Chapter stool analysis and using microscpic

this chapter is about stool analysis and how to anaylse viewfeuses. it gives overview of stool analysis, using microscopic and chemical analysis
this chapter is about stool analysis and how to anaylse viewfeuses. it gives overview of stool analysis, using microscopic and chemical analysis
this chapter is about stool analysis and how to anaylse viewfeuses. it gives overview of stool analysis, using microscopic and chemical analysis

1. Chapter four Collection and Preservation of Urine Specimen

2. Objectives It is expected that the information presented in this chapter will enable the student to: Identfy factors affecting the quality of a specimen. List the basic rules of urine collection. Describe types of urine specimens. Identify the commonly used preservatives and know the advantages and disadvantages of their use.

3. Collection of Urine Specimen In order to make Urinalysis reliable the urine must be properly collected. Improper collection may invalidate the results of the laboratory procedures, no matter how carefully and skillfully the tests are performed.

4. Urine Containers There are many types of containers used for collecting urine. Before specimens are collected, the containers must be cleaned and thoroughly dried. Disposable containers of plastic or coated paper are available in many sizes and are provided with lids to reduce bacterial and other types of contamination.

5. Special polyethylene bags are available for collection of urine from infants and children who are not toilet trained. URIN-TEK disposable collection system is available for use in collecting, storing, transporting, and testing specimens of urine. The system consists of a flat-bottomed paper collection cup, a 15 ml plastic tube with a plastic snap-cap and self-adhesive identification label.

6. Methods of Obtaining Specimens A freshly voided urine specimen is adequate for most urinalysis except the microbiological culture. The patient should be instructed to void directly into a clean, dry container, or a clean, dry bedpan so that the specimen can be transferred to an appropriate container. Specimens from infants and young children can be collected in a disposable collection apparatus. If a urine specimen is likely to be contaminated with vaginal discharge or menstrual blood, this period has to be avoided and the patient must be informed to bring a clean-voided specimen. All specimens should be immediately covered and taken to the laboratory.

7. Second-voided Specimen - In this case first morning specimen is discarded and the second specimen is collected and tested. Such type of specimen is good for: Reflection of blood glucose. Keeping of formed elements intact.

8. Procedure for Collection of 24 hour Urine Specimen

9. Sources of Errors in the Collection of Urine Bacteriologically or chemically contaminated specimen. Wrong type/amount of preservative. Partial loss of specimen or inclusion of two-morning specimen in the 24 hr collection. Inadequate mixing of specimen before examination. Careless measuring of the 24 hr volume.

10. Preservation of Urine Specimen Urine should be examined immeditely as much as possible after it is passed, because some urinary components are unstable. If urine specimen can not be examined immediately, it must be refrigerated or preserved by using different chemical presevatives . The maximum time that urinary contents to be maintained in urine specimen is one hour.Long standing of urine at room temperature can cause : Growth of bacteia Break down of urea to ammonia by bacteria leading to an increase in the pH of the urine and this may cause the precipitation of calcium and phosphates. Oxidation of urobilingen to urobilin . Distruction of glucose by bacteria. Lysis of RBCs, WBCs and casts.

11. Some Methods of Preservation, and their Advantages and Disadvantages Methods Advantages Disadvantages Refregeration (2-6 o C ) No chemical Interference Use for a short period of time (3-6 hours). For prolonged periods additonal preservatives must be used Freezing For specimen transport May destroy formed elements Toluene (Till it forms thin layer over the urine) Preserves acetone, Reducing Substances, protein Flammable Thymole ( small crystal 5 mm diametre /100ml urine) Preserves most consitiuents Can cause false positves for proteins Chloroform (1 tablet/60 ml urine) Preserves urine aldosterole level Settles to the bottom of the urine containers Formaldehyde (1 drop/30 ml urine) Preserves formed elements Interfers with glucose evaluation HCL (1 drop/15 ml urine) Stablizes steroides, catecolamines Formed elements are destroyed, Boric acid Preserves chemicals and formed elements Precipitate uric acid Sodium Carbonate Preserves porphyrines and urobilinogen Interfers with other urine constituents