Complete Urinalysis and Host Defense Mechanisms

Complete Urinalysis

• Urinalysis is used to diagnose and monitor medical conditions, including UTIs, diabetes, kidney problems, pregnancy, and liver problems.
• Urine analysis may include physical properties (color, appearance, odor), chemical tests (pH, specific gravity, protein, glucose, ketones, bilirubin, urobilinogen, blood, nitrite, leukocyte esterase), and microscopic examination (red blood cells, white blood cells, casts, crystals, epithelial cells, bacteria).

Urinary Tract Host Defense Mechanisms

• Urine plays a crucial role in defending against pathogens.
• Acidic pH, high urine osmolality, and urinary inhibitors of bacterial adherence create an environment unfavorable to microbial growth.
• Competitive inhibitors of attachment to uroepithelial cells prevent pathogen colonization.
• The mechanical flushing action of urine flow helps remove pathogens.
• Mucosal immunity, including urothelial secretion of cytokines and chemokines, and mucopolysaccharide lining, further hinders bacterial penetration.
• Mucosal IgA and, in males, prostatic secretions (with bactericidal zinc) contribute to defense.

Risk Factors for UTI (Urinary Tract Infection)

• Iatrogenic factors
• Behavioral factors
• Anatomical/Physiological factors
• Genetic susceptibility of uroepithelial cells and mucus properties.

Important Aspects of Microbiological Examination of UTIs

• Pre-analytical stage, including urine collection techniques.
• Analytical stage of urine analysis.
• Post-analytical stage, including interpretation of lab results.

Methods of Urine Collection

• Random sample: collected at any time during the day, routine screening only.
• First voided sample: First morning specimen, most concentrated, preferred for pregnancy testing and bacterial cultures.
• Timed samples: collected at specific intervals, used for hormone and creatinine clearance tests.
• Clean-catch midstream sample: if urine is for bacterial culture or cytology.
• Suprapubic sample: for patients unable to follow instructions.
• Catheterized sample: a sterile flexible tube inserted into the bladder to withdraw urine.

Methods of Specimens Collection

• Mid-stream urine
• Adhesive bag
• Catheter sample
• Suprapubic aspiration
• Random specimens
• 24-hour collection

Urine Volume

• Normal volume for average adult: 1 to 2 Liters/day.
• Polyuria: output exceeding 2 Liters/day.
• Oliguria: output is less than 500 mL/day.
• Anuria: 0-100 mL/day.
• Low output may result from kidney disease, dehydration, circulatory shock, or prostate enlargement.

Chemical Analysis of Urine

• Chemical analysis uses reagent strips to determine various substances (pH, specific gravity, glucose, ketones, protein, blood, etc.) indicative of specific conditions.

Urine Microscopy

• Microscopic examination identifies various constituents found in urine like crystals, cells, bacteria, or other microorganisms.

Normal Urine Physical and Chemical Ranges

• Physical traits, like appearance (opaque or colorless), odor, and color are evaluated.
• Several chemical properties of urine, such as pH, glucose, specific gravity, protein, blood, ketone, and nitrite levels help distinguish normal from abnormal conditions.

Turbidity

• Physiological causes of turbidity include mucus, squamous epithelial cells, sperm, crystaluria, and fecal contamination.
• Pathological causes include white blood cells, red blood cells, bacteria, yeast, crystals, lymph fluids, and lipids.

Abnormalities in Urine Color

• Dark yellow urine may indicate decreased fluid intake, excessive sweating, or dehydration. Vitamin A can also contribute to orange tones.
• Colorless or pale yellow urine may be due to excessive fluid intake, diuretics, or diabetes. Alcohol ingestion can also contribute. Antibiotic use against E. coli can cause urine discoloration.

Parasite-Urinary Schistosomiasis

• Schistosoma haematobium is a parasitic infection causing urinary schistosomiasis.
• The parasite's life cycle includes stages in humans and snails, resulting in various symptoms.

Diagnostic Symptoms of Schistosomiasis (longer-term effects)

• Symptoms might be delayed, often occurring after several years of infection.
• Possible symptoms include discomfort in the stomach, swelling of the liver (hepatomegaly), presence of blood in the urine, pain or difficulties while urinating, blood in the feces, and miscarriage.

UTI Treatment

• Medications commonly used for simple UTIs include Trimethoprim/sulfamethoxazole, Fosfomycin, Nitrofurantoin, Cephalexin, and Ceftriaxone.
• In cases involving complications, like a kidney infection, Fluoroquinolones are administered if other treatments are ineffective.

Factors Affecting Zone of Inhibition

• Acidic pH in the medium can increase the zone size for certain antibiotics, while alkaline pH increases zone size for other antibiotics.
• Subjective factors, like errors in identifying the boundaries of the inhibition zones, media depth, plate size, and disc spacing can influence measured zone sizes.

Antibiotic Sensitivity and Resistance Pattern

• Results from antibiotic susceptibility testing show the effectiveness of various medications against specific bacterial species. Different bacterial species have different susceptibility patterns.

Formed Elements from the Genitourinary Tract

• Casts and epithelial cells may originate from the nephron, kidney, pelvis, ureters, bladder, urethra and prostate.
• Cells from blood, and various parts of the tract, may also be present in the urine.
• Chemical substances, including crystals, may be present in the urine.

Bacteria in Urine Analysis

• The presence of bacteria is common, often due to vaginal or urethral flora, which needs clinical interpretation relative to symptoms.
• Significant bacteriuria (over 100,000/mL) is commonly an indication of infection.

Microscopic Examination Techniques

• Techniques for microscopic examination of urine deposits:
• Centrifugation of a sufficient sample (5-10 mL).
• Removal of supernatant (upper liquid layer).
• Mixing of the deposited material with a few drops of urine.
• Application to slide, covering, and microscopic visualization at low power.

Types of Epithelial Cells

• Squamous epithelial cells, transitional epithelial cells, and renal tubular epithelial cells (RTE).
• Squamous epithelial cells may point to contamination, while RTE may signify kidney damage.

Microscopic Observations of Urine Sediment (Differentiating Lower and Upper UTIs)

• Lower UTIs are usually correlated with transitional epithelial cells originating from the bladder and urethra.
• Upper UTIs are more likely associated with renal tubular epithelial cells (RTE) that line the nephron. The presence of RTE in urine is practically a strong indication of renal damage.