nephrology/urology/urinalysis

characteristics of an ideal GFR marker

1. not bound to plasma protein

2. filtered from blood into tubule

3. not reabsorbed once in tubule

Blood urea nitrogen (BUN)

end-product of protein metabolism→ formed in the liver and excreted in the urine

Proteins -> amino acids -> ammonia processed in liver into urea which is excreted by kidneys

decreased BUN from

1. liver disease (bc cant turn ammonia into urea)

2. fluid overload (dilute blood)

3. malnutrition/malabsorption (less protein intake → less breakdown)

increased BUN from

1. renal disease (cant excrete)

2. high protein diet (more protein breakdown)

3. GI bleed (digested blood rich in protein)

4. corticosteroids (inc protein catabolism)

5. tetracycline (tissue breakdown)

azotemia

high levels of BUN

prerenal azotemia

before urea gets to the kidneys

1. hemorrhage

2. shock

3. trauma

4. sepsis

5. diets high in protein

6. increased protein catabolism (tumors)

7. dehydration

postrenal azomtemia

after urea gets to the kidney →

urethral obstruction

serum creatinine

Catabolic product of creatine phosphate-(skeletal muscle), depends on muscle mass → more stable than BUN (bc muscle mass more constant than protein consumption)

is BUN or serum creatinine more of a direct reflection of kidney function

serum creatinine (more stable)

when does serum creatinine start to rise

approximately ½ nephrons or more lose function (more chronic indication than BUN rise)

which drugs affect creatinine levels

Drugs filtered by kidneys such as

1. NSAIDS

2. Levaquin

3. diuretics

elevated serum creatinine from

1. decreased renal function or renal blood flow

2. diabetic nephropathy

3. urinary tract obstruction

4. rhabdomyolysis

5. increased muscle mass

decreased serum creatinine from

loss of muscle mass

normal BUN:creatinine ratio

15:1

if BUN:creatinine is >15:1

prerenal

if BUN:creatinine is = 15:1

renal disease if both are elevated at the same ratio

if BUN:creatinine is <15:1

liver disease, low protein diets

cystatin C

Protein produced at a constant rate by all nucleated cells that is NOT influenced by factors like BUN and creatinine

use of cystatin C

predict the risk of developing kidney dysfunction & several types CVD

creatinine clearance normal decline

after age 40, CrCl declines by 0.8mL/min/yr

what is creatinine clearance used for

estimate GFR

supine abdominal radiograph

KUB (Kidney-Ureter-Bladder)

intravenous pyelography (IVP)

X-ray study that uses radiopaque contrast material to visualize the kidneys, renal pelvis, ureters and bladder (so renal pelvis, ureters, and bladder r white)

benefits of ultrasound

1. no radiation

2. safe for impaired renal function

what diagnostic should be used in suspected renal vascular disease

renal ultrasound with doppler

1st line for detecting malformations and ectopic kidney

renal ultrasound

bladder ultrasound (bladder scan) used for

Usually used to measure the amount of urine after micturition (post void residual)

can easily be done bedside

CT for renal system prefers with or w/o contrast?

with contrast unless nephrolithiasis

1st line diagnostic for renal artery stenosis

CTA

what diagnostic can distinguish renal cortex from medulla

MRI

function of nuclear medicine in renal imaging

perfusion, function and structure of the kidneys

what can diagnose renal transplant rejection

Nuclear Medicine Renal Imaging - perfusion scan

T or F: nuclear medicine scans are safe for patients allergic to iodine

TRUE! → no iodine dye, just radioisotope

which diagnostic determines the presence and source of renovascular hypertension after administration of and ACE inhibitor

renal hypertension scan (basically perfusion scan but with ACE inhibitor)

renal blood flow scan

perfusion scan →Evaluates blood flow to each kidney

• Renal artery stenosis,

• renovascular HTN,

• transplant rejection,

• hypervascular lesions (renal cell carcinoma)

Renal Structural Scan

Outline the structure of the kidneys

Looks for tumor, cysts, abscess, congenital disorders

renal function scan (renogram)

Looks at renal function by determining capability of kidney to take up particular isotopes and excrete it

Renal Obstruction Scan

The radionuclide in the unobstructed kidney can be seen to rapidly wash out (be excreted) from the kidney after diuretic (Lasix) is administered

Voiding Cystourethrography

Fill bladder with contrast material to visualize bladder on filling radiograph, then patient voids and you are able to see the bladder empty

• hematuria,

• frequent UTIs,

• suspected bladder trauma

• Pelvic tumor

• hematoma

• vesicoureteral reflux

• perforation

• fistula of bladder

Urodynamic Studies

measure urine pressure and flow between the bladder and urethra to identify bladder function problems

• Neuromuscular function of the bladder by measuring efficiency of detrusor muscle, intravesical pressure and capacity, and bladder’s response to thermal stimulation

