2 Urinalysis And K Disorders Flashcards
What are the three components of the UA?
Gross Examination
Urine Dipstick
Microscopic Analysis
Proper collection technique for UA
Local disinfection of urethral meats with a nonfoaming disinfectant (allow to dry to avoid mixing the disinfectant with the urine specimen)
Spread the labia or retract the foreskin
Discard the first voided portion which may contain urethral contaminants
Collect midstream specimen
What are you assessing on gross examination of the UA?
Color
Turbidity
Odor
Normal color for urine
Pale straw-colored to dark amber in very concentrated urine
What does red or red-brown urine indicate?
Blood (hematuria) or hemoglobin (hemoglobinuria)
R/o menstrual contamination
Consider myoglobin, food dyes, or ingestion of beets or rhubarb
What does dark brown or black urine indicate?
Bile or bilirubin due to liver or biliary disease
Alkaptonuria
Malignant melanoma
What is Alkaptonuria?
Rare disorder with lack of enzyme homogentisic acid oxidase (urine turns black on standing)
Why does malignant melanoma change the color of urine?
Melanogen turns it black
Turbity can also be described as…
Cloudy
Turbity is due to a bunch of stuff in the urine, such as…
Crystal precipitation (called “amorphous material”) Bacteria, yeast WBCs, RBCs Mucus, squamous epithelial cells Sperm, prostatic fluids, lipids
Normal odor for urine
Faint, aromatic odor due to volatile acids from food products
Sometimes distinctive food odors: asparagus, onions, garlic
A putrid, foul odor suggests …
UTI (from bacteria)
Fruit odor suggests…
Ketone bodies
“Ash tray” urine smell suggests
Cigarette smoker
Duh
What all does a urine dipstick test?
PH Specific gravity Glucose Ketones Proteins Blood Nitrite Leukocyte Esterase Bilirubin Urobilinogen
How are urine dipstick results reported?
As a value, as a positive/negative, or on a scale (+1, +2, +3, +4 or Small, Medium, Large)
Normal range for urine pH
4.5 - 8.0
What is considered to be “acidic” urine
4.5 - 5.5 pH
What is considered to be “alkaline” urine?
6.5 - 8.0 pH
A pH of < ____ or > _____ is not physiologically possible.
< 4.5 or > 8.0
PH > 8 indicates delay in processing with overgrowth of urease-producing bacteria
Urine pH parallels…
Serum pH
Most often used clinically in patients with metabolic acidosis
A measure of the weight of a substance (urine) compared with an equal volume of pure, solute-free water at the same temperature
Specific Gravity
The specific gravity of water is 1.000
Because urine is water containing dissolved substances (primarily urea, sodium, and chloride), the normal range of urine specific gravity is …
1.003-1.035
The more concentrated the urine, the higher the SG
SG reflects the ability of the kidney to…
Concentrate and dilute urine
What is Isosthenuria?
With kidney disease, the ability to concentrate urine may be lost, and the SG may become fixed at ~1.010 (similar to the initial plasma filtrate at the glomerulus)
Normal range of Urine volume
500cc - 2000cc/24 hours
What is Oliguria?
< 500cc in 24 hours
What is Anuria?
< 100cc in 24 hours
What is polyuria?
Excessive amounts of urine, usually quite dilute with SG 1.000-1.002
When do you get glucose in the urine?
Not normally detectable
When plasma glucose is about 150-180mg/dL, the renal “threshold” is exceeded and the patient will “spill” glucose in the urine
What can cause a false negative for urinary glucose?
Ascorbic acid
Aspirin
Products of incomplete fat metabolism, occurring when carbohydrate stores are diminished
Ketones
Their presence in urine may indicate acidosis (seen in DKA, rapid weight loss, fasting, starvation, pregnancy)
The urine dipstick test for protein is most sensitive to …
Albumin
Urine proteins are an indication of …
Renal endothelial dysfunction - an early sign of kidney disease
What are some limitations to the protein test on urine dipstick?
A dilute urine will underestimate the degree of albuminuria and vice versa
Moderately increased albuminuria in the range of 30 to 300 mg/day typically cannot be detected with dipstick testing
What might cause a false positive for urine protein?
Pyridium
Moderately Increased Albumin (formerly known as microalbuminuria) is a marker for …
Staging and prognosis for kidney disease
Albumin-to-Creatinine ratio on a random (spot) urine
24-hour urine collection
Especially useful in screening for kidney damage in high risk patients (BM, HTN, CVD)
Persistently positive dipstick test for protein should also have…
Albuminuria quantified
Dipstick can detect presence of RBCs, Hb from lysed RBCs, and myoglobin, but…
Must centrifuge and do micro to determine which
Sensitivity is 5-10 RBCs or 0.05-0.3mg/dL of Hb
Result SHOULD be negative
False negatives for blood on dipstick can be due to …
Ascorbic acid
Nitrites are produced by what type of bacteria?
Those that are capable of reducing nitrates to nitrite (ENTEROBACTERIACEAE)
Test should normally be negative
Nitrite test is ~50% sensitive in the diagnosis of …
UTI
What can cause a false negative for urine nitrites?
