During pregnancy and in the first years of a child’s life, urine tests are a routine examination that can reveal important information about health. One of the parameters often monitored is the presence of nitrites in urine, an indicator that can signal potential urinary tract infections.
In this article, we will explore what nitrites in urine are, their significance in pregnancy and in children, and when it is necessary to worry.
What are nitrites in urine?
Nitrites are chemical substances that normally should not be present in urine. Their detection during a urine test is often an indication of the presence of bacteria, particularly those belonging to the Enterobacteriaceae family (such as Escherichia coli), responsible for most urinary tract infections.
These bacteria transform nitrates (normally present in urine) into nitrites through an enzyme called nitrate reductase. It is important to emphasize that not all bacteria possess this enzyme, so a negative test for nitrites does not completely exclude the possibility of an infection.
Why is the nitrites test important in pregnancy?
During pregnancy, the body undergoes numerous physiological changes that can increase susceptibility to urinary tract infections. Pregnancy hormones, such as progesterone and estrogen, cause a relaxation of the urinary tract muscles, slowing the flow of urine and creating a more favorable environment for bacterial proliferation.
Additionally, the growing uterus can exert pressure on the bladder, hindering complete emptying and further increasing the risk of infections. For these reasons, urine tests are a routine examination during prenatal visits.
The presence of nitrites in the urine of a pregnant woman requires immediate attention, as untreated urinary tract infections in pregnancy can have serious consequences, including:
- Increased risk of preterm birth
- Low birth weight
- Hypertension and preeclampsia
- In severe cases, infections that can reach the kidneys (pyelonephritis)
It is important to emphasize that many women with UTIs in pregnancy do not exhibit obvious symptoms, making urine tests even more crucial for early diagnosis.
Nitrites in children’s urine: what does it mean?
In children, especially younger ones, urinary tract infections can manifest differently than in adults. Symptoms can be vague and include:
- Fever with no apparent cause
- Irritability
- Poor appetite
- Vomiting or diarrhea
- Crying during urination
- Foul-smelling or cloudy urine
- Bedwetting in previously “dry” children
The detection of nitrites in a child’s urine, especially if accompanied by other indicators such as the presence of leukocytes or blood, is generally considered a sign of infection that requires medical evaluation.
Untreated urinary infections in children can lead to complications such as kidney damage, especially if recurrent or associated with vesicoureteral reflux (a condition in which urine flows backward from the kidneys).
How is the test for nitrites performed?
The test for nitrites is part of the standard urine examination and can be performed in different ways:
Urine dipsticks (Rapid Tests)
These tests use reactive strips that change color in the presence of nitrites. They are simple, rapid, and economical, ideal for screening. However, they have some limitations:
- They require that the urine has remained in the bladder for at least 4 hours to allow bacteria to convert nitrates into nitrites
- They can give false negatives if the bacteria present do not produce nitrate reductase
- They can be influenced by certain foods or medications
Complete laboratory urine examination
More accurate, it includes microscopic observation and can identify other important elements such as leukocytes, erythrocytes, and crystals. It is the preferred method when an infection is suspected.
Urine culture
If nitrites are positive or if there are symptoms of infection despite a negative test, the doctor might prescribe a urine culture to identify the specific responsible bacterium and determine the most appropriate antibiotic therapy.
How to correctly collect a urine sample?
Correct sample collection is fundamental to avoid contaminations that could lead to misleading results:
For pregnant women
- Wash the genital area thoroughly with water and neutral soap
- Discard the first stream of urine
- Collect the midstream in a sterile container
- Close the container immediately
Always remember to follow the instructions given by your doctor or pharmacist, because they know better how the local laboratory operates. Each laboratory has its procedures and these are general guidelines.
For children
Collection can be more complicated, especially in newborns and young children. Options include:
- For children who can control urination: follow the same instructions as adults with the assistance of a parent
- For younger children: use sterile adhesive collection bags specifically for urine
- In cases requiring greater precision: catheterization or suprapubic aspiration (procedures performed by medical personnel)
It is important to deliver the sample to the laboratory within 1-2 hours of collection or store it in the refrigerator if this is not possible.
What is the treatment in case of positive nitrites?
If the nitrites test is positive and a urinary tract infection is confirmed, the treatment varies based on the age and conditions of the patient:
During pregnancy
Treatment is essential even in the absence of symptoms. The prescribed antibiotics must be safe for the fetus, and therapy generally lasts 7-14 days. It is important to complete the entire course of therapy even if symptoms improve, and to perform a follow-up test after treatment to confirm healing.
In children
Treatment depends on age, severity of the infection, and the presence of any anatomical abnormalities. In young children or with severe infections, a brief hospitalization might be necessary for intravenous administration of antibiotics. In less severe cases, oral antibiotics are generally effective.
After a urinary infection, especially in younger children, the pediatrician might recommend further examinations such as a renal ultrasound or voiding cystourethrogram to exclude predisposing anatomical abnormalities.
Prevention of urinary infections
There are various preventive strategies that can reduce the risk of urinary infections:
For pregnant women
- Drink plenty of water (at least 1.5-2 liters per day)
- Urinate frequently, not holding urine
- Maintain proper intimate hygiene, cleansing from front to back
- Wear cotton underwear
- Evaluate with your doctor the use of cranberry-based supplements
For children
- Ensure adequate fluid intake
- Teach children proper personal hygiene
- Avoid baths with foaming additives or perfumed oils
- In young children, change diapers frequently
- In older children, encourage complete emptying of the bladder
When to Consult a Doctor
It is important to consult a doctor immediately if nitrites are found in the urine during pregnancy, even in the absence of symptoms.
For children, it is necessary to consult a pediatrician in the presence of:
- Fever with no apparent cause
- Pain during urination
- Frequent and urgent urination
- Cloudy or foul-smelling urine
- Abdominal or lower back pain
- Vomiting or refusal to eat
False positives and negatives: how do I discover them?
It is important to be aware that the nitrites test can sometimes give misleading results. False positives can occur due to contamination of the sample, after consuming foods rich in nitrates (beets, spinach) and the use of certain medications.
False negatives, on the other hand, are more common and can be due to an infection caused by bacteria that do not produce nitrate reductase (such as enterococci or staphylococci), urine that is too diluted, insufficient time of urine retention in the bladder, or a low concentration of nitrates in the diet.
For this reason, medical evaluation is not based solely on the nitrites test, but also considers other parameters such as the presence of leukocytes, clinical symptoms, and, if necessary, urine culture.
What role does food play?
Diet can influence both the prevention of urinary infections and the accuracy of the nitrites test:
- Foods such as cranberries contain substances that can reduce the adhesiveness of bacteria to the walls of the urinary tract
- Good hydration is fundamental to regularly “flush” the urinary tract
- Limiting the intake of acidifying foods and beverages, refined sugars, and caffeine can be useful for those predisposed to infections
It is important to note that some foods rich in nitrates (such as beets, celery, lettuce, spinach, and radishes) can influence test results, although this effect is generally limited.
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SOURCES
Papava V, Didbaridze T, Zaalishvili Z, Gogokhia N, Maziashvili G. The Role of Urinary Nitrite in Predicting Bacterial Resistance in Urine Culture Analysis Among Patients With Uncomplicated Urinary Tract Infection. Cureus. 2022 Jun 17;14(6):e26032. doi: 10.7759/cureus.26032. PMID: 35865430; PMCID: PMC9291437.