Urinalysis Flashcards
What is the excretory function?
- Elimination of a toxic and waste products (urea, etc.)
Excretion = filtration + secretion - reabsorption - Electrolyte, fluid, & Acid/Base Balance
What is the endocrine function (renal)?
- Erythropoietin
2. Renin
What is the renal metabolic function?
- Vitamin D activation
- Gluconeogenesis
- Insulin and Steroid metabolism
What circulatory aspects are part of the urinary system?
- Oxygenated: Aorta, renal arteries, afferent arterioles
- Glomerulus
- Deoxygenated: efferent arterioles, renal veins, inferior vena cava
What are the aspects of the urinary collecting system?
ureter, bladder, urethra
How many nephrons are in the kidney?
- 1 millon (2 million total)
What is the rate of blood flow into the kidney?
1 liter/minute
125 mL/min are filtered
0.8 mL/min are urine
What are the components of the nephron?
- Bowman’s capsule (Glomerulus–Filters size/charge)
- Proximal tubule (reabsorption)
- Loop of Henle (Na, water flux)
- Distal convoluted tubule (ALD)
- Collecting Duct (ADH)
- Ureter, Bladder, Urethra
What is the capacity of the bladder?
400 mL
@ 150 mL micturition sensation will occur
How long is the urethra in the male/female respectively?
- Male = 24 cm
2. Female = 4 cm
How can you assess how well the kidneys are working?
- Clinical S/S
2. Laboratory evidence (excretory, metabolic, endocrine)–Serum Creatinine
Why would you assess renal function?
- To dx renal disease
- To monitor disease progress
- To monitor response to treatment
- To find changes in function that may impact drug therapy
What GFR results in ‘kidney damage with normal or increased GFR’?
> 90 mL/min/1.73m2 (most prevalent)
What GFR results in ‘kidney damage with small decrease in GFR’?
60-89 mL/min/1.73m2 (2)
What GFR results in ‘kidney damage with moderate decrease in GFR’?
30-59 mL/min/1.73m2 (3)
What GFR results in ‘kidney damage with large decrease in GFR’?
15-29 mL/min/1.73m2 (4)
What GFR results in ‘kidney failure with need for dialysis’?
<15 mL/min/1.73m2 (5)
As creatinine clearance gets smaller what do you need to do to the dosage of drugs?
Decrease the dose or spread out the interval
How can you define renal function?
- GFR: the volume (mL) of plasma completely cleared of a substance per unit of time (min)
- Clearance
How many L of blood does that adult body filter per day?
- 180 L*
- 1.5 L are excreted
- 99% reabsorbed
What different variables can affect ‘renal function’?
- Renal blood flow
- Hydrostatic/Oncotic pressures across the glomerulus
- Integrity of the glomerulus
When completing a physical exam what clinical evidence would support renal dysfunction?
- Edema, Skin turgor
- Fontanelle, membranes
- weight
- intake/output
- BP/Pulse
- Pulmonary auscultation
- JVD
- Bladder palpation
What patient complaints with warrant clinical evidence of renal dysfunction?
- Voiding habits
- Force of stream
- Pain
- SOB
What is an ‘ideal renal function test’?
Desired properties
1. Reflects glomerular filtration
(100% filtered, no secretion, no reabsorption)
2. Not influenced by other disease states
3. Easy to obtain
How can you quantify renal function?
Insulin, dyes, radio-labeled compounds
Accurate… but expensive, time consuming, and impractical (research only)
What is a BUN?
Blood urea nitrogen
What are the limits of BUN?
- Filtered then 50% reabsorbed
- Protein intake
- Liver function (AA to NH4+ to urea)
What is the normal SCr level of male/femal respectively?
- Adult Male: 0.9-1.3 mg/dL
- <19 y Male: 0.4-1.3 mg/dL
- Adult Female: 0.6-1.1 mg/dL
- <19 y Female: 0.4-1.3 mg/dL
Given ____, CrCl can be approximated.
- [SCl]
____ is a proxy for CFR
CrCl
What are the physiological limitations of SCr?
- Cr is 90% filtered and 10% secreted by tubules
- Variable muscle mass
- Sex, Age, Health
What are other limitations of SCr?
- Changing renal function
- Diet (protein meal)
- best in AM - Concomitant drug therapy
How do the kidneys handle SCr?
- Tubular secretion– Min effect = 10% & increased proportion as filtration increases
- Drugs & Cr compete for secretion
What can effect Cr entry (Crin) physiologically?
- Sex, Age, Health, Habitus, Diet
What can effect CrCl physiologically?
Tubular secretion & medications
What are the limits to measured CrCl?
- Tubular Secretion
- Sample Loss
- Time (24 hours)
What is the Cockcroft & Gault equation for estimated CrCl?
(140 - age) x Weight / (SCr x 72) = mL/min
FOR ADULT WOMEN MULTIPLY RESULT BY 0.85
What are the limitations of the Cockcroft/Gault equation?
- Not for peds!
- Unreliable with rapidly changing renal function
- Muscle mass should be considered (Obesity over estimates, cachexia)
- Drugs may alter secretion
- Diminished MM with elderly and malnourished
How can you estimate CrCl in kids?
- Traub equation
2. Schwartz equation
What are the different renal function tests?
- Inulin (best accuracy)
- Iothalamate (better accuracy)
- 24-hour CrCl (good accuracy)
- SCr (with equations) (best-ish accuracy)
Increasing Clinical Use
Decreasing Cost
What conditions may yield a “falsely” low SCr, and thereby a falsely elevated calculated estimate of CrCl?
