BF Module 1

How many nephrons are in a kidney?

1-1.5 mil

nephron > aka functional unit

What is the Bowmans capsule?

beginning of renal tubules, surrounds the glomerulus and catches the filtrate

what is the Proximal convoluted tubule?

Reabsorption and secretion

What is the loop of henle?

Major exchange of water and electrolytes for concentration

What is the distal convoluted tubule?

does the final concentration of the urine that is then sent to the collecting duct where urine is collected and sent to the bladder

What is the blood flow through the kidneys?

Afferent arteriole > Glomerulus (capillaries that filters blood) > Efferent arteriole

About 1200mL/min is filtered

What is blood pressure controlled by?

The RAA system: Renin-Angiotensin-Aldosterone. started by decreased renal BP/sodium

Angiotensinogen > + Renin > Angiotensin I > + converting enzyme > Angiotensin II > either Aldosterone which leads to sodium retention, or vessel constriction

What is the GFR?

Glomerular filtration rate: 120mL/min

What can get through the intact Glomerulus?

Glucose

Electrolytes (Ca, K, Na)

Water

(nothing with protein or attached to protein can get through)

What does the shield of negativity do?

Repels molecules with a negative charge, such as proteins

Where does most of the reabsorption happen?

In the PCTwith 60-85% happening there.

(amino acids, glucose, essential electrolytes)

What is the glucose renal threshold?

160-180 mg/dL

This is good to know for differentiating diabetes mellitus from a renal tubular problem (too much of a substance vs inability to reabsorb)

What is tubular secretion and why is it there?

It is a where the tubules absorb things secreted by the blood. It is a way for larger wastes and H+ ions (ABGs) to be secreted out. (mostly in the PCT)

Larger wastes = Medications, protein bound things

Without it there would be a big disruption in the H+ secretion, leading to renal tubular acidosis or metabolic acidosis.

What is Concentration and why is it important?

This is the final reabsorption of any water, will depend on hydration state.

Starts in the Loop of Henle and goes through to the final spot in the collecting duct.

Is controlled by ADH (anti diuretic hormone aka vasopressin)

What triggers ADH?

The prescence of increased plasma sodium.

The ADH acts on the collecting duct walls to make them more permeable and reabsorb more water, making more concentrated urine.

What is the broad sequence of making urine?

Blood flow > Glomerular filtration > Reabsorption > Secretion > Concentration

What is the composition of Urine?

95% water

5% solutes:

Urea: end product of amino acid/protein metabolism

Uric acid: end product of purine (nucleic acid) metabolism

Creatinine:” end product of muscle metabolism

Cl, Na, K, H

Few foprmed elements: RBCs, WBCs, crystals, epis, casts, bacteria.

What are the 2 most helpful things in differentiating urine vs othr body fluids?

Urea and Creatinine.

What is the average output of urine?

600-2400 mLs per 24hrs.

What is Oliguria?

Decreased output, <400mLs per day.

Is severe dehydration caused by vomiting, diarhea, sever burns, sweating.

What is Anuria?

No output.

From severe renal disease, renal failure.

What is Polyuria?

Increased output, >2500mLs per day.

From Diabetes mellitus/insipidus, diuretic use, caffeine/alcohol intake.

What is Dysuria?

Painful flow.

From UTI/yeast infections.

What is Nocturia?

Increased output at night.

From elderly and prgnant women.

Why is a urinalysis even done?

Aid in diagnosis

Monitor for progression of disease or therpy/meds used.

Screen for congenital/hereditary diseases.

What makes up the physical exam of urine?

Color

Carity

SG

How is color affected in urine?

By substances eaten, metaboism, diseases, physical activity, hydration.

Normal color is caused by Urochrome, which is a by product of hemoglobin breakdown.

Determine color by holding against a whie background.

What causes dark yellow to amber urine?

Concentrated/dehydrated.

What causes colorless/pale yellow/straw colored urine?

Dilute uine

Possibly diabtes I/M

What causes Amber-Brown/orange urine?

Icteric: prescence of bilirubin in urine, will have yellow foam when shaken.

Is from jaundice.

