Clin Path- Urinary 1

drraythe's version from 2015-12-05 15:09

Quick review/Important stuff to know before you start

Question Answer
tubular secretion--> which way is stuff moving?this is when things are secreted from plasma/interstitium back into tubules
If you dec GFR, what happens to the excretion of metabolic waster?also dec.
which substance is 100% resorbed and shouldn't be excreted into urine?glucose. glucose DOES get filtered in the glomerulus but 100% should be resorbed. If you see Glucose in the Urine that means it's levels are higher than the renal threshold for Glucose = PROBLEMS
What is osmolality? What would you say about urine's osmolality?total solute concentration. Urine's is much higher than blood plasma. (Unit is mmol/kg)
what happens in the proximal collecting tubule?removes volume, no change in concentration (about 75% of water resorbed, about 75% net solute resorbed)
what happens in the descending loop of henle?removes H20, INC INC INC solute concentration
what happens in the ascending loop of henle?removes solute, dilutes (dec dec concentration) Removes Na+, K+, Cl−, Ca2+, Mg2+, and H2O STAYS in the tubules
what happens in the distal nephron?The H2O permeability is VARIABLE, so if H2O is removed, the conc inc.(this is the usual case). OR, If H2O remains, the urine stays dilute
*what is azotemia?INC in non-protein nitrogen compounds in SERUM/PLASMA (such as an inc in urea conc, or an inc in creatinine conc)
*what are the three types of azotemia that might be possible when you see there is azotemia (inc in non-protein nitrogen compounds in serum/plasma)PRErenal azotemia (this is usually due to dec blood flow), RENAL azotemia, and POST-renal azotemia.
*Uremia usually indicates what? what are the clinical signs?RENAL FAILURE. Usually see vomiting, diarrhea, convulsions, coma, ammonia-scented breath.... "uremia" is referring to the clinical signs
*what are the 4 stages of chronic renal insufficiency/failure? how are they defined? when is or isnt there azotemia/signs?(1) Diminished renal reserve: ≈ 50 % function (NOT YET AZOTEMIC)
(2) Chronic renal insufficiency: ≈ 20-50 % function(azotemia, anemia, dec concentrating ability)
(3) Chronic renal failure: < 20-25 % function(azotemia, anemia, dec concentrating ability)(electrolyte imbalance, uremia clinical signs)
(4) End-stage renal disease: < 5 % function (terminal uremia signs)
*which stage of chronic renal insufficiency/failure does NOT have azotemia?the first stage, Diminished renal reserve (apprx 50% fxn)
*which stages of chronic renal insufficiency/failure are usually synonyms clinically, but have diff definitions? what is the major clinical sign they both share?(stage 2) chronic renal insufficiency (apprx 20-25% fxn) and (stage 3) chronic renal failure (<20-25% fxn). BOTH HAVE POLYURIA
*which stages of chronic renal insufficiency/failure are characterized by POLYURIA?(stage 2) chronic renal insufficiency (apprx 20-25% fxn) and (stage 3) chronic renal failure (<20-25% fxn)
*there are percentages which are used to characterize the stages of renal failure. in which animal are these percentages not accurate?these %s are true for most, but NOT true for cats.
*what are the two major criteria for a diagnosis of Chronic renal insufficiency? results of this?evidence of dec GFR(-->azotemia), and evidence of dec conc ability(USG aka urine specific gravity is apprx 1.007–1.013)
*as a pt progresses through the stages of renal failure, how does the urine volume which is voided change?polyuria -->oliguria-->anuria.
*describe what is going on in ACUTE renal insufficiency/failure. is it reversible or irreversible? causes?Reversible or irreversible renal dysfunction resulting abruptly from renal disease or insult that markedly decreases GFR and leads to azotemia. Some causes might be toxins, ischemia, infections
*what is the urine volume and USG-ref (urine specific gravity reference interval) for ACUTE renal failure? what is the OTHER problem that is frequently seen in ARF?frequently oliguria or anuria.. USG-ref may vary considerably. Also can see Acid-Base problems
do you see acid-base problems in acute or chronic renal failure?acute
what is the time frame differences between acute and chronic renal failure?chronic is mo to yr. acute is hr to days.

