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The Urinalysis

The urinalysis is a cheap and effective way to discover the health of:

  • GU tract
    • Infection
    • Calculi
    • Glomerular health
    • Concentrating ability of nephron units
  • Vascular
    • Fluid status
    • Hemolysis
  • Oncology
    • Multiple Myeloma
  • Endocrine
    • Blood Glucose
CIS Orders

Urinalysis with reflex to micro
Urinalysis with reflex to culture

The Parts of a Urinalysis

  • Appearance
  • Specific Gravity
  • Urinary pH
  • Glucose
  • Ketones
  • Protein
  • Bilirubin
  • Urobilinogen
  • Nitrites
  • Leukocyte Esterase
  • RBCs
  • WBCs

 

Appearance

Color

Cause

Yellow-Amber

Concentrated Urine

Carrots

Bilirubin, nitrofurantoin, chloroquine, sulfasalazine, riboflavin, serotonin

White-Cloudy

Pyuria, chyluria, lipiduria

Diet of purine rich foods

Phosphaturia

Red-Brown

Bile pigments, myoglobin

Flagyl, levadopa, nitrofurantoin

Phenazopyridine, phenothiazines, senna, rhubarb, cascara, beets, melanin, porphyrins

Brown-Black

Bile pigments, melanin, methemoglobin, prophobilinogen

Anti-malarials, methyldopa, flagyl

Cascara, senna

Blue-Green

Biliverdin, pseudomonal UTI

Amitriptyline, methylene blue, propofol, amitriptyline, tagamet, phenergan

Differential of Reddish-Brown Urine

  • Reddish-brown + muddy casts: acute tubular necrosis
  • Reddish-brown without heme: beeturia, porphyria, phenazopyridine, medications
  • Reddish-brown with heme: hematuria or myoglobinuria

Specific Gravity

  • The kidney changes urine osmolality to maintain plasma osmolality.
  • Specific gravity is defined as the weight of a solution compared with an equal amount of water.
  • Water has a specific gravity of 1.0, therefore the larger the difference between the specific gravity of urine and 1.0, the more concentrated it is.

Normal range is 1.003 to 1.030, typically between 1.008 and 1.015

Interpretation

  • Ignoring other processes that may be going on, a specific gravity of less than 1.010 indicates the body is relatively well hydrated and a specific gravity of greater than 1.020 indicates relative dehydration
  • Differential Diagnosis of Low Urine Specific Gravity
    • Diuretic use
    • Diabetes insipidus
    • Adrenal insufficiency
    • Aldosteronism
    • Impaired renal function
  • Differential Diagnosis of Elevated Urine Specific Gravity
    • Dehydration
    • Large molecules such as mannitol or radiocontrast media
    • SIADH

Urinary pH

Normal range is from 4.5 – 8.0 with normal usually being 5.5 to 6.5
Except in RTA, urinary pH is a reflection of serum pH and is most helpful in the assessment of metabolic acidosis which causes increased renal excretion of hydrogen ions.

  • Acidotic Urine (pH < 5.5)
    • Renal Tubular Acidosis
    • Risk of crystal or stone formation from uric acid, sulfadiazine, or methotrexate
  • Alkaline Urine (pH > 7.0)
    • Distal renal tubular acidosis
    • Colonization with urease producing organisms (Proteus mirabilis)
    • Risk of crystal or stone formation from calcium phosphate or indinavir

Urine Protein

Pathophysiology

  • A healthy glomerulus is impermeable to proteins greater than 20,000 Daltons
  • Microproteins are reabsorbed or excreted
  • Normal urinary proteins include albumin, serum globulins and others
  • Proteinuria: excretion of 150mg or more per day
  • Micoalbuminuria is an early sign of renal disease and is defined as albumin excretion of 30 to 150 mg per day
  • Albumin is the only protein detected on dipstick (does not test for immunoglobulins including Bence Jones proteins)

Dipstick

 

Reading

Concentration

1+

30 mg/dL

2+

100 mg/dL

3+

300 mg/dL

4+

1000 mg/dL

Dilute urine can underrepresent the degree of proteinuria and concentrated urine or alkalosis can overrepresent it.
Radiocontrast can cause a false-positive and therefore the urine protein should not be checked within 24 hours of receiving contrast.

