Acute pyelonephritis is a serious and common medical complication of pregnancy. It is estimated to occur in up to 1%-2% of pregnancies and is a common nonobstetrical indication for antepartum hospital admissions. Its prevalence is probably even higher in obstetrical clinics serving underserved inner-city populations such as ours in Newark, N.J.
The diagnosis of acute pyelonephritis is based on clinical signs and symptoms. Patients usually feel ill and have fever, chills, flank pain (usually right-sided), dysuria, and urgency and frequency. Nausea and vomiting also may be present. Laboratory abnormalities may include pyuria and bacteriuria, with white blood cell counts often predictive of pyelonephritis. A urine culture and sensitivity will often reveal Escherichia coli, but other less commonly found causative organisms may be detected as well.
It is the prevailing view that most pregnant women with acute pyelonephritis should be hospitalized for careful monitoring, evaluated for possible sepsis, and treated with parenteral antibiotics. Recently published retrospective cohort studies, as well as our own experience, have emphasized that the risks of preterm labor and delivery in these patients can be significant, as can the risks of septic shock and other complications. Treatment, therefore, should be aggressive, with careful monitoring and charting of vital signs, including urinary output; and fetal monitoring and monitoring of uterine contractions. That way one can identify patients who are not responding to treatment or who may be developing septic shock or preterm labor.
Studies have shown that 10%-12% of all pregnant women have asymptomatic bacteriuria. Because physiologic changes associated with pregnancy encourage urinary stasis, there is an increased risk of progression to acute pyelonephritis with the potential for serious infectious complications, even in pregnant women who are otherwise healthy. By and large, however, pyelonephritis is usually a preventable problem given access to prenatal care. Screening for asymptomatic bacteriuria during the first prenatal visit is important, and repeat screening in each trimester in women who are at high risk for recurrent infection is critical for preventing symptomatic and possibly severe infection.
Our screening preference is to perform a urine culture and sensitivity test at the first prenatal visit. Other providers may utilize a urinalysis and leukocyte esterase test initially, but as this approach is not as sensitive or specific, it must be followed by a urine culture and sensitivity testing if the urinalysis results are positive. Obstetricians and others providing prenatal care should utilize whatever approach works best for their patients and environment. Most importantly, screening for asymptomatic bacteriuria must occur early in the pregnancy.
Additional urine culture and sensitivity testing are advisable for patients who are at high risk for urinary tract infections, such as those who have had frequent UTIs before pregnancy and those who have anemia, sickle cell trait, a history of renal stones, diabetes mellitus, obesity, or neurologic disorders (such as neurogenic bladder and multiple sclerosis). Considering the increase in prevalence of obesity and diabetes, these high-risk patients represent a growing proportion of the obstetric population and appear to be at increased risk of UTIs as well. Women of increasing age and increasing parity also may be at higher risk of developing UTIs during pregnancy.
Cranberry juice has been touted for years as an effective remedy for the prevention and treatment of UTIs in women, and I advise my patients who have a UTI during pregnancy, who have diabetes, or who have other risk factors, to drink a glass of unsweetened cranberry juice each day. No definitive mechanism of action has been established, but it appears that cranberry juice prevents or interferes with the adherence of bacteria (particularly E. coli) to uroepithelial cells. It is important to emphasize to patients to consume unsweetened cranberry juice and not cranberry juice cocktail because of the high sugar content in the latter.
Recent research has emphasized that pregnancies of women who develop pyelonephritis are more likely to be complicated by spontaneous preterm birth, septicemia, and other adverse outcomes. In a retrospective cohort study of more than 546,000 singleton pregnancies delivered in all Kaiser Permanente of Southern California hospitals from 1993 to 2010, women with pyelonephritis were almost 57 times more likely than those without pyelonephritis to develop septicemia and 1.3 times more likely to have spontaneous preterm birth.
In addition, pregnancies of women with pyelonephritis were 2.6 times more likely than those of the baseline obstetric population to be complicated by anemia and 16.5 times more likely to be complicated by acute renal failure (Am. J. Obstet. Gynecol. 2014;210:219.e1-6). The overall incidence of acute antepartum pyelonephritis in this cohort study was relatively low compared with the incidence in other populations – 0.5% – which is not surprising given that patients in Kaiser’s integrated health care system routinely receive prenatal screening for asymptomatic bacteriuria.