Urine sampling and analysis

Abstract

PHOTOS 1-3: Urine samples are important diagnostic tools. Urine can be collected by free catch collection, manual compression of the urinary bladder, cystocentesis or catheterization. Cytological examination of urine can be used to diagnose several pathological conditions. The Sternheimer – Malbin stain is compounded of gentian violet and safranin and is used for the examination of urinary deposits. It is useful in the diagnosis of urinary tract infections and for the differentiation between pyelonephritis and cystitis. The Sternheimer – Malbin stain divides urinary leucocytes into two types of which the nuclei stain either dark reddish purple or pale blue. Cells with blue staining nuclei are characteristic of pyelonephritis. PHOTOS 4-5: Once urine has been collected it should be examined within 30 minutes. Delay of examination may allow the growth of contaminating bacteria and a change of urine pH. Delay in examination will also allow time for fragmentation and disruption of cells and loss of casts. If a delay is unavoidable the urine sample should be refrigerated. The urine sample is centrifuged and the pellet resuspended. A few drops of stain can be added. Staining of urine with Methylene blue or the Sternheimer – Malbin stain facilitates differential staining of cells and nuclei. A drop of the resulting fluid is placed on a clean glass slide and a coverslip is placed over it. Bright field microscopic evaluation of urine sediment is done with reduced illumination. The chemical dipstick analysis is performed on urine at room temperature before centrifugation. The colour reactions on the dipstick should be read within the specified time interval as these reactions are a function of time. PHOTO 6: The chemical dipstick analysis is performed on urine at room temperature before centrifugation. The colour reactions on the dipstick should be read within the specified time interval as these reactions are a function of time. The chemical reagent dipstick colour reactions are influenced by urine concentration and are subject to limitations. The pH is read immediately after dipping. The pH of urine is usually acidic. The dipstick measures protein, glucose, ketones, blood, bilirubin and urobilinogen in urine.

REFERENCES: PHOTOS 1-6: 1. Bovee, KC (ed) 1984, ‘Canine nephrology’, Harwal, Pennsylvania, pp. 240-241. 2. Harris, DM 1968, ‘The incidence and nature of pyuria in experimental murine pyelonephritis : a re-appraisal of the Sternheimer-Malbin stain’, The Journal of Pathology and Bacteriology, vol. 96, no.1, pp. 77-87. [http://onlinelibrary.wiley.com]. 3. Holt, PE 1994, ‘Color atlas and text of small animal urology’, Mosby- Wolfe, London, pp.34-43.