Urine is the filtration product of the blood, which, in turn, picks up toxins from around the system. Measurement of the toxicity and contents of urine gives a clear indication of the state of the body. In days gone by, simple examination by visual assessment, microscopy, measurement of density and even taste were of great advantage to the physician. Nowadays, computers have given practitioners insights into the very functioning of the body’s cells.
A basic urine analysis measures the acidity, water level, the presence of sugar or glucose and certain biochemical products manufactured by the liver. Measurement of these latter compounds – bilinogen and urobilinogen – is a simple noninvasive method of assessing the health of the liver. Basic analysis also includes checking for red and white blood cells and protein, none of which should be found in the urine because it is indicative of ill-health.
Ketones are breakdown products of fat metabolism. They show up in the urine if there is any suggestion of starvation or poor fat/sugar metabolism control.
Urine Chemistry pH 7.0
RBCs Not seen
Casts Not seen
Epithelial cells +
Crystals Not seen
CULTURE No bacterial growth
First morning urine samples are generally preferred for assessment of the body’s metabolism but for any suggestion of infection a mid-stream urine is preferred. This reduces the chances of contamination of a sample by bacteria that may have bred at the opening of the urethra and, in the male, elements of seminal fluid that may pass into a sample with the final contractions of the urethra. Such samples undergo what is known as culture, microscopy and sensitivity . The sample is looked at under a microscope and then a portion is placed in a laboratory dish containing a special medium that allows bacteria to grow. If any bacterial growth occurs it is known as a culture, and then different antibiotics are placed on the dish to see which ones kill the bugs. This technique allows physicians to assess which antibiotics a particular breed or strain of bacteria are resistant to and select out those that are effective in killing the bugs. A bacterium is said to be ‘sensitive’ to these agents.
A sample of any excretion or discharge may be collected either directly into a sample pot or using a swab. These are then provided to a laboratory or technician who will prepare them . Certain stains may be applied to colour particular bacterial agents or the presence of other compounds and a variety of technical assessments may be used.
Anything that is coughed up or spat out is collectively known as a sputum sample and certain skin samples may be taken by gently scraping the skin – known as skin scrapings. Other areas may be swabbed by a medical ‘ear bud’ and, as one bible for the junior doctor describes, ‘there is no body cavity that a sample cannot be taken from by using a long needle and a brave attitude’.
Biopsy is the sampling of a tissue for examination under a microscope or for some other test. Theoretically any part of the body can be biopsied, but the risk/benefit ratio has to be examined. Tissue biopsy from the skin, or needle-aspiration from a cyst can be done in the doctor’s surgery but other tissues need to be biopsied under anaesthetic. Local anaesthetic is used for muscle biopsy of organs that are more easily accessible with a long biopsy needle and an acceptable level of experience. General anaesthetic is required if brain tissue samples are required or if a suspicion of cancer is high, in which case a further procedure may be required wherein the tissue sample is sent to the pathologist immediately and a report produced swiftly to enable the surgeon to proceed with the operation if necessary. This is common in suspicious breast lumps during lumpectomy.
Biopsies are generally to be considered necessary because they can create a firm diagnosis and allow a treatment protocol to be accurately prescribed.