Clin Lab Exam 3
Terms in this set (168)
What is the filter of the kidney?
Approximately how many mLs of plasma are filtered by the kidneys each minute?
What occurs in the tubules?
Substances important to the body are reabsorbed from urine back into bloodstream.
Define renal threshold.
The plasma concentration at which active transport stops.
What happens when renal threshold is reached?
The kidney has reabsorbed as much as it can, and excess substance is secreted into the urine.
What exceeds its renal threshold in diabetes mellitus?
What is tubular secretion?
Passage of substances from blood into tubular filtrate. This is how waste products and foreign substances are eliminated.
What role does tubular secretion play in acid-base balance?
Secretion and elimination of H+ ions
Where does final concentration of urine occur?
Late distal convoluted tubule & collecting duct
** What role does ADH play in urine concentration?
Renders the walls of the distal tubule & collecting duct permeable to water.
** Concentration of urine depends on what hormone?
** In a dehydrated state, what happens to the levels of ADH being produced?
Increase so that more water is reabsorbed
** What determines levels of ADH?
Hydration state of body
** Define oliguria.
Decreased urine output
When is oliguria seen?
States of dehydration -- vomiting, diarrhea, sweating, severe burns, etc.
** Define anuria.
Complete cessation of urine flow -- may result from any serious damage to kidneys or from a decrease in renal blood flow
** Define polyuria.
Increased daily urine output (more than 3 L per day)
What is polyuria commonly associated with?
Diabetes mellitus & insipidus
** What hormone is malfunctioning in diabetes insipidus?
Why do diabetes mellitus patients lose a lot of fluid in their urine?
Glucose is osmotically active; it carries water with it out of the body
A urine sample should be delivered to the lab within what time frame?
Within 1 hour of collection
If a urine sample cannot be immediately delivered to the lab, what should be done with it?
Name the 4 types of urine collection.
Random Urine, First Morning Urine, Midstream Clean-Catch Urine, Timed Urine
What is a random urine sample used for?
What is the best specimen for pregnancy testing?
First morning urine
Why is first morning urine a better specimen for routine urinalysis than random urine?
Why is a midstream clean-catch urine sample important?
By voiding first into the toilet, bacteria is cleared from the urethra before the sample is collected.
What is the most common bacteria causing a UTI?
Why is a timed urine container dark?
To reduce exposure of urine to light, which can break down substances in urine.
What is unique about a timed urine sample?
Gives quantitative results
True or False: The patient's first and last voids in the time period are collected.
False -- only the last void. The first void of the morning is not kept.
What is the normal color of urine?
Pale yellow, straw-colored, or dark yellow/amber
What chemical gives urine its yellow color?
What precursor does urobilin come from?
Where is urobilinogen from?
Breakdown of RBCs
Variations in yellow color of urine reflect what?
Body's hydration state
Which is more concentrated: dark or light colored urine?
What is indicated by dark amber ("beer brown") urine?
Conjugated bilirubin is present. The liver is processing bilirubin but it is not leaving the body properly.
What does pink or red urine indicate?
Blood. Could be RBCs, hemoglobin, porphyrins, or myoglobin.
Intact red blood cells give the urine a ______ appearance.
Hemolyzed RBCs give the blood a ______ appearance.
Red urine that has a negative chemical test for blood indicates what?
Presence of porphyrins: porphyria
Porphyrins can cause urine to be what color(s)?
Red, brown, purple -- the brown-purple color change usually occurs upon standing
Is a urine specimen containing hemoglobin or myoglobin clear or cloudy?
Urine containing methemoglobin is what color?
Brown or black
Urine that turns from red to brown/black upon standing contains what?
What is methemoglobin?
Iron in the 3+ state
Hemoglobin in acidic urine will be oxidized to what?
Does urine containing methemoglobin test positive for blood?
What turns urine black?
Methemoglobin, homogentisic acid, melanin
The disease Alkaptonuria is characterized by what component in the urine?
Homogentisic acid. Alkaline urine will turn brownish-black upon standing.
Melanin in the urine could be an indicator of what?
If a urine sample is dark orange, what would you suspect?
Patient is on pyridium, a urinary tract analgesic dye (commonly used in UTIs)
What is indicated by blue-green urine?
Is normal urine hazy?
Yes -- could be clear or hazy. Abnormal is cloudy or turbid.
What might normal haziness of urine be due to?
amorphous crytals, squamos epithelial cells, seminal fluid, fecal contamination, mucus
Abnormal cloudy/turbic urine might be caused by what factors?
white blood cells (infection),
red blood cells (intact),
bacteria, renal epithelial cells, microorganisms, crystals
Freshly voided urine has what odor?
Why does the ammonia smell of urine become especially strong as the specimen stands?
What is the smell of urine in someone with a bacterial infection?
Noxious, fetid stink
Elevated ketones give the urine what characteristic odor?
What is Maple Syrup Disease and what will urine smell like?