What drug specifically causes orange urine?

Pyridium (UTI drug)

What causes a green to blue urie?

Drugs

Dyes

Certain bacterias

Asparagus

What is the difference between a red cloudy urine vs. a red clear urine (might be a little brown)?

Red cloudy is from intact RBCs (Hematuria).

Red/brown clear is from hemoglobin or myoglobin (hemoglobinuria/myoglobinuria respectively)

Also could be from some foods (beets/blackberries) or meds (rifampin)

What causes the Port wine, red-purple, burgundy color in urine?

Porphyrins.

From heme process.

What causes the brown-black colored urine?

Melanin (malignant melanoma), as soon as its in oxygen it’ll begin to change darker.

Homogentisic acid (alkaptonuria), turns upon standing as the pH rises (more alkaline).

Meds (anti-malarial, levodopa, metronidazole).

Urine turns dark upon standing, or when pH rises.

What causes a purple urine?

Bacterial infections: Proteus, Kleb, Providencia, Morganella.

What are the definitions of clarity?

Clear

Hazy

Cloudy

Turbid

Milky: from fats or proteins, possibly from nephrotic syndrome or a lymphatic obstruction (rich in triglycerides)

What are some causes of altered clarity?

Non pathologic: Talc powder/cream, Sperm, Mucus, Fecal contamination, Epis, Certain crystals.

Pathologic: Bacteria/yeast, RBCs, WBCs, Lipids, Renal epis, Certain crystals.

What is the definition of Specific Gravity?

The measure of dissolved substances in a solution.

It is the density of a solution compared to an equal volume of pure water at RT.

This is influenced by size and number of particles. The larger the particle, the more contributed.

Also, by hydration, the more hydrated = more dilute. More dehydrated = more concentrated.

What substances make up the SG?

Normally urea, uric acid, creatinine.

Abnormally glucose, yeast, radiographic/contrast dyes.

What is the measuring of SG for? Why is it done?

To assess the kidneys’ ability to reabsorb water.

What are the standard known SG values?

Pure water = 1.000

Normal urine = 1.003-1.035

Glomerular filtrate = 1.010

What Sg indicates renal failure?

A fixed Sg of 1.010 over several samples.

Means that the kidneys can’t filter/concentrate past the glomerulus.

What is the general Sg range?

1.003-1.035

What 3 ways is SG measured?

Dipstick

Refractometer

Harmonic oscillation: uses sound waves.

What is the principle of the Refractometer?

Comparing the velocity of light in air with the velocity of light in a solution.

The density of the particles dissolved in the solution determines the angle the light passes through the solution.

What is the procedure for SG?

1-2 drops placed on prism.

Close daylight plate, make sure urine spreads over fully

View through eyepiece.

Read where boundary line hits. Look for the UG or SG specifically.

Wipe sample off.

What do you do when a Sg reading is off the scale and why would it be so high?

Dilute urine and retest, then multiply only the decimal result by dilution factor.

Radiographic contrast materials (IV pyelogram to assess kidney function), High molecular weight IV fluids (Dextran/plasma expanders), high levels of glucose/proteins.

The SG will return to normal once these are cleared from the body.

What are some low SG (<1.010) causes?

Diabetes Insipidus

High water intake

What are some high SG (>1.030) causes?

Proteinuria

Diabetes mellitus with glucosuria

Dehydration

Radiographic dyes

High molecular weight IV fluids

What are the causes of white and yellow foam?

A little white foam is normal, but a lot means protein.

Yellow foam is from bilirubin.

What are some urine odors and their causes?

Faintly aromatic: normal

Strong unpleasant ammonia like: Bacterial infection

Sweet/fruity: Diabetes mellitus, from the ketones

Maple syrup: leucine, body is unable to process it.

Sulfur: inability to reabsorb cysteine in tubules.

Mousy: phenylketonuria, unable to break down phenylalaline.

What are the Manual vs. Automated Reagent strip tests based on?

Manual is comparing the color found on the dipstick to the color on the manufacturers guide. This color interpretation is the biggest variable for the manual reading.

Automated uses the principle of Reflectance.

