Type of test Urine

Normal findings

Appearance: clear

Color: amber yellow

 Odor: aromatic

pH: 4.6 to 8 (average 6)

 Protein : 0-8 mg/dL , 50-80 mg/24 hr (at rest), < 250 mg/24 hr (exercise)

 Specific gravity

Adult: 1.005-1.03 (usually 1.01-1.025), Elderly: values decrease with age , Newborn: 1.001-1.02

Leukocyte esterase: negative

Nitrites: negative

Ketones: negative

e Crystals: negative

 Casts: none present

 Glucose

 Fresh specimen: negative , 24-hour specimen: 50-300 mg/day or 0.3-1.7 mmol/day (SI units)

White blood cells (WBCs): 0-4 per low-power field

WBC casts: negative Red blood cells (RBCs): ≤ 2

 RBC casts: none

Test explanation and related physiology

 A total urinalysis involves multiple routine tests on a urine specimen. This specimen is not necessarily a clean-catch specimen. However, if urinary tract infection (UTI) is suspected, often a midstream clean-catch specimen is obtained. This urine is then split into two parts. One is sent for urinalysis, and the other is held in the laboratory refrigerator and cultured if the urinalysis indicates infection. Abnormalities detected by urinalysis may reflect either urinary tract diseases (e.g., infection, glomerulonephritis, loss of concentrating capacity) or extrarenal disease processes (e.g., glucosuria in diabetes, proteinuria in monoclonal gammopathies, bilirubinuria in liver disease).

Urinalysis routinely includes remarks about the color, appearance, and odor of the urine. The pH is determined. The urine is tested for the presence of proteins, glucose, ketones, blood, and leukocyte esterase. The urine is examined microscopically for RBCs, WBCs, casts, crystals, and bacteria.

Examination of the urine sediment provides a significant amount of information about the urinary system. Reference ranges have been provided to recognize marked abnormalities.

Appearance and color

Urine appearance and color are noted as part of routine urinalysis. The appearance of a normal urine specimen should be clear. Cloudy urine may be caused by the presence of pus, RBCs, or bacteria; however, normal urine also may be cloudy because of ingestion of certain foods (e.g., large amounts of fat, urates, or phosphates). The color of urine ranges from pale yellow to amber because of the pigment urochrome. The color indicates the concentration of the urine and varies with specific gravity. Dilute urine is straw colored, and concentrated urine is deep amber.

Abnormally colored urine may result from a pathologic condition or the ingestion of certain foods or medicines. For example, bleeding from the kidney produces dark red urine, whereas bleeding from the lower urinary tract produces bright red urine. Dark yellow urine may indicate the presence of urobilinogen or bilirubin. Pseudomonas organisms may produce green urine. Beets may cause red urine, and rhubarb can color the urine brown. Many frequently used drugs also may affect urine color (Table 1).

Table1. Frequently used drugs that may affect urine color

Odor

Determination of urine odor is a part of routine urinalysis. The aromatic odor of fresh, normal urine is caused by the presence of volatile acids. Urine of patients with diabetic ketoacidosis has the strong, sweet smell of acetone. In patients with UTIs, the urine may have a very foul odor. Patients with a fecal odor to their urine may have an enterovesical fistula.

pH

Urine pH is affected by diet, medications, systemic acid base disturbances, and renal tubular function. An alkaline pH is obtained in a patient with alkalemia. Also, bacteria, UTI, or a diet high in citrus fruits or vegetables may cause an increased urine pH. An alkaline urine pH is common after eating. Certain medications (e.g., streptomycin, neomycin, kanamycin) are effective in treating UTIs when the urine is alkaline. Slightly acidic urine is normal. Normal average pH is 7.0, slightly acidic compared with average blood pH of 7.4. However, acidic urine is observed in patients with acidemia, which can result from metabolic or respiratory acidosis, starvation, dehydration, or a diet high in meat products or cranberries. In patients with renal tubular acidosis, however, the blood is acidic, and the urine is alkaline.

The urine pH is useful in identifying crystals in the urine and determining the predisposition to form a given type of stone. Acidic urine is associated with xanthine, cystine, uric acid, and calcium oxalate stones. To treat or prevent these urinary calculi, urine should be kept alkaline. Alkaline urine is associated with calcium carbonate, calcium phosphate, and magnesium phosphate stones; for these stones urine should be kept acidic.