Amino acid metabolism disorder, more common in kids;
Urine smells like burnt sugar or syrup
Why do foods such as asparagus or garlic give the urine a distinct smell?
These foods contain sulfur.
What is indicated by white foam in urine?
Increased protein levels
What is indicated by a yellow/brown foam in urine?
Is normal urine acidic or alkaline?
Acidic because this is how excess H+ ions are excreted
Does the pH of the urine change with fluid intake or diet?
Yes -- changes with both
What is the clinical significance of testing urine pH?
To identify acid-base disorders
What might cause acid urine?
Diet, sleep, metabolic/respiratory acidosis, renal diseases (depending on the disease), medications
What might cause alkaline urine?
Diet, respiratory/metabolic alkalosis, renal diseases (depending on the disease), alkaline medications
Why would you clinically alter pH?
To prevent the formation of kidney stones, enhance UTI treatment (i.e., drink cranberry juice), or to enhance elimination of drugs
Should there be protein in the urine?
Negative or trace amounts only
What is the main urine protein?
What is Tamm-Horsfall protein?
A mucoprotein synthesized by distal tubular cells & involved in cast formation
In addition to Tamm-Horsfall protein, what other proteins might be seen in urine?
Urokinase, secretory IgA
A dipstick test is most sensitive to what protein?
Albumin -- the main circulating plasma protein
What is albumin in the urine indicative of?
What is the risk of dipstick tests being most sensitive to albumin?
You may miss disorders in which proteinuria is due to proteins other than albumin
If the dipstick test is positive for proteinuria, what should you do next?
Confirm with Sulfosalicylic Acid (SSA) test. [[Also a 24-hour urine specimen to quantify the urine protein levels]]
What is the Sulfosalicylic Acid (SSA) test?
A confirmatory test for the presence of protein in urine. Used to retest all specimens with positive dipstick results.
What does the SSA confirm?
That there are no other proteins present in the urine besides albumin.
Proteinuria is considered pathological when levels exceed what daily amount?
Proteinuria is the first indicator that what organ is diseased?
Name a functional cause of proteinuria.
Standing too long; excercising hard; pregnancy. No discernible renal disease or damage.
After a positive dipstick test and a 24 hour urine, what should be done?
Electrophoresis to ID the proportions of albumin and other proteins.
What is prerenal proteinuria associated with?
Non-renal diseases; the kidneys are working properly
Name some causes of prerenal proteinuria.
Multiple myeloma, CHF, renal hypoxia, hypertension, fever
Loss of ability of the glomerulus to filter is what kind of renal proteinuria?
Primary or induced golmerular proteinuria
What are some causes of renal proteinurias?
glomerulonephritis, nephrotic syndrome, drugs or toxins, pre-eclampsia
Name causes of tubular proteinemias (3)
pyelonephritis, Fanconi's syndrome, toxins
Where is the defect in postrenal proteinurias?
In the urinary tract below the kidney
Name some postrenal proteinurias.
Pyelonephritis, cystitis, urethritis, prostatitis
Is glucose in the urine normal?
What sugars does the dipstick (glucose oxidase) test for?
Only glucose! Specific for glucose.
What vitamin produces a false negative result on a glucose dipstick test?
What confirmatory sugar test will detect sugars other than glucose?
What is the most clinically significant "other" sugar detected by Clinitest?
Galactose -- increased galactose in urine indicates an inability to convert galactose to glucose. This is galactacemia.
If a sample is negative for the glucose dip test but positive for Clinitest, what can you conclude?
There is a sugar other than glucose being spilled into the urine.
Glucosuria without hyperglycemia might be seen in patients who --
are pregnant, have Fanconi's syndrome, or have heavy metal poisoning
Glucosuria with hyperglycemia is most often associated with what disease?
Also gestational diabetes and other endocrine disorders
Should ketones be seen in urine?
A ketone dipstick test is positive. What is the confirmatory test?
Acetest Tablet -- proves that there are ketones present
What is ketonuria indicative of?
Inability to utilize carbohydrates
What disease is most often implicated by ketonuria?
Diabetes mellitus -- metabolizing fats instead of sugars
RBCs in urine
What might cause hematuria?
strenuous exercise, UTIs, stones, cancer
Hemoglobin in urine
What might cause hemoglobinuria?
abnormal intravascular hemolysis (hemolytic transfusion reactions), strenuous exercise
What is indicated by myoglobinuria?
Cardiac muscle breakdown, particularly from AMI
Is bilirubin a normal component of urine?
No, should be negative
If bilirubin is found in urine by a dipstick, what confirmatory test should be utilized?
A positive bilirubin test indicates what form of bilirubin in the urine?
Why might conjugated bilirubin be seen in the urine?
hepatocellular disease, cirrhosis, hepatitis, liver congestion, posthepatic obstructions such as stones
Is urobilinogen a normal urine component?
Why should urobilinogen testing be carried out quickly after sample collection?
