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Diagnostic Tests: Renal

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Test that should be done Q-3mo for DM
HBA1c
Three parameters of renal tests
Glomerular fx
Tubular fx
Glomerular or tubular damage
Five risk factors for Renal Dz
CHIP FaD:
Cardiovascular Dz; HTN; Ix; Polycystic kidney Dz; FamHx; Diabetes
S/s of Renal Dz
Hematuria; Oligouria; Malodorous; HTN; Flank Pain
Top 3 Renal Risk Factors
1: DM
2:HTN
3:CV Dz
Nitrogen retention, demonstrated in BUN
Azotemia
Retention of urea in end-stage kidney failure
Uremia
Reduced renal fx for >3 mo. Name and reasons
Chronic Renal Failure (CRF)
DM, HTN, CV-Dz
The primary cause of azotemia
Pre-renal kidney dDz: Vascular Dz that reduces blood flow to kidneys
The second most common cause of azotemia
Renal kidney Dz: Damage to the renal parenchyma; glomeruli are damaged and won't filter effectively.
Obstruction of the ureters, bladder or urethra
Post-renal azotemia
Waste product of fast twitch muscles that enters the glomerulus at the proximal tubule
Creatinine
Creatinine is naturally higher in ___ than ____ (gender)
Males; females
Relationship between creatine and GFR
Creatine DOUBLES when GFR is cut in HALF
Two places to measure creatine
Serum and urine
Normal values for creatinine
0.4-1.5 mg/dL
Normal BUN value
<20 mg/dL
Three parameters that INCREASE BUN & why
1. Dehydration (concentrates urea)
2. High Protein intake (produce more urea)
3. Blood in GI (GFR drops, so blood urea rises)
Three factors that DECREASE BUN & why
1. Liver failure: (not producing urea)
2. Malnutrition/Kwashiorkor: (no amine groups to make urea from) 3. SIADH (dilute urea)
Paired test used to distinguish pre- or post-renal azotemia from renal azotemia.
BUN/Creatine.
Normal: 10:1 w/ normal range values
Pre-renal: 20:1 (urea builds up as blood is "held back" from kidney
Renal: 10:1 (both elevate, but ratio holds)
Post-renal (early): 20:1 (urine "backs up" in system)
The only direct measure of renal fx
GFR
Millilitres of body fluid cleared by kidneys per unit time
GFR
Most direct predictor of future kidney failure
GFR
Persistent decrease in GFR is an indicator for ____
Chronic kidney Dz
Range of average values for GFR
115 (age 20) to 75 (age 70)
Units for GFR calculations
mL/min/1.73m2
Race and gender variations in GFR
Women: 25% lower than men;
Blacks: higher in both sexes
GFR cut-offs for Kidney Dz
<60: Chronic Kidney Dz;
<30: Refer to nephrologist;
<15: Dialyze
Renal Fx test that parallels GFR by 10%. When to order & drawbacks
CREATININE CLEARANCE test. Order when unsure on GFR or if approaching kidney failure.
Drawbacks: Affected by large red meat intake, requires 24-hour collection time
Formula to calculate creatine clearance
Males: wt X (140 - age)/72(serum creatinine);
Females: multiply above by 0.85
Malodorous urine types
1. "Fruity:" DM ketoacidosis;
2. Foul or fishy: UTI or STD (from urea splitting to NH3)
Measure of urine density
Specific gravity
Normal specific gravity for urine
1.010 - 1.025 is normal
Hypo-osmolar and Hyper-osmolar Specific Gravity values
Hypo: <1.010;
Hyper: >1.025
Causes of hazy or cloudy urine
WBCs, RBCs, pus; Can occur w/ pH shifts
It is better for urine to be too ____ than too ____ (concentration values) Why? Follow-up test?
concentrated; dilute
Because dilute urine can indicate kidney failure. Follow-up w/ URINE OSMOLALITY test
Normal pH values for urine
5.0 - 6.0
Four sources of hematuria
C-I-S-T:
CA, Infection, Stones, Trauma
HEMAturia usually indicates damage or D/o where?
Renal (within in kidney/urinary tract)
HEMAGLOBINuria usually indicates damage or D/o where?
Pre-renal (vascular system leading to kidney)
Most common causes of hemoglobinuria
Hemolysis/hemolytic anemia/hemolytic uremic syndrome
Dipstick POS for blood but no RBCs indicates ____
Myoglobinuria from muscle damage (Rhabdo?!)
The "prime sign" of Kidney Dz, esp for DM patients
Proteinuria
If your dipstick is POS for proteins, you should ______
Do a 24-hr timed test
Test you should order annually for Type 2 DM pts & annually after 5 yrs in DM1
Microalbumin
What to do if pt test POS for Microalbumin
Repeat w/in 3 mos. If POS--> Stage 3 nephropathy
Tx for stage 3 nephropathy
ACE-I (Angiotensin Converting Enzyme inhibitor) or ARB (Angiotensin Receptor Blocker)
Popular diet that produces ketonuria
Adkins diet
Test that identifies UTI & who to test
Nitrites (made from nitrates by UTI bacteria);
Test elderly, pregnant and symptomatic
Tests for female UTI or amniotic Ix in pregnancy, esp if vaginal discharge; reasons for false POS
Leucocyte Esterase; False POS: bleeding, parasites, heavy mucus; also Nitrite test (bacteria convert nitrate-->nitrite)
Pair of tests for liver damage & GB damage
Bilirubin & Urobilinogen.
Bilirubin should always be absent from urine.
Some Urobilinogen should always be present--
Elevated: Hepatic damage or hemolysis;
Depressed: Biliary obstruction
How much bilirubin in urine is normal
Absolutely none
Urinary volumes and definitions
Oliguria: 100-400 mL/day;
Polyuria: >3000 mL/day
Anuria: <100 ml/day
If glucose is elevated in urine, what next?
Confirm w/ serum glucose test
Causes of False Positive in Leukocyte Esterase test
Vaginal discharge/Ix/mucus, Parasites
Three extended times used in urinalysis
2-hour, 3-hr (Glu tolerance) and 24-hr