Part 1: serum [UN] & [Crt] with urine specific gravity

Question Answer
what is UN concentration? what is it often aka? what are the units?Urea nitrogen concentration. it measures [urea] in serum, plasma, or blood. It can be AKA BUN, but this isn't really very accurate because we are measuring the urea conc in PLASMA, not whole blood. UN and Urea common units are mg/dL. The SI are mmol/L
what does Creatinine (Crt) concentration measure? what are the units?measures the conc of CRT in SERUM/PLASMA. Units are: mg/dLof Crt --> mmol/L Crt(SI unit)
describe the life of a urea molecule (where is it made, where does it go, etc) (5)(1) It is created in the hepatocytes (Fixes NH4+, aka puts ammonia into the urea cycle to make urea) (2) Passes thru glomerular barrier into ultrafiltrate (3) some is resorbed by tubules (4) excreted in urine (5) excreted into intestine (from BVs)
describe the life of a creatinine molecule (where is it made, where does it go, etc) (5)(1) Produced from degradation of creatine or creatine-PO4(phosphate) (2) Passes thru glomerular barrier into ultrafiltrate (3) Not resorbed by tubules (4) excreted into urine (5) excreted into intestine
which substance is NOT resorbed by tubules (absorbed from tubule back into body)creatinine
*Pathologic mechanisms of PRE-renal azotemia. Clin path values affected? (2)(1) dec in renal blood flow (could be from shock, or dehydration). causes DEC GFR, INC [UN] and INC [Crt]. (2) Steep inc in urea production. This wont affect the GFR, there will be an inc in [UN] but not effect on [Crt]
*Pathologic mechanisms of RENAL azotemia. Clin path values affected?dec in functional nephrons (> 75% loss) This will dec the GFR and it will INC [UN] AND [Crt]
*Pathologic mechanisms of POST-renal azotemia. Clin path values affected? (2)(1) Obstructive uropathy. This will lead to a dec in GFR, and an inc in [UN] AND [Crt] (2) Urine leakage (e.g., uroperitoneum). This will have no affect on the GFR, but there will be an inc in [UN] AND [Crt]
*explain how dehydration results in a dec in GFR, along with 3 diff ways [UN] inc and 1 way [Crt] incdehydration causes hypovolemia. the hypovolemia stimulates JG cells to release renin, which causes the release of angiotensin II, which constricts glom arterioles. which DEC the GFR, which means less Urea and Crt are filtered, so their conc go up. Also, the flow rate in the tubules dec, which means that fluid stays in there longer, which means that more urea is resorbed so inc [UN] (remember Crt doesnt do resorption). Concurrent to Renin being released, ADH is being released, which inc resorption of urea in distal nephron
*explain why urea production might be steeply increasedif there is a inc in protein degradation, more ammonia is formed from the broken down protein, which the liver then converts the ammonia to urea, and then the [UN] will inc. This could happen in something like an intestinal hemorrhage, where hemoglobin is degraded. So, mild azotemia can result if there are Large amounts of digested blood in upper intestine (making more urea), AND then there is concurrent hypovolemia (due to gross loss of blood), which means that "rate of production" > "rate of clearance"
*explain how a dec in renal function leads to azotemia(>75% loss). the loss of nephrons means blood is flowing through the fewer gloms (same amount of liquid, fewer holes to go escape thru = slow)--> dec in GFR. this decreases the overall clearance/filtration of urea and crt from blood, so their blood conc inc.
*explain how a blockage can lead to azotemia (chronic and acute situation)in response to a block, the body will release vasoactive substances which constrict glom arterioles, dec blood flow--> dec GFR, which reduce clearance of urea and crt which inc their conc in the blood. if there is AN ACUTE OBSTRUCTION, it also INC hydrostatic pressure in tubules, and this also DEC the GFR. But pressure decreases soon because of seepage of fluid out of tubules & dec fluid entering tubules
*explain how a leakage of urine can lead to azotemia.(can be leaking from bladder, ureter, etc. can be due to urolithiasis, neoplasms, injuries). there is fluid in extravascular tissues that is high in urea and crt, and the conc gradient means they will diffuse into the plasma or into the lymphatics. (UREA DIFFUSES FASTER, prolly bc smaller molecule). IN THIS CASE, YOU GET AZOTEMA WITHOUT DEC IN GFR
explain where the location of the prob is in prerenal, renal, and postrenal azotemiapre= prior to glom. renal=too few nephrons. post=cause AFTER nephrons
*describe some diseases associated with prerenal azotemiahypovolemia resulting from dev blood vol, dehydration, cardiac insufficiency leading to dec cardiac output. Also could be from shock.
*describe some diseases associated with renal azotemia. Understand there can be ACUTE or CHRONIC conditions of this.Inflammatory causes (GlomNephritis, pyelonephritis, tub-inter. nephritis), Amyloidosis, Toxic nephrosis (hypercalcemia, ethylene glycol, etc), *Renal ischemia or hypoxia (poor renal perfusion) also Congenital hypoplasia or aplasia, Hydronephrosis, Neoplasia (metastatic)
