The appearance of nitrites in the urine is detected by a specific examination that can complement the diagnosis of urinary infection. These substances should not normally be found at any concentration in the urinary fluid. Your presence is abnormal.
The urine forms in the kidneys, from the blood leak. This filtering has the function of removing too many molecules that we do not use, excess water, and metabolism waste to the outside. Among the waste we have nitrates, and their transformation into the urinary duct results in nitrites. Let’s see how the process happens.
Why Do The Nitrites Appear in The Urine?
Nitrates enter the body when we eat them with meals. They are present in green leafy vegetables, such as spinach, as well as in some fruits and even in the drinking water of certain geographical areas. Beets and radishes are also sources of these molecules.
Most nitrates are absorbed through the intestinal mucosa and passed into the blood. From there, they go up to the tissues to form nitrosamines and participate in different metabolic processes. Some derivatives of nitrates are vasodilators, as mentioned in a publication of the Chilean Journal of Nutrition. That is, they help relax the walls of the blood vessels. Once they complete their biochemical cycle, they must be expelled. So they are filtered by the kidneys and excreted in the urine.
A small fraction of nitrates reach the large intestine, without being absorbed. There, in the colon, anaerobic reducing bacteria, such as Escherichia coli, transform them into nitrites. However, they will not appear in the urine but will be expelled with the stool. The nitrites we detect in the urine are nitrates that were transformed by bacteria present in the urinary ducts. That’s why they are considered a sign of infection.
Nitrites in the urine indirectly indicate that there are bacteria.
But nitrites don’t just exist when a bacteria intervenes. There are commonly used substances in the food industry that are mainly used to give more color to red meats. This is potassium nitrite and sodium nitrite, which also act as preservatives.
Which Bacteria Form Nitrites in The Urine?
The bacteria involved in the formation of urinary nitrites are not all. They must have the reduced capacity to carry out the transformation. In general, they are strict optional anaerobic or anaerobic microorganisms.
Different strains of Escherichia coli are responsible for this process. They do it within the digestive tract and urinary system.
Other bacteria involved include:
- Proteus spp.
- Klebsiella spp.
- Pseudomonas.
- Enterobacter spp.
How is The Nitrite Test Done in Your Urine?
The quickest and easiest way to value nitrites in the urine is with a reactive strip. It is a strip with different colors that can react when submerged in the liquid. The reaction causes a change of color. Then, this new tone is compared to a chromatic table that indicates the approximate concentration of nitrites.
1. Collection of The Sample
But first, there is the collection of the urinary sample. A bad technique at this point will ruin the result of reactive strips and could show false positives or false negatives. When collecting the urine sample, the first jet that comes out of the urethra should be ruled out. That one is removed from the toilet. The second jet or medium is the one we gather in a container.
If you get a sample that comes from several hours before without urinary, you will be more reliable. For example, in the morning, when you wake up. However, in the face of an emergency, the sample can be taken at the moment.
2. Use of Reactive Strip
Once the liquid is in your possession, the biochemist or doctor introduces a reactive strip. In general, the strips available do not measure only nitrites but also bring reagents for glucose, mats, proteins, and other substances. Ordinary reagents in urine are often decanted in pink when detected as positive. Still, the chromatic scale of each brand must always be corroborated.
It is worth clarifying that reactive strips only offer an approximate value of what they measure. That is, they do not have the accuracy of a urine culture to diagnose urinary infection, according to a publication in Rwanda Medical Journal.
When is The Nitrite Test Indicated in The Urine?
Some symptoms are characteristic of a urinary infection and that induce the suspicion of this condition. In these scenarios, your doctor may require a quick diagnosis to define whether or not you prescribe antibiotics. The uroculture denotes for sure whether there are bacteria in the urine, but usually takes several days. That is why reactive strips appear as the economic, fast, and simple option to apply.
Doctors suspect urinary infection when the following symptoms occur:
- Fever.
- Arrive when urinating.
- Dirth or difficulty urinating.
- Changes in urine coloring.
- Polaquiuria or imperative need to urinate at every time.
It is common for your doctor to be guided not only by nitrites in your urine. Reactive strips will also indicate whether or not there are white blood cells, whether there is glucose, urinary pH, and even density. Another option is to combine the nitrite test with a general urine test. This involves visualizing the liquid under the microscope, which will take the results for a few hours.
What if I Have Positive Nitrites in My Urine?
If the nitrite test in the urine gives a positive result, this indicates a high probability of bacteria in the urinary tract and infection. As this is an approximate and not accurate result, the performance of an uroculture cannot be excluded.
The doctor will define the way forward:
- Antibiotic treatment may be initiated and a sample for cultivation can be set aside. Then, when the result is there, the antibiotic plan of being positive will be completed or it will be suspended from being negative.
- A more specific result of the general urine test may be awaited to start the antibiotic if the symptoms are not clear or another disease is suspected.
- The observation could be maintained without medication if positive nitrites do not contradict other results of the reactive strip. For example, there are no white blood cells in your urine. Or if the symptoms are very mild and tangential to those of a urinary infection.
Treatment of infection will be based on the use of antibiotics. The most prescribed are amoxicillin, norfloxacin, ciprofloxacin, and nitrofurantoin. The decision will be made by the doctor.
Guidance But Not Final Examination
Although doctors may use only the result of the reactive strip to initiate antibiotic treatment, you should know that their decision is based on other factors. They also consider the symptoms for which you go to consult. Sometimes, the nitrite test in the urine is not enough for the professional. Therefore, you will be asked for a general crop or examination with a biochemist.
Don’t worry about those cases. The aim is to achieve the most precise possible outcome for appropriate treatment.
