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

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