*describe some diseases associated with post-renal azotemia.Urinary tract obstruction: urolithiasis, etc. Leakage of urine from urinary tract: trauma, etc
*Decreased [UN] can be caused by dec urea synth. what kinda dz would cause this?Hepatic insufficiencies, such as: hepatocellular disease, portosystemic shunts, Urea cycle enzyme deficiencies
*Decreased [UN] can be caused by increased renal excretion of urea, what kinda dzs would cause this?Disorders that cause impaired proximal tubular resorption of urea: (e.g., glucosuria)-->Central or renal diabetes insipidus (osmotic pressure is keeping solutes in)
Decreased [Crt] in serum or plasma means...we don't care. not clinically relevant.
what is a better gauge of a DEC GFR in horses... [UN] or [Crt]?[Crt] is a more accurate gauge.
what are Abnormal routine serum chemistry results in azotemic animals?inc in phosphorus [Pi], inc [tCa2+] (total calcium), inc [K+] (potassium) and blood pH, inc Serum amylase & lipase activities. (note, there are sp diffs)
sp diff of healthy urine of horses?will be hazy-turbid because of mucus in urine
sp diff of healthy urine of dogs?small amounts of protein and bilirubin is not abnormal.
what is the pH diffs between herbivores and carnivores?carnis will have more acidic urine, herbis will have more basic urine
*what gives urine its normal yellow color?urochromes and flavins
*Red and clear urine prolly contains what?Hemoglobinuria, myoglobinuria (heme)
*Red and cloudy urine prolly contains what?Hematuria (RBCs present) (heme)
*Orange to brown urine prolly contains what?Bilirubin (heme)
*Coffee-brown urine prolly contains what?Myoglobinuria, Methemoglobinuria (heme)
*diff between clear and hazy/cloudy urine?clear is expected, solutes are dissolved. in cloudy urine, there are suspended particles.
diff between specific gravity, and refractive index(USGref)?SG is a true measurement, it isnt used anymore. USGref is used all the time, and it is measured using a refractometer.
the Refractive index (USGref) measurement depends on/works by...?the number of particles(in health, usually the electrolytes, urea and creatinine) per volume, and the type of particles----> total solids percentage (g solute / 100 g urine)
what is Osmolality? what is osmolality of urine manipulated?Osmolality is the solute concentration of a solution. # of particles/volume... Renal tubules change osmolality of excreted urine
what is resorption of water in the distal tubule dependent on?depends on osmotic gradients! NOT the specific gravity(SG) or refractive index(USGref).
*how are osmolality& USGref related? why?usually they are directly correlated, if one inc the other inc. this is bc Both change with # of particles/volume; i.e., [solute]. (USGref also changes with type of particle)
*how do you estimate osmolality from USGref?you take the last two numbers of your USGref (so if it was 1.025, youd take the 25), and mult by 30 (30 is apprx the mean urine OSM:USGref of the data), which gives you the osmolality in mmol/kg. so USGref=1.025. 25x30=750 mmol/kg
*what situations make it more difficult to determine osmolality from USGref? what happens, and how do you compensate for that?USGref overestimates the solute concentration if there is very high protein or glucose concentrations (because USGref also is affected by TYPE of particle, where osmolality isn't). To figure out the osmolality from the USGref when there is high prot or gluc, you need to subtract a specific range of numbers (protein 1 g/dL-->0.003-0.005), (glucose 1 g/dL-->0.004-0.005) from the initial USGref number, THEN mult by 30. So if USGref=1.021, but there is high prot/gluc, so 1.021-0.005= 1.016. THEN 16x30= 480mmol/kg
*what is Hypersthenuria? what are the values of this for dogs and cats?very concentrated urine. Dogs= > 1.050. Cats= > 1.060
*what is Eusthenuria? what are the values of this for dog and cat? horse and ox?"normal" concentration (this term isnt used much). Dogs and cat= 1.030. Horse and ox= 1.025
*what is Isosthenuria? what are the USGref values associated with it? how does osmolality play into this? it is when Urine osmolality is about the same as plasma osmolality! (USGref 1.007 –1.013). The Urine osmolality will be 200–400 mmol/kg, and the plasma osmolality will be apprx 300 mmol/kg
*what is Hyposthenuria? what is the USGref value associated with it? how does osmolality relate?VERY LOW conc urine. USGref< 1.007. The Urine osmolality < plasma osmolality.
*what are three major requirements needed to produce concentrated urine?(1) ADH must be present(antidiuretic hormone, produced from pituitary) (2) Tubules must respond to ADH(open water pores) (3) conc gradient must be present ((so, interstitial fluid has a high osmolality, and the ADH opens opens the waterpores to let the water flow through)
*what are the two major requirements needed to produce hyposthenuric(low conc) urine?(1) Need functional loop of henle (ascending branch) to remove solute but not water
(2) Need ADH to not be present (water pores closed, water is excreted = dilute urine)

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