Page 473 - Concise Pathology for Exam Preparation ( PDFDrive )

458 SECTION II Diseases of Organ Systems

Q. Enumerate and describe the different methods of collection of
urine.
Ans. Collection of urine
• Urine should be collected in a clean and dry container.
• It should be freshly voided (collected within 2 h of voiding).
• If analysis is delayed, specimens should be refrigerated or preserved.
• The desired volume of urine to be collected is 50–60 mL as the minimum quality of
urine required for estimation of specific gravity by a urinometer is 30 mL.
Types of urinary specimens:
1. Voided specimens: Suitable for chemical and microscopic examinations.
(a) First morning specimen is best for proteins, nitrites, microscopic examination
and cytology (preferred because of large volume and concentrated urine).
(b) 24-h urine specimen is optimum for quantitative protein/sugar/urobilinogen
estimation.
Method of collection: Patient is carefully instructed to empty bladder at 8 a.m. and
discard the urine. All subsequent samples are collected, including that at 8 a.m., the
following morning. Urine should be pooled and thoroughly mixed prior to analysis.
(c) Midstream sample is best for bacterial examination.
Method of collection: Using complete aseptic precautions, separate labia, expose
urethral orifice (labia kept separated throughout the collection), clean the area
surrounding the meatus with soap balls and then the meatus itself, allow the
initial stream of urine to drain and catch the subsequent midstream sample. In
males, glans is exposed, thoroughly cleaned with a mild antiseptic solution and
dried, foreskin retracted, midstream sample collected.
2. Catheterized specimens may be obtained by:
(a) Ureteric catheterization
(b) Urethral catheterization
Catheterized specimen is best for cytological examination as it is free of seminal fluid,
vaginal cells, inflammatory cells and microorganisms.

Q. Enumerate the different chemical and cytological preservatives
for urine.

Ans. Reliable results are obtained when a fresh specimen has been properly refrigerated
up to 48 h. Chemical or cytological preservatives should be added if the analysis is delayed
any further.

Chemical Preservatives

• Mineral acids/vitamin C lower pH
• Boric acid inhibits bacterial multiplication
• Benzoic acid, phenol, thymol, toluene, chloroform, formaldehyde and mercury com-
pounds prevent bacterial growth
• Sodium fluoride decreases glycolysis in cells and bacteria and is therefore used for glucose
estimation in a concentration of less than 0.5 g per 3–4 L urine.

Cytology Preservative
Equal volume of 50% alcohol.

Q. Write in detail on examination of a urine specimen.

Ans. Examination of a urinary specimen entails physical, chemical and microscopic
examination.

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