Protein

Protein is a sensitive indicator of glomerular and tubular renal function. Normally, less than 30 mg of protein per day is in urine. This is not detectable in the routine protein analysis. Microalbumin can be detected, however. If the glomerular filtration membrane is injured, as in glomerulonephritis, the spaces become much larger, and protein seeps out into the filtrate and then into the urine. Renal tubules are a site of protein reabsorption. If tubular disease exists, protein is in the urine. If proteinuria persists at a significant rate, the patient can become hypoproteinemic because of the severe protein loss through the kidneys. This decreases the normal capillary oncotic pressure that holds fluid in the vasculature and causes severe interstitial edema. The combination of proteinuria and edema is known as the nephrotic syndrome.

Proteinuria (usually albumin) is probably the most important indicator of renal disease. The urine of all pregnant women is routinely checked for proteinuria, which can be an indicator of preeclampsia. In addition to screening for nephrotic syndrome, urinary protein also screens for complications of diabetes mellitus, glomerulonephritis, amyloidosis, and multiple myeloma.

If significant protein is noted at urinalysis, a 24-hour urine specimen should be collected to measure the quantity of protein. This estimate of 24-hour protein excretion is usually performed with a urine creatinine because hydration status and other factors may influence urine concentration. The normal protein/creatinine ratio is less than 0.15.

Glucose

 This can be an effective screening test for the presence of glucose in the urine that may identify diabetes mellitus or other causes of glucose intolerance. Although urine glucose tests previously were used to monitor the effective ness of diabetes therapy, today glucose monitoring is largely done by fingerstick determinations of blood glucose levels.

Glucose is filtered from the blood by the glomeruli of the kidney. Normally, all of the glucose is resorbed in the proximal renal tubules. When the blood glucose level exceeds the capability of the renal threshold to resorb the glucose (normally ~180 mg/ dL), it begins to spill over into the urine (glycosuria). As the blood glucose level increases further, greater amounts of glucose are spilled into the urine.

Glucosuria may occur immediately after eating a high- carbohydrate meal in patients with a low tubular maximum for glucose. Similarly, glucosuria can occur with a normal serum glucose level when kidney disease affects the renal tubule. The renal threshold for glucose becomes abnormally low, and glucosuria occurs. Glucosuria is not abnormal, however, in patients receiving dextrose-containing intravenous fluids. Patients with acute severe physical stress or injury can have a transient glucosuria caused by normal compensatory endocrine-mediated responses.

Specific gravity

 Specific gravity is a measure of the concentration of particles, including wastes and electrolytes, in the urine. A high specific gravity indicates concentrated urine; a low specific gravity indicates dilute urine. Specific gravity refers to the weight of the urine compared with that of distilled water (which has a specific gravity of 1.000). Particles in the urine give it weight or specific gravity.

Specific gravity is used to evaluate the concentrating and excretory power of the kidney. Renal disease tends to diminish the concentrating capability of the kidney. As a result, chronic renal diseases are associated with a low specific gravity. Nephrogenic diabetes insipidus is associated with very little variation in specific gravity of the urine because the kidney cannot respond to such variables as hydration and solute load. Specific gravity is also a measurement of the hydration status of the patient. An overhydrated patient will have a more dilute urine with a lower specific gravity. The specific gravity of the urine in a dehydrated patient can be expected to be abnormally high. Specific gravity correlates roughly with osmolality.

Leukocyte (WBC) esterase

 Leukocyte (WBC) esterase is a screening test used to detect leukocytes in the urine. When positive, this test indicates a UTI. This examination uses chemical testing with a leukocyte esterase dipstick; a shade of purple is considered a positive result. Some laboratories have established screening protocols in which a microscopic examination is performed only if a leukocyte esterase test is positive.

Nitrites

Like the leukocyte esterase test, the nitrite test is a screening test for the identification of UTIs. This test is based on the principle that many, but not all, bacteria produce an enzyme called reductase, which can reduce urinary nitrates to nitrites. Chemical testing is done with a dipstick containing a reagent that reacts with nitrites to produce a pink color, thus indirectly suggesting the presence of bacteria. A positive test result indicates the need for a urine culture. Nitrite screening enhances the sensitivity of the leukocyte esterase test to detect UTIs.