More color (more chemical) = less light transmitted back

Less color (less chemical) = more light transmitted back.

What are sources of error for strip testing?

Not mixing the sample.

Extended dipping/not blotting the edge, reagents will leach over into other pads.

Not reading at manufacturers specified times.

Urine is not at RT.

Pigmented urines also for obvious reasons.

What are the tests found on a dipstick?

Leukocytes

Nitrites

Urobilinogen

Protein

pH

Blood

SG

Ketones

Bilirubin

Glucose

aka: LNUPPBSKBG

What is the normal range for pH and why do the kidneys filter out H+ ions/bicarbonate?

4.5-8.0

The kidneys are part of the balancing of the acid base gases, helps keep the blood pH.

What are the causes of an Acidic pH?

H+

Ketones (keto acids)

Dehydration

Cranberries

What are some causes of an Alkaline urine?

Certain UTIs

Old urine (>8.5hrs)

What is the principle of the pH dipstick test and what are some interfering factors?

A double indicator system.

Methyl red covers 4-6, turns red to yellow.

Bromothymol blue covers 6-9, turns yellow to blue.

Each reacts according to the pH of the urine.

Not a lot will interfere, mostly just an old sample or bacterial growth and ammonia production that raise the pH.

What is the normal range for the dipstick protein and why is it measured?

Negative to Trace (<10mg/dL), it measures albumin (the most abundant protein in the serum).

It is the best indicator of renal disease; proteins don’t get through the Sheild of negativity in the glomerulus.

Clinical proteinuria is =/+ 30mg/dL.

What are the causes of Pre-renal Proteinuria?

Pre-renal protein: before kidneys.

Bence jones proteins: associated with multiple myeloma (over production of immunoglobulins and the light chains exceed the renal threshold). A suspicion, looking for something else by physician (bone pain, brain fog, fatigue, nausea, weight loss).

Hemoglobinuria: intravascular hemolysis.

Myoglobinuria: muscle injuries.

What are the causes of Renal proteinuria?

Is done by the kidneys.

Glomerular disease: immune complexes of SLE and untreated Strep A infections.

Diabetes mellitus neuropathy: glucose in blood deteriorates the glomeruli and the proteins slip through. Hence microalbumin.

Pre-Eclampsia: Increased blood pressure in the glomerulus that pushes proteins through.

Tubular disorders: that affect the reabsorption of the albumin; a little normally can make it through, but it’s also normally reabsorbed without a problem.

Orthostatic/postural proteinuria: a benign condition in young, will disappear with age. Can be the upright position pushes the proteins through. (1st morning specimen is negative but after standing a while will be positive. Can be normal due to prego, fever, cold, stress, dehydration.

What are reasons for Post renal proteinuria?

Lower UTIs: will produce exudates with protein.

Injury/trauma.

Kidney stones in ureters/bladder.

Menstrual contamination.

Sperm/prostate secretions.

Vaginal secretions.

What is the principle for the protein dipstick test?

Error of Indicators: the proteins can accept an H+ ion from the indicator on the pad, causing a yellow to blue color change.

More protein = more H+ ions lost from the indicator.

What are some interfering factors for the protein dipstick test?

False positive: Alkaline urine (check pH)

False negatives: Proteins other than albumin (Bence jones), Microalbumin.

What is the protein confirmation test and when will it be done?

Sulfosalicylic acid (SSA)

If the protein is more than trace.

What is the principle of the SSA test?

The sulfosalicylic acid binds to any proteins and precipitates them out of the solution.

Equal parts urine and SSA are used; is graded by precipitation instead of standards.

If the protein is positive on the dipstick, but negative for SSA, what could be the cause?

Bence Jones proteins, dyes, or drugs.

What is the most frequently measured urine test?

Glucose

What is the normal range for Glucose and when is it found in the urine?

Negative to minute.

Though a little can be pushed through the glomerulus, a completely healthy person will fully reabsorb all of it. And is called Glycosuria/glucosuria when it passes the renal threshold of 160-180mg/dL.

Patient has tubular dysfunction and can’t reabsorb the glucose that made it through.

In gestational diabetes, the Prego hormones block the insulin taking the glucose down.

