History:

Early in the history of medicine, urine played an important part in the physicians diagnostic and prognostic kit. At first, uroscopy or the diagnostic analysis of urine, was achieved mostly by inspection, and aromatic interpretation. Doctors would ‘prognosticate’ over their patients urine specimens which, to save time for a busy doctor, could be mixed together for batch diagnoses and even sent for examination without the patient being present at all (an early example of tele-medicine?).

Of course it didn’t take long for the earliest medical equipment industry to see a niche market here. In the late 16th century a scientist by the name of Leonhardt Thurneiser (130-1595) considered that urine collected important information on the functioning of the body, picking up particles from all parts as it flowed through it. In order to interpret this information a device known as an ‘anatomical furnace’ was produced to boil the urine. Fumes and splatterings would erupt from the furnace, adhering to an external surface of the device corresponding to the anatomical ailment or the ‘locus morbi’.

For this a cylindrical vessel divided along its length into 24 equal parts…it is juxtaposed to the figure of a man exhibiting the same proportions. This vessel is used for the distillation of urine in a tripartite furnace.
With this equipment, all the chemical anatomy of a man can be studied. The urine represents “spagyrical” and anatomical man hidden in his own urine….humours or vapours ascend from that part which corresponds to the site of the human heart towards the anterior part of the vessel, the disease is due to too much joy; if to the posterior part, to sadness; if to the apex, to wrath (cholera); if to the lower part to fright etc.
If the humour at the first distillation is tinged with many different colours such as blue, yellow, green, it indicates that the uterus is ‘infected’ by sperms….

Today urinalysis can be performed manually with a dipstick or via an automated machine.
Here are a few pointers on urinalysis interpretation:

Urinalysis:

  1. ALWAYS wear gloves whilst messing about with another persons pee.
    Eye protection is a pretty good idea too. Those dipsticks make a pretty good catapult for drops of eyeball-seeking urine.
  2. Immerse the dipstick completely in the specimen of fresh urine. Withdraw immediately, drawing or gently tapping edge along rim of container to remove excess.
  3. Take your time. Some of the reactions can take up to 2 minutes to cook. Many nurses simply dip, pause, read; potentially missing abnormal results.

Smell:

The normal smell of urine can be described as urinoid.
Other smells of interest include:

  • Faecal smell: gastrointestinal-bladder fistula
  • Fruity or sweet smell: diabetic ketoacidosis
  • Smell of ammonia: alkaline fermentation.
  • Smell of asparagus: um…er….eating a lot of asparagus.

Colour:

Normal urine colour is often described as straw, yellow or amber.This colour may be altered by medications, food sources or disease.
Vitamin tablets often result in a bright yellow urine, as does the presence of bilirubin (a bile pigment).
Red urine may be due to blood, haemoglobin, or beetroot.
Iron supplements may cause a dark brown specimen, as might amounts of prophobilin or urobilin (a chemical produced in the intestines)

Normal urine is also transparent. Turbid or cloudy urine may result from infection the presence of blood cells, bacteria or yeast (eg Candida).
A foamy urine may indicate either the presence of glucose or protien.

Leukocytes:

Detects white cells in the urine (pyuria) which is associated with urinary tract infection.

Nitrites:

Nitrites are formed by the breakdown of urinary nitrates. This us usually caused by Gram-negative and some Gram-positive bacteria.
So the presence of nitrites suggests bacterial infection such as E.coli, Staphylococcus and Klebsiella.
Commonly found during a urinary tract infection.

Urobilinogen:

Normally present in the urine in small quantity. Less than 1% of urobilinogen is passed by the kidneys the remainder is excreted in the faeces or transported back to the liver and converted into bile.

Raised levels may be due to:

  • Cirrhosis
  • Hepatitis
  • Hepatic necrosis
  • Haemolytic and pernicious anaemia
  • Malaria

Protein:

This is measuring the amount of albumin in the urine. Normally there should be no detectable quantities.
Elevated protein levels are known as proteinuria. Albumin is one of the smaller protiens, and if the kidneys begin to dysfuncion it may show an early sign of kidney disease.

Other conditions which may lead to protein in the urine include:

  • Injury to the urinary tract, bladder or urethra
  • Inflammation, malignancies.
  • Multiple myeloma.

pH (that’s pee-H not ffff-H):

Measures the hydrogen ion concentration of the urine.
It is important that a fresh sample be used as urine becomes more alkaline over time as bacteria convert urea to ammonia (which is very alkaline).
Urine is normally acidic but its normal pH ranges from 4.5 to 8.

