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Urianalysis

Interpretation

Gross assessment

Urine dipstick

Urine sediment

(Microscopic exam)

Turbidity

White urine: Polyuria, phosphate crystals, chyluria

Pink urine: Uric acid crystals, propofol.

Green urine: Methylene blue, propofol or amitriptyline

Black urine: Hemoglobinuria, myoglobulinuria, melanuria or ochronosis (alkaptonuria)

Purple urine: Bacteriuria in patients with urinary catheters

Urine color

High: Infection, as a result of precipitated crystals or chyluria

Yellow

Lighter: Dilute

Darker: Concentrated ( water restriction).

Red to brown → Centrifugation

Only in the sediment

Only in the supernatant

Hematuria

Urine dipstick

Positive for heme: Hemoglobinuria or myoglobinuria

Negative for heme: Unusual conditions

Intravascular hemolysis or myonecrosis

- Meds ( rifampin or phenytoin)

- Consumption of food dyes

- Ingestion of beets

- Acute intermittent porphyria

HEME (pseudoperoxidase)

- Semen (false positive)

- Free hemoglobin

- Hemoglobin

- RBC (requires microscopy)

Leukocyte esterase ( released by lysed PMN

- Neutrophils and macrophages

- False-negative result: Concentrated urine, proteinuria and glucosuria

Nitrite (Nitrate reductase)

- Many Enterobacteriaceae sp bacteriuria or frank infection

- False negative result: Organisms expressing low levels of nitrate reductase or urine dwell time in the bladder is short.

Protein (most sensitive to albumin)

- False negative: Microalbuminuria (30-300 mg/day); Important in high risk patients such as diabetes, ACEI/ARB therapy. And very dilute urine.

- Semiquantitative categories are not necessarily reliable.

- Iodinated radiocontrast agents can induce transient albuminuria.

- Regular dipstick is insensitive to non-albumin proteins. For that use sulfosalicylic acid test.

If positive, quantify albuminuria with albumin-creatinine ratio on a random urine sample or with a 24-hour urine collection.

pH (4.8-8)

Aciduria: Due to metabolic acidosis, renal tubular acidosis.

Alcaluria: Due to urease producers pathogen such as P. mirabilis

Glucose

False negative cause: Ascorbic acid

Positive: Above 180 mg/dl (normal kidney function)

Due to: Inability of the kidney to reabsorb filtered glucose in the proximal tube

High plasma glucose concentration overwhelming the capacity to reabsorb it.

In normal plasma glucose: Discard primary defect of proximal tubule reabsorption ( consider additional manifestations of tubular dysfunction, fanconi syndrome)

White blood cells

Red Blood Cells

Epithelial cells

Microscopic hematuria: Above 2 RBC/field

- Transient: Common in young patients and may occur following exercise or sexual intercourse.

Menstruation.

Malignancy ( patients over 50 years).

UTI.

- Persistent: Kidney stones, malignancy, glomerular disease

Non-glomerular

Glomelular

Dysmorphic RBC

Isomorphic RBC

Neutrophils

Bacteriuria

Interstitial nephritis

Renal tuberculosis

Nephrolitiasis

Eosinophils

Acute interstitial nephritis

Renal tubular cells

Transitional cells ( anywhere from renal pelvis to proximal urethra)

Squamous epithelial (Distal urethra or external genitalia)

Casts

RBC casts

Underlying proliferative glomerulonephritis

Other causes

WBC casts

Interstitial or glomerular inflammation (not discard it)

Renal tubular ep casts (desquamation of the tubular ep)

Acute tubular necrosis

Acute interstitial nephritis

Proliferative glomerulonephritis

Granular casts ( Degenerated cellular casts or aggregation of protein within a cast matrix)

Acute tubular necrosis

Hyaline casts

Non specific

Small volumes of concentrated urine or diuretic

Waxy casts

Non specific

May be in acute and chronic kidney diseases

Associated with advanced chronic kidney disease

Broad casts

Crystals

Uric acid crystals

Acid urine

Calcium oxalate or calcium phosphate crystals

Alkaline urine

+ AKI: Ethylene glycol ingestion

Cystine crystals

Cystinuria

Magnesium ammonium phosphate crystals

Increased ammonium production and urine pH is elevated

UTI by Proteus or Klebsiella