This section is organized into the three causes of dysuria: cystitis, pyelonephritis, and urethritis. Cystitis is infection of the urinary bladder. Pyelonephritis is an infection that involves the renal parenchyma, calyces, and pelvis of the kidney. Urethritis is an infection of the urethra. Of these three diseases, pyelonephritis is the one most likely to cause fever. The common causes for cystitis are Escherichia coli, Proteus group, and Staphylococcus saprophiticus. In catherized patients, Staphylococcus epidermidis is the most likely cause. However, indwelling catheters are a risk factor for all causes of cystitis. The most common cause of pyelonephritis is Escherichia coli. The common causes for urethritis are Neisseria gonorrhoeae and Chlamydia trachomatis. Cystitis and pyeloneophritis are much more common in females than males, while urethritis is more apt to be symptomatic in males.
Labs are not necessarily used in the clinical setting. These lab results should be used as "hints" in realizing the causative agent.
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CystitisEscherichia coliA 25 year old female who recently returned from her honeymoon comes into the family practice clinic complaining of pain on urination and severe urgency. Labs: Gram negative rods that are motile, do not ferment sorbitol, ferment lactose, utilize acetate as its only source of carbon, and use tryptophan to produce indole. Culture reveals colonies with green sheen on EMB agar. Discussion: The diagnosis of cystitis by Escherichia coli is made by culturing urine samples. The clinical picture of Escherichia coli cystitis can not be used to distinguish Escherichia coli from other causes of cystitis. Escherichia coli is the most common cause of community acquired acute cystitis. It occurs more often in women and is nicknamed the "honeymoon infection." It is also a common cause of hospital-acquired urinary tract infection especially when indwelling catheters are used. The absence of RBC or WBC casts rules out pyelonephritis. For more information Escherichia coli, click here. Proteus groupA 25 year old hospital patient complains of pain and frequency of urination. Recent surgery requires that she use an indwelling urinary catheter. A diagnosis of cystitis is made. Labs: Culturing urine samples on blood agar reveals highly motile gram negative rods. These organisms produce urease. Non-lactose-fermenting colorless colonies formed on MacConkey's agar. Discussion: The diagnosis of cystitis by the Proteus species is made by culturing urine samples. The clinical picture of cystitis can not be used to distinguish Proteus from other causes of cystitis. Proteus mirabilis is the species of Proteus that causes most of the infections. The urinary tract infections caused by the Proteus group is both community- and hospital-acquired. Hospital-acquired infections can be prevented by removal of urinary catheters. For more information Proteus mirabilis, click here. Staphylococcus saprophyticusA 25 year old sexually active female comes into the student health clinic complaining of painful and frequent urination. She does not report seeing any blood in her urine. Further testing shows no RBC or WBC casts which indicates that only the bladder is involved. Labs: Catalase positive, coagulase negative gram-positive cocci in grapelike clusters that are resistant to novobiocin. Discussion: The diagnosis of cystitis by Staphylococcus saprophyticus is made by culturing urine samples. The clinical picture of Staphylococcus saprophyticus cystitis can not be used to distinguish Staphylococcus saprophyticus from other causes of cystitis. Unlike Staphylococcus aureus, Staphylococcus saprophyticus and Staphylococcus epidermis is coagulase negative. Unlike Staphylococcus epidermis, Staphylococcus saprophyticus is resistant to novobiocin. Staphylococcus saprophyticus causes urinary tract infections in sexually active young women. The absence of RBC or WBC casts rules out pyelonephritis. For more information Staphylococcus saprophyticus, click here. |
PyelonephritisEscherichia coliA 28 year old female presents to her doctor with fever, chills and flank pain. Further testing shows WBC casts indicating that there is kidney involvement. Labs: Gram negative rods that are motile, do not ferment sorbitol, ferment lactose, utilize acetate as its only source of carbon, and use tryptophan to produce indole. Culture reveals colonies with green sheen on EMB agar. Discussion: The diagnosis of cystitis by Escherichia coli is made by culturing urine samples. Escherichia coli is a common cause of pyelonephritis as well as cystitis. The presence of WBC casts and also the fever indicates that there is kidney involvement. Therefore the diagnosis is pyelonephritis as opposed to cystitis. The infection is an ascending infection and occurs more often in sexually active young women. For more information Escherichia coli, click here. |
UrethritisNeisseria gonorrhoeaeA 31 year old single man presents in the clinic with painful, burning urination and greenish-yellow, mucopurulent discharge. He admits to having several sexual partners. Labs: intracellular gram negative diplococci in the PMNs. Organism is inoculated on Thayer-Martin media. Aerobic, oxidase positive. Discussion: Physical exam and lab test determine that this is urethritis caused by Neisseria gonorrhoeae. It is the lab in this instance that differentiates Neisseria gonorrhoeae from Chlamydia trachomatis. Neisseria gonorrhoeae is a sexually transmitted disease. Signs and symptoms for men is characterized by painful urination and purulent discharge. Discharge may be white or greenish-yellow and mucopurulent. The patient may also be asymptomatic. With Neisseria gonorrhoeae, a presumptive infection of Chlamydia trachomatis must be treated. For more information on Neisseria gonorrhoeae (aka gonococcus), click here.
Chlamydia trachomatisA 34 year old male presents in the clinic with painful urination and watery discharge. A gram stain of the penile discharge is negative for pathogenic organisms. He admits to having been involved in a menage-a-trois a week ago. He says that it seemed like a very good idea at the time.Labs: Inclusion bodies in Giemsa stain. Obligate intracellular bacteria. PCR is also a useful tool. Discussion: It is the lab in this instance that differentiates Neisseria gonorrhoeae from Chlamydia trachomatis. Discharge may be slightly more watery in Chlamydia trachomatis than in Neisseria gonorrhoeae but this should not be used as a determining factor. An infection of one organism is presumptive for an infection of the other. Signs and symptoms for men is characterized by painful urination and purulent discharge. The patient may also be asymptomatic. These signs and symptoms look like gonorrhea. For more information on Chlamydia trachomatis, click here.
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