1 Renal Diagnostics Flashcards
What are the three main laboratory studies used to monitor kidney function?
Serum Creatinine
BUN
BUN/Cr ratio
Product of creatine catabolism in skeletal muscle and from dietary meat intake
Serum Creatinine (0.5-1.2)
Why is Serum Creatinine a good measure of kidney function?
It is released into the circulation at a RELATIVELY CONSTANT RATE —> STABLE PLASMA CONCENTRATION
It is freely filtered across the glomerulus and excreted by the kidney
An elevated Serum Creatinine typically indicates
There’s something wrong with the kidney
BUT - must keep the patient’s baseline Cr in mind (based on diet, muscle mass, etc)
A product of protein catabolism in the liver that is excreted by the kidneys
BUN (normal 10-20)
When would you see an increased BUN?
Dehydration
GI bleed
Use of certain meds (ie steroids or tetracyclines)
Ratio commonly used as a marker for volume status
BUN/Creatinine
Glomerular Filtration Rate is equal to…
The sum of the filtration rates in all of the functioning nephrons
Gives a rough measure of the number of functioning nephrons
—> used to track progression/regression of disease and to dose meds
GFR is dependent upon…
Age
Sex
Race
Body Size
What are normal values for GFR in men and women?
Men ~130mL/min/1.73m2
Women ~120mL/min/1.73m2
What is the Cockcroft-Gault formula?
Method to determine the Creatinine Clearance (and to approximate GFR)
CCr(men) = [(140-age) x LBW(kg)]/[PCr x 72]
CCr(women) = 0.85 x CCr(men)
Presence of kidney damage or decreased kidney function for 3 or more months, irrespective of the cause
Chronic Kidney Disease (CKD)
What lab should you run if you suspect:
Systemic Lupus Erythematosus (SLE)
Antinuclear antibodies (ANA)
Double-stranded DNA antibody levels
What lab should you run if you suspect:
Granulomatosis with Polyangitis
Cytoplasmic and perinuclear pattern antineutrophil cytoplasmic antibody (C-ANCA and P-ANCA) levels
What lab should you run if you suspect:
Goodpasture syndrom
Anti-glomerular basement membrane (anti-GBM) antibodies
What lab should you run if you suspect:
Forms of glomerulonephritis
Hep B and C
HIV
Venereal Disease Research Lab (VDRL) serology
Serum complement levels
What lab should you run if you suspect:
Post-streptococcal glomerulonephritis
Antistreptolysin O
What lab should you run if you suspect:
Multiple myeloma
Serum and urine protein electrophoresis (SPEP, UPEP)
What lab should you run if you want to improve estimates of GFR
Cystatin C
Glycoprotein found in high concentrations in the prostatic lumen that can be used as a screening method for early detection of prostate cancer and to monitor the disease after treatment
Prostate-Specific Antigen (PSA)
Normal = <4ng/mL
PSA levels are detectable in every male but are increased in …
Prostate cancer
BPH
Prostate tissue
Following prostate manipulation (ultrasound, biopsy)
What is one of the first signs of kidney disease in the U/A?
Proteinuria
NEVER ignore protein on a UA
What are the components of a urinalysis?
pH Specific gravity Glucose Ketones Protein Blood Nitrite Leukocyte esterase WBCs Bilirubin Urobilinogen
Component of the U/A that reflects the ability of the kidney to concentrate and dilute urine
Specific gravity
Ketones in the urine are suggestive of…
Dehydration
Malnutrition
DKA
Blood in a UA could indicate…
Calculi, glomerular damage, neoplasm, acute tubular necrosis, trauma, infection
What different things are you looking for when doing microscopic analysis of a urine sample?
RBC casts WBC casts Epithelial cell casts Hyaline casts Crystals
RBC casts in microscopic UA
Glomerulonephritis
Vasculitis
WBC casts in microscopic U/A
Tubulointerstitial disease
Acute pyelonephritis
Glomerular disorders
Epithelial cell casts in microscopic UA
Acute tubular necrosis (kidney ischemia)
Glomerulonephritis
Contrast nephrotoxicity
Hyaline casts in microscopic UA
Dehydration
What are the different types of crystals you might see in a microscopic UA?
Uric acid
Calcium phosphate or calcium oxalate
Cystine
Magnesium ammonium phosphate (struvite)
Why do a urine culture and sensitivity?
Identifies the causative organism of a urinary infection
Shows sensitive and resistant abx
The earliest clinically detectable stage of diabetic nephropathy or other early kidney damage
Microalbumin
Urine eosinophils are most commonly seen in…
Acute interstitial nephritis
May also be seen in transplant rejection, pyelonephritis, prostatitis, cystitis, atheroembolic disease, and rapidly progressive glomerulonephritis
What type of urine study provides a better quantitative measurement for proteinuria or GFR determination?
