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Urinary Tract Infections

STDs and UTIs commonly affect the urinary system and because of that, there is overlap in the symptoms and signs of STDs and UTIs. So, many patients present to you with a complaint of burning with urination or dysuria and that can be a manifestation of numerous infectious causes, as you all know. Sometimes the urethral syndrome which we sometimes call the presentation of dysuria or burning with urination comes from cystitis. It can be associated with pyelonephritis, gonorrhea, chlamydia, trichomonas, M. Ureaplasma and herpes. Of course, you can also see this in the presence of vaginitis.

Sometimes the associated symptoms can give you some clues as to whether you are dealing with an STD or a UTI. If the patient has associated flank pain, nausea, vomiting and fever, you may suspect pyelonephritis. Whereas the presence of concomitant vaginal symptoms might indicate an STD. But I think the one thing you have to keep in mind is that both UTIs and STDs can present with isolated dysuria and I think the tendency sometimes is to really blame isolated dysuria.

You can find out a little bit more about whatís going on if you take a careful history and really find out an exact description of what the patient means when they say, "It burns when I urinate." In cystitis, there is often the sudden onset of internal dysuria which is described as sort of a deep, a dull pain.

Patients with STD urethritis may tell you that they have had a new sex partner within a few days of the symptom onset. They may report a purulent urethral discharge and, of course, this is much more copious and common with gonorrhea than it is with chlamydia.

In patients with vaginitis, they may complain of vaginal discharge and external dysuria where the pain is not so deep and dull but located more about the labia or the urethral orifice in the case of women.

So after you clarify that, you may be led in one direction or the other. At this point, Iím going to start with UTIs and then we will move on to STDs a little bit later on in the talk. Youíre probably all familiar with how to diagnose UTIs and that is done in a lot of different ways.

For example, if you have more than 10 white cells per milliliter which is equivalent to 1 to 2 white cells per high power field on a microscope, this correlates with either symptomatic or asymptomatic bacteruria Ė the presence of bacteria in the urine. If you have a higher number of white cells per field.

The reason you want to kind of know how these numbers correlate with symptomatic and asymptomatic bacteruria is that there are only some circumstances where asymptomatic bacteruria should be treated and I will talk about that a little bit later.

A lot of people look at leukocyte esterase to diagnose UTIs. Itís basically a surrogate for detecting white cells but it does have limitations in sensitivity. It also does not allow you to examine the specimen for vaginal epithelial cells. So sometimes you donít know about the quality of your specimen and white cells can sometimes come from vaginal pathology rather than from the urinary tract. So you might get a misleading result in some cases if you rely entirely.

Another component of urinary tract infection diagnosis depends on tests for the detection of bacteria. One of these tests is the nitrite test but like the leukocyte esterase test, it does have limited sensitivity. Even when it is positive sometimes it may not actually indicate infection or the need for therapy. A Gram stained unspun urine that shows 1 bacteria per oil immersion field correlates with more than 100,000 colony forming units of bacteria per milliliter of urine.

In other settings, asymptomatic bacteruria is generally not something that needs to be treated. So I think the key then is to look for asymptomatic bacteruria in those patient groups and really not go fishing for it in other groups because you may get some gray area results and you wonder, "What should I do with it?" Quite honestly, in an asymptomatic patient those two circumstances are clear-cut.

In the range between 10,000 and 100,000 colony forming units per milliliter there is a 95% chance that the culture reflects contamination if there are anaerobe bacteroidaceae in an asymptomatic woman. However, Gram positives, fungi and fastidious bacterium may actually be indicative of true bacteruria even with these lower colony forming unit counts. So in the person who is pregnant or going to have a procedure, when they have less than 100,000 colony forming units per milliliter, if they are in this category.

What are the bugs that cause the vast majority of urinary tract infections? In reality there are relatively few of them. 80-90% of the infections are caused by E. coli. Staph saprophyticus can cause from 2-20% and then Proteus, Klebsiella, Enterococcus and other enteric pathogens are all less than 10% of the cases in an outpatient setting. So the vast majority of the time you are going to be talking about E. coli.

If we go from asymptomatic women to symptomatic women, youíll see that the interpretation of quantitative culture is different. With greater than or equal to 100,000 colony forming units per milliliter, this indicates a true positive 95% of the time. If itís less than 100,000 colony forming units per milliliter, itís a true positive only one-third of the time. I think one important exception to remember is women with symptoms who have more than 100 colony forming units.

So I mentioned short course therapy and, again, weíre talking about three day regimens and they have been shown to be superior to single dose regimens. Probably the most cost effective therapy, at least in controlled studies where they looked at incidence of relapse and incidence of concomitant vaginitis related to antibiotic therapy, trimethoprim sulfa is very cost effective and is more cost effective than nitrofurantoin, cefadroxil or amoxicillin.

It may be kind of surprising that three days of ofloxacin was similarly cost effective because we know how much more expensive the drug is. But thatís because in the patients that were studied, they had a lower incidence of relapse and a lower incidence of vaginitis after that had to be treated as a result of their antibiotic therapy. So the overall cost was similar to trimethoprim sulfa.

Now, just a word on amoxicillin and ampicillin. Itís really not a very practical affair for empiric choice because across the U.S. about one-third of E. coli are resistant to ampicillin. I do fear that trimethoprim sulfa will follow in the footsteps of ampicillin too but I think for now, because of its extremely low cost.

You should also note that some people are not suitable for short course therapy. Diabetics would probably fall into this category because they are a little more likely to have pyelonephritis. In those patients, you may want to give them more like a week of therapy. If a patient has had symptoms for more than seven days before they see you, they are also more likely to have pyelonephritis and you may want to avoid short course therapy in them.

Patients who use a diaphragm. Patients who are older than age 65 also have a higher incidence of recurrence with short course therapy. Keep in mind that in the elderly post menopausal woman who is not on any estrogen or hormone replacement, vaginal atrophy may contribute to vaginal colonization with urinary tract infection pathogens and that can contribute to recurrences. So hormone replacement therapy can sometimes play a big role in decreasing the recurrences in the post menopausal female.

Ofloxacin and trimethoprim sulfamethoxazole are the most cost-effective agents, with lower cost and highest percent cure rate compared to amoxicillin, cefadroxil and nitrofurantoin.

In pregnancy. I mentioned before that bacteruria should be treated whether itís symptomatic or not and that is to reduce the incidence of adverse outcomes for the pregnancy. Thereís not really a lot of data on short course therapy in that setting although it is attractive because we like to minimize drug exposure to pregnant women. But in pregnancy, beta-lactams tend to favored because of more experience and trimethoprim sulfa used in the third trimester can result in kernicterus of the newborn because of displacement of bilirubin from plasma proteins. So you probably donít want to use trimethoprim sulfa in the pregnant woman nor tetracyclines nor quinolones.

In pregnancy, also because of the critical nature of curing these infections, you do want a follow up culture after therapy in one to two weeks and you may want to monitor them monthly for the remainder of gestation.