This measures the amount of free hydrogen ions excreted by the body. A pH of 7.0 is neutral. A pH of below 7.0 is said to be acidic and a pH of greater than 7.0 is said to be alkaline. The pH of a person’s urine varies with diet, medication, kidney disease and metabolic disease such as diabetes mellitus. Normal kidneys are capable of producing urine that can vary from pH of 4.5 to slightly more than 8.0.
Specific Gravity (SG)
The SG of the urine gives an indication of the amount of dissolved solids in the fluid. Thus, SG is high in diabetes mellitus due to the sugar in the urine. Physiologically, dehydration (reduced fluid intake) can also result in a high SG. SG is a convenient way of assessing the concentrating and diluting function of the kidney.
The presence of protein in the urine is an indication of renal disease as damage to the glomeruli (tubules in the kidney) increases their permeability and allows plasma protein to escape into the urine. A trace amount of protein may be present after strenuous exercise or severe emotional stress and is of no significance.
Urine Glucose (Sugar)
Glucose is not present in the urine of a healthy person. Routine screening of a urine sample for glucose helps in the detection of diabetes mellitus in patients who would otherwise have no symptoms of the disease.
Ketones formed in the liver are normally completely metabolised. Altered carbohydrate metabolism causes ketones to be detected in the urine. Ketones are usually present in urine of those who are on prolonged fasting or suffering from acute diabetes mellitus.
Bilirubin in the urine indicates the presence of liver disease or obstruction of the bile duct. Since bilirubin may often appear in the urine before other signs of liver dysfunction are apparent, it is a useful diagnostic test for liver disease.
Urine Blood (Red Blood Cell)
RBC is detected in the urine as haemoglobin from lysed and intact RBC. The presence of RBC gives an indication of urinary tract and kidney diseases. In females, menstrual blood can sometimes contaminate the urine sample.
Certain bacteria when in high concentration in urine metabolise nitrates to nitrite in urine. Hence, a positive nitrite test indicates significant number of bacteria in the urine. This may be indicative of a urinary tract infection especially if the urine sample is a clean-voided midstream sample collected in a sterile container.
Bilirubin, which is excreted by the liver into the bile, is converted by bacterial action in the intestinal tract to urobilinogen. Small amounts of the urobilinogen are normally excreted in the urine. Excretion is increased in any condition that gives rise to increase production of bilirubin, such as excessive breakdown of RBCs as in hemolytic anaemias or liver diseases such as hepatitis. Test for urinary urobilinogen serves as a useful guide in detecting and differentiating liver disease, haemolytic disease and biliary obstruction.