What is the principle of the Glucose dipstick test?

The Double sequential enzyme.

The glucose oxidase catalyzes a reaction with oxygen and glucose, this makes gluconic acid and Peroxide. Some Peroxidase will then catalyze a reaction with the peroxide and the chromogen to produce a colored compound.

Glucose + Oxygen —Glucose oxidase—> Gluconic acid + Peroxide —Peroxidase—> Peroxide + Chromogen + colored compound that is directly equal to the amount of glucose.

It uses the glucose oxidase that reacts only with glucose.

What are the fals positives and negatives of the glucose dipstick test?

False Positives: none due to being specific for glucose.

False negatives: Ascorbic acid (vit C, prevents oxidation and color change), High SG (decreases reaction sensitivity), Unpreserved specimens (bacteria eat the glucose).

What is the Glucose confirmation test and its principle?

Copper reduction test: Reacts with all reducing sugars, galactose is most significant. Is based on the ability of glucose/sugars to reduce copper sulfate to cuprous oxide in heat and alkali.

Makes a color change from Blue (negative) through green, yellow, and orange red.

Checks for all the -oses.

What are Ketones, which does the dipstick test for?

They are one of the 3 by products of Fat, cholesterol/glucose/ketone bodies.

There are 3: acetone, acetic acid, beta-hydroxybutyric acid.

Normally there is no ketones in the urine, but when more are produced than can be broken down, they spill over.

If there is a trace amount of glucose in the urine, will the clinitest pick it up?

No, it is less specific for glucose than the dipstick test.

If the dipstick is showing 2+-4+, but the Clinitest is negative, what could be the issue?

There’s an error/interfering substance present.

What is the significance of the Ketones in the urine?

Diabetes mellitus, starvation, carb free diets, vomiting, malabsorption.

Increased Ketones can lead to electrolyte imbalances, dehydration, and then acidosis and a coma

What are the signs of uncontrolled Diabetes mellitus?

Glucosuria

Ketonuria

Acid pH of blood and urine

Positive glucose and urine

Risk of Diabetic ketoacidosis (DKA)

What is the principle of the Ketones dipstick test?

Sodium Nitroprusside reacts with acetoacetic acid to produce a purple color.

The other two ketones are made from acetoacetic acid, so they aren’t individually measured.

What are the false positives and Negatives of the ketones dipstick test?

False positives: highly pigmented urines (drugs, meds, dyes).

False negative: Evaporation, improper storage (some bacteria can utilize ketones for energy).

What is the Ketone confirmation test principle?

Acetest: a tablet form of sodium nitroprusside with lactose added (to give better color differing).

Can be used with serum, urine, and other body fluids.

Why could there be blood in the urine?

Hematuria: intact RBCs, red/hazy-cloudy.Sometimes can be microscopic hematuria, where the blood cells are not visible. Trauma/injury, Tumors, stones, Glomerular disease, UTI, Menstrual contamination, Strenuous exercise (runners hematuria).

Keep in mind that you should see RBCs on the microscopic too.

I PEE RBCS: infection, pseudohematuria, exercise, external trauma, renal glomerular disease, benign prostatic hypertrophy, cancer, stones.

Hemoglobinuria: (free hemoglobin) transfusion reactions, hemolytic anemias, burns, sepsis/infections, bites from brown recluse, malaria.

The iron can be reabsorbed by tubules, though may show up in urine sediment as hemosiderin granules.

Myoglobinuria: (free myoglobin) muscle crush injuries, muscle wasting (rhabdomyolysis), burns/seizures, acute myocardial infarctions, strenuous exercise in untrained people.

What is the princile of the Blood dipstick test?

Pseudo peroxidase activity of Hemoglobin: Catalyzes a reaction between chromogen and heme component to produce a blue-green color change.

The speckled are intact RBCs, but if there are enough, they can come up as a smooth pattern.

Smooth is generally the hemoglobin/myoglobin. Must correlate with microscopic.

What are the interfering factors for the blood dipstick test?

False positives: menstrual contamination, other peroxidases (veggies, bacteria).

