Routine urine examination tells about the presence or absence of certain substances the glucose, proteins, ketones, nitrites, bilirubin which could be an indication of certain diseases like diabetes mellitus, jaundice, infection etc. Blood in urine could indicate infection, stones etc. Pus cells could indicate infection. Casts could indicate renal disease. Crystals like oxalate, urate etc. are seen following high dietary intake of food rich in these minerals. Culture of urine helps to isolate bacteria causing infection.
Routine examination is done by directly visualizing urine under the microscope and doing certain chemical tests on the urine sample which takes a few minutes. In culture, the urine is plated on culture media which provide nutrition for the bacteria to grow. After overnight incubation bacteria grow on the media and then are replated on media on which different antibiotic discs are put and again after overnight incubation we see which antibiotics are able to prevent the growth of the bacteria.
Morning sample of urine is the ideal sample for culture, but a sample can be collected at any time of the day after proper cleaning and washing the area with soap and water to prevent bacteria from the surrounding areas from entering the urine or this will give you erroneous result.
Urine sample should be brought to the lab as soon as possible (within 1-2 hours of collection) as the urine provides an excellent source of nutrition to the bacteria present and the bacteria multiply and will give a wrong result when tested after a longer time interval In case there is a delay the sample can be placed inside the refrigerator (not freezer)
Stool specimens should be delivered to the laboratory within few hour as the organisms die out quickly and will not be detected.