Urine in bladder for <4 hours (no time to reduce)
Bacteria which do not have necessary enzymes
________ is released by lysed neutrophils and macrophages and is a marker for _______________.
Leukocyte Esterase
Marker for the presence of WBCs, indicating infection
What can give you a false positive for Leukocyte esterase?
Vaginal contamination
Trichomonads
Sensitivity for UTI increases if both…
+LE and +Nitrite
_______ & _________ are used in conjunction to determine underlying pathology
Bilirubin & Urobilinogen
Dipstick is normally negative for both
Urine turns _____ in the presence of bilirubin
BROWN
Urine pH can be used to determine…
Metabolic acidosis or alkalosis
What do we look at on the dipstick if concerned about acute kidney failure?
Specific Gravity
Urinary ______ on dipstick = diabetes
Glucose
Ketones in urine?
DKA
Protein in the urine?
Kidney disease
Moderately increased albumin in the urine?
Early kidney disease
WBCs and RBCs on microscopy are reported as ….
The number per high power field (HPF)
Casts are reported on microscopy as …
Number per low power field (LPF)
On microscopy, RBCs in urine appear as…
Refractive disks
With hypertonicity of the urine, the RBCs begin to have a crenated appearance (shrunken)
> _____ RBC/HPF is abnormal
> 3
Conditions in which you will see increased RBCs
Renal or lower urinary tract trauma Kidney stones Glomerular damage Tumors UTIs Acute tubular necrosis Nephrotoxicity Contamination from vaginal bleeding
Causes of hematuria more common in young patients?
Transient/unexplained UTI Stones Exercise Trauma
Causes of hematuria more common in the elderly
Cancer (bladder, kidney, prostate)***
BPH
Can also be transient, UTI, stone, or trauma related
If positive blood on dipstick, what do you do first?
Centrifuge result
If sediment red —> hematuria
If supernatant red —> Dipstick heme
• If negative —> Beeturia, porphyria, other cause
• If positive —> could be myoglobin or hemoglobin
—> centrifuge blood sample —> clear plasma is myoglobinuria, red is hemoglobinuria
How do you recognize WBCs on microscopy?
WBCs have lobed nuclei and refractive cytoplasmic granules
0-5 WBC/HPF is normal (>5 abnormal)
10-20 WBC/HPF is suspicious for UTI
≥ 20 WBC/HPF usually indicates UTI
How are bacteria reported in urine microscopy?
As 0-4+/HPF
Are bacteria in urine microscopy significant?
Maybe, maybe not
Depends on method of collection - clean catch midstream vs catheterized
Depends on how soon after collection the specimen is examined
• The longer it stands, the more bacteria grow
• Refrigeration will delay bacterial growth
What are renal tubular and transitional epithelial cells?
Normally occur in small numbers; slough from tubule lining
Occur in larger numbers if there is tubular degeneration
Degenerated tubular cells containing abundant lipoproteins, which appear refractile
Oval fat bodies
Exhibit “Maltese cross” configuration by polarized light microscopy
Indicative of NEPHROTIC syndromes
Large polygonal squamous epithelial cells with small nuclei in increased numbers usually indicate…
A contaminated specimen of skin or external urethral origin (NOT A CLEAN CATCH)
Urine casts are formed only in the _________ or __________.
Distal convoluted tubule (DCT) or collecting duct (CD)
They are not formed in the proximal convoluted tubule or loop of Henle
_______ casts appear very pale and slightly refractile
Hyaline casts
Composed primarily of a mucoprotein (Tamm-Horsfall Protein) secreted by tubule cells
Common finding in normal urine
Red cell casts suggest…
A glomerular or renal tubular injury
GLOMERULONEPHRITIS
White blood cell casts suggest…
Acute pyelonephritis
May also be present in glomerulonephritis
Renal tubular cell casts suggest…
Injury to the tubular epithelium
ACUTE TUBULAR NECROSIS
What are granular casts?
Cellular casts which remain in tubules may break down, so that the cells forming them degenerate into granular debris
Initially coarse, then finely granular, then waxy cast
A non-specific finding
Uric acid crystals in acidic urine
Secondary to hyperuricemia
Cystine crystals?
Cystinuria
Rare genetic cause of kidney stones
Struvite crystals in alkaline urine?
Secondary to infection by urease-producing bacteria
Calcium oxylate crystals independent of pH
Cause of kidney stones
Can be monohydrate or dihydrate
What do you use to confirm the presence of bacteriuria and to provide abx susceptibility info on the causative organism
Urine culture
> 100,000 colonies/ml most consistent with infection
Why might you say that a UTI could still be present even with fewer than 100,000 colonies on urine culture?
If dysuria, frequency, and microscopic evidence of pyuria are present
_____ is the major intracellular cation
Potassium
What is the major route of elimination of K+?
Renal excretion
Regulation of renal K+ excretion and total body K+ balance occurs in distal nephron
What are the main actions of aldosterone?
