Renal Function Tests

1. Filtration and elimination of toxins/products of metabolism

2. Maintain fluid balance

3. Maintain body pH

4. Maintain electrolyte balance

5. Regulate BP

6. Stimulate RBC production

7. Vitamin D activation

What are the main functions of the kidneys?

1. Blood tests

2. Urine tests

3. Vital signs

4. Physical exam

How do we measure the functions of the kidneys?

Establish health of kidney, monitor therapy and natural history of disease, and diagnose renal injury

Why measure renal function?

Prerenal, intrarenal, and postrenal

What 3 types of disease result in abnormal renal function tests?

impair perfusion

Prerenal diseases typically...

cause direct damage

Intrarenal diseases typically...

involve obstruction

Postrenal diseases/conditions typically...

Prerenal

What type of disease would the following condition classify as? Dehydration

Prerenal

What type of disease would the following condition classify as? Acute/chronic heart failure

Prerenal, intrarenal, and postrenal

What type of disease would the following condition classify as? Diabetes mellitus I and II

Intrarenal

What type of disease would the following condition classify as? Hypertension

Intrarenal

What type of disease would the following condition classify as? Pharmacological/DOA effects

Postrenal

What type of disease would the following condition classify as? Bladder outlet obstruction

Postrenal

What type of disease would the following condition classify as? Kidney stones

a constant rate

Creatinine is produced at...

only by the kidneys

Creatinine is filtered...

Only marker that's only filtered by the kidneys

What makes creatinine the best marker for renal function?

Blood urea nitrogen

Urea produced predominately by the liver during protein breakdown and is filtered out of the body through the kidneys

many systems (not just kidneys)

Serum BUN is affected by...

20:1

What is a normal BUN-creatinine ratio?

pre-renal uremia/azotemia

A high BUN-creatinine ratio (>20:1) can be indicative of...

Glomerular filtration rate (GFR)

Measure of renal filtration

By acquiring a 24-hour urine sample and measuring creatinine clearance in the urine

How does one obtain the most accurate GFR?

Calculate an estimated GFR (eGFR) based on serum creatinine, age, gender, and ethnicity

How do we typically determine GFR?

>60mL/min/1.73m^2

What is a normal eGFR?

Low cost, easily obtained, and more accurately reflect past 24 hours

How are urine samples better than blood tests?

To monitor or detect renal and urinary tract health

Why perform an urinalysis?

Random sample

Most common type of urine sample taken

clean catch

Random samples should be a ____________ whenever possible, which includes cleaning the opening of the urinary tract

First morning sample

Type of sample taken in the early morning because it is most concentrated and good for pregnancy and STIs

Catheterization, suprapubic aspiration, U-bag, and condom catheter

What are some additional methods of collecting urine (minus normal method)?

1. Appearance, color and odor

2. Chemistry

3. Microscopic exam

What is included in a typical urinalysis?

Pale yellow, amber, or clear

What is the normal color and appearance of urine?

Mild and musky

What is the normal odor of urine?

Lungs and kidneys

What two organs are responsible for pH balance?

Organisms causing the UTI are resistant to nitrofurantoin

A patient presents with a UTI and is treated with nitrofurantoin. After a period of treatment, the pH of the individual's urine was at 8.2. What does this indicate?

1.005 or 1.030 (can also just indicate as underlined part)

What is a normal specific gravity of urine?

The kidney's ability to concentrate and excrete urine/waste products and reabsorb water and electrolytes

What does the specific gravity (SpG) of urine evaluate?

should not

Glucose should/should not be found in urine

Glycosuria

Presence of glucose in urine

When blood glucose exceeds renal threshold for reabsorption

When does glycosuria occur?

should not

Protein should/should not be found in urine

Diabetes mellitus and hypertension

What are common causes for protein being found in urine?

Microalbuminuria

Presence of albumin in the urine at low levels

It can serve as a prognostic factor of future heart and kidney disease

Why is albumin (microalbuminuria) tested for in the urine?

should not; dehydration and diabetic ketoacidosis (DKA)

Ketones/acetone should/should not normally be found in urine, but can be with...

should not

Hemoglobin/blood should/should not be found in urine

liver and gallbladder; should not

Bilirubin is produced by the ____________ and should/should not be found in urine

False, can be, just trace amounts (0.01-1 units)

T/F? Urobilinogen should not be found in urine at all

Biliary or liver obstruction

If bilirubin and urobilinogen are found in excessive amounts in the urine, what does this indicate?

should not

Nitrite and leukocyte esterase should/should not be found in urine

To screen for or diagnose bacterial UTIs or STIs

What is the purpose for testing for nitrite and leukocyte esterase in urine?

Not all bacteria produce nitrites, and if urine doesn't remain in the bladder very long, there isn't enough time for bacteria to produce nitrites that accumulate into traceable amounts

What are some reasons that a bacterial UTI may be present, but nitrites might not be present in the urine, despite most bacterial organisms producing nitrites as a byproduct of metabolism?

Enterococcus

One bacterium that does not produce nitrites

Leukocyte esterase

____________ screens for WBCs in the urine

>10^2-3 (100-1000) colony forming units (CFUs)

What concentration of bacterial organisms in a symptomatic patient makes an individual positive for a UTI?

>10^5 CFUs

What concentration of bacterial organisms in a asymptomatic patient makes an individual positive for a UTI?

sensitivity; resistance

A urine culture and sensitivity helps establish antibiotic _______________ and ________________ of the microorganism causing the UTI to different treatments

UA with reflex C&S (culture and sensitivity)

How is a urinalysis ordered to determine possible treatment options?

If patient is a child under 12, if concerns about complicated UTI or resistant organisms, if signs of a UTI during pregnancy, or if a treatment fails or infection recurs within a month

When should a UA with reflex C&S be done?

clean catch

If doing a UA with reflex C&S, it must be a...

True

T/F? Certain uropathogens are less likely to be associated with pyuria in symptomatic children

top; below

In results for a urine test, the organisms and CFU are found at the ____________, and medications with associated sensitivity/resistance indicator are found _____________

small

In the microscopic part of urinalysis, there are typically ___________ amounts of cells and formed elements

Yes

Is it normal for a few epithelial cells to be visible on a urinalysis?

should not

Microscopic crystals should/should not be present in urine

renal calculi are imminent or present, asymptomatic

The presence of crystals is indicative that ____________________, but can be ________________

Cast

Amorphous material coalescing in the renal tubules

Hyaline and cellular casts

What are the two types of casts?

Small numbers

How many hyaline casts are normal?

renal disease

Casts may be seen in _____________ and other conditions