Diagnostics - GU Flashcards
Urinalysis (UA)
- Informative, noninvasive, cost effective, accessible
- Obtaining a specimen - midstream
- Gross Evaluation - using eyes, what does it look like
Dipstick analysis
- Heme: If positive, absolutely must f/u with micro exam - how many intact RBC
- Leukocyte esterase : True pyuria = infection/bacteriuria, Sterile pyuria = interstitial nephritis, renal TB, nephrolithiasis
- Nitrites: Enterobacteriacea species, Pyridium
- Protein: Not sensitive –consider quantitative 24 hour urine collection
- pH (4.5-8): Depends on systemic acid-base balance, High pH may indicate renal tubular acidosis, Infections with urease producing bacteria (Proteus, Klebsiella)
- Specific gravity: Varies with osmolality (solute concentration), Mediated by ADH
- Glucose: Renal glycosuria, Urinary spillage d/t abnormally high plasma glucose concentrations in DM (plasma typically >180 ml/dL)
- Bilirubin: Waste product of old RBC’s, normally removed by the liver in bile, Presence in urine may be a sign of liver disease
Urinalysis - Microscopic Exam
- Crystals : Uric acid, calcium phosphate, calcium oxalate, cystine, magnesium ammonia phosphate (struvite)
- Microorganisms: Bacteria, Fungi
- Cells: RBC (Stones, renal disease, neoplasm), WBC (Infection, colonization, stones, interstitial nephritis, glomerulonephritis), Epithelial cells, Casts (Present in normal individuals or may represent significant renal disease)
positive urine culture
≥100,000 Colony forming U/mL together with pyuria
-Pyuria = leukocyte count ≥100,000 WBC/mL
Exception = Acute urethral syndrome
- Fecal contamination ruled out with irritative voiding symptom
- Earlier stage of infection
- Bladder washout during normal micturition
Sensitivity testing
-To ensure targeted antibiotic therapy
Urine Cytology
- Standard approach for detecting new and recurrent urothelial tumors
- Sensitivity 34%
- Specificity 99%
- Not widely used for screening
- Need a pathologist for interpretation
- High cost
- Remains an important technique for surveillance in those with a prior history of urothelial carcinoma and those with suspicious symptoms (ie - hematuria)
PSA = Prostate specific antigen
- Glycoprotein expressed by normal and neoplastic prostate tissue
- Serum test
Utility
- Screening method to detect prostate cancer
- Determine extent of prostate cancer
- Assess response to prostate cancer treatment
rises for 4 reasons
- Prostate cancer
- Benign prostatic hypertrophy (BPH)
- Prostate infection or inflammation
- Perineal trauma
PSA – How do I know if it’s elevated
-Reference Range: 0-4 ng/mL
-Highly controversial
-Age-specific reference ranges due to expected BPH
40 to 49 years-old — 0 to 2.5 ng/mL
50 to 59 years-old — 0 to 3.5 ng/mL
60 to 69 years-old — 0 to 4.5 ng/mL
70 to 79 years-old — 0 to 6.5 ng/mL
-Reduces sensitivity of detecting early prostate cancer while increasing specificity
-Risk is missing clinically significant cancers in older men
Age to start screening
- 50 if life expectancy is >10 years
- 40-45 in men with increased risk factors, strong family history, African American race
Digital Rectal Exam (DRE)
Utility
-Prostate cancer
-Prostatitis
-BPH
Abnormal prostate findings
-Nodules
-Asymmetry
-Induration
Limitations
-85% of prostate cancers arise in the posterior and lateral aspects
-Stage T1 cancers are nonpalpable by definition
-No reduction in the morbidity or mortality when detected by DRE at any stage
-Majority of cancers detected by DRE are clinically or pathologically advanced
-Greatest value of DRE may be its paired use with PSA testing
Prostate Biopsy
Indications
- Abnormal DRE: Nodules, induration, or asymmetry
- Rising PSA levels that do not respond to ABX
- Rapid PSA velocity
- Repeat biopsies for inadequate initial sampling or continued high clinical suspicion for prostate cancer
Procedure Details
- In urology office by a urologist
- Transrectal ultrasound (TRUS) guidance
- Template-guided to ensure uniformly distributed sampling
- Pre-procedure antibiotic prophylaxis
Risks
