The pathophysiology of urinary tract infection involves the infection of urinary tract organs such as the urethra, bladder, ureters, and kidneys. Although different microorganisms can cause UTI, the pathophysiology of urinary tract infection is similar for each organism. Normal urine is sterile, but when bacterial urinary infection occurs, microorganisms enter through the urethra and may travel up or ascend to other parts of the urinary system. It is important to treat UTI to avoid complications.
In all cases, the pathophysiology of urinary tract infection begins with the entry of microorganisms through the outermost part of the urinary system called the urethra. Normal urine is acidic and resistant to bacterial growth, and urine flow is always toward the external environment. Other protective mechanisms against bacterial urinary infection include bladder emptying, the presence of contracting muscles called sphincters, and the availability of immune cells and antibodies in the urinary mucosa. In men, secretions of the prostate gland minimize bacterial growth.
Bacterial agents, such as Escherichia coli (E. coli), may be transferred from the anus to the urethral opening, leading to urethral infection. E. coli is an organism that lives in the colon and is passed out in the stools during defecation. The relationship between the anus and the urethra explains why UTI occurs more frequently in women than in men. In women, the anal and urethral openings are closer to each other, and the urethral length is shorter. This leads to easier bacterial translocation and ascension to the upper parts of the urinary tract.
UTI symptoms differ according to what part of the urinary tract is infected. The symptoms of urethra infection or urethritis may be limited to increased frequency of urination as well as burning pain while urinating, called dysuria. With bladder infection or cystitis, there may be additional symptoms of pain over the abdominal and pubic regions, and also a low-grade fever. Kidney infection, or pyelonephritis systemic, symptoms include high fever, chills, nausea, and vomiting. In some cases, blood in the urine and loss of appetite may be experienced.
Different risk factors contribute to the pathophysiology of urinary tract infection. Congenital anatomical abnormalities and acquired diseases, such as kidney stones, can predispose a person to getting UTI. Among sexually active people, the frequency of intercourse and the mode of intercourse increase UTI risk. In elderly men, enlargement of the prostate gland impedes urine flow, leading to increased risk of infection. Immunocompromised states, such as diabetes, contribute to an increased UTI risk because the immune cells of the body are not able to fight against the infection.
Treatment of UTI usually involves antibiotics, such as co-trimoxazole. It is important to follow the full antibiotic course recommended by the doctor. This is needed to avoid complications such as scarring of the urethra, strictures, and destruction of the kidney parenchyma.