A urinary tract infection (UTI) occurs anywhere in the urinary system. While many UTIs are confined to the lower tract, some can travel upward in a process known as an ascending UTI. This infection moves from the lower urinary structures, like the bladder, to the upper sections, including the kidneys.
The Pathway of Infection
The path of an ascending UTI begins when bacteria enter the urethra. The most common culprit is Escherichia coli (E. coli), which resides in the gut. These bacteria colonize the urethra and, if not cleared, can migrate upward into the bladder. This initial stage of infection, when confined to the bladder, is known as cystitis.
For many, the infection stops there, resulting in a lower UTI. In an ascending infection, the bacteria continue their journey from the bladder up through the ureters, the two tubes that carry urine from the kidneys to the bladder.
Once bacteria reach the kidneys, they can cause a more serious infection called pyelonephritis. This upper UTI occurs when the infection becomes a systemic problem affecting the kidneys. The continuous, one-way flow of urine is a natural defense, but if this is compromised, bacteria can more easily make this upward journey.
Recognizing the Symptoms
Symptoms change as the infection ascends, indicating its location. When an infection is limited to the lower urinary tract, symptoms are localized and can include:
- A persistent urge to urinate or increased frequency
- A painful or burning sensation during urination (dysuria)
- Cloudy, dark, or reddish-tinted urine
- Discomfort in the lower abdomen
If the bacteria travel up the ureters to the kidneys, a more serious set of symptoms emerges. The onset of this upper UTI, or pyelonephritis, is marked by systemic signs that indicate a more widespread illness. These include a high fever, shaking chills, and a distinct pain in the flank or lower back, corresponding to the location of the infected kidney. Nausea and vomiting are also common. The presence of fever, flank pain, or vomiting alongside urinary symptoms warrants immediate medical evaluation.
Factors That Increase Risk
Several factors can make a person more susceptible to a UTI. Anatomical differences are a primary contributor; the female urethra is shorter than the male urethra, providing a more direct route for bacteria to reach the bladder. This is a main reason why UTIs are more common in women.
Behavioral patterns also play a part. Sexual activity can introduce bacteria from the perineal area into the urethra. Holding urine for extended periods also contributes, as it allows bacteria more time to multiply within the bladder rather than being flushed out.
Certain medical conditions can also increase risk. Any blockage in the urinary system, such as a kidney stone or an enlarged prostate, can obstruct the normal flow of urine, creating a stagnant environment where bacteria can thrive. Individuals with weakened immune systems or those who use urinary catheters are also at an elevated risk.
Diagnosis and Medical Treatment
When an ascending UTI is suspected, a medical provider will begin with a physical examination and a discussion of symptoms. A urinalysis tests a urine sample for signs of infection, such as the presence of white blood cells or nitrites. For a more definitive diagnosis, a urine culture is performed. This lab test grows the bacteria from the sample to identify the specific pathogen and determine its susceptibility to various antibiotics.
Treatment for an ascending UTI involves antibiotics to eliminate the infection. For a lower UTI or a mild case of pyelonephritis, a course of oral antibiotics is prescribed, such as nitrofurantoin or sulfamethoxazole/trimethoprim. The choice of antibiotic depends on local resistance patterns and the bacteria identified in the culture.
If the kidney infection is severe, causing high fever, intense pain, or an inability to keep down oral medications, hospitalization may be necessary. In a hospital, antibiotics are administered through an intravenous (IV) line for a rapid effect. After initial treatment, a patient is often transitioned to oral antibiotics to complete the therapy at home.
Preventive Measures
Preventing an initial UTI is the most effective way to avoid an ascending infection. A primary strategy is to stay well-hydrated, as drinking plenty of water helps dilute urine and ensures more frequent urination. This process flushes bacteria from the urinary tract before an infection can establish itself.
Hygiene practices are also important. For women, wiping from front to back after using the toilet helps prevent the transfer of E. coli from the anal region to the urethra. Urinating shortly after sexual intercourse can also help clear any bacteria that may have been introduced.
Do not hold urine for long periods. Regularly emptying the bladder gives bacteria less opportunity to multiply, making the urinary tract a less hospitable environment for them.