Common Causes of Proteinuria

Transient

Persistent

 

1˚ Glomerular

2˚ Glomerular

Tubular

Overflow

CHF
Dehydration
Exercise
Fever
Orthostatic
Seizures

Focal Segmental
IgA Nephropathy
IgM Nephropathy
Membranoproliferative
Membranous Nephropathy
Minimal Change

Alport’s
Amyloidosis
Collagen vascular
DM
Drugs
Fabry’s
Infections
Malignancies
Sarcoidosis
Sickle Cell

Aminoaciduria
Drugs
Fanconi
Heavy metal
HTN nephrosclerosis
Interstitial Nephritis

Hemoglobinuria
MM
Myoglobinuria

Further Evaluation

  • 24 hour urine protein
  • Spot urinary protein-Cr ratio
  • Microscopy
  • Urinary protein electrophoresis
  • Assessment of renal function

Urine Blood/Heme

Definition

  • Microscopy
    • 3 or more RBCs per HPF in 2 of 3 urine samples
  • Dipstick
    • Checks for RBCs via a peroxidase reaction that is catalyzed by both myoglobin and hemoglobin
    • A urine dipstick is very sensitive for blood/heme and therefore a negative rules out hematuria.
    • The urine dipstick is not specific because it will read positive for heme-pigments (myoglobin), ingestion of large amounts of of ascorbic acid, beets, and medications (rifampin and chloroquine

Common Causes of Hematuria

Glomerular

Renal (non-GM)

Urologic

Other

Familial
Fabry
Alports
Nail-Patella
Thin BM

Primary
FSG
Goodpasture’s
Berger’s
Mesangioproliferative

Secondary
HUS
Lupus
TTP
Vasculitis

AV Malformation
Hypercalciuria
Hyperuricosuria
Loin pain-hematuria syndrome
Malignant HTN
Medullary Spongy kidney
Papillary Necrosis
Polycystic kidney
Renal artery embolism
Renal vein thrombosis
Sickle-cell

BPH
Cancer
Cystitis
Pyelonephritis
Prostatitis
Schistosoma
TB

Drugs (NSAIDs, heparin, warfarin, cytoxan)
Trauma

 

Type

Findings

Evaluation

Glomerular

Dysmorphic RBCs
RBC casts
Significant proteinuria

Renal function
24 hour protein
US
Biopsy

Renal (non-GM)

Significant proteinuria
No dysmorphic RBCs
No RBC casts

Renal function
24 hour protein
US
Biopsy

Urologic

No proteinuria
No dysmorphic RBCs
No RBC casts

Cystoscopy
CT scan

Urine Glucose

Significant glycosuria does not occur until glucose concentration is approximately 180 mg/dL. Glucose in the urine can also be caused by states other than hyperglycemia.

Etiologies:

  • Hyperglycemia
  • Multiple Myeloma
  • Cushing’s
  • Fanconi’s syndrome
  • Drugs that injure the proximal tubule
    • Adefovir, cidofovir, tenofovir

Urine Ketones

Only tests for acetoacetic acid, not acetone or B-hydroxybutyric acid (which predominant in starvation ketosis)

Differential

  • Uncontrolled DM
  • Pregnancy
  • Carbohydrate free diets
  • Starvation

Urine Leukocyte Esterase

Leukocyte esterase is produced by neutrophils and represents the appearance of white blood cells in the urine.

  • Infection
  • Sterile Pyuria (negative cultures and bacteria)
    • Tubulointerstitial nephritis
      • Crystalluria
      • Nephrolithiasis
    • Renal mycobacterial infection
    • Ureaplasma urealyticum and Chlamydia
    • Balanitis
    • Bladder tumor
    • Viral infection (adenovirus, polyomavirus, cytomegalovirus)
    • Glomerularnephritis
    • Cytoxan

This test is sensitive (48-68%) but not specific (17-93%).