Ketones

Normally no ketones are present in the urine; however, a patient with poorly controlled diabetes who is hyperglycemic may have massive fatty acid catabolism. Ketones (beta-hydroxybutyric acid, acetoacetic acid, and acetone) are the end products of this fatty acid breakdown. As with glucose, ketones (predominantly acetoacetic acid) spill over into the urine when the blood levels of patients with diabetes are elevated. The excess production of ketones in the urine is usually associated with poorly controlled diabetes. This test for ketonuria is also important in evaluating ketoacidosis associated with alcoholism, fasting, starvation, high protein diets, and isopropanol ingestion. Ketonuria may occur with acute febrile illnesses, especially in infants and children.

Bilirubin and urobilinogen

Bilirubin is a major constituent of bile. If bilirubin excretion is inhibited, conjugated (direct) hyperbilirubinemia will result. Unlike the unconjugated form, conjugated bilirubin is water soluble and can be excreted into the urine. Therefore bilirubin in urine suggests disease affecting bilirubin metabolism after conjugation or with defects in excretion (e.g., gallstones). Unconjugated bilirubin caused by prehepatic jaundice will not be excreted in the urine because it is not water soluble.

Bilirubin is excreted by way of the bile ducts into the bowel. There, some of the bilirubin is transformed into urobilinogen by the action of bacteria in the bowel. Most of the urobilinogen is excreted from the liver back into the bowel, but some is excreted by the kidneys.

Crystals

 Crystals found in urinary sediment on microscopic exami nation indicate that renal stone formulation is imminent, if not already present. Urea crystals occur in patients with high serum uric acid levels (gout). Phosphate and calcium oxalate crystals occur in the urine of patients with parathyroid abnormalities or malabsorption states. The type of crystal found varies with the disease and the pH of the urine.

Casts

Casts are rectangular clumps of materials or cells that are formed in the renal distal and collecting tubules, where the mate rial is maximally concentrated. These clumps of material and cells take on the shape of the tubule, thus the term cast. Casts are usually associated with some degree of proteinuria and stasis in the renal tubules. There are two kinds of casts: hyaline and cellular.

Hyaline casts are conglomerations of protein and indicate proteinuria. A few hyaline casts are normally found, especially after strenuous exercise or dehydration.

Cellular casts, which are conglomerations of degenerated cells, are described in the following paragraphs.

Granular casts result from the disintegration of cellular mate rial into granular particles within a WBC or epithelial cell cast. Granular casts are found after exercise and in patients with various renal diseases.

In some diseases, the epithelial cells desquamate into the renal tubule. As the cells degenerate, fatty deposits in the cells coalesce and become incorporated with protein into fatty casts. These casts are all associated with glomerular disease or the nephrotic syndrome or nephrosis. Free oval fat bodies may also be associated with fatty emboli that occur in patients with bone fractures.

Waxy casts may be cell casts, hyaline casts, or renal failure casts. Waxy casts probably represent further degeneration of granular casts. They occur when urine flow through the renal tubule is diminished, giving time for granular casts to degenerate. Waxy casts are found especially in patients with chronic renal diseases and are associated with chronic renal failure. They also occur in patients with diabetic nephropathy, malignant hypertension, and glomerulonephritis.

Epithelial cells can enter the urine anywhere along the process of urinary excretion. The presence of occasional epithelial cells is not remarkable. Large numbers, however, are abnormal and can conglomerate into tubular (epithelial) casts. These are most suggestive of renal tubular disease or toxicity.

Normally, few WBCs are found in urine sediment on microscopic examination. The presence of five or more WBCs in the urine indicates a UTI involving the bladder, kidney, or both. A clean-catch urine culture should be done for further evaluation. WBC casts are most commonly found in infections of the kidney, such as acute pyelonephritis.

Any disruption in the blood–urine barrier, whether at the glomerular, tubular, or bladder level, will cause RBCs to enter the urine. The bleeding can be microscopic or gross hematuria. Patients with more than three RBCs per high power field in two of three properly collected urine specimens should be considered to have microhematuria and hence be evaluated for possible pathologic causes. RBC casts suggest glomerulonephritis. RBC casts are also seen in patients with acute tubular necrosis, pyelonephritis, renal trauma, or renal tumor.

Interfering factors

Appearance and color

• Sperm in the urethra can cause the urine to appear cloudy.

• Urine that has been refrigerated for longer than 1 hour can become cloudy.

