Lecture Notes: Basics of Urinalysis
Types of Urine Specimens
1. Random Specimen
- Collection Time: Any time of day.
- Common Usage: Most common for ER assessments.
- Disadvantages: Often dilute, low solute concentration, can miss pathological metabolites, diet affects results.
2. First Morning Specimen
- Collection Time: Upon arising from bed.
- Characteristics: More concentrated, lower pH, higher specific gravity.
- Advantages: Preferred for urinalysis, pregnancy testing, detecting UTIs, and diabetes.
- Limitations: Not feasible in emergency situations; can be collected for inpatients or with take-home instructions.
3. Postprandial Specimen
- Collection Time: Two hours after eating a meal.
- Usage: Detection of glycosuria (urine glucose) for diabetes diagnosis.
- Key Requirement: Patient must void before eating to ensure accuracy.
4. 24-hour Specimen
- Collection Time: Over a 24-hour period, starting after bladder is emptied.
- Purpose: Detect solutes with diurnal variation.
- Instructions: Ensure all urine is collected, kept on ice/refrigerated if necessary.
5. Catheterized Specimen
- Purpose: For microbiology testing, kidney function assessment when unable to void.
- Risks: Discomfort, infection risk from improper site cleaning.
6. Suprapubic Specimen
- Collection Method: Introduce needle into bladder.
- Usage: Collected under sterile conditions; suitable for microbiology; UTI source detection.
- Risks: Discomfort, infection risk.
7. Midstream Clean Catch Specimen
- Procedure: Clean urethra, start voiding, collect midstream.
- Advantages: Limits contamination, suitable for sediment evaluation and UTI detection.
Sources of Contamination in Urine Specimens
Menstrual Blood
- Impact: False positives for blood/protein tests, misleading results.
- Solution: Catheterization if heavy flow, midstream clean catch if light.
Vaginal Secretions
- Impact: Increased epithelial cells, obscured sediment components, mistaken for hyaline casts.
Fecal Material
- Identification: Undigested plant/animal tissues in urine.
- Causes: Improper bathroom technique, commode water substitution, vesicointestinal fistula.
- Characteristics: Brown color, many bacteria, fecal odor.
This concludes the discussion on urine specimens and potential contamination.