Urinalysis ACS lecture 2

Urine production

Kidneys filter blood, the filtrate is urine.

The glomerulus is...

A capillary

Red blood cells go through...

Capillary of glomerulus

What doesn't go through the capillary of the glomerulus?

Big molecules like protein, glucose and other materials that diffuse out of urine

After diffuse out of glomerulus capillaries...

The body reabsorbs its materials

At high blood glucose levels

Your kidneys cannot reabsorb all the glucose being filtered out, so it gets pee'd out.

Obtaining a urine sample

Midstream "Clean Catch" Urine Acquisition

- Sterile Container

- Sterile Wipes

Catheter Acquisition

- Indwelling-Foley

- One-time Sampling

Uralysis photo

Examination urinalysis

Urine color and appearance

Analysis via reagent dipstick of urinalysis

Specific gravity, pH, bilirubin, urobilinogen, blood, protein, glucose, ketones, nitrites, leukocytes esterase

Microscopy urinalysis

WBC, RBC, Bacteria, urine casts, urine crystals

LabCorp documentation

Urine dipstick photo

Yellow urine color

Pale: Volume replete, hydrated

Dark: Volume depleted, hyperbilirubinemia

Red urine color

Can centerfigue

Gross Hematuria

- Red Sediment

Hemoglobinuria

-Red Supernatant

Myoglobinuria

-Red Supernatant

Diet-Related: Beets, Rhubarb, Blackberries

Orange urine color

Medication-induced: Rifampin, Azo (Phenazopyridine for urinary pain, it is OTC)

Blue-green

P. Aeruginosa UTI

Urine appearance

Normal = clear, Cloudy = Pyuria (infection), Foam/Frothy: Proteinuria

Urine specific gravity/osmolality

Measured with dipstick, normal: 1.009-1.030

Measure of urine relative to water

Presence of urinary glucose, protein or RBCs can invalidate assessment and urine osmolality must be used (in lab)

Urine osmolality

Concentration of particles per kg of a solution

Normal: 50-1200 mOsmol/kg

Specific gravity correlation with urine osmolality

1.001 = 40 mOsmol/kg

1.030 = 1200 mOsmol/kg

Dilute urine

Will have a lower specific gravity or osmolality

Concentrated urine

Will have a higher specific gravity or osmolality

Arginine vasopressin (AVP) aka Antidiuretic hormone (ADH)

Acts on renal tubules to increase water retention. Increases concentrations of the urine

Diabetes insipidus

Their body has inadequate AVP production

- Nephrogenic: Impaired AVP Action on Kidney

Clinical Manifestations

- Polyuria, Polydipsia, Large Urine Output

- Hypernatremia

- Low Urine Specific Gravity

Syndrome of inappropriate antidiuretic hormone (SIADH)

Excessive production of AVP

- Neoplasms, CNS disorders, medications or infections

Clinical manifestations:

- H/A, confusion, N/V, coma

- Hypoatremia

- Elevated urine specific gravity

Specific gravity can indicate...

Diabetes insipidus or SIADH

Acidotic urine

Urine pH <5

Metabolic acidosis

Alkalotic urine

Urinary pH >7

Metabolic Alkalosis

Infection with Urea Causing Organisms (Proteus spp.)

Standing Urine Samples (Delayed Analysis)

Urine bilirubin

Bilirubin is either direct (conjugated) or indirect (unconjugated).

Unconjugated bilirubin

Is bound to albumin so not filtered by the kidney

Conjugated bilirubin

Is filer but most is reabsorbed within the proximal tubules

Presence of bilirubin in urine

is always conjugated bilirubin and is typically indicative of a hepatocellular disease (liver damage)

May occur in presence of jaundice.

Urobilinogen

Conjugated Bilirubin is catabolized by Gut Bacteria and leads to the formation and absorption of urobilinogen.

Most is excreted via liver and small amounts are excreted by kidneys

In liver failure

The liver will be unable to clear urobilinogen, leading to increased levels of urinary excretion

Urinary blood

Urine dipsticks assess for heme molecules within urine.

Positive heme means positive microscopic RBC.

Gross hematuria and microscopic hematuria will be positive.

Positive heme, negative microscopic RBC

Hemoglobinuria (hemolysis), and myoglobinuria (Rhabdomyolysis, can be from working out or drugs).

Distinguished by clinical diagnosis.

Obstructive jaundice

Urinalysis

Color: Dark yellow

Bilirubin: Positive (conjugative)

Urobilinogen: Variable depending on degree of obstruction (if completely blocked, we get none)

Blood: Negative

Hemolysis

Color: Red

Bilirubin: Negative

Urine gen: Positive

Blood: Positive

Microscopy: RBC = none (Hemoglobinuria)

Urine protein

Protein molecules are too large to pass through the glomeruli and in theory urine should be absent of proteins.

Urine Dipsticks can detect albumin concentrations from 200 to 300 mg/L.

- Urine Dipsticks typically are insensitive for non-albumin proteins

- Semi-Quantitative

-Measure as Negative, 1+, 2+, 3+, 4+

-Used as a screening tool for Renal Disease

Protein in urine

Renal disease

Glucose in urine

DM

Medications like sodium-glucose co-transporters 2 (SGLT 2) inhibitors

Sodium-glucose co-transporters 2 (SGLT2) inhibitors

Increase urinary output of glucose to reduce blood sugar

Urine glucose

Glucose is continuously filtered by glomeruli and reabsorbed within the renal tubules.

