection
When are renal bx’s contraindicated?
Basically whenever you have one kidney or they are on their last legs (ie: horseshoe kidney, ESRD). Also CI for bleeding disorders,and known renal neoplasm
When approaching a newly suspected kidney disease, what should be included in your eval?
estimation of dz duration, UA, GFR, careful H&P
The retention of urea nitrogen and creatinine in the blood is called _____________
azotemia
Acute kidney injury/failure is a loss of kidney function over ______________, where chronic kidney injury/failure is loss of funtion over________.
hours/days vs months/years
______________is the term for “low or insufficient urine output”
Oligouria
Can you think of any reason why the RBC’s might be affected by kidney dz?
Erythropoietin comes from the kidneys….anemia
On imaging, the size of the kidneys could be a clue as to whether kidney dysfunction is acute or chronic. Large kidneys are a/w ________ dz and small kidneys are a/w ___________dz.
Large=both chronic and acute (lame)
Small=chronic
tests included in the UA are:
pH, protein, hgb, glucose, bili, nitrites, WBC’s, spec gravity, ketones
“mickey mouse ears”
dysmorphic red blood cells indicate filtration problem aka glomerulonephritis
What two things are commonly seen in the urine of a patient with glomerulonephritis?
dysmorphic RBC’s and protein
Could see RBC casts as well
If you see pigmented granular casts or renal tubular epithelial cells (alone or in casts) in a patient’s urine, what are you concerned about?
Renal tubular necrosis.
The presence of excess proteinuria with no detectable renal problem is a red flag for ______________
multiple myeloma (bence jones proteins)
What is the GFR actually measuring?
Kidney function at the level of the glomerulus.
what is creatinine?
Product of muscle metabolism
How reliable is creatinine/GRF in predicting kidney function? Why?
so-so, creatinine levels vary with age, muscle mass, meat intake, and some medications
What is BUN?
the end product of protein catabolism synthesized in the liver and then filtered in renal tubules.
Why do we use the BUN:creatinine ratio as the most accurate rating of kidney fxn?
BUN clearance underestimates GFR and Creatinine clearance overestimates GFR, so the ratio typically evens out the discrepancies.
What is a normal BUN:creat ratio?
10:1
whats a normal sized kidney?
9-12cm in length. Size difference >1.5cm indicates pathology in one kidney.
