Exam 1: Nephrology/Urology & Dermatology Flashcards
Which of the following tests on a dipstick are reliable?
Leukocytes, protein, pH, SG, blood, urobilinogen, glucose, ketones
Protein, pH, blood, glucose, ketones are reliable.
Ignore results from leukocytes, SG & urobilinogen
What is renal failure?
Clinical syndrome that occurs when kidneys are no longer able to maintain regulatory function, excretory function and endocrine function.
What percentage of nephrons must be nonfunctional before renal failure occurs?
75%
What is renal disease and how does it differ from renal failure?
The presence of morphological or functional lesions in one or both kidneys regardless of extent.
Renal failure relies on extent (75% nephron loss). Renal disease may or may not result in azotemia, decreased USG, etc.
What is uremia?
The constellation of clinical signs and biochemical abnormalities associated with critical loss of functional nephrons resulting in extra-renal manifestations of renal failure such as uremic gastropathy, hyperparathyroidism, etc.
What other abnormalities (biochemistry) may occur with uremia?
Azotemia, hypoalbuminemia, hypercholesterolemia, metabolic acidosis, hypocalcemia, hyperparathyroidism, hyperkalemia.
What is the gold standard for determination of GFR?
Renal scintigraphy
Usually only found in university settings
What are the accurate methods of determining GFR?
Renal scintigraphy, iohexal clearance, inulin clearance, creantinine clearance.
What are the indirect methods used to determine GFR?
Serum urea levels, serum creatinine levels, Cystatin C, SDMA
What extra-renal factors may influence serum [urea]?
species/age liver function (synthesized in the liver) Dietary protein content (high protein diet = higher BUN) Endogenous protein catabolism (same as high protein diet)
What are the limitations in using serum [urea] to evaluate GFR?
Urea is reabsorbed in the tubules (falsely decreases GFR) High protein diet (protein --> ammonia --> urea) GIT bleeding (similar as high protein diet)
What are the limitations in used serum [creatinine] to evaluate GFR?
Will not show elevated values until GFR has decreased to 25%.
Dependent on muscle mass:
Implies lower GFR in heavily muscled animals - higher serum [creatinine]
Implies higher GFR in poorly muscled animals such as geriatric and/or cachexic patients - lower serum [creatinine]
What biochemistry changes can be seen in blood work when 40% of GFR has occurred?
SDMA increase
What is the gold standard for determining urine concentration? What’s most often used in practice and what are it’s limitations?
Gold standard is osmolality.
Most often used is urine specific gravity.
USG is influenced by the number and size of particles (e.g. glucosuria falsely increases concentration)
What are the ranges for minimally concentrated USG?
1.013-1.030
What are the ranges for inadequately concentrated urine?
1.013<1.022
Reference range for normal USG in dogs?
> 1.030
Reference range for normal USG in cats?
> 1.035
What are the ddx’s for hyposthenuric urine?
Diabetes insipidus, psychogenic polydypsia
When performing a water deprivation test, at what point would you expect maximal stimulation of ADH release?
after 5% loss of body weight
What is fractional excretion and how is it used when evaluating kidney function?
Fractional excretion measures electrolytes in the urine compared with creatinine to evaluate for renal tubular dysfunction.
If the kidneys are functioning properly, there shouldn’t be >1% Na+ lost in the urine. If the FE <1%, there may be prerenal disease present.
What changes occur as urine sits at room temperature before the sediment is run?
Growth of crystals
Disintegration of casts and cells
What may cause a false positive on a urine protein creatinine ratio and how might you avoid this false positive?
Lower urinary tract disease
Run a sediment to r/o UTI prior to UPC.
Urine sample is red. What could cause that? How would you determine which is the culprit?
Red discoloration in the urine may be caused by RBCs, hemoglobin or myoglobin.
Centrifuge the sample: if a red pellet forms at the bottom, RBCs were the cause.
If the supernatant is still discolored red: look at the patient’s centrifuged blood sample. Myoglobin doesn’t accumulate in the blood stream so if the serum/plasma is discolored, it’s hemoglobin. Alternatively, run a CK: muscle damage = myoglobin
Hematuria is
presence of intact RBCs in the urine
Pseudohematuria is
Reddish or brownish color without the presence of intact RBCs (hemoglobin, myoglobin, chemicals)
What is the normal urine output for dogs and cats?
1 mL/kg/hr
Renal Carcinoma:
More common in: dogs or cats?
Unilateral or bilateral?
Early clinical signs?
Paraneoplastic syndrome?
Occurs dogs > cats
Unilateral > Bilateral
Very few early c/s’s (d/t reserve capacity - healthy kidney picks up the slack)
Paraneoplastic syndrome results from disruptions in normal endocrine function of the affected kidney: polycythemia (from EPO and/or renal hypoxia), hypertrophic osteopathy (abnormal Ca+/Phos- metabolism). May also cause neurological signs.
What’s the treatment and prognosis for renal carcinoma?
Nephrectomy (after ensuring the remaining kidney is functioning adequately).
Mean survival time after tx = 16 months (dogs)
What diagnostics can be performed if renal neoplasia is suspected?
Ultrasound & U/S-guided FNA
Renal lymphoma:
More common in dog or cat?
Unilateral or bilateral?
Clinical presentation?
Cats > dogs
Bilateral > unilateral
Presents with: renomegaly, weight loss, inappetance, PU/PD, renal azotemia. Often systemic at the time of diagnosis so there may be other signs of lymphoma such as mediastinal mass, neuro signs from mets, and lymphadenopathy).