Glucosuria occurs when the Renal threshold for glucose reabsorption is exceeded.

- This is typically associated with serum glucose levels > 180 mg/dL

UTIs and glucose

Increased UTIs when blood glucose is high

Urine ketones

Ketones are a byproduct of fatty acid metabolism (Lipolysis)

Theoretically, ketones should not be present in the urine.

Ketonuria

Uncontrolled DM, ketogenic diet, starvation.

Can be associated with a metabolic acidosis.

Urine nitrite

Common by-product of certain species of gram-negative nitrate metabolism.

Common agents: E. coli and other Enterobacteriaceae — includes Klebsiella spp. & Proteus spp

NOT produced by gram-positive organisms

Leukocyte esterase

An enzyme within WBCs

Will be positive in cases of infection or possibly inflammation

Urine microscopy

Urinary casts: Distal tubules and collecting ducts

Red/white blood cells and bacteria

Urinary crystals

Urinary casts

gelatinous structures that take the shape of the renal tubules

Acute tubular necrosis

Renal tubular damage which results in AKI

Major causes: Ischemia, nephrotoxins, sepsis

Signs/syms: AKI + Reduced urinary output

Glomerulonephritis

Inflammation of the renal glomeruli

Major causes: Autoimmune process, infection related

Signs/symps: Hematuria, AKI, edema, proteinuria, HTN

Nephrotic disease

Spectrum of glomerular disease which results in alterations of basement membrane permeability

Major causes: DM, amyloidosis

Signs/symps: Proteinuria, hypoalbumemia, edema, HLD

Hyaline casts

Faint, colorless

Concentration of mucoproteins secreted from renal tubules

Non-specific; Present in normal/non- renal disease patients

Granular casts

Broad, fine or coarse

Composed of degraded cellular products and serum proteins (Albumin, IgG, Transferrin, etc.)

Non-specific, Indicative of Renal Parenchymal Disease; ATN

Renal Tubular Epithelial Cell Casts

Collection of Renal Tubular Epithelial Cells

Associated with Acute Tubular Necrosis (ATN)

Fatty casts

Hyaline casts which contain lipid droplets and can be overserved in patients with Liguria

Associated with nephrotic syndromes

Asymptomatic microscopic hematuria

Bladder or renal cell cancer until otherwise determined.

RBC, WBC and bacteria in microscopic

Graded in cells/hpf. (Can add information to initial dipstick)

Initial Gram Staining to guide in treatment choice

Followed by subsequent Culture and Sensitivity

Urine stones and crystals

Calcium oxalate, uric acid, stuvite, cystine

Calcium oxalate

Small Square crystals with Central Cross

Most Common Stone Type

Uric acid

Rhomboids, Hexagons, or Squares

Acidic Urine (Gout)

Struviate (staghorn)

Triple phosphate

"Coffin-lids"

Alkaline urine

Drystone

Colorless hexagons, seen in patients with cystinuria

Red blood cell casts

Collection of grouped red blood cells which have leaked into the renal tubules through damage of the glomerular basement membranes.

Occurs in glomerulonephritis

24 hour urine collection procedure

Procedure

1. First Urine is voided and discarded.

a. The time is recorded. This is the beginning of the 24 hour urine study

2. Each subsequent urine is collected in a container

3. Urinate one last time at the end of the 24 hour period.

a. This is the end of the 24 hour urine collection

4. Urine is then analyzed for various electrolytes, proteins, catecholamines, etc.

Keep in fridge

White blood cell casts

Collection of white blood cells which have leaked into the renal tubules.

Typically occur in upper urinary tract infections (pyelonephritis)

Pathologies for 24 hr urine collection

Calcium

- Increased: Hyperparathyroidism, Sarcoidosis, Hyperthyroidism

- Decreased: Hypothyroidism, Renal Failure

Catecholamines

- Increased: Pheochromocytoma

Free Cortisol

- Increased: Cushing Syndrome (Screening Test of Choice)

Creatinine

- Decreased: Renal Disease (Used to help calculated Creatinine Clearance in conjunction with Serum Creatinine)

Protein

- Nephrotic Syndromes, Preeclampsia

Urine microalbumin

Used as a screening tool for diabetic patients to determine their risk of developing nephropathy. Dipsticks don't normally pick this up until it is in macro levels, so we typically send it out to a lab for this specific test if necessary.

Often used for diabetics

Urine Microalbumin levels

Normoalbuminuria

< 30 mcg/g Cr (Spot Urine)

< 30 mg/24 Hr

Microalbuminuria

30 - 299 mcg/g Cr (Spot Urine)

30 - 299 mg/24 Hr

Macroalbuminuria

> 300 mcg/g Cr (Spot Urine)

> 300 mg/24 Hr

Spot urine microalbumin often used for

Diabetes monitoring

Those diagnosed with microalbumin uric are given...

ACE inhibitor or ARB therapy

Urine spot testing

Can be used for various electrolyte abnormalities and metabolic states.