Urinalysis Flashcards
Why does the volume & colour of urine produced by the kidney vary so much?
- varies concentration of irony components according to need to conserve water
- darker color (dehydrated)
- lighter colour (hydrated)
- done via ADH (pituitary hormone) which promotes water reabsorption into the blood in the distal tubule
Why does urine always contain urea
- urea = product of broken down amino acids from proteins
- body only uses amount of Protein needed -> rest is broken down
= body constantly breaking down protein & replacing with others -> urine always contains urea
Why are glucose & amino acids reabsorbed in the nephron
- small enough to be filtered from blood at nephron = enter kidney tubules
- body needs & reuses some substances -> special mechanisms evolved in proximal tubules = reabsorb substances from the blood
Why can’t the kidney just excrete the filtered plasma without adjusting its content?
- homeostasis would not be maintained
- water & solute levels constantly fluctuating according to environment
Interpretation of results:
Colour
Influenced by
- Chemical composition
- Urine concentration
- vitamin B = intensely yellow colour
- normal urine = clear
Interpretation of results:
Volume
- water intake
- 2 liters daily
Interpretation of results:
Specific gravity
(1.005-1.025)
- reflects ability of kidneys to concentrate urine
- higher sp = more concentrated urine
=> excretion of large amounts of salt or urea/ conservation of water by the kidney
Interpretation of results:
pH
(5 to 9)
- < 7= acidic — large component of meat in diet
- > 7 = basic — large component of plant-based material in diet & bacterial growth
Interpretation of results:
Glucose
(<30mg/dL)
- very small amounts excreted (reabsorbed in proximal convoluted tubule)
- normally -I’ve in urine
- positive result indicates more glucose in the blood being filtered than the kidney can reabsorb
Interpretation of results:
Protein
(<15mg/dL)
- very little protein normally present in the urine = not filtered in glomerulus (proteins too large to be filtered at the glomerulus filtration barrier)
- amino acids reabsorbed in proximal convoluted tubule
- normally: no protein in urine
(If protein):
1. Kidney disease
2. Strenuous exercise
Interpretation of results:
Blood
Positive test = positive for red blood cells OR haemoglobin
- either = abnormal
- test = positive even if no cells are visible under microscope
- blood:
- Trauma to renal tubule, ureter, bladder or urethra
Interpretation of results:
Ketones
- normal: no ketones detectable in urine
- ketones in blood= burning body fat for energy
- presence in urine:
- Ketoacidosis
- Fasting
- Strenuous exercise
- Pregnancy
- Metabolic disorder (I.e. diabetes)
Interpretation of results:
Bilirubin/ urobilinogin
- bilirubin = normally negative
- bilirubin & uro = breakdown of red blood cells & recycling of haemoglobin in body
1. Blood cells may be dying too rapidly
2. May be reduction in liver function required to recycle normal number of red blood cells
Interpretation of results:
Nitrite
- product of bacterial reduction of nitrate
- indicates presence of bacterial infection
- normal: no nitrite in urine as urine is sterile
- painful urination= typical of lower urinary tract (urethra and bladder) infections —> travel up to kidney if left untreated
- May be sexually transmitted
- antibiotics used to treat infections
- bacterial culture = important to guide antibiotic therapy
Interpretation of results:
Sediment
- common urine sediment = epithelial cells, blood cells, casts & crystals
- white blood cells suggest infection
- small no. Red cells may be present but sig no. Are not
- presence of crystals = increased risk of forming kidney stones
—> result from excess o slate in diet (nuts, dark green veggies)
—> made worse by high concentration/ high pH (causes oxalate to precipitate out of solution) - calcium oxalate stones = most common, but Utica acid and certain other minerals can precipitate out of urine
