Urine Infection (cont.)

Most clinicians think there are several reasons (links) that make a pregnant female more susceptible to UTIs than nonpregnant women. Investigators suggest that hormones cause the bladder and ureters to dilate; this slows urine flow and may decrease bladder emptying which, in turn, increases the likelihood that bacteria can survive and multiply. Also during pregnancy, the acidity of urine decreases and this favors bacterial growth. The enlarging uterus puts pressure on the bladder, so the urge to urinate is more frequent in pregnancy. But many times, pregnant women wait to urinate for various reasons and this further slows flow. In some women, the pressure from the uterus prevents complete bladder emptying, again favoring bacterial growth. In general, pregnancy predisposes women to more kidney infections than bladder infections.

The caregiver should obtain a detailed history from the patient, and if a UTI is suspected, a urine sample is usually obtained. The best sample is a midstream sample of urine placed in a sterile cup because it usually contains only the pathogenic organisms instead of the transient organisms that may be washed from adjacent surfaces when the urine stream begins. Male patients with foreskin should retract the foreskin before providing a midstream urine sample. In some patients who cannot provide a midstream sample, a sample can be obtained by a catheter. The urine sample is then sent for urinalysis. Patients with a "discharge," or possibility of having an STD, usually will have the discharge tested for STD organisms (for example, Neisseria and Chlamydia). A positive urinalysis is usually detection of about two to five leukocytes (white blood cells), about 15 bacteria per high-power microscopic field, and a positive nitrite test and/or positive leukocyte esterase test. Some clinicians and labs consider a positive test at least two of the above findings; still others report a positive for bacteria as >1,000 bacteria cultured per milliliter of urine. At best, the initial urinalysis, depending on the various criteria used by clinicians and labs, provides a presumptive positive test for a UTI. Most clinicians believe this presumptive test is adequate enough to begin treatment. A definitive test is usually considered to be isolation and identification of the infecting pathogen at a level of about 100,000 bacteria per cc of urine with the genus of the pathogen (usually bacterial) identified and antibiotic sensitivity determined by lab studies. This test takes 24-48 hours to obtain the results and your health care professional will usually start treatment before this result is available. Sometimes blood in the urine is a sign of a UTI but it may also indicate other problems, such as a urinary calculus or “stone.”

In young children, infants, and some elderly patients, the best urine specimen is obtained by catheterization, as they are unable to deliver a “clean catch" urine sample as described above. Urine can also be collected from "bags" placed over the urethral outlet (genital area), but these bagged specimens are only used for presumptive urinalysis as they are unreliable for culture. Some investigators consider any bagged urine samples as unreliable. Urine samples not processed within an hour of collection should either be discarded or be refrigerated before an hour passes because bacterial growth in urine at room temperature can yield false-positive tests. Special culture media and other tests are done for the infrequent or rare pathogens (for example, fungi and parasites).

Other tests may be ordered to further define the extent of a UTI. They may include blood cultures, a complete blood count (CBC), intravenous pyelogram, a CT scan, or other specialized tests.

Source: MedicineNet.com
http://www.medicinenet.com/urine_infection/article.htm