Physical properties

Volume

The kidneys produce about 200 liters of glomerlular filtrate per day. The cells of the nephron tubules reabsorb 99% of the filtrate leaving 1% to be excreted as urine. Urine output varies widely, but on average, adult urine output is 800 to 1200 ml of urine per/day (Tkacs N.C., 2021), at an average rate of approximately 25 to 30 ml/hr.

Children void smaller quantities than adults, but the total volume voided is greater than adults in proportion to their body size. The amount voided over any period is directly related to the individual's fluid intake, temperature, climatic conditions, and amount of perspiration.

Polyuria refers to an increase in the volume of excreted urine. Polyuria is a physiologic response to increased fluid intake, diuretic medications, hypothermia, nervousness or anxiety, large-volume intravenous fluid infusion, or disease conditions such as diabetes mellitus, diabetes insipidus, or renal disease. Oliguria is a term that refers to a decreased urinary output. Anuria refers to a total lack of urine production.

Clarity

• Normal: clear or translucent
• Abnormal: turbidity due to bacteria, blood clots, contrast media, a diet high in purine-rich foods, fecal contamination or material (i.e., gastrointestinal-bladder fistula), lipids such as chyluria (chylomicrons in the urine), lymph fluid, mucus, precipitation of cells (red blood cells (RBC), white blood cells (WBC), squamous and non-squamous epithelial cells), casts or crystals (calcium phosphate, calcium oxalate, uric acid), pyuria, semen, small calculi, talcum powder, vaginal creams or secretions, yeast or non-specific/normal

Color

The normal color of urine ranges from light yellow to dark amber, depending on the concentration of solutes in the urine. Urechrome is the pigment that gives urine its characteristic yellow color. Medications and foods can cause the urine to change color.

• Red or Pink:
  • Blood
  • Beets, blackberries, rhubarb
  • Rifampin
• Orange:
  • Medications: sulfasalazine (Azulfidine); phenazopyridine (Pyridium); some laxatives; and certain chemotherapy drugs
  • Medical conditions: orange urine can accompany hepatitis or bile duct obstruction. Dehydration can concentrate urine making it appear orange.
• Blue or green urine
  • Food dyes can cause green urine
  • Methylene blue, mitriptyline, indomethacin, propofol
  • Pseudomonas UTI can cause green urine
• Dark brown or cola-colored urine
  • Food - Eating large amounts of fava beans, rhubarb or aloe can cause dark brown urine.
  • Medications - A number of drugs can darken urine, including the antimalarial drugs chloroquine and primaquine, the antibiotics metronidazole (Flagyl) and nitrofurantoin (Furadantin), laxatives containing cascara or senna, and methocarbamol — a muscle relaxant.
  • Medical conditions - Some liver and kidney disorders and some urinary tract infections can turn urine dark brown.
  • Extreme exercise - Muscle injury from extreme exercise can result in pink or cola-colored urine and kidney damage (Mayo Clinic, N.D.).

Odor

Normally urine should only a mild ammonia scent. Dehydration is the most common cause of strong smelling urine. Dehydration cause the concentration of ammonia waste in the to increase, which increases the scent and darkens the color. Other benign causes of smelly urine odor might include: eating asparagus, vitamins, especially B2, and medications. 

Urine that has been standing for a period of time at room temperature has a distinct odor. After urine is voided from the bladder, bacteria split urea molecules in the urine into ammonia. If a freshly voided specimen has a foul odor, this may indicate that bacteria are converting urea to ammonia within the bladder, a sign of a urinary tract infection.

In some infants, metabolic abnormalities produced by genetic deficits can cause unusual urinary odors.

Foamy or frothy urine may result from protein in the urine, which can signal a kidney disorder.

Reference

Mayo Clinic (N.D.) Patient Care & Health Information > Disease & Conditions - Urine color. Accessed 7/30/21 from https://www.mayoclinic.org/diseases-conditions/urine-color/symptoms-causes/syc-20367333

Tkacs, N. C., Herrmann, L. L., & Johnson, R. L. (2021). Advanced physiology and pathophysiology: Essentials for clinical practice. Springer Publishing Company.

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