• Certain foods affect urine color: carrots may cause dark yellow urine; beets may cause red urine; rhubarb may cause reddish or brownish urine.

 • Urine darkens with prolonged standing because of oxidation of bilirubin metabolites.

* Many drugs, given the right environment, can alter the color of urine (see Table 1).

 Odor

 • Some foods (e.g., asparagus) produce a characteristic odor.

• When urine stands for a long time and begins to decompose, it has an ammonia-like smell.

 pH

 • Urine pH becomes alkaline on standing, because of the action of urea-splitting bacteria, which produce ammonia.

• The urine pH of an uncovered specimen will become alkaline because carbon dioxide vaporizes from the urine.

• Dietary factors affect urine pH. Whereas ingestion of large quantities of citrus fruits, dairy products, and vegetables pro duces alkaline urine, a diet high in meat and certain foods (e.g., cranberries) produces acidic urine.

* Drugs that increase urine pH include acetazolamide, bicarbonate antacids, and carbonic anhydrase inhibitors.

* Drugs that decrease urine pH include ammonium chloride, chlorothiazide, and mandelic acid.

 Protein

• Transient proteinuria may be associated with severe emotional stress, excessive exercise, and cold baths.

• Radiopaque contrast media administered within 3 days may cause false-positive results for proteinuria.

• Urine contaminated with prostate or vaginal secretions commonly causes proteinuria.

• Diets high in protein can cause proteinuria.

• Highly concentrated urine may have a higher concentration of protein than more dilute urine.

• Hemoglobin may cause a positive result with the dipstick method.

• Bence Jones protein may not appear with the dipstick method.

* Drugs that may cause increased protein levels include acetazolamide, aminoglycosides, amphotericin B, cephalosporins, colistin, griseofulvin, lithium, methicillin, nafcillin, nephrotoxic drugs, oxacillin, penicillamine, penicillin G, phenazopyridine, polymyxin B, salicylates, sulfonamides, tolbutamide, and vancomycin.

Specific gravity

• Recent use of radiographic dyes increases specific gravity.

 • Cold temperatures cause falsely high specific gravity.

* Drugs that may cause increased specific gravity include dextran, mannitol, and sucrose.

 Leukocyte esterase

• False-positive results may occur in specimens contaminated by vaginal secretions (e.g., heavy menstrual dis charge, Trichomonas infection, parasites) that contain WBCs.

• False-negative results may occur in specimens containing high levels of protein or ascorbic acid.

Ketones

• Special diets (carbohydrate-free, high-protein, high-fat) may cause ketonuria.

* Drugs that may cause false-positive results include bromosulfophthalein, isoniazid, isopropanol, levodopa, paraldehyde, phenazopyridine, and phenolsulfonphthalein.

 Bilirubin and urobilinogen

• Bilirubin is not stable in urine, especially when exposed to light.

• pH can affect urobilinogen levels. Alkaline urine indicates higher levels; acidic urine may show lower levels.

* Phenazopyridine colors the urine orange. This may give the false impression that the patient has jaundice.

* Cholestatic drugs may decrease urobilinogen levels.

* Antibiotics reduce intestinal flora, which in turn decreases urobilinogen levels.

 Crystals

• Radiographic contrast media may cause urinary crystals.

WBCs

• Vaginal discharge may contaminate the urine specimen and factitiously cause WBCs in the urine.

RBCs

• Strenuous physical exercise may cause RBC casts.

• Traumatic urethral catheterization may cause RBCs.

• Overaggressive anticoagulant therapy or bleeding disorders tend to cause RBCs in the urine without concomitant disease.

Abnormal findings

Appearance and color

- Bacteria  -Pus  -Red blood cells  -Certain foods (e.g., beets, carrots)

- Drug therapy (see Table 1)  -Pathologic conditions (e.g., bleeding from the kidney)

- Dehydration  -Overhydration -Diabetes insipidus -Fever -Excessive sweating

-Jaundice

Odor

- Infection – Ketonuria -  UTI  - Rectal fistula - Maple syrup urine disease

- Phenylketonuria  -Hepatic failure

pH Increased levels

- Respiratory alkalosis -Metabolic alkalosis -Urea-splitting bacteria -Vegetarian diet -Renal failure with inability to form ammonia -Gastric suction -Vomiting -Diuretic therapy -Renal tubular acidosis -UTI

pH Decreased levels

-Metabolic acidosis -Diabetes mellitus -Diarrhea -Starvation -Respiratory acidosis -Sleep -Pyrexia

