78 - Nitrites in urine

KYJ 78 -  Nitrites on a urine test.

When we test urine using the colour coded dip stick there are many reagents that can indicate abnormality. One of the common illness to screen for is urinary tract infection (UTI).   This problem is most common in women and relates to the simple fact that a female urethra is much shorter than a male's.  It has been estimated that 50% of all women will experience a UTI at least once.

Bacteria and other flora can ascend the urethra and invade the bladder causing inflammation (cystitis) then, in severe cases, ascend the ureters, and infect the kidneys (pyelonephritis).

The most common organism is Escherichia coli or E.coli to his mates.  This is a gram negative bacteria that normally lives in the bowel and are often referred to as "Normal Flora".  They serve a good function of preventing "bad bacteria" proliferation and they manufacture Vit K.

Things turn nasty when they take leave from poo central, and migrate north to the sprinkle fields. Once invading the urethral meatus, the are usually flushed with every pee, but poor hydration, high sugar diet and other factors can provide the perfect environment to proliferate and cause inflammation.

As these bacteria multiply they attach to the bladder wall and secrete a gel that acts like a shield to hide from the immune system.  Here they proliferate and overwhelm the immune defence causing symptoms of stinging, burning, frequency, urgency and offensive urine odour.  Occasionally urine may be pink tinged, or cloudy in appearance.   In severe pyelonephritis, it can almost look like pea-soup.

Diagnosis is usually clinically based on the history and these symptoms, but urine testing for blood, especially leukocytes (white blood cells WBC), and Nitrites is all suggestive of UTI.

As inflammation sets in, bladder capillaries engorge and become permeable to white and red blood cells leaching into the bladder. In infections this proliferation serves to cause more immune fighting neutrophils, and phagocytes to fight the bacterial invasion. This clouds the urine and pus is produced as dead WBC and bacteria accumulate.

Bacteria like E. coli secrete a chemical waste called Nitrite during their proliferative stage, and this accumulation of nitrites in urine is always a strong indicator of UTI.   Long before leukocytes are seen on a dipstick test, nitrites will be present.

Occasionally the bacteria can turn the urine acidic which gives rise to the symptoms of stinging and burning during voiding.  If you encourage water intake this has a soothing and acid dilution effect, as well as assisting to flush the bacteria away.  Urinary alkalinisers are also effective for comfort, (Ural or Citravescent ) but don't kill the bacteria.

Treatment includes antibiotics, most commonly Trimethoprim taken once/day, at bedtime for 3 -7 days.

Trimethoprim is a bacteriostatic agent which doesn't kill E.coli, but prevents them from reproducing. They then die out or are flushed out.

Trimethoprim use is indiscriminate.  It sterilises the E.coli in the UTI, but also affects all your good E.coli in the gut serving their important function.  People on Trimethoprim, like other similar antibiotics should consider recolonising their gut simultaneously with a Probiotic (good bacteria) and /or a few tubs of yoghurt.