renal tests Flashcards
normal functions of the kidney
Water balance
Acid-base balance (H+, HCO3-)
Electrolyte balance
Hormone production (Erythropoietin, Calcitriol, renin), Hormone removal (Gastrin)
Activation of Vitamin D3
tests to evaluate renal functions
-blood urea nitrogen (BUN)
-serum creatinine
-phosphate
-SDMA
why is BUN and creatin levels insensitive measures of renal disease
However, it’s a very insensitive measure of renal disease since at least 3/4 of the functional kidney mass would have to be destroyed, before azotemia is seen.
tell me about BUN (understanding)
by product of protein catablism-> ammonia-> urea
BUN means there is a lot of urea in the blood
normal function: kidney filters the urea out of blood into urine
so high BUN-> something wrong with kidney
tell me about creatinine
originates from creatinin in muscles (muslces produce them)
freely filtered by glommerulus, not reabsorbed by tubules (suppose to be in glommerulus filtrate, in urine)
what is azotemia
increased concentration of urea and/or creatinine in blood (high BUN creatinine)
what are the different causes of azotemia
Pre-renal – when the cause of the azotemia happens before the kidney, resulting in an underperfusion of the kidney. (not enough blood flowing to kindey)
Egs. Dehydration, CHF, Burns, Severe blood loss
Renal – when the cause of the azotemia happens at the kidney
Egs. Acute tubular necrosis, chronic interstitial nephritis
Post-renal – When the cause of the azotemia happens after the kidney along the urinary tract, resulting in urinary flow obstruction.
Egs. Prostatitis, Prostate cancer, kidney stones, Bladder tumours
what is hyperphosphatemia
high levels of phosphorus in blood
phosphorus is normally excreted by kidneys
stages of kidney disease
-25% of kidney affected
-50% of kidney affected (acute renal disease)
-75% of kidney affected (chronic renal failure)
what happens when 25% of the kidney is affected
-patient is fine
-no changes in BUA/CREA
-no changes in urinalysis
-no clinal signs
what happens when 50% of the kidney is affected
+/- mild increase in BUN/ CREA
-minimally concentrated urine (USG: 1.013-1.029)
-proteinuria
-usually no clinical signs
what happens when 75% of the kidney is affected
increase in BUN/CREA (azotemia)
+/- in phosphate
isothenuria ( USG 1.008-1.012)
-proteinuria
-clinical signs present: wight loss polyuria/ polydyspia, inappetance
tell me about SDMA
see azothemia-> do this test (more sensative)
-sensative and early biomarker of deterioating GFR, allow early intervension
what is the test for minimum data base
-urinalysis
-complete blood count
-serum biochemistry test
