#separator:tab #html:false What is Specific Gravity?- A measurement of urine concentration (The proportion of solutes to water) - Higher Specific Gracity, the More concentrated the urine In normal urine, what are the two most prevalent solutes?1. Urea 2. NaCl What does the concentration of the urine depend on?- The amount of water in which the solutes are dissolved Does the number of solutes excreted in urine usually vary?- Solutes does not vary significantly - Therefore concentration depends on amount of water soltes are dissolved in. What is Osmolality?- A more accurate measurement of urine concentration than specific gravity - Not usually determined as part of routine urinalysis What is the normal range of specific gravity of a random urine?1.003-1.035 Why is the range of specific gravity quite wide?- Individuals' fluid intake can vary throughout the day - Tubules will adjust the volume of water reabsorbed depending on the need to conserve water. How does fluid intake affect water reabsorption?Greater Fluid IntakeLess Water ReabsorbedMore water excretedUrine more diluteLess Fluid IntakeMore Water ReabsorbedLess water excretedUrine more concentrated What are 4 cuases of a decreased Specific Gravity (SG) or Osmolality?1. Increase Ingestion of Fluid 2. Diabete Insipidus 3. Renal tubular damage 4. Diuretics What are 4 causes of High Specific Gravity (SG) or Osmolality?1. Dehydration 2. Glycosuria (glucose in the urine) 3. Proteinuria 4. Radiographic contrast media - Found in urine of patients who have recently had radiographic IV contrast What organ concentrates urine?- Kidney What are the 2 ways of measuring Specific Gravity?1. Reagent Test Strip 2. Refractometer Principle How does a Reagent Test Strip measure Specific Gravity?"- Measures using ions in urine - Concentration of ions affects the dissociation of hydrogen ions from treated ""polyelectrolytes"" on the strip. - Colour change proportional to the ionic concentration of the urine" What may cause a difference between measuring Specific Gravity using the Reagent Test Strip and the Refractometer Principle?- Reagent Test Strip measures ionic solutes, non-ionic solutes (e.g. glucose) cannot be measured, this causes the result to be slightly lower than on a refractometer. How does the Refractometer Principle work?- Light rays pass through a drop of urine and are slowed and bent. - Greater the concentration the more the slowing and bending and higher up the Specific gravity scale they are projected. - Read to 3 decimals and is where the light-dark interface intersects the scale. Based on the limits of a Reagent Strip to measure Specific Gravity, when should a refractometer be used to confirm accurate measurement?- When SG is <1.005 or >1.030 What should be done if Specific Gravity is beyond the scale on a Refractometer?- Dilute using distilled water and reread the SG - Multiply the decimal value by the dilution factor to obtain the undiluted urine SG What is the acceptable temperature range for a sample to be read on a Refractometer?15C to 37C Therefore refrigerated samples must be allowed to warm prior to measuring the specific gravity On a reagent strip, what are the two indicators used and impregnated in the reagent strip?- Methyl red - Bromothymol blue What is the upper limit of Red Blood Cells in normal urine?2-5/HPF (2 to 5 per High Power field) What is an increased number of RBCs in urine called?Hematuria When red blood cells are accompanied by red blood cell casts, what is this and what is the likely source?Called: Hematuria Likely Source: Renal Where is the likely source when there is increased red blood cells in the absence of red blood cell casts? What is this called?Source: Urinary tract other than the kidney Called: Hematuria What 2 factors of a urine can affect the appearance of red blood cells?1. Osmotic Pressure (OP) 2. pH of the urine What would happen to Red Blood Cells if the osmotic pressure is high?Red Blood Cells will appear Crenated How would Red Blood Cells appear if osmotic pressure is low?Red Blood Cells will be swollen or lysed How would Red Blood Cells appear if the pH of the urine is very alkaline?Red Blood Cells will be swollen or lysed "What are ""Ghost cells""?"When lysing occurs, the microscopic examination may show the empty red blood cell membranes which are difficult to see What are the empty red blood cell membranes after lysing occurs which are difficult to see during a microscopic examination called?"""Ghost Cells""" List the 5 conditions that require a microscopic analysis on a specimen if present?1. Sample is Cloudy 2. Blood 3. Leukocytes 4. Nitrites 5. Protein If a specimen has less than the optimum volume what is the general protocol?A Comment should be added to the microscopic report to indicate taht the evaluation was done on a smaller than normal volume. What is the formula for Relative Centrifugal Force (RCF)?RCG(g) = 1.118*10^-5 * Radius in cm * (rpm)^2 At what g for 5 minutes will allow an adequate sediment to form without disruption of the fragile formed elements?400-450g Before doing a microscopic examination, is the supernatant removed?Yes, supernatant is removed frmo the sediment so that all sediment volumes are consistent. Sediment may or may not be stained before as well. What kind of light must be used during a microscopic examination?Subdued light to provide adequate contrast What action should be continuously done while performing a microscopic examination?The Fine focus should be continuously adjusted to ensure that objects on a differnt focal plane are counted and identified. What magnification should a microscopic examination be performed on?Casts are counted on10x but identified on 40x. All other elements are counted or observed on 40x How many fields should be scanned during a microscopic examination? How are final counts deteremined?10 fields and final counts are an average of those fields To confirm the presence of RBCs, what should be checked?The blood portion of the reagent strip should be positive if there are at least 5-10 RBC/HPF What is the upper limit of leukocytes in normal urine?5-8/HPF How might leukocytes enter the urine of healthy individuals?Through diapedesis from the glomerular membrane or the tubular cells What is an increased number of leukocytes in urine called?Pyuria What is the most common type of leukocyte seen in urine?Neutrophil which can sometimes be identified by the multilobed nucleus What might occur in a healthy individual following strenuous exercise or stress?Slight pyuria along with proteinuria Hyaline or granular casts may also be observed What is Pyuria associated with?An inflammatory process in or adjacent to the urinary tract When is acute infection of the urinary tract suggested?When 50 or more leukocytes per HPF are seen. Especially when they occur in clumps. When 50 or more leukocytes per HPF are seen, especially when they occur in clumps, what is suggested?Acute infection of the urinary tract