Urine Nitrite

Some bacteria convert urinary nitrate to nitrite (including E. coli, Proteus, Pseudomonas, and Klebsiella).

This test is specific (85-98%) but no sensitive (45-60%).

Combined Leukocyte Esterase and Nitrite

If both are positive the sensitivity of a UTI is 68-88%. If both are negative there is a high negative predictive value for UTI.

Urine Bilirubin and Urobilinogen

Free bilirubin is produced by the reticuloendothelial system from heme. In the liver free bilirubin is converted to conjugated bilirubin. Conjugated bilirubin and urobilinogen are excreted in bile. Bilirubin is converted to urobilinogen in the intestines. Urobilinogen is reabsorbed and then excreted in the urine.

Condition

Urine Bilirubin

Urine Urobilinogen

Normal

-

+

Hepatitis

+

+

Hepatotoxins

+

+

Biliary Obstruction

+

-

Cirrhosis

+

+

Urine Sediment

Red Blood Cells (Hematuria)
Microscopic hematuria is defined as 3+ RBCs per high power field.
Persistent hematuria most often signals:

  • Nephrolithiasis
  • Glomerular pathology
  • Malignancy of the kidneys or urinary tract
  • Menstruation
  • Strenuous exercise

White Blood Cells (pyuria)
Pyuria is defined as 4+ WBCs per high power field.

  • Neutrophils (multilobed nuclei)
    • Most common
    • Infection
  • Eosinophils (bilobed nuclei)
    • Acute interstitial nephritis
    • Cholesterol emboli
    • Septic emboli
    • Vasculitis
    • Glomerulonephritis (postinfectious)
    • Urinary tract infection
    • Prostatitis
  • Lymphocytes (circular, uniform nucleus)
    • Sarcoidosis
    • Uveitis-tubulointerstitial nephritis syndrome

Epithelial Cells
May be due to shedding of renal tubular cells or from uroepithelial cells of the lower urinary tract.

Malignant Cells

Decoy Cells

  • Can confirm the presence of BK-polyoma virus infection in renal transplant patients treated with tacrolimus or mycophenylate

Urine Casts

Hyaline Casts

  • Acellular
  • Not associated with disease

Red Blood Cell Casts

  • Even one RBC cast is significant
  • Differential
    • Glomerulonephritis
    • Vasculitis

White Blood Cell Casts

  • Differential
    • Pyelonephritis
    • Tubulointerstitial disease
    • Acute interstitial nephritis
    • Vasculitis
    • Cholesterol emboli

Epithelial Cell Casts

  • Differential
    • Tubular injury
    • Glomerulonephritis
    • Vasculitis

Granular Casts

  • Differential
    • Tubular necrosis
    • Chronic kidney disease
    • Can also be degenerated WBCs or RBCs

Waxy Casts

  • Formed by the degeneration of granular casts
  • Suggestive of advanced kidney disease

Broad Casts

  • May be indicative of advanced kidney disease

Fatty Casts

  • Observed in nephritic syndrome

Muddy Brown Casts

  • Acute tubular necrosis

Urine Crystals

 

Urinary Protein


Urinalysis and Kidney Disease

Test

Prerenal

Vasculitis

GN

ATN

AIN

Postrenal

SG

High
> 1.020

Normal/High
1.010-1.020

Normal/High
1.010-1.020

Isosmotic
1.010

Isosmotic
1.010

Isosmotic
1.010

Blood

Neg.

Pos.

Pos./Neg.

Pos./Neg.

Pos./Neg.

Neg.

Protein

Neg.

Pos.

Neg.

Negative

Pos./Neg.

Neg.

Sediment

Neg., hyaline

RBC casts, Dysmorphic RBCs

RBC casts, Dysmorphic RBCs

Granular casts, Renal tubular epithelial cells

WBC casts, eosinophils

Neg, sometimes WBC/RBCs

 

Last Updated July 12, 2010