The urinary tract includes two kidneys, two ureters, one bladder and one urethra. After the kidneys make the urine, it goes through muscular tubes called the ureters and collects in the bladder. The urine then leaves the body through the urethra. A urine infection can involve any part of the urinary tract.
Bacteria
Intestinal bacteria cause most urinary tract infections, or UTIs. When people have a sudden infection, physicians usually find that one type of bacteria is the cause. Most of the time in chronic or long-term infections, two or more bacteria are involved, according to Maxwell Meng, M.D., Associate Professor in the Department of Urology at the University of California in “Current Medical Diagnosis & Treatment.” The E. coli bacteria cause most of the infections. They migrate from the large intestines down to the anus, reach the urethra which is nearby and then migrate upwards. Women have much shorter urethras than men and are more susceptible to UTIs caused by intestinal bacteria.
Fungi
A urinary tract infection caused by the Candida fungi usually happens from using a catheter after taking antibiotics for a bacterial UTI. Many times, people have a bacterial and candidal UTI at the same time, writes Stewart Shankel, M.D., Director of Clinical Medicine at the University of California in “The Merck Manual for Healthcare Professionals.” Those with an impaired immune system are at a higher risk for developing a UTI from fungi. This includes diabetics, people taking chemotherapy or getting renal transplants, and those with AIDS. Candida can also spread through the bloodstream and infect the kidneys.
Vesicoureteral reflux
Normally, urine should always flow through the ureters to the bladder and never go backwards from the bladder to the ureters, especially when people are urinating. This protects the kidneys from becoming contaminated and protects them from the high pressure within the bladder, as explained by Emil Tanagho, M.D., Professor Emeritus of Urology at the University of California School of Medicine in “Smith’s General Urology.” To prevent any backward flow, also referred to as reflux, there are one-way valves where the ureters first enter the bladder. If there are any problems with these valves, people will have a reflux of urine. This can lead to UTIs. Many urinary tract infections in children are due to reflux.
Benign Prostatic Hyperplasia
By one estimate, 19 percent of men between 55 and 74 years old have benign prostatic hyperplasia, or BPH, according to Gerald Andriole, M.D., Chief of Urologic Surgery at Barnes-Jewish Hospital in “The Merck Manual for Healthcare Professionals.” The urethra passes through the prostate gland, and in BPH, several nodules develop within the gland, near the urethra. The nodules make the prostate get bigger and, as the gland enlarges, it presses on the urethra. The hyperplastic prostate gland, or the enlarged gland, now interferes with the flow of urine. This can lead to UTI and even renal failure.