24-hour urine collection
TEDIOUS - usually only collected inpatient
When might you perform a urine protein immunoelectrophoresis?
If you suspect Multiple Myeloma
You would see Bence Jones proteins on UPEP
What is a KUB xray?
Kidneys, Ureters, and Bladder
Not the most useful but often used as an initial diagnostic tool
Can show calcium-containing, struvite, and cystine stones in the urinary tract, but will miss smaller stones, uric acid stone (radiolucent) or stones overlying bony structures
What kind of kidney stones are radiolucent?
Uric acid
Besides stones, what are some other findings you might see on KUB?
Prostatic calculi Bladder distension Pancreatic calculi Calcified arteries Calcification in biliary tract Bowel gas pattern Free air secondary to a ruptured viscus
Appropriate initial test in patients with renal failure of unknown etiology
Renal Ultrasonography
Test of choice to exclude urinary tract obstruction
Renal ultrasonography
What sorts of things can be identified on renal ultrasonography?
Nephrolithiasis Severity and length of urethral strictures Renal cysts (PCKD) and masses Hydronephrosis Renal or perinephric abscesses Strophic kidneys Urethral diverticuli
When might you want to do a renal DOPPLER ultrasonography?
Renal vein thrombosis Renal infarction RENAL ARTERY STENOSIS Intracranial vascular disease Arteriosclerosis
Good DDx for persistent HTN?
Renal artery stenosis
Why perform a CT scan for diagnosing renal conditions?
Provides more detailed info than ultrasound
Helps distinguish between benign and malignant cysts
Used to evaluate and stage renal cell carcinoma
When is NON-contract CT performed?
Diagnostic test of choice for nephrolithiasis
Can detect radiolucent stones that my not appear on KUB
When would you perform a CT angiography?
To identify renal vascular problems
Renal artery stenosis or renal vein thrombosis
What to remember about CT contrast
It is potentially nephrotoxic
Hold metformin for 48 hours afterwards
Gold standard for diagnosis of renal vein thrombosis
MRI
Can also use MRA
Contraindications to MRI/A
Gadolinium may increase risk for nephrogenic systemic fibrosis in patients with chronic renal failure (GFR < 30mL/min/1.73m2) or acute renal failure of any severity
How is intravenous pyelograpm (IVP) used?
To evaluate size/shape of kidneys, ureters, and bladder; look for kidney stones/obstruction
NOT used frequently b/c it requires contrast dye and other Dx tests exist
How is an intravenous pyelogram performed?
Contrast dye is injected and x-rays taken
Excretory function of the kidneys is measured by the length of time for passage of contrast through the kidneys
“Live action” x-rays of renal vasculature
Renal angiography
Used less frequently due to the fact that other Dx tests are available
Still used for pre-op mapping of renal vasculature if needed
“String of pearls” appearance on angiography
Fibromuscular Dysplasia
Inflammation of medium sized arteries throughout the body but will show up on renal angiography
When might you want to do a renal biopsy?
Unexplained acute renal failure Nephrotic syndrome Acute nephrotic syndrome Renal mass Assessment for rejection following transplant
***Can be US-guided or surgical
The bladder is filled with contrast and x-rays are taken while patient is voiding to visualize the contrast flow
Cystourethrogram
Primary bladder conditions are better seen with this study as compared to IVP
Cystourethrogram
Cystourethrogram is used to detect…
Vesicoureteral reflux
Distortion of the bladder (due to tumor)
Fistula
Perforation
How is a cystoscopy performed?
Thin fiber optic tube in a hollow sheath is inserted into the urethra and advanced into the bladder
Post-procedure hematuria is expected and should clear within three voids
Potential complications of cystoscopy
Sepsis
Hemorrhage
Perforation of the bladder
Post-procedure dysuria
Indications for a cystoscopy
To assess bladder/urethral involvement due to malignancies
To evaluate urogynecologic conditions (incontinence, sterile hematuria/pyuria, recurrent infection, urethral diverticula, fistula)
To diagnose intrinsic bladder disease (interstitial cystitis, bladder tumors, stones, or scarring)
Noninvasive, quick diagnostic tool for the evaluation of testicular/scrotal masses, testicular size, testicular/scrotal pain
Testicular ultrasound
Can also use to determine location of undescended testes
When evaluating testicular torsion, it’s important that the testicular ultrasound is…
DOPPLER - to evaluate blood flow
Prostate U/S and biopsy is performed…
Transrectally (TRUS)
Helpful in detection of prostate cancer in patients with increased PSA