Increase renal sodium reabsorption
Increase renal potassium excretion
Hyperkalemia is a serum [K+] of …
> 5.0 mEq/L
K+ > 6.0-6.5 may cause serious problems
Elevated potassium may be caused by …
False elevation (pseudohyperkalemia)
Inadequate excretion by kidneys
Redistribution from ICF to ECF space
Excess administration
Pseudohyperkalemia is artificially high K+ occurring from …
Hemolysis due to poor venipuncture technique
If you get a high K+, promptly repeat K+ to check for artificial elevation
Typical etiologies for the inadequate excretion of K+
Renal failure: Check BUN/Cr
Meds that inhibit K+ excretion:
• Aldosterone antagonists
• K+ sparing diuretics
• ACEI/ARBs
Hypoaldosteronism • Adrenal insufficiency (Addison’s) • Congenital adrenal hyperplasia • NSAIDS (uncommon) • Renal tubular dysfunction
Hyperkalemia due to redistribution of K+ occur when?
With conditions which move K+ from intracellular to extracellular space
Examples:
• Tissue damage (ie Rhabdomyolysis)
• Acidosis
• Decreased insulin
In acidosis, a 0.1 decrease in pH raises serum K+ approximately ________.
0.5-1.0 mEq/L due to ECF shift
What should you watch out for in patients with some renal impairment to avoid excess administration hyperkalemia?
Potassium-containing salt substitutes
Beware K+ administration in pt with impaired kidney function
Clinical features of hyperkalemia
Generally occur when serum potassium ≥ 7
Muscle weakness
• Begins with legs and ascends to trunk and arms
• Can lead to flaccid paralysis
Conduction abnormalities and arrhythmias if K+ rises high enough
Classic ECG finding in hyperkalemia
Peaked T waves
Prolonged SR segment
Hyperkalemia! It’s A FACT!
A = arrhythmias
F = flaccid paralysis A = ascending muscle weakness C = conduction abnormalities T = T waves
Urgency of treatment for hyperkalemia depends on …
Degree of K+ elevation and clinical SSx
Send the patient to the ER or ICU for monitoring if K+ > _____
> 6.5
How do we rapidly correct hyperkalemia?
Calcium Chloride IV
Maneuvers to shift K+ from ECF to ICF:
• Sodium bicarbonate IV to increase pH
• D50W plus insulin IV
Slow correction of hyperkalemia is usually through…
Loop or thiazides diuretics (beware decreased renal function)
Hemodialysis if kidney failure, esp severe, refractory
The real key to correcting hyperkalemia?
Correct the underlying cause
Stop potassium-sparing diuretics
Stop ACEIs, ARBs, K+ supplements etc
Mineralocorticoid replacement (Addison’s)
What is considered Hypokalemia?
Serum K+ < 3.5 mEq/L
Potassium <3.0 is potentially dangerous
Low potassium may be caused by…
Inadequate intake
GI tract loss
Renal loss
Redistribution from ECF to ICF
___________ is most likely to be a problem if patient is taking a medication that promotes K+ loss (ie Thiazides/loops)
Inadequate K+ intake
Potassium-containing foods or potassium supplements are often advised in order to prevent the development of hypokalemia
_______ is a very common cause for low potassium
GI Loss
Upper GI Loss:
• Vomiting, NG suction
• Causes metabolic ALKALosis which promotes renal potassium loss
NOTE: lower GI loss (diarrhea) usually causes metabolic ACIDosis
Causes of renal loss of potassium
Diuretics (very common)
Bicarbonate excretion
Mineralocorticoid excess (hyperaldosteronism or Cushings)
Causes of redistribution of K+ from ECF to ICF
Metabolic ALKALOSIS (each 0.1 increase in pH lowers serum K+ by 0.5-1.0 mEq/L)
Insulin administration
Beta-adrenergic agonists (not ß-blockers!) induce cellular uptake of K+ and promote insulin secretion by pancreas
Hypokalemia periodic paralysis
Clinical features of hypokalemia
Muscle weakness/paralysis - ascending pattern
Respiratory failure
Muscle cramping/rhabdomyolysis (vs flaccid paralysis in hyper)
GI distress (anorexia, N/V)
Cardiac arrhythmias (ECG - U Waves, flattened T waves, ST depression)
Classic ECG findings in Hypokalemia
U WAVES, flattened T waves, ST depression
Ed’s silly mnemonic for HYPOKALEMIA
“YOU CRAMP”
hYpOkalemia U waves
Cramping Respiratory failure/Rhabdomyolysis Anorexia, N/V Muscle weakness Paralysis
Urgency of treatment for hypokalemia depends upon…
Severity of symptoms and K+ level
Correct the underlying cause if possible
Check for hypomagnesemia (causes potassium wasting), low K+ is harder to correct if Mg not corrected also
If Dx of hypokalemia is unclear…
Get 24˚ urine potassium
If < 20 mEq/d suggests extrarenal/redistribution
If > 20 mEq/d suggests renal losses
How do you rapidly correct hypokalemia?
Cardiac monitor
IV potassium chloride
Check stat K+ every 2-4 hours
Slow correction? Orally