GFR appears better than it truly is
- Diminished muscle mass
- tubular secretion of Cr (@ low GFR)
What are the advantages of a random urine collection?
collect anytime, convenient for patient & examiner
What are the advantages of a first void urine collection?
best for chemical and microscopic examination
What are the advantages of a 24-hour urine collection?
quantify urine substances
What are the advantages of a fasting urine collection?
glucose metabolism
What are the advantages of a post-prandial urine collection?
glucose metabolism
What are the advantages of a post-void residual urine collection?
evaluated residual urine in bladder after voiding (work-up of obstruction/incontinence)
What is the normal urine output of an adult?
1.2-1.5 L/day
What constitutes polyuria? Why?
- > 2,000 mL/day
2. Water vs. solute
What constitutes nocturia?
polyuria at night
What constitutes oliguria? Why?
- < 400 mL/day (Peds <0.5 mL/kg/hr)
2. Pre-renal, intrinsic, post-renal
What constitutes anuria?
complete absence of urine production
Yellow urine
urochrome
Green urine
infection/drug
Pink/red urine
blood/drug
orange urine
bili/drug
foam urine
protein (albumin)
faint odor urine
normal
strong ammonia odor urine
bacteria convert to urea
UTI
fruity odor urine
ketones (fat metabolism)
What does a positive test for nitrates imply?
bacteria presence due to bacterial enzymes reducing nitrate to nitrite
false (-)/false (+) possible
What is the normal pH of urine?
4.5-8 (help to confirm not dx)
What does acidic urine imply?
metabolic acidosis, DM, dehydration, diarrhea, gout, respiratory acidosis, UTI
what does alkaline urine imply?
metabolic alkalosis, respiratory alkalosis, UTI, acute/chronic renal failure, RTA, diuretics, alkaline drugs (bacteria produce NH4+ with increase pH)
what are the normal protein-urine levels?
- < 150 mg/day
2. Albumin < 30 mg/day
what would constitute microalbuminuria?
30 to 300 mg/day
consider albumin:creatinine ration in urine
what would constitute albuminuria?
> 300 mg/24 hours
what would constitute proteinuria?
> 500 mg/day
Ranges from trace to 4+
What is the etiology of pre-renal proteinuria?
Overflow–increased plasma proteins
hemoglobinuria: hemolysis (casts)
myoglobinuria: myolysis (casts)
What is the etiology of renal/glomerular proteinuria?
selective glomerular <1 gm/day
-membrane is intact but charge is lost
What sorts of diseases can cause proteinuria?
- Autoimmune (glomerulonephritis)
- Systemic Disease (DM, Lupus)
- Drugs (Li)
What happens in nonselective glomerular proteinuria?
- glomerular barrier seriously compromised
- massive amounts of protein (casts)
- lipid bodies may also pass into urine
- patient will have systemic complaints (edema, etc.)
- Disease states (glomerulonephritis)
What is the etiology of renal/tubular proteinuria?
- Tubular injury secondary to antibiotics
- Loss of proteins normally filtered then reabsorbed
- Disease states/Drugs
What is the etiology of post- renal proteinuria?
- Urinary tract proteins (<2g/day)
- Inflammation, malignancy, injury
what is the etiology of non-pathological proteinuria?
- exercise
- pregnancy
- fever
All usually < 2 gm/day
What is pre-renal glucosuria?
elevated blood glucose
40 mg/min
what is renal glucosuria?
defective renal absorption of glucose due to pregnancy or heavy metal poisoning
60 mg/min
What can result in hyperglycemia without glycosuria?
Abnormal glucose filtration
-Poor renal perfusion, renal atherosclerosis
0 mg/min
What is ketonuria?
Ketones present in the urine (absence = normal)
- Acetone
- Acetoacetic acid
- betahydroxybutyric acid
- metabolites of lipid catabolism
What is the normal level of urobilinogen in the urine?
0.2-1 mg/dL
What happens in the body with there is urobilinogen in the urine?
- reduction of conjugated bilirubin by intestinal bacteria
- reabsorption from gut, some renal excreted
- False (+)/False (-
What is bilirubin?
intermediated product of Hgb breakdown
–bound… NO renal elimination
What can cause bilirubin to be in the urine?
- Cellular diseases
2. Obstructive diseases
What is hematuria?
presence of blood in the urine
what would cause blood to be present in the urine?
Source: kidney (glomerulus, tubules), urinary tract, or contaminant
what are the two different aspects of hemoglobinuria?
- Isolates = hemolysis
2. RBCs + Hgb = lysed RBCs in urine
What is the normal specific gravity of urine?
1.002-1.030
What can cause high specific gravity in urine?
sugar, protein, contrast dye, dehydration
What can cause low specific gravity in the urine?
DI, renal disease, dilute urine, inability to concentrate
What is notable about leukocyte esterase’s?
- enzyme released by neutrophils
- pyuria = presence of pus in the urine
- good correlation with a UTI
What are urine casts?
- precipitation of mucoproteins
2. shape indicates origin
Where would you find squamous cells in the urinary tract?
lower 3rd of the urethra and vagina
Where would you find transitional cells in the urinary tract?
present in the ureter and bladder
Where would you find renal tubular cells in the urinary tract?
renal tubules
Crystals in urine
uric acid calcium oxalate sulfonamides ampicillin radiopaque dye
Bacteria present in urine
> 100,000 colonies
only in 30-50% of cases
When would you consider a contamination in urine sample with microorganisms?
no PMNs
>3 bacteria present
yeast in urine sample
UTI vs contamination
trichomonas vaginitis urine sample
vaginal contamination
spermatozoa urine sample
male: normal
female: contaminant
ova and parasites in urine
ova and parasites
fecal vs vaginal
