Diagnostics Flashcards
How is a general urinalysis carried out?
- Cleanse external genitalia to avoid contamination
- Collecting urine mid-stream
- Centrifuge urine at 3,000 rpm/min for 3-5 minutes
- Pour supernatant into separate tube and re-suspend sediment
- Prepare slide with sediment
- Analyze supernatant and sediment
What things can a dipstick check? If positive, what can it indicate? (7)
- pH (normal = 5-6.5)
- > 7.5-8.0 indicates UTI with urea-splitting organism - Leukocytesterase
- Presence indicates leukocytes in urine - Glucose
- Presence indicates high plasma glucose or proximal tubular defect - Ketones
- Present indicates ketoacidosis - Proteins (bilirubin, urobilinogen, peroxidase)
- Presnece indicates kidney damage - Nitrite
- Presence indicates gram-negative bacteria - Heme
- Presence indicates blood in urine, intravascular hemolysis, or rhabdomyolysis
What is a “cast” in the context of urine microscopy. What does it indicate?
Precipitated protines and cells forming within the tubular lumen of the kidney
- If present, this indicates possible urinary stasis
- If composed of white blood cells, this indicates pyelonephritis
- Hyaline casts indicate they were made in the lumen of the nephron
- Granular casts indicate a proteinuric condition
- Waxy casts indiate the cells are generating (time?)
What is specific gravity of a urine sample and what does high or low indicate?
A parameter based off the concentration of excreted molecules in urine and used to evaluate kidney function.
- Increase = > 1.030
- May indicate dehydration, diarrhea, emesis, excess sweating, UTI, glucosiuria, renal artery stenosis, hepatorenal syndrome, decreased blood flow (heart failure), or excess ADH - Decrease = <1.000
- May indicate renal failure, pyelonephritis, diabetes insipidus, acute tubular necrosis, interstitial nephritis, psychogenic polydipsia
What can be found on a urine microscopy test and what do things indicate?
- Red blood cells
- Presence as a cast indicates glomerulonephritis or vasculitis
- Presence as fragments indicates glomerular bleeding
- If round and uniform, or if clots, this indicates they have an extra-renal origin
2. White blood cells - Presence indicates infection or inflammation
- If present as a cast, indicates acute pyelonephritis or tubulointerstitial disease
3. Protein - If present >500 mg/day, indicates glomerular or tubular lesion
- If present >3,000 mg/day, indicates a glomerular lesion
4. Epithelial cells - If present in a cast, indicates kidney origin
5. Lipids - If present, indicates glomerular disease and nephrotic syndrome
6. Crystals - Indicates cystinuria if cystine crystals
What is a normal blood urea nitrogen (BUN) to creatinine ratio in the kidneys?
5-20:1
What are 9 ways to measure GFR?
Which 2 are most widely used equations?
What is the most widely used clinically?
Which is the gold standard?
- Serum creatinine
- Cockcroft-Gault formula
- Cystatin c
- Modification of Diet in Renal Disease equations
- CKD-EPI equations
- 24-hour urine creatinine clearance
- 24-hour mean urea and creatinine
- Iothalamate (and other radioisotopes)
- Inulin clearance methods
Most common = MDRD and CKD-EPI
Clinically common = serum creatinine
Gold standard = inulin clearance
What is the RIFLE criteria? R
R = risk = serum creatinine increased 1.5x = <0.5 mL/kg/h urine output for 6 hours
I = injury = serum creatinine increased 2.0x = <0.5 mL/kg/h urine output for 12 hours
F = failure = serum creatinine increased 3.0x (or 355+ uM with acute rise >44 uM) = <0.3 ml/kg/h urine output for 24 hours (or anuria for 12 hours)
L = loss = persistent acute failure, complete loss of kidney function longer than 4 weeks
E = end-stage renal disease = longer than 3 months (CKD)
Define the following renal function tests:
- Urine albumin creatinine ratio
- Urine protein
- Serum creatinine
- Serum albumin
- BUN
Which is unaffected by variation in urine concentration / protein levels in the blood
1 unaffected
- A ratio of how much albumin (mg) per creatinine (g) is present in the urine
- A measure in mg of how much protein is in the urine over 24 hours
- A measure of how many uM of creatinine is in a litre of blood
- A measure of how much albumin is present in a litre of blood
- A measure of how much urea nitrogen is present in a litre of blood
Amniocentesis:
- Define
- What tests may it include?
- What does it screen for?
- When is it done?
- What is its risk?
- What are its benefits?
- Sampling of amniotic fluid, about 1 cc per week of GA) using a hollow needle inserted into the uterus
- QFPCR, AFP levels, Karyotype, Microarray
- Trisomy 13/18/21, XXY, X0, spina bifida, specific mutations
- >15/16 weeks gestation
- Risk of miscarriage 1/1000
- Outpatient procedures with no freezing
Chorionic Villus Sampling:
- Define
- What tests may it include?
- What does it screen for?
- When is it done?
- What is its risk?
- Tissue sampling from the chorion villi of the fetal placenta, either transabdominally or transcervically
- QFPCR, karyotype, microarray
- Numerous genetic disorders
- Week 11-14
- Risk of miscarriage of 1/100
First Trimester U/S - what is the normal progression of visualizing fetal components?
- Chorionic Sac (bhCG 6,000)
- Yolk Sac (bhCG 7,000)
- Embryo (bhCG 11,000)
- Fetal movement (week 7)
- Fetal cardiac activity (week 8)
- Normal bowel herniation (week 8)
- Arms and legs (week 8)
What are 4 things that must always be commented on in a fetal U/S
- Gestational age (crown-rump length)
- Fetal number
- Nuchal translucency
- Non-pregnancy anomalies to uterus, adnexa, and cul-de-sac
What are 7 features examined in a second trimester U/S?
What are 2 additional features examined in a third trimester U/S?
Second Trimester:
- Amniotic fluid volume
- Placental location
- Umbilical cord (# of vessels, placental insertion, fetal insertion)
- Cervical length
- Anatomic suvery (18-22 weeks)
- Gestation age
- Uterus/adnexa
Third trimester: (the above plus)
- Estimated fetal weight (femur length, abdominal circumference, biparietal diameter)
- Anatomical survey for new anomalies
- What is the glucose challenge test?
- How is it done?
- What is a positive result?
- A test used to determine risk of gestational diabetes
- Administer 50 grams of glucose; take blood at time 0 and 1 hour
- >7.8 mmol/L after 1 hour