-Infection, Bleeding , Hematuria, rectal bleeding, hematospermia, Drug resistant bacteria complicate choice of prophylaxis
Serum Creatinine (SCr)
- Breakdown product of creatine phosphate in muscle
- Usually produced at a fairly constant rate depending on muscle mass
Reference Range
- Female = 0.5 - 1.0 mg/dl
- Male = 0.7 - 1.2 mg/dl
Important Factors
- Race
- Muscle Mass: Amputees (particularly LE amputees), Malnutrition, Muscle wasting, Diet, Vegetarian, Creatine supplements
Serum Blood Urea Nitrogen (BUN)
Blood urea nitrogen (BUN)
- Liver produces ammonia (which contains nitrogen) from protein breakdown
- Nitrogen combines with carbon, hydrogen and O2 to form urea
- Urea is a chemical waste product
- Travels from the liver to the kidneys via the bloodstream
- Healthy kidneys filter urea which is excreted in urine
Elevated BUN indicates:
- Renal dysfunction
- Increased protein intake
- Dehydration
- Poor circulation
Decreased BUN indicates:
- Liver disease or damage
- Malnutrition
BUN : SCr Ratio
Ratio >20:1
- BUN reabsorption is increased
- Prerenal etiology
- Dehydration
- Decreased blood flow due to CHF
- GI bleeding
- Increased dietary protein
Ratio 10-20:1
- Normal
- Possible postrenal etiology
Ratio <10:1
-Renal damage causes reduced reabsorption of BUN
Etiology:
-Intrarenal etiology: Glomerulonephritis, Acute tubular necrosis
-Liver disease
-Malnutrition
Glomerular Filtration Rate (GFR)
Utility
- Assess degree of kidney impairment
- Follow course of kidney disease
GFR = Sum of filtration rates of all functioning nephrons
- Glomeruli filter approx. 180 liters per day (125 mL/min) of plasma
- Normal value for GFR depends on age, sex, and body size
- Men average GFR ~ 130 mL/min
- Women average GFR ~ 120 mL/min
Reducation in GFR
- Progression of underlying renal disease
- Development of a superimposed and often reversible problem
- Decreased renal perfusion due to volume depletion
Limitations
- Does not provide information on the cause of kidney disease
- Not an exact correlation between loss of kidney mass and loss of GFR
- Kidney adapts to the loss of some nephrons by compensatory hyperfiltration and/or increasing solute and water reabsorption in the remaining, normal nephrons
Measurement versus Estimation
- Measurement is complex, time consuming and cumbersome in clinical practice
- GFR is usually estimated from serum markers
- Is the GFR (and therefore disease severity) changing or is it stable?
- Usually determined by monitoring the change in serum creatinine or estimated GFR in most patients with a relatively constant body mass and diet
Renal Biopsy
Goal
- Establish a diagnosis
- Help guide therapy
- Ascertain degree of active and chronic changes
Indications
- Hematuria with proteinuria or evidence of renal insufficiency
- Unexplained acute renal failure
- Idiopathic nephrotic syndrome
- Heavy proteinuria, hypoalbuminemia, and peripheral edema
- Systemic lupus erythematosus
- Acute nephritic syndrome
- Hematuria, cellular casts, proteinuria, hypertension, renal insufficiency
- Often caused by a systemic disease
- Renal transplant rejection
Percutaneous Renal Biopsy
Prebiopsy Evaluation
- H&P, ensure BP well-controlled
- Skin at biopsy site free of signs of infection
- Lab tests: CMP, CBC, platelets, PT, PTT, bleeding time
Renal ultrasound (often performed at the time of biopsy)
- Assess size of and/or presence of any anatomic abnormalities
- Solitary kidney
- Polycystic kidney
- Malpositioned or horseshoe kidney
- Small echogenic kidneys
- Hydronephrosis
-Hold ASA, NSAIDs, antiplatelet or antithrombotic agents for 1-2 weeks prior to biopsy and for 1-2 weeks after biopsy
Percutaneous Renal Biopsy - Technique
- Informed consent
- Peripheral IV access
- Patient prone with pillow under abdomen
- Ultrasonic guidance with local anesthesia: 1% lidocaine hydrochloride
- Locate the lower pole, mark skin where biopsy needle will be inserted
- Sterilely prep site
- Under u/s a spinal needle is used to locate the capsule and to provide anesthesia for the biopsy needle tract
- Make skin incision, insert biopsy needle
