Evolution of urinary tract infection

Normally, urinary tract infections respond well to antibiotic treatment, so the symptoms and the infection disappear.  

Sometimes, however, urinary tract infection is recurrent. Recurrent urinary tract infection is considered as 3 episodes within 12 months or 2 episodes within 6 months. It is a common problem in young, sexually active women, in pregnancy, in menopause and in patients with urological pathology.  

It is important to differentiate between recurrent infection and reinfection when urinary tract infection returns:  

Recurrent infection 

This is due to the persistence of the same strain of bacteria that caused the first infection. It represents 20% of repeated infections. This usually occurs within 2 weeks of the disappearance of symptoms. It may be because this microorganism has remained in a place that was not accessible to the antibiotic, or that the antibiotic treatment was inadequate or the treatment period was too short.  

In these cases, the infection can become complicated, especially if it ascends to the prostate (prostatitis), or the concomitant kidney (pyelonephritis). Pyelonephritis can be complicated by the formation of a stone that causes an associated obstructive problem or a renal abscess (purulent collection inside the renal parenchyma) may occur. 

Reinfection 

This represents 80% of repeated infections. These are new urinary tract infections caused by different strains of bacteria than those that caused the first infection. Reinfections usually take longer to appear than recurrences. Generally, 2 weeks after the first infection disappeared. 

Reinfections usually occur in young sexually active women, women with menopause, patients with different urological diseases or some people with previous surgeries.  

Complications  

Repeated urinary tract infection can cause significant sequelae, such as the formation of kidney stones, which can lead to obstruction of the ureters and cause a kidney infection. It can cause urinary sepsis, pyonephrosis (pus collects and causes distension of the kidney), kidney abscesses and, in more advanced cases, loss of kidney function.  

These complications are infrequent, except in the case of patients with altered immunity (e.g. transplant recipients or patients with oncological treatment), anatomical alterations of the urinary system or uncontrolled kidney stones.