Dr. Sarah Livelo 24 Nov 2021

Urinary tract infections (UTI) are one of the most common medical conditions in both children and adults. Every year, nearly 200,000 people in the United States are hospitalized due to acute pyelonephritis, the severe form of the infection.

UTI can happen in children of any age, especially in females who begin toilet training (3 to 5 years old). Males who are uncircumcised also have a higher chance of acquiring this infection. In adult women, UTI is the most common bacterial infection, with 50% of all women becoming infected at least once.

The culprits are often bacteria that come from the gastrointestinal tract. This includes E. coli, S. aureus, S. saprophyticus, Klebsiella, Proteus, and Enterobacter.


UTI starts when gut bacteria infiltrate the tissues between the anal area and the genital area (called the perineum), climbing upwards through the duct where urine flows out (known as the urethra). There may be symptoms already by the time these bacteria reach the bladder. The infection gets worse as the bacteria further ascend through the tubes connecting the bladder and the kidney (the ureters), more so when these reach the kidneys.

Bacteria attach to the cells of the bladder and increase their numbers in the urine, but some can resist antibiotics when they are able to enter the cells of the bladder, causing recurrent UTIs despite strong antibiotics.

Risk Factors

There are various risk factors for acquiring UTI. These include the female sex, uncircumcised males, the presence of vesicoureteral reflux (when urine flows back from the bladder and into the kidneys), ongoing toilet training in children, constipation, sexual activity, pregnancy, any irritation, and any anatomic abnormalities along the passageway of urine.

Types of Urinary Tract Infections

Urinary tract infections may be very severe or may even have no symptoms at all. There are four main types of UTI.

Asymptomatic bacteriuria

Most females and elderly patients, especially those 80 years and older, are prone to have bacteria in the urine but feel no symptoms. This is called asymptomatic bacteriuria. It’s rarely diagnosed in infants and toddlers, present in 15% of people aged 65-80 years old, and increases to 50% beyond 80 years of age. It may also be seen in pregnant women and patients who have undergone urologic procedures or kidney transplants. There are no signs or symptoms in cases of asymptomatic bacteriuria.


In cystitis, only the urinary bladder is infected with bacteria. This can affect all age groups, but is most commonly seen in women, with about 50% of those aged 30-35 having had at least one bout of UTI. Cystitis is categorized into two subtypes: uncomplicated cystitis (men, non-pregnant women), and complicated cystitis. The latter may lead to further infection due to certain conditions, such as diabetes, immunocompromised states, renal insufficiency, kidney stones, and the presence of a urinary catheter.

Acute hemorrhagic cystitis is a variation of cystitis involving minor bleeding from the cells of the urinary bladder. In children, this can be due to a viral or bacterial infection, especially in the immunocompromised. In adults, hemorrhagic cystitis may come from exposure to radiotherapy or chemotherapy.

Patients may experience pain or tenderness in the area of the abdomen below the belly button (called the suprapubic area), pain when urinating, more frequent urination (usually in small amounts), difficulty controlling urination, and a constant need to urinate. The urine itself may be foul-smelling. The urine may be tea-colored in cases of hemorrhagic cystitis.


Acute pyelonephritis is a serious infection which occurs when bacteria get as far as the kidneys. Majority of cases are young women who are sexually active, but infants, pregnant women, and the elderly are prone to this condition. Like cystitis, pyelonephritis may be uncomplicated or complicated (patients who have co-morbidities, are immunocompromised, or are pregnant).

In newborns, signs and symptoms include weight loss, jaundice, poor feeding, and irritability. Children and older patients may develop fever, back pains, flank pains, abdominal pain, nausea, vomiting, diarrhea, or an overall feeling of discomfort. Some patients may have a high heart rate.

Renal abscesses

A renal abscess is a relatively rare complication of urinary tract infections. commonly due to the spread of Staphylococcus aureus bacteria through the blood and into supporting tissues of the kidney, such as the kidney capsule and the perirenal fat. Signs and symptoms include fever, abdominal pain, flank pain, loss of appetite, and fatigue.


Tests are used to confirm the diagnosis of urinary tract infection. Asymptomatic bacteriuria is usually discovered when a routine urinalysis reveals bacteria in the urine. The diagnosis can be confirmed through a urine culture. For acute cystitis, urine dipstick testing or urinalysis are typically requested. If acute pyelonephritis is suspected, urine culture may also be included.

For cases of UTI that are less than 2 years old, additional imaging tests may be requested. These include a kidney and bladder ultrasound, a voiding cystourethrogram (VCUG), or a dimercapto succinic acid scan (DMSA). If renal abscesses are being considered, CT scan and blood tests may be done. Healthcare providers decide which diagnostic tests are required on a case-to-case basis.


Antibiotics are typically used for treatment of UTIs. This may take as quick as 3-5 days, or as long as 14-21 days, depending on the age, type of UTI, and even the prevalence of resistant bacteria in the area where the patient is being treated.

For asymptomatic bacteriuria, most cases are not treated with antibiotics due to the high possibility of developing antibiotic-resistant bacteria. Pregnant women, on the other hand, may be treated with antibiotics for 3 to 7 days.

For renal abscesses, the main treatment options include antibiotics and drainage of the pus. which may be done surgically.

Some cases may require hospital admission. These include patients who are:

  • of young age
  • pregnant women with pyelonephritis
  • dehydrated
  • unable to drink oral antibiotics
  • cases with possible sepsis
  • other complications

Some improvement in symptoms may be seen two days after the start of treatment for cases of cystitis, and three days after the start of treatment for pyelonephritis.

Prevention and Screening

Eliminating or avoiding certain risk factors for UTI can help prevent the infection. Studies show that breastfeeding plays a significant role in decreasing the rate of UTI in newborns and infants. Constipation in children may be addressed with behavioral modifications. For pregnant women, screening for asymptomatic bacteriuria should be done, typically during the first prenatal visit or when they are 3-4 months pregnant.


UTI is a common medical condition affecting both children and adults, and comes from gut bacteria that invade the bladder, ureters, or kidneys. The infection may be subtle or may be severe with complications. Treatment focuses on antibiotics; drainage may be necessary for cases of renal abscess.

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About the Author:
Dr. Sarah Livelo is a licensed physician with specialty training in Pediatrics. When she isn't seeing patients, she delves into healthcare and medical writing. She is also interested in advancements on nutrition and fitness. She graduated with a medical degree from the De La Salle Health Sciences Institute in Cavite, Philippines and had further medical training in Makati Medical Center for three years.


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