Urinalysis Introduction and Vascular Disease in the Kidney Flashcards
Urine: Physical Properties
- color
- turbidity
- specific gravity
- odor
Urine - Color
- Normal urine should be clear to pale yellow to amber due to urochrome pigment
- Abnormal color due to:
- Dark – Bilirubin, carrots, drugs, blood
- Pale – Dilutional (diabetes, increased fluids)
- RED - Beets, hemoglobin, myoglobin
- BLACK - Melanin
- YELLOW-GREEN – Biliverden, rhubarb
- BLUE-GREEN – Pseudomonas, drugs
- WHITE - Chyluria (lymph)
- RED-PURPLE - porphyria
Urine - Turbidity
– Various contaminants:
• Crystals, lipid, sperm, mucus, WBC’s, RBC’s, epithelial cells, fecal matter, bacteria, yeast
Urine - Specific Gravity
– Normal: between 1.015 – 1.025
– Increased SG
• Glucose, proteins, recent IVP, administrations of high molecular weight IV fluids
Urine - Odor
– Highly variable, affected by diet
– Distinct odors:
• Bacterial infections, ketone excretions, certain metabolic diseases
Chemical Examination of Urine
- Glucose
- Protein
- Blood
- pH
- Ketone Bodies
- Bilirubin
- Urobilinogen
- Nitrite
- Leukocyte
- Specific Gravity
pH
- pH has a wide range of acceptable values, usually falling between 4.5 and 8.0.
- Acidic urine is common in diabetes, starvation, and emphysema.
- Alkaline urine is common in vegetable diets and diuretic therapy.
- Respiratory or metabolic acidosis will lead to and acidic urine; respiratory or metabolic alkalosis will lead to an alkaline urine.
- Certain crystals will precipitate depending on the pH of the urine.
- Maintaining a certain pH may change the consequences of certain diseases, such as acid pH decreasing bacterial multiplication (often successfully done by drinking cranberry juice).
Protein
- Normal urine protein is usually less than 10 mg/dL.
- Benign increases in protein include orthostatic or postural proteinuria, exposure to cold, strenuous exercise, fever, dehydration, the acute phase of certain severe illnesses, and pregnancy.
- Increased protein however, may be one of the indicators of renal disease.
- Protein levels may be high in glomerular membrane damage, diseases with podocyte injury, altered tubular reabsorption, and with increased serum protein levels (i.e. Bence Jones protein in multiple myeloma).
- Microalbuminuria is detected early in renal disease due to diabetes.
Glucose
•Glucose will be increased in diabetes, impaired renal tubular absorption, CNS damage, thyroid disorders, pregnancy, and following high glucose content meals.
Ketones
•Ketones are increased in diabetes (and may be helpful in monitoring insulin dosage), starvation (including severe weight reduction diets), and with loss of carbohydrates from severe vomiting.
Blood
•Hematuria may be seen due to urinary tract calculi, glomerulonephritis, pyelonephritis, tumors of the kidney or urinary tract, trauma, chemical or drug exposures, thrombocytopenia, hemophilia, or following strenuous exercise.
Hemoglobin
•Hemoglobinuria (the presence of RBC breakdown products) may be seen following a hemolytic transfusion reaction, with hemolytic anemia, secondary to severe burns, associated with infections, or following strenuous exercise.
Myoglobin
•Myoglobin, or muscle protein, may be present in urine after muscle trauma, prolonged coma, convulsions, extensive exertion/exercise, or hyperthermia. Muscle wasting diseases may also present with increased urinary myoglobin.
Bilirubin
- Conjugated bilirubin, a degradation product of hemoglobin, may appear in the urine secondary to obstruction of bile ducts by calculi or carcinoma, carcinoma of the pancreas or biliary tract, or for other causes of damage to the integrity of the liver such as hepatitis or cirrhosis.
- Unconjugated bilirubin is not soluble in water and will not be seen in the urine in cases of uncomplicated hemolytic anemia.
Urobilnogen
•Increased urobilinogen may be seen in early liver disease, porphyrinuria, or with hemolytic disorders.
Nitrites
- Urinary nitrite constitutes a rapid screening test for urinary tract infections (UTIs) including cystitis and pyelonephritis, as it reflects the presence of bacteria which reduce nitrate to nitrite.
- They may also serve as a way to monitor effectiveness of antibiotic therapy or to monitor patients who are high-risk for recurring UTIs.
Leukocyte Esterase
- The presence of leukocyte esterase indicates the presence of leukocytes or fragments of leukocytes, and is a good sign that the patient has a UTI.
- Increased leukocyte esterase can also be seen in the absence of bacteria, such as following antibiotic therapy, or in inflammatory conditions not caused by infection.
- Leukocyte esterase test may be negative however in the presence of infection in someone immune compromised and unable to mount a significant white blood cell response.
Reducing Substances
- Reducing substances are increased in glycosuria, galactosuria, overt diabetes, and pentosuria.
- This is an inexpensive screening test for sick newborns and children suspected of having errors of carbohydrate metabolism.
- Positive samples that are negative for glucose should be further evaluated by carbohydrate chromatography.
Microscopic Examination of Urine
- Urine must be concentrated before examination
- 12 ml of fresh urine is spun at 400 to 500 RCF (relative centrifugal force) for five minutes
- Urine is decanted off, leaving 1 ml of concentrated sediment
- Sediment is re-suspended and examined on a glass slide under a microscope
Constituents of Normal Urine
Normal RBCs
Crenated RBCs
Uric Acid
Calcium Oxylate