Urinalysis Flashcards
what is the urinary system composed of
- 2 x Kidneys
- 2 x Ureters
- Urinary bladder
- Urethra
what are functions of the urinary system
- Filter waste products
- Regulate ion levels in the plasma
- Regulate pH of blood
- Conserve nutrients
- Regulate blood volume
- Regulate red blood cell production
- Stores urine
- Excretes urine
describe structure of kidneys
Structure:
• Fibrous outer capsule
• Inner composed of: Cortex and Medulla
The Nephron - functional unit of the kidney (1x106/kidney)
3 main structures:
• Glomerulus- knot of porous capillaries
• Bowman’s capsule - 2 walled
• Renal Artery
Collecting capsule housing glomerulus – inner wall duct composed of podocytes which surround glomerulus and the spaces in these (filtration slits) Renal Tubules – composed of: • Proximal Convoluted Tubule • Loop of Henle • Distal Convoluted Tubule
the kidneys Filter blood and produce urine though 3 specific processes - describe
• Filtration of water (180 l/day) and dissolved substances out of the blood in the glomeruli and into Bowman’s capule
Nobody excretes 180l of urine/day because:
• Reabsorption ofwater(178l/day),glucose and sodium out of the kidney tubules back into the blood (prevents substances needed by the body from being lost in the urine)
• Secretion H+, K+, NH , and some drugs out 3 of the blood and into the kidney tubules, where they are eventually eliminated in the urine.
describe purpose of control of urine
Urine is a carefully regulated excreted bodily fluid containing cellular waste products.
Purpose of the control of urine:
• To eliminate cellular waste products
• To control the amount of water and chemicals in the body
The volume of urine we produce each day is a reflection of how much extracellular fluid and sodium our bodies have to spare
The kidney regulation of salt and water in our bodies is the most imp factor controlling urine volume
describe Control of Urine through hormones – Renin- Angiotensin-Aldosterone system
Purpose:
• Maintain osmotic pressure
• Maintain Arterial pressure
Low fluid volume - Renin is released to bloodstream by the kidney
Action : Begin to convert angiotensin to AngiotensinII which stimulates aldosterone and AVP
describe Control of Urine through hormones
Urine volume must be controlled precisely. The body’s main requirement is to maintain a balance of fluids and chemicals (especially sodium) that flow throughout the system.
2 glands regulate fluid balance:
• Adrenal gland – aldesterone – controls kidneys conservation of Na+ and excretion of K+
• Pituitary gland – arginine vasopressin (AVP/ADH) – released in response to Na+ concentration in the body to help the body retain fluid
Why analyse urine content
Changes in the composition of urine can reveal diseases that have gone unnoticed because of the lack of signs and symptoms. E.g. Diabetes mellitus, Glomerulonephritis, chronic UTIs.
Urine can be obtained relatively easily, “urine analysis” was one of the first laboratory tests performed and related to diseases.
• General evaluation of health
• To diagnose diseases and disorders of the kidney and urinary tract
• To diagnose systemic disease e.g. Diabetes mellitus
describe creatine
Creatinine is non-toxic breakdown product of muscle that doesn’t vary much with diet or physical activity. It is removed from the blood only by the kidneys
Creatinine levels are a good evaluation of kidney function. Serum up, urine down = impaired kidney function.
how do we analyse urine
Gross exam
- colour
- turbidity
- odour
Dipstick
- pH
- protein
- blood
- glucose
- ketones
- leukocytes
- nitrite
- urobilinogen
Microscopic
- cells
- casts
- bacteria
- yeast
- parasites
- crystals
- artifcatcts
describe Urine Analysis – Biochemical Analysis Specific Gravity
Semi-quantitive measure of urine density/ concentration i.e. Ability of the kidney to concentrate or dilute the urine
Although dipsticks measure this but approx and most labs use refractometers
Normal range 1.002-1.035 with normal kidney function
Low = high fluid intake
Over 1.035 = contaminated sample or high glucose
If 12h without food or drink does not increase > 1.022 indicates renal impairment or nephrogenic diabetes insipidus
describe Urine Analysis – Biochemical Analysis pH (concentration of H+ ions)
In blood pH is under tight regulation pH 7.35-7.45
H+ produced by metabolism and regulated by:
• Lungs –expulsion of CO2 (short term)
• Buffering (short term)
• Regulation in the kidneys
We produce about 60mmol H + each day which without these regulatory mechanisms would increase the acidity of ECF by 4 fold
Urine has a wide range of pH from 4.5-8 but is usually acidic due to expulsion of H +
Alkaline urine can point to UTIs where urea-splitting bacteria are active.
describe Urine Analysis – Biochemical Analysis H+ excretion in the kidneys
H+ that has been buffered by HCO3- must be excreted by the kidneys
This serves to reclaim HCO3- and then to regenerate any that has been lost in the buffering process
H+ in the urine must be buffered to compensate for the high levels of H +
Phosphate and ammonium are the buffers responsible for this
describe Urine Analysis – Biochemical Analysis acid/base balance in kidney
H+ is produced from CO2 and H2O
H + dependent on how much CO2 is present and
concentration of HCO3-
So adding H +, removing HCO3- or increased pCO2 will cause an increase in H+
Removing H +, adding HCO3- or decreasing pCO2 will cause a decrease in H +
Metabolic acid-base disorders caused by a change in [HCO3-] Eg Diabetes or duodenal fistula
The body aims to maintain a steady state but where any part of this is compromised then the body tries to compensate:
• Where lung function is compromised then the body tries to compensate by increasing H+ excretion by the kidneys – slow
• Where kidney function is compromised then the lung will compensate - fast
describe Urine Analysis – Biochemical Analysis acid-base balance - ketones
ketones might be produced and lead to ketoacidosis under the following circumstances:
• Uncontrolled Diabetes Mellitus
• Pregnancy
• Low carbohydrate diet
• Starvation
All lead to production of acetoacetate and b-hydroxybutyric acid What would be the bodies compensatory mechanism for this?
Hypervention– increased H+ stimulates respiration