Urobilinogen is quickly oxidized to urobilin
Abnormal urobilinogen is indicative of failure in what organ?
Prehepatic causes of abnormal urobilinogen.
hemolytic conditions, ineffective erythropoiesis
Increased urobilinogen & negative bilirubin indicates what?
Normal or decreased urobilinogen with positive bilirubin indicates what?
hepatic cause -- hepatocellular disease such as hepatitis or cirrhosis
Decreased or absent urobilinogen with positive bilirubin indicates what?
Posthepatic cause -- stones, fibrosis, carcinoma
Is nitrite a normal component of urine?
What might cause false negative nitrate dipstick results?
UTI pathogen that doesn't reduce nitrate, high bacterial count
What might cause false positive nitrate dipstick results?
improperly preserved urine specimen
What does nitrite in urine indicate?
Bacterial presence! An infection of the urinary system, nephron to bladder.
Is leukocyte esterase (LE) a normal urine component?
Positive leukocyte esterase in the urine indicates what?
White blood cells in the urine (pyuria)
Why would leukocyte esterase (WBCs) be in urine?
Infection or inflammation of genitourinary system
WBCs (LE) and nitrites together in a urine sample indicate what?
A bacterial infection
Define specific gravity.
Mass of a fluid relative to an equal volume of water
When is specific gravity most concentrated?
In the morning
What does specific gravity indicate?
Hydration state of body
High specific gravity indicates what conditions?
Normal if it is first void of the morning; dehydration with oliguria (decreased output); diabetes mellitus (glucose in urine)
Low specific gravity indicates what conditions?
Diabetes insipidus (low ADH); diabetic nephropathy (kidneys lose ability to concentrate urine); hypertensive renal disease; pyelonephritis; polydipsia
Excretion of urine at a constant specific gravity. Indicates poor tubular reabsorption -- a chronic renal problem. SG doesn't change in relation to food & water intake.
What could cause RBCs in the urine?
urinary tract stones, neoplasms (geriatric patients), prostatitis, UTIs, menstruation, glomerular disease
Define nephronal hematuria and what UA results are seen with it.
bleeding anywhere along the nephron;
proteinuria, red cell casts, RBCs in urine
When would you see WBCs in urine?
Infection or inflammation of genitourinary system
Where is the infection most likely to be if you see WBCs, proteinuria, leukocyte casts, and hematuria?
Kidney -- patient also has low back pain & fever
WBCs are in the urine sample. What do neutrophils indicate? What do lymphocytes or macrophages indicate?
Neutrophils indicate bacterial infection
Macrophages & lymphocytes indicate inflammation
Are squamos epithelial cells normal to see in urine?
Yes -- derived from vagina or urethral lining
What type of epithelial cell is commonly seen after catheterization?
Transitional epithelial cells (these line the renal pelvis, ureters, and bladder)
What type of epithelial cell should NOT be seen in urine?
Renal epithelial cells -- this indicates an intrinsic kidney problem
What causes oval fat bodies?
Renal tubular cells have absorbed lipids
Do casts in the urine pertain to the bladder, the kidney, or both?
Kidney specific! Unique to the kidney!
What are the 4 factors that enhance the formation of casts? (KNOW for exam!)
Acid pH, high urine concentration, proteinuria, stasis/oliguria/diminished outflow
Casts are an indicator of disease in what organ?
Hyaline casts are composed primarily of what protein?
What are non-pathological causes of hyaline casts?
Exercise, dehydration, fever, emotional stress
What are pathological causes of hyaline casts?
glomerulonephritis, pyelonephritis, chronic renal disease, CHF
RBC casts contain RBCs. When these cells disintegrate, what are the casts called?
What are hemoglobin casts primarily associated wtih?
What conditions might show RBC casts?
Glomerulonephritis, SLE, endocarditis, pyelonephritis, renal trauma
What do WBC casts indicate?
nephronal infection or inflammation
What disease state is indicated by renal epithelial cell casts?
Renal tubular disease
What are some non-pathologic causes of granular casts?
Protein metabolism; strenuous exercise
What is indicated by waxy casts?
urine stasis in renal tubules
What disease states might present waxy casts?
chronic renal failure, malignant HTN, diabetic nephropathy
** What are fatty casts associated with?
Can be seen under polarized light
When are broad casts formed?
Severe stasis (anuria). May be referred to as "End Stage Renal Failure Casts"
Crystals that form in alkaline pH are generally of _____.
No clinical significance
What type of crystal forms in alkaline pH but is a negative sign?
Triple phosphate crystals
What type of crystal is associated with hyperuricemia (gout)?
What urine pH do amorphous urates form in?
** What do tyrosine crystals in acidic pH indicate?
Severe liver disease
Which crystals have no clinical significance?
Amorphous phosphates, calcium phosphate, ammonium biurate, calcium carbonate
Why do diabetics often have yeast in their urine?
Sugar in the urine is a fuel source for yeast
What kind of yeast is most common in urine?
What parasite is most frequently seen in urine?
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