Urinary Tract Infection



Bacterial infection of the lower urinary tract is one of the more common infectious processes. However, considering the fre­quency of lower tract infection, renal parenchy­mal infection (pyelonephritis] is not common.

Infection of the renal parenchyma, pyelone­phritis, is caused by bacteria ascending the ureters from the bladder. Parenchymal infections origi­nating from the blood are almost always abscesses and are frequently seen in intravenous drug abu­sers. The syndrome of acute pyelonephritis al­most always includes symptoms of lower tract in­fection plus bacteriuria. The diagnosis of chronic pyelonephritis has been used to describe the his­tological finding of renal interstitial inflammation and scarring in persons with histories of recurrent or chronic urinary tract infection. However, there is no clear evidence that long-standing renal pa­renchymal infection occurs or that significant renal damage follows such infection except in cer­tain susceptible hosts. These include persons with diabetes mellitus, chronic renal insuffi­ciency, and chronic urinary tract obstruction. The more common pathological finding of interstitial inflammation and scarring is usually due to a ster­ile, toxic renal injury (as in analgesic nephropa­thy).

Simple urinary tract infection usually presents as dysuria, urinary urgency, and frequency. Fever may be present but is frequently absent. Flank pain or tenderness at the costovertebral angle may be present in uncomplicated infection of the lower urinary tract; these are nonspecific find­ings. High fever, often with nausea and vomiting, in addition to the above findings more often in­dicates true pyelonephritis. In either case, the ur­inalysis consistently reveals pyuria, but micro­scopic hematuria or minimal proteinuria may also be present. The standard test for diagnosis of uri­nary tract infection is growth of greater than 105 colonies/ml of a recognized pathogen from a clean-catch, midstream urine specimen. Urinary tract infection in the male demands an exami­nation of the urinary tract, preferably by IVP, for structural abnormalities.

For the vast majority of uncomplicated urinary w tract infections, especially in females, treatmentmay be started immediately after a urine specimen jj| for culture is obtained. Any of a number of antibiotics with activity against coliform bacteria is fs acceptable: ampicillin, a tetracycline, or a sulfa |1 compound. However, urinary tract infections ac- j| quired in the hospital, infections associated with -43| obstruction or stones, and cases of acute pyelo- JK nephritis often require addition of an antibiotic
effective against noncoliform, gram-negative rods; aminoglycoside antibiotics are the most frequent choice.

Prompt treatment of urinary tract infection is critical in several circumstances. Pregnancy is as­sociated with a 10 per cent incidence of urinary tract infection. Untreated, about half of these otherwise simple infections will progress to acute pyelonephritis in the pregnant female. Surveil­lance for and prompt treatment of bacteriuria is thus an important part of prenatal care. While di­abetics have no clear increase in frequency of uri­nary tract infections, they do have more compli­cations, including pyelonephritis and sepsis, arising from simple infections of the urinary tract. Patients with known urinary tract obstruction, po­lycystic kidney disease, or renal calculi should be monitored closely and receive prompt, vigorous treatment for urinary tract infection.