Protein Increased levels

- Nephrotic syndrome -Diabetes mellitus -Multiple myeloma -Preeclampsia -Glomerulonephritis -Congestive heart failure -Malignant hypertension -Polycystic kidney disease -Diabetic glomerulosclerosis -Bladder tumor  - Amyloidosis - Systemic lupus erythematosus -Goodpasture syndrome -Renal vein thrombosis -Heavy-metal poisoning -Galactosemia -Bacterial pyelonephritis -Nephrotoxic drug therapy

Glucose Increased levels

- Diabetes mellitus -Pregnancy -Renal glycosuria -Hereditary defects in metabolism of other reducing substances (e.g., galactose, fructose, pentose) -Nephrotoxic chemicals (e.g., carbon monoxide, mercury, lead)

Specific gravity Increased levels

- Dehydration -Pituitary tumor or trauma that causes syndrome of inappropriate antidiuretic hormone (SIADH)

-Decrease in renal blood flow (as in heart failure, renal artery stenosis, or hypotension)  -Glycosuria and proteinuria  -Water restriction -Fever -Excessive sweating -Vomiting -Diarrhea -X-ray contrast dye

Specific gravity Decreased levels

- Overhydration - Diabetes insipidus -Renal failure -Diuresis -Hypothermia -Glomerulonephritis -Pyelonephritis

Leukocyte esterase: Possible UTI

Nitrites: Possible UTI

Ketones

- Uncontrolled diabetes mellitus -Starvation -Excessive aspirin ingestion -Ketoacidosis of alcoholism -Febrile illnesses in infants and children -Weight reduction diets -After anesthesia -Prolonged vomiting -Anorexia nervosa -Fasting -High-protein diets -Isopropanol ingestion -Dehydration

Crystals

- Renal stone formation  -Drug therapy  -UTI

Granular casts

- Acute tubular necrosis -UTI  -Glomerulonephritis -Pyelonephritis -Nephrosclerosis

- Chronic lead poisoning -Reaction after exercise -Stress -Renal transplant rejection

Fatty casts

- Nephrotic syndrome -Diabetic nephropathy - Glomerulonephritis -Chronic renal disease

Epithelial casts

- Glomerulonephritis -Eclampsia -Heavy-metal poisoning - Ethylene glycol intoxication -Acute renal allograft rejection

Waxy casts

- Chronic renal disease -Chronic renal failure -Diabetic nephropathy -Malignant hypertension  - Glomerulonephritis -Renal transplant rejection -Nephrotic syndrome

Hyaline casts

- Proteinuria -Fever -Strenuous exercise -Stress - Glomerulonephritis -Pyelonephritis -Congestive heart failure -Chronic renal failure

Red blood cells and casts

Increased RBC levels

- Glomerulonephritis -Interstitial nephritis -Acute tubular necrosis -Pyelonephritis -Renal trauma -Renal tumor -Renal stones -Cystitis -Prostatitis -Traumatic bladder catheterization

Increased RBC cast levels

- Glomerulonephritis -Subacute bacterial endocarditis -Renal infarct -Goodpasture syndrome -Vasculitis -Sickle cell anemia -Malignant hypertension -Systemic lupus erythematosus

White blood cells and casts

Increased WBC levels

- Bacterial infection in the urinary tract

Increased WBC cast levels

- Acute pyelonephritis -Glomerulonephritis -Lupus nephritis

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مواضيع ذات صلة

ultrasound of the thyroid (US Thyroid, Thyroid echogram, Thyroid sonogram)

zinc protoporphyrin (ZPP)

Laboratory Investigations of Ovarian Hormones

Zika virus (ZIKV)

d-xylose absorption test (Xylose tolerance test)

wound culture and sensitivity (C&S)

white blood cell scan (WBC scan, Inflammatory scan)

white blood cell count and differential count (WBC and differential, Leukocyte count)

vitamin D (25-hydroxy vitamin D2 and D3 ; 1,25-dihydroxyvitamin D [1,25(OH)2 D])

Basal Hormone Measurements of Testis

vitamin B12 (Cyanocobalamin and methylmalonic acid [MMA])

virus testing