Pyelonephritis is defined as a UTI of the renal parenchyma and collecting system manifested by the clinical syndrome of fever, chills, and flank pain. For the young, otherwise healthy, non-pregnant female patient, the treatment regimen is generally performed on an outpatient basis.
Unless the patient is very ill-appearing, unreliable, or is in a high-risk category, appropriate antibiotics, pain medications, and if needed, antiemetics, are prescribed. Generally a one- to two-day follow-up is recommended. The classic criterion for admission for pyelonephritis has been one of five patient characteristics: clinical toxicity, inability to take oral medications, an immunocompromised state, urological abnormalities, and pregnancy.1 This article will explore the evolving concept of outpatient treatment of pyelonephritis in otherwise healthy pregnant women.
Pyelonephritis in pregnancy is thought to occur from a combination of bacteriuria and the relative obstruction of the ureters. The obstruction is due to hormonal (progesterone) and mechanical factors (the enlarged uterus). In one review of 656 women with acute pyelonephritis, 73 percent occurred in the second or third trimester.2 Approximately two percent of all pregnant women will develop pyelonephritis, with about 20 percent of these having recurrences during the same pregnancy.3
Risk factors for the development of a UTI in pregnancy include lower socioeconomic status, sickle cell anemia, diabetes, a prior history of UTIs, and neurogenic bladder.4 The cost-effectiveness of screening and treatment of asymptomatic bacteriuria in pregnant women has been proven and should be part of all prenatal primary care, but in the ED we are often faced with women with inconsistent or no prenatal care.
Clinically, pregnant patients with pyelonephritis will present with the constellation symptoms that we recognize as classic pyelonephritis: back pain, fever, chills with nausea, and sometimes vomiting. Lower tract symptoms, such as dysuria, frequency, and urgency are often but not always present.
Microbiology of Pyelonephritis
The microbiology of pyelonephritis in pregnant women is similar to that in nonpregnant women. E. coli is by far the most common organism found, reaching 80 percent of all culture positive cases in most studies; other gram-negative rods such as Proteus mirabilis and Klebsiella pneumoniae are less common organisms.
Gram-positive bacteria are much less common, but one, group B streptococcus, has serious implications. Group B streptococcus (GBS) accounts for approximately five percent of all UTIs.Vaginal colonization is associated with neonatal sepsis, premature rupture of membranes, and preterm labor and delivery. The evidence of whether a GBS UTI imparts these risks is unclear, however.
Antibiotic choices obviously need to take into account any effects on the fetus, but also need good urinary tract penetration and coverage of the most likely organisms. Historically, ampicillin alone was one of the drugs of choice, but due to high rates of resistance, this is no longer a reasonable choice. An important development that began in Europe in the 1980s and hit the United States shortly after is the development of extended-spectrum beta-lactamases (ESBL). This plasmid-mediated enzyme imparts high levels of resistance to not only the third-generation cephalosporins but also quinolones, aminoglycosides, and TMP/SMX.
ESBLs are most common in K. pneumoniae, but also are found in E. coli. The current recommendations for antibiotic choices for inpatient treatment are as follows: a first-generation cephalosporin, gentamicin (with or without ampicillin), a third-generation cephalosporin, or only in the first or second trimester, TMP/SMX. Most outpatient protocols use ceftriaxone due to its 24-hour dosing. The current recommendations for overcoming ESBLs are using either cefipime or a carbapenem.5 This scenario would present simply as a treatment failure to a reasonable antibiotic with no other explanation (vomiting medications and/or noncompliance).
The practice of admitting all pregnant patients with pyelonephritis came as a result of several animal and human studies, the majority from the 1960s through the early 1980s. These papers linked pyelonephritis to ARDS,6,7 hemolytic anemia,8 premature labor/low birth weight,9,10 and septic shock.11 The generally accepted incidence of ARDS is two percent and septic shock is one to two percent.
Interestingly, a more recent prospective study has shown no difference between pregnant women with bacteriuria and uninfected controls in terms of premature delivery, anemia, or low birth weight.12 Those earlier studies are probably what has led to our practice of admitting all pregnant patients with pyelonephritis.