Has a tendency to spread to the CNS
Treatment and prognosis of renal lymphoma?
Multi-agent chemotherapy
~60% go into complete remission (cats)
MST = 91 days with treatment
If azotemia doesn’t improve with chemotherapy = poorer prognosis b/c indicative of larger portion of those kidneys have been destroyed.
What are the DDx’s for renomegaly?
Neoplasia: carcinoma vs. lymphoma vs. sarcoma vs. nephroblastoma vs. metastatic mass (e.g. hemangiosarcoma)
Renal inflammation: acute nephrosis, acute pyelonephritis, FIP, leptospirosis
Amyloidosis
Hydronephrosis
Polycystic kidney disease
Portosystemic shunts
Polycystic kidney disease.
More common in ___.
Results in ___.
Caused by ___.
More common in cats > dogs.
Results in renal failure from pressure necrosis of nephrons.
Caused by an autosomal dominant defect in PKD-1 gene in persian cats OR an inherited condition > in Bull terriers, cairn terriers and Westies.
DDx’s for renal pain.
Pyelonephritis, renal calculi, acute nephrosis, hydronephrosis (early), renal trauma, abscesses, neoplasia (rare)
What are pre-renal causes of AKI?
Hypoperfusion to the kidneys: cardiac disease, hypovolemia, hypotension, PGE inhibition (from NSAIDs).
Hypoxia
In what way can post-renal causes of acute renal injury result in diabetes insipidus?
Pressure on the collecting tubules will damage the aquaporin channels resulting in nephrogenic DI.
What are the four phases of acute renal failure and what distinguishes them?
Initial phase - Usually an ischemic event triggers it. No clinical signs, decreased urine output or increase in creat.
Extension Phase - continued hypoxia and inflammation. Na:K pumps become damaged which results in cellular swelling, Ca accumulates in the cells which eventually leads to tubular cell death.
Maintenance phase - damage is done, you’re now waiting to see if it will improve.
Recovery phase - PU and extreme Na+ loss. takes weeks to months to recover.
What’s the significance of reduced central venous pressure?
Indicative of hypovolemia. CV system is pulling as much blood from the veins as possible.
In what way are calcium channel blockers renoprotective?
They prevent the intracellular hypercalcemia which results in cell death.
E.g. Amlodipine
In what way are (selective) Dopamine-2 agonists renoprotective?
They cause vasodilation.
Be mindful of dose - there are dose-dependent effects
In what way are (selective) Dopamine-1 agonists renoprotective?
They prevent vasoconstriction.
E.g. Fenoldopam
In what way are EPO analogs renoprotective?
They increase [RBC] which increases O2 delivery to tissues (including kidneys)
What systolic BP should be maintained to ensure adequate perfusion to the kidneys?
> /= 80 mm Hg
What parameters can be monitored to evaluate renal perfusion?
BP, central venous pressure, PCV/SpO2/PaO2 (hypoxic?), ECG (hyperkalemia-induced bradyarrhythmias)
How can acute kidney injury and acute renal failure be diagnosed?
Reduced urine output
Renal tubular epithelial cell casts in urine sediment.
Azotemia
Fractional Excretion >1% Na+.
Renal tubular biomarkers relative to creatinine (GGT: creat, NAG: creat). These biomarkers enter the filtrate through areas of the nephron where RTE cells have died; they do not enter through the glomerulus.
Shock fluid dose for a dog: ___.
60-90 mL/kg/hr
administer in 25% of shock dose every 15 minutes and reassess hydration before administering another dose.
Shock fluid dose for a cat: ___.
45 mL/kg/hr
administer in 25% of shock dose every 15 minutes and reassess hydration before administering another dose.
How do you determine fluid dose to correct patient dehydration?
% Dehydration * BW (kg) = Fluid dose (L).
What needs to be factored in when choosing a maintenance fluid rate? What about if the patient is dehydrated?
Insensible losses (respiration and sweating) = 22 mL/kg/day
Sensible losses (urine output) = (usually) 44 mL/kg/day monitor your patient’s urine output to determine
Ongoing losses (vomiting, diarrhea, etc - estimate)
Dehydrated patient rate = {% dehydration * BW (kg)} = L to be administered over the course of 6-12 hours
What is oliguria?
Reduce urine output (<0.5 mL/kg/hr)
What treatments for oliguric patients are supported by evidence based medicine?
NONE
What treatments can be used for oliguric patients?
Fluid therapy!! Mannitol, furosemide, dopamine, calcium channel blockers
How does that administration of mannitol aid in the treatment of ARF? When would it be contraindicated?
Osmotic diuretic = increases circulatory volume which flushes tubules., decreases cell swelling and cellular aggregation, scavenges free radicals, blunts the influx of calcium intracellularly.
This treatment is contraindicated in patients that are anuric and/or dehydrated.
How does that administration of furosemide aid in the treatment of ARF? When would it be contraindicated?
Loop diuretic - it decreases the Na-K ATPase pump which reduces the oxygen requirements.
It increases urine production without increasing GFR
Contraindicated in dehydration, lethargy, tachycardia, ototoxicity.
What is used in the treatment of ethylene glycol toxicosis?
4-methylpyrazole > ethanol
What is used in the treatment of NSAID toxicosis?
Misoprostal (PGE-analog)