A 27-year-old G2 P1 woman who is in her 6th month of gestation suddenly develops an obvious fever and shaking chills, along with nausea and vomiting. She also has some dysuria with urgency and frequency, but she did not notice any urinary symptoms prior to the onset of fever and chills. Shortly after the fever and chills appear, she develops excruciating flank pain, becomes concerned, and comes to see you for advice. Her vital signs are: T = 39.5ºC, P = 115, R = 18, and BP = 110/70 mm Hg. Physical examination reveals marked tenderness on deep pressure in both costovertebral angles, but there are no other remarkable findings. The fetal heart tones are present at a rate of 130 to 140/minute.

Question 3.1: What is your preliminary diagnosis and how can you confirm it?

The dysuria, frequency, and urgency point to a UTI, and the flank pain and costovertebral angle tenderness imply involvement of the kidneys. The systemic symptoms (fever, nausea, vomiting, tachycardia, etc.) are not overly definitive by themselves. In combination with the other symptoms, however, they are all consistent with a kidney infection (i.e., pyelonephritis). Without any additional information, then, a UTI involving pyelonephritis seems likely. UTIs are most easily confirmed with a urinalysis (including microscopic examination) and urine culture. Additional tests that might be useful include a CBC with differential, a renal panel, and a blood culture.

Question 3.2: What is the differential diagnosis for these symptoms?

Other possibilities include nephrolithiasis, appendicitis, ovarian cyst torsion or rupture, acute glomerulonephritis, pelvic inflammatory disease, etc.

Lab Results

Microscopic examination of the urine sample reveals the presence of Gram-negative rod-shaped bacterial cells, leukocytes, and leukocyte casts. The urine culture detects 106 bacterial cells/mL and grows a Gram-negative, fermentative rod that is oxidase negative and has red colonies on MacConkey agar. It is indole positive. The blood culture is negative. A CBC shows Hgb 12.8 g/dL, Hct 38.5%, MCV 75 fL, WBC count 13,880/µL, and differential count 75 segs, 7 bands, 13 lymphs, 4 monos, and 1 eosinophil.

Question 3.3: Do the lab results confirm your preliminary diagnosis? What is the most likely complication that might occur with this disease and is there any reason to think that it has happened in this case?

Yes, they are consistent with a UTI that involves pyelonephritis. Pyelonephritis often involves septicemia, but that does not appear to be the case here because the blood culture is negative. She does not have hypotension. The baby's fetal heart tones are normal.

Question 3.4: How did this patient's current condition come about? What predisposing factors(s) die she have?

Women are relatively susceptible to UTIs. Uncomplicated UTIs that are not nosocomial in origin typically get started when fecal bacteria make their way into the urinary system. The female urethra is particularly prone to colonization by fecal bacteria because of its proximity to the anus. The comparatively short length of the female urethra also facilitates transport of bacteria upward from the periurethral area into the bladder. This patient probably had a typical ascending infection that first reached the bladder and then managed to move into the kidneys. In all likelihood, the patient had an asymptomatic bacteriuria for some time before the organism reached the kidneys and produced the acute symptoms described in this case. Asymptomatic bacteriuria occurs frequently in women between the ages of 20 and 50. A number of factors can predispose a person to pyelonephritis from an ascending UTI. The most likely one in this particular case is the women's pregnancy. Decreased ureteral tone, decreased ureteral peristalsis, and temporary incompetence of the vesicoureteral valves facilitate the movement of bacteria from the bladder to the kidney(s). As a result, 20 to 30% of pregnant women with symptomatic bacteriuria develop pyelonephritis.

Question 3.5: What is the most likely causative agent and how should this case be treated?

Antibiotic therapy generally must be continued for 10-14 days to effectively eliminate pyelonephritis (14-21 days in the case of a relapse). This appears to be an uncomplicated UTI and there is no reason to suspect that it is nosocomial. More than 80% of uncomplicated UTIs are caused by Escherichia coli, and the Gram stain and lab findings are consistent with E. coli in this case. Therefore, it is probably not necessary to do a sensitivity screen (as would be the case with nosocomial infections that are usually caused by resistant strains). Reasonable treatment regimens in this situation would be oral trimethoprim-sulfamethoxazole DS (bid for 15-20 days). Note that quinolones generally are not used during pregnancy because of their effect on growing bones, etc.

Question 3.6: Should the patient be checked for possible alternative causes of the current problem?

In a young pregant woman with no prior history of UTIs, no further workup is warranted. In patients with recurrent UTIs, then an underlying cause, such as vesicoureteral reflux, urinary tract calculi, or other problem may be determined from further workup as indicated.