• includes urine flow studies → cystometry, uroflowmetry, urethral pressure profile (UPP)

which diagnostic used to determine if bladder function abnormality caused by neurologic, infectious or obstructive disease

cystometry

Uroflowmetry

Measures the volume of urine expelled from the bladder per second

Urethral pressure profile (UPP)

Fluid pressure that would hypothetically be required to force open the collapsed urethra and so allow urine to flow

does urethral pressure profile stay constant throughout the length of the urethra

no. Varies from point-point within urethra

cystoscopy

Endoscopic test used to evaluate structure and function of the urethra, bladder, ureters and prostate

Can be diagnostic and therapeutic

complication of cystoscopy

1. Perforation,

2. sepsis,

3. hematuria,

4. urinary retention

contraindications of Voiding Cystourethrography and urodynamic studies

UTI

indications of renal biopsy

1. Diagnose the cause of renal disease

2. detect primary and metastatic malignancy of the kidney in a patient who may be a candidate for surgery

3. evaluate kidney transplant rejection

CI of renal biopsy

1. Coagulation disorders (bc kidney highly vascular)

2. patient with operable kidney tumor (seeding tumor cells)

3. hydronephrosis

4. UTI/infection (spread infection)

complications of renal biopsy

1. Bleeding/hemorrhage

2. puncture of other organs

3. infection (increased with open procedure)

common urine collection techniques

1. Routine Void Specimen → No preparation, nonsterile container

2. Midstream and Clean-Catch Specimens → If culture and sensitivity is required

3. 24 Hour Urine Collections → 24 hours of urine collected (first void discarded)

how to get an anaerobic culture from urine specimen

suprapubic aspiration (directly get urine from bladder)

ways we can collect urine sample from peds

1. Pediatric collection bag

2. Urethral catheterization

3. Suprapubic aspiration

normal urine color

clear amber yellow

normal urine pH

4.6-8 (average is 6)

normal urine specific gravity

1.005-1.030

green urine indicates

pseudomonas infection

dark yellow urine

Bilirubin or urobilinogen

deep amber color

concentrated urine

red urine

beets

strong and sweet urine smell

DKA

foul odor of urine

UTI

fecal odor of urine

Enterobladder fistula

alkaline pH of urine from

1. Alkalosis

2. UTI

3. bacteria

4. diet high in citrus fruits or vegetables (COMMON AFTER EATING)

which stones are formed in alkaline urine

1. calcium carbonate,

2. calcium phosphate,

3. magnesium phosphate stones

acidic pH urine from

1. acidemia

2. starvation

3. dehydration

4. diet high in meat or cranberries

which stones are formed in acidic urine

1. xanthine

2. cystine

3. uric acid

4. calcium oxalate

presence of what is one of the Most important indicator of renal disease

protein

what is routinely checked in all pregnant women to assess for preeclampsia

protein

what should be done after significant protein is noted in urine sample

may need 24 hour urine to quantify protein

at what point will glucose start to spill into urine

once blood glucose level exceeds 160-180 mg/dl

what does specific gravity correlate with

osmolality

high specific gravity indicates? what about low?

high → concentrated urine

low → dilute urine

positive leukocyte esterase suggests

UTI (lab would do microscopic exam)

nitrites indicates presence of

e.coli

ketones in urine suggest

ketoacidosis from

• uncontrolled DM,

• alcoholism,

• fasting,

• starvation,

• high-protein diet

• isopropanol ingestion

what happens if bilirubin excretion is inhibited

conjugated hyperbilirubinemia

presence of what can indicate contaminated specimen on microscopic exam of urine

epithelial cells

acellular casts

1. hyaline (protein)

2. fatty

how many WBC in urine suggests infection

>5

Granular casts

from disintegration of cellular material into granular particles within a WBC or epithelial cell

Waxy casts

further degradation of cellular casts (urine flow through renal tubules is diminished)

causes of hyaline cast

its made of proteins

• proteinuria

• strenuous exercise

• fever

• CHF

• chronic renal failure

cellular casts made of

collection of degenerated cells

WBC casts found in

1. Most frequently found in infections of the kidney

2. Pyelonephritis

3. Interstitial Nephritis

4. Postinfectious glomerulonephritis

5. Inflammatory nephritis (SLE)

RBC casts most common cause

glomerulonephritis

epithelial cell casts associated with

acute tubular necrosis

fatty casts associated with

nephrotic syndrome

crystals associated with parathyroid abnormalities or malabsorption states

1. phosphate

2. calcium oxalate

crystals in urine suggest

potential or alr present kidney stone

hexagonal crystal

cystine

coffin-lid shaped crystal

struvite

calcium oxalate shapes

monohydrate → dumbell shaped

dihydrate → pyramid shaped

rectangle/rhomboidal crystals

uric acid

how much bacteria present in urine for positive urine culture

>100,000

Urine Culture and sensitivity indicated in

1. diagnose UTI in patient with urinary symptoms

2. in patients with fever of unknown origin

how long does urine culture and sensitivity take

24-48 hours

abx therapy initiated before or after culture and sensitivity?

AFTER. do C&S 1st