False negatives: High SG (crenates RBCs and they are unable to release the hemoglobin), failure to mix specimen.

Why is Bilirubin tested for in the urine?

Bilirubin is a byproduct of hemoglobin breakdown in the liver.

Is normally negative.

Will cause the yellow foam and amber/brown-orange coloring.

Can be an early sign of liver disease and is seen long before jaundice.

What is the process of bilirubin being made?

Hemoglobin is broken into iron, protein, protophyrin.

The iron and protein get recycled, but the protophyrin is converted to bilirubin.

That bilirubin is then released from the spleen into the blood bound to albumin aka unconjugated bilirubin (cant pass through glomerulus either).

It passes through liver where it loses the protein and is conjugated with glucuronic acid to become water soluble.

It now passes through the glomerulus.

Though it usually doesn’t appear in urine, but instead is in the intestines after the liver.

WHy is it normal to find some Urobilinogen in the urine?

After the indirect bilirubin (unconjugated, protein bound) passes through the liver, it is now conjugated and goes to the intestines where it is then made into urobilinogen, but some makes it way back into circulation and that is filtered out.

About <=1mg/dL per day.

The rest is oxidizd to urobilin and in the feces.

What are reasons for a positive blirubin?

Liver disease: the liver can’t process the bilirubin correctly and the conjugated bilirubin passes through the glomerulus.

The urobilinogen may also increase cause the liver can’t handle the reabsorbed urobilinogen in circulation.

Bile duct obstructions: the liver processes fine, but it can’t get to the intestines. So it’s back in circulaton and passes into urine. Also means no urobilinogen is produced.

Stools will be very pale in color.

Also shows jaundice.

what is the principle for the Bilirubin dipstick test?

Diazo reaction

Diazo = 2 nitrogen atoms at the terminal position of a compound.

Bilirubin combines with the diazo and produces azo dye, a color from tan to pink to violet.

This is a very hard reaction to grade since the other pigments highly influence this.

What are some false positives and negatives of the bilirubin dipstick test?

False positives: pigmented dyes from drugs, meds, urine.

False negatives: Exposure to light, is rapidly oxidized to biliverdin, and can’t be detected.

What confirmation tes is used for Bilirubin?

Ictotest: is 4x more sensitive than the strip, will detect 0.-1mg/dL and is less affected by interfering substances.

Purple is positive.

What is Urobilinogn and why is it measured?

A breakdown product of heme. Is formed by intesinal bactria from bilirubin.

Norml range is <=1 mg/dL (ehrlich unit).

Comes out in feces as Urobilin.

What are the causes of an increased Urobilinogen?

Hemolytic anemia + Intravascular hemolysis: the liver can handle the processing, but theres so much that it spills over.

What are causes of decreased/negative Urobilinogen?

Bile duct obstructions: since the bilirubin can’t get into the intestines to be mde into urobilinogen, theres no urobilinogen and more bilirubin.

What is the Urobilinogen dipstick test reaction?

Ehrlich’s reaction: makes colors from light to dark pink.

Is unable to detect the abscence of urobilinogen.

What are the false positives and negatives for urobilinogen?

False positives: other ehrlich reactive substances (porpho, indican), highly pigmentd urines.

False negatives: exposure to light.

Why is nitrite measured in urine?

Some bacteria will turn nitrate into nitrite, espcially enterics. It is used to monitor and screen patients with UTIs or infections there. Should correlate with pH (ammonia with bacteria)

Cystitis = bladder infection

Pyelonephritis = kidney infection

What is the reaction used to measure Nitrites on the dipstick?

Griess reaction: the nitrites ract with the sulfa compound at acid pH to make a diazonium compound. Makes pink color.

What are the false results of a Nitrite dipstick test?

False positives: improper storage (external bacteria grows), highly pigmented urines.

False negatives: not all bacteria do this process, not long enough in the bladder (need time for the conversion), not enough nitrates there, if theres too many bacteria they can continue the process into nitrogen (not detected).

What is the point of measuring Leukocyte esteras in urine?

It is an enzyme in granulocytic WBCs, no lymphs. Is indicative of an infection.

Pyuria = WBCs in urine.