With costs and hospital days being looked at more closely, the idea of not admitting a small subset of these patients has been investigated. Several studies throughout the 1990s have looked at many of the issues concerning outpatient treatment protocols. One study compared admitted patients given an oral first-generation cephalosporin with an IV first-generation cephalosporin,12 and another compared inpatient IV antibiotics with inpatient IM ceftriaxone.13 Both found no difference in outcomes.
The concept of inpatient vs. outpatient treatment also was studied, and in 1995 Millar directly compared inpatient IV cefazolin with outpatient IM ceftriaxone, and found no difference in outcome. Interestingly, the utility of blood and urine cultures also has been investigated in the obstetrics literature, and found not useful in directing management (as in our literature). The investigators concluded that the decision to change antibiotics should be based solely on clinical course rather than culture results.13
These studies, along with economic pressures in modern medicine, have led to the development of criteria and protocols for the outpatient management of pyelonephritis in pregnant women. One author's4 criteria for outpatient management are tolerance of oral medications, no signs or symptoms of sepsis, no evidence of hemolysis or ARDS, available home health care follow-up, and ideally a 23-hour observation period.
In a former institution of mine, a high-volume county hospital in California, the outpatient protocol was that patients deemed nontoxic and reliable received ceftriaxone in the ED and followed up daily in the obstetrics clinic for IM ceftriaxone for two to three days. They then received oral antibiotics for 14 days. Certainly, any patient you are considering discharging will need to be done in close coordination with the patient's obstetrician.
Although certainly not done everywhere, the practice of not admitting a pregnant woman with pyelonephritis, once something that no one would ever contemplate, is a situation that we should begin to become comfortable with. This does not mean every pregnant woman with pyelonephritis can be discharged, but with strict patient selection and good outpatient follow-up, we all may be doing this more than we ever thought.
Classic Criterion for Admission for Pyelonephritis
(One of five patient characteristics)
- Clinical toxicity
- Inability to take oral medications
- Immunocompromised state
- Urological abnormalities
Source: Rosen's Emergency Medicine: Concepts and Clinical Practice. 5th Ed., Electronic Pages. p. 1410.
1. Rosen's Emergency Medicine: Concepts and Clinical Practice
Ed., Electronic Pages. p. 1410.
2. Gilstrap LC, Faro S. Urinary tract infections in pregnancy. In Infections in Pregnancy
, ed 2. New York, Wiley-Liss, 1997, p. 21.
3. Delzell JE Jr. Urinary tract infections during pregnancy. Am Fam Physician
4. Gilstrap LC, Ramin S. Urinary tract infections in pregnancy. in Obstetrics and Gynecology Clinics
. September 2001, Vol.28, No.3.
5. Patterson TF. Bacteriuria in pregnancy. Infect Dis Clin North Am
6. Cunningham FG, Leveno KJ, et al. Respiratory insufficiency associated with pyelonephritis during pregnancy. Obstet Gynecol
7. Cunningham FG, Lucas MJ, Hankins GDV. Pulmonary injury complicating antepartum pyelonephritis. Am J Obstet Gynecol
8. Cox SM, Shelburne P, et al. Mechanisms of hemolysis and anemia associated with pyelonephritis during pregnancy. Am J Obstet Gynecol
9. Gilstrap LC, Leveno KJ, et al. Renal infections and pregnancy outcome. Am J Obstet Gynecol
10. Kass EH. The role of asymptomatic bacteriuria in the pathogenesis of pyelonephritis. in Quinn EL, Kass EH(eds): Biology of Pyelonephritis
. Boston, Little, Brown. 1960, p. 399.
11. Cunningham FG, Morris GB, Mickal A. Acute pyelonephritis of pregnancy: A clinical review. Obstet Gynecol 1973;42:112.
12. Gilstrap LC, Cunningham FC, Whalley PJ. Acute pyelonephritis in pregnancy: An anterospective study. Obstet Gynecol
13. Wing DA, Park AS, et al.: Limited clinical utility of blood and urine cultures in the treatment of acute pyelonephritis during pregnancy: Am J Obstet Gynecol