LabDx

11/22/99

 

Casts

• A clinical marker for correlation
• Bacteria
• Common urine specimens b/c of the abundant normal microbial flora of the vagina and external urethral meatus and b/c of their ability to rapidly multiply in urine standing at room temp
• Microbial organisms found in all but the most scrupulously collected urines should be interpreted in view of clinical symptoms
• Dx of bacteriuria in a case of suspected UTI requires culture
• Colony count must also be done to see if significant numbers of bacteria are present
• More than 100,000/mL of one organism reflects significant bacteriuria
• Multiple organisms reflect contamination
• The presence of any organism in catherized or suprapubic tap specimens should be considered significant
• Yeast
• Contaminated
• Diabetes
• Crystals
• Common crystals
• Calcium oxalate
• Triple phosphate crystals
• Amorphous phosphates
• Very uncommon crystals include: cholesterol, cystine crystals in urine of neonates w/congenital cystinuria or septic liver ds, tyrosine crystals w/congenital tyrosinosis or marked liver impairment, or leucine crystal pt w/severe liver ds or w/maple syrup urine ds
• Common w/green leafy vegetable
• Misc.
• General "crude" or unidentifiable objects may find their way into a specimen, particularly those that are at home
• Methods of urine collection
• Random collection taken at nay time of day w/no precautions regarding contamination.  The sample may be dilute, isotonic, or Hypertonic and may contain WBC, bacteria and squamous epithelium as contaminants
• Early morning collection—very concentrated, before ingestion of fluids—1.022
• Clean-catch, midstream—following cleansing
• Catherization of the bladder
• Needle aspiration of bladder
• 24 hour urine collection—all aspects of one circadian cycle—proteinuria

 

Dipstick urine screen

1. Negative Dx: normal
2. Isolated proteinuria—repeat dipstick
1. Negative—Dx: transient proteinuria
2. Positive—1^st AM dipstick urine screen

                                                               i.      Negative—Dx: orthostatic proteinuria—no follow up

                                                             ii.      Positive—24 hr urine for total protein

1.      <0.150—Dx: normal or transient proteinuria

2.      0.15-3.5 g—constant proteinuria (+3)

3.      >3.5g—Nephrotic level proteinuria—renal injury or pathology (+4)

Nephrology consult for constant or Nephrotic

3. Proteinuria and hematuria—microscopic urinalysis
1. Pyuria bacteria—culture

                                                               i.      Positive

1.      UTI—pyelonephritis

                                                             ii.      Negative—renal function tests

2. White cell casts—renal function tests
3. Red cell casts—renal function tests

Renal function tests: 24hr urine for total protein, albumin, cholesterol levels, radiologic studies, Nephrology consult

            GFR

            BUN

            Creatinine

            Creatinin clearance

            Intravenous pyelogram—IVP

            Dx Ultrasound

            CT scan

            MRI competes w/CT

• Kidneys produce 80-120ml/minute
• Common causes
• Diabetes
• HTN
• CHF

 

Microscopic hematuria on urinalysis

Urine culture®infection®antibiotics®hematuria resolves

      ¯                                         ¯

negative                              hematuria persists

      ¯                                 

intravenous pyelography®renal mass®CT 1.  solid mass®surgery

      ¯                                                                      2.  cyst®no further evaluation

negative

      ¯

cystoscopy/cystology®bladder tumor®transurethral rxn

      ¯

negative

      ¯

renal ultrasonography®solid mass®CT   (MRI will take over this step in the next few years)