Urinalysis (Urine Chemistry) Ishmael Kunateh Alhassan Field Epidemiologist Medical Laboratory Scientist Head of Microbiology Unit (WMHL) Urine What How it is formed Composition Urine What • Urine is a waste product that is produced by the kidneys in their process of cleaning the blood and is made up of water and dissolved waste products • Pale yellow and clear How it is formed Composition Urine What • Urine is a waste product that is produced by the kidneys in their process of cleaning the blood and is made up of water and dissolved waste products • Pale yellow and clear How it is formed Composition Urine What • Urine is a waste product that is produced by the kidneys in their process of cleaning the blood and is made up of water and dissolved waste products • Pale yellow and clear How it is formed Composition • Water: 95% • Urea: 2.6% • Uric acid (0.3%) • Chloride • Sodium • Potassium • Creatinine • Other dissolved ions • inorganic and organic compounds (proteins, hormone, metabolites) Urinalysis • Laboratory analysis of urine samples to make clinical inferences and for diagnostic purposes • Analysing urine was actually the beginning of laboratory medicine • Urine specimen is a readily available and easily collected • Urine contains information about most of the body’s major metabolic functions • Inexpensive laboratory tests • Sample types: random, early/first morning, midstream/clean catch, fasting, 2-hour postprandial, Timed/24hr urine • Sample integrity: delivered and tested within 2hr • else store between 2 – 8oC for <24hrs • 3 main components of urinalysis Macroscopy Urine Chemistry Microscopy Urinalysis • 3 main components of urinalysis Macroscopy Colour Appearance/ turbidity Urine Chemistry Microscopy Urinalysis • 3 main components of urinalysis Macroscopy Urine Chemistry PH Specific gravity Protein Blood Glucose Ketone Nitrite Bilirubin Urobilinogen Leukocytes Microscopy Urinalysis • 3 main components of urinalysis Macroscopy Urine Chemistry Microscopy Pus cell/WBCs Epithelial cells RBCs Yeast Parasites Crystals Casts Urinalysis • 3 main components of urinalysis Macroscopy Urine Chemistry Colour Appearance/ turbidity PH Specific gravity Protein Blood Glucose Ketone Nitrite Bilirubin Urobilinogen Leukocytes Microscopy Pus cell/WBCs Epithelial cells RBCs Yeast Parasites Crystals Casts Reagent Strip Testing • Chemical reactions ‘miniaturized’ • Required less urine • Test results within minutes • Easy to perform • Results may be qualitative (positive or negative) or semi-quantitative (trace, 1+, 2+, 3+, 4+) 11 Urine Chemistry - pH • Urine pH reflects acid-base status of body • Normal: ranges from 4.5 – 8.0 • First morning void: acidic • Physiologically impossible: <4.5 >8.5 1. Urine not handled properly 2. Old urine 3. Treatment induced • Treatment protocol may require urine pH be maintained at a specific pH Urine Chemistry – Specific gravity • Evaluates the concentrating and diluting ability of the kidney • Density is related to the amount of substances (solutes) in solution • Increased density ~ increased solute in solution ~ hypertonic urine ~ concentrated urine • Decreased density ~ decreased solute in solution ~ hypotonic urine ~ dilute urine • Dependent upon hydration status • Majority of urines: 1.010 – 1.025 • SG of glomerular filtrate is believed to be around 1.007 (formerly 1.010) • Hyposthenuria: consistently low specific gravity (<1.007) – concentration problem, excessive fluid intake, pyelonephritis, hypertension, protein malnutrition, polydipsia, diabetes insipidus, diuretic medication, coffee, alcohol • Hypersthenuria: consistently high SG; can due to water deprivation, dehydration, proteinuria, glycosuria, eclampsia • Isosthenuria: fixed specific gravity of 1.010; can be due to poor tubular reabsorption Urine Chemistry – Protein • The protein that is found in urine comes from • Bloodstream • Urinary tract • Proteinuria can be an indicator of early renal disease (Microalbuminuria) • Classification of proteinuria • • • • Pre-renal – plasma related Renal: glomerular Renal: tubular Post-renal Urine Chemistry – Blood • Two forms found in urine • Intact RBC • Hemolyzed RBC • Positive reagent strip test result indicates the presence of: • red blood cells • hemoglobin or • myoglobin Urine Chemistry – Glucose • Almost all the glucose filtered by the glomerulus is reabsorbed in the PCT • Glucosuria can be caused by renal and non-renal disease • Pre-renal glycosuria: plasma glucose level exceeds renal threshold (diabetes mellitus) • Renal glycosuria: plasma glucose level below renal threshold, but tubules cannot reabsorb glucose back into bloodstream Urine Chemistry – Ketones • Ketones are intermediary products of fat metabolism • Formed when carbohydrate metabolism is compromised and body results to fat metabolism • Ketone bodies: Acetone, Acetoacetic acid and Beta-hydroxybutyric acid • Reasons for increased fat metabolism: • inability to metabolize carbohydrate (eg. in diabetes mellitus) • increased loss of carbohydrate from vomiting • inadequate intake of carbohydrate associated with starvation or malabsorption Urine Chemistry – Nitrite • Serves as rapid screening test for UTI • Some bacteria can reduce nitrate in urine to nitrite • Urine has to stay in bladder for about 4hrs; best to use first/early morning urine • Not intended to replace the urine culture as the primary test for diagnosing and monitoring bacterial infection Urine Chemistry – Bilirubin • Bilirubin, a highly pigmented yellow compound, is a degradation product of hemoglobin • Bilirubin in the urine can provide an early indication of liver disease • Conjugated bilirubin appears in the urine when: • the normal degradation cycle is disrupted by obstruction of the bile duct (e.g., gallstones or cancer) • the integrity of the liver is damaged, allowing leakage of conjugated bilirubin into the circulation Urine Chemistry – Urobilinogen • Intestinal bacteria convert conjugated bilirubin into urobilinogen and stercobilinogen • Some of the urobilinogen is reabsorbed from the intestine into the blood; and then to the kidney for excretion • Small amount of urobilinogen (less than 1 mg/dL) is normally found in the urine • Reported as Normal or Increased (1+, 2+, 3+) • Increased urine urobilinogen: liver disease and hemolytic disorders Urine Chemistry – Leukocytes • Detects the presence of esterase in the granulocytic WBCs (neutrophils, eosinophils, and basophils) and monocytes • Neutrophils most common type of WBC found in urine • Detects both intact and lysed WBCs • Esterases are also present in Trichomonas • Positive test indicates: • Bacterial and nonbacterial urinary tract infection • Inflammation of the urinary tract Summary • Urine chemistry results can give a good indication of metabolic, renal and urinary tract disorders • Urine chemistry alone can be requested when the full parameters of Urine R/E is not needed or cannot be carried out • Early/first morning urine sample still remains the best sample for urinalysis THANK YOU Any additions?