Low pH (acidic):

  • Foods such as acidic fruits (cranberries) can lower the pH, as can high a high protein diet.
  • As urine generally reflects the blood pH, metabolic or respiratory acidosis can make it more acidic.
  • Other causes of acidic urine include diabetes, diarrhoea and starvation.

High pH (alkaline):

  • Low carb or vegetarian diet
  • May be associated with renal calculi.
  • Respiratory or metabolic alkalosis
  • Urinary tract infection

Haematuria:

Classified as microscopic or macroscopic. Microscopic means that the blood is not visible with the naked eye.
Blood may be present in the urine following trauma, smoking, infection, renal calculi or strenuous exercise.

It may also be present with:

  • Urinary tract infections.
  • Damage to the glomerulas or tumours which erode the urinary tract.
  • Acute tubular necrosis.
  • Traumatic catheterization.
  • Damage caused by the passage of kidney stones.
  • Contamination from the vagina during menstruation.

The presence of myoglobin (myoglobinuria) after muscle injury will also cause the reagent strip to indicate blood.

Specific Gravity:

The specific gravity (SG) of urine signifies the concentration of dissolved solutes and reflects the effectiveness of the renal tubules to concentrate it ( when the body needs to conserve fluid). If there were no solutes present the urines SG would be 1.000, the same as pure water.
The SG of urine is around 1.010 but can vary greatly:

Decreased SG may be due to:

  • Excessive fluid intake (oral or IV fluids)
  • Renal failure
  • Acute golmerulonephritis, pyelonephritis, acute tubular necrosis
  • Diabetes insipidus

Increased SG may be due to:

  • Dehydration due to poor fluid intake, vomiting or diarrhoea
  • Heart failure
  • Liver failure
  • Inappropriate antidiuretic hormone secretion

It also reflects a high solute concentration which may be from glucose (diabetes or IV glucose) or protein.

Ketones:

Not normally found in the urine, ketones are produced during fat metabolism.
Presence of ketones may indicate:

  • diabetes
  • alcoholism
  • eclampsia
  • a state of starvation
  • pregnancy

Bilirubin:

Produced as a by-product during the degradation of RBC in the liver and normally excreted in the bile. Once in the intestine it is excreted in the faeces (as stercobilin) or by the kidneys (as urobilinogen).
Presence of bilirubin in the urine may therefore indicate:

  • liver disease
  • biliary tract infection
  • pancreatic causes of obstructive jaundice.

Glucose:

Glucose is not normally present in the urine.
Once the level of glucose in the blood reaches a ‘renal threshold’ the kidneys begin to excrete it into the urine in an attempt to decrease the blood concentration. So high blood concentrations lead to glucosuria, as does conditions that may reduce this renal threshold.

  • Diabetes
  • Liver disease
  • Medications such as tetracycline, lithium, penicillin, cephalosporins
  • Pregnancy.

Reference:

Urine Dipstick Analysis (patient.co.uk)

Urinalysis (Life in the Fast Lane)

Urinalysis (enotes.com)

11 Responses to “Urinalysis for dummies.”

  1. I just read about an iPhone app called uChek that the FDA is investigating.
    uChek seems to be basically just reading the strips from the phone camera, using a light box as an attachment to keep the strip in and the phone over. I am not sure how accurate it is, but they seem to have compared it against the lab method. Will be interested to see how FDA takes these apps – for now, it is available on the App Store.

  2. I am sorry, but the photo above shows incorrect position of the test strip against the color chart on the Multistix bottle. It must be across the rows for each analyte, and not along the pads of the same row.
    Read times for each test pad are critical.

  3. what could cause diluted if a person only took in minimal fluid ie one cup coffee and approx6oz water

  4. If my memory serves me correctly, large amounts of protein during pregnancy, along with a few other sx (headache etc) can be indicative of pre-eclampsia… not good. if the pt is seizing, then you have eclampsia. Protein becomes redundant then, as you have bigger fish to fry

  5. Thank you. Watta great site.

  6. People are misdiagnosed every day. I took care of a patient who had starved herself. Her ketones were high, her glucose was high. She said ‘WOO-HOO” she was starving herself. She didn’t know that she was pregnant.

  7. mmm asparagus urine, unmistakeable!

  8. Yes, how things have changed. When I first started my training in 1975 we used a hydrometer, then came the strips, then came the computerised urine analyzer that gives a print out. This came in really handy as my eyes are not what they used to be.

  9. I’d be lying if I said impactednurse isn’t slowly and surely replacing all my textbooks. (:

  10. Another cause for a change in urine colour….
    Propofol is known to cause urine to have a dark green colour. Once the patient is off the propofol infusion, the urine should return to “normal” colour.

  11. Yay! Way way helpful… Thanks for this!

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