Last Update: 4/26/2016
Initial infection: 1-2.5% of pregnancies when routine screening for asymptomatic bacteriuria (ASB) occurs. Most common nonobstetric cause of hospitalization during pregnancy.
Recurrent infection: in 10-18% of cases with suppressive antimicrobial therapy.
- A history of pyelonephritis during the current pregnancy – 60% of women will have recurrence without suppressive antibiotics
- ASB – Up to 40% of women with untreated ASB will develop acute pyelonephritis.
- Obstructive/neurologic diseases affecting the urinary tract
- Ureteral/renal calculi
Several factors during pregnancy facilitate bacterial replication in urine and ascent to the upper urinary tract:
- Decreased tone, increased capacity, and incomplete emptying in the urinary bladder leads to vesicoureteric reflux to occur.
- Physiologic hydronephrosis of pregnancy facilitates ascent of bacteria into the upper urinary tract.
- Alterations in the physical and chemical properties of urine during pregnancy:
- Elevated urinary pH during pregnancy.
- Glycosuria enhances bacterial growth.
- Increased urinary excretion of estrogen (which has been shown to accelerate the growth of strains of E. coli that cause pyelonephritis).
Effects of pyelonephritis on pregnancy:
- Increased risk for preterm labor and delivery if not appropriately treated.
- Threat to maternal well-being. Up to 20% of pregnant women with acute pyelonephritis develop evidence of multiorgan system (renal dysfunction, pulmonary insufficiency/ARDS) involvement secondary to endotoxemia and the sepsis syndrome.
- Hypovolemia – from sepsis, nausea and vomiting – leads to hypotension
- DIC, hemolytic anemia – complications of sepsis/endotoxemia
Symptoms: chills, flank pain, dysuria, urgency, frequency, nausea and vomiting. Abrupt onset of symptoms
Signs: fever (universal) and costovertebral angle tenderness (unilateral on the right side in 50% of cases in pregnancy).
Laboratory abnormalities: pyuria and bacteriuria; white blood cell casts are highly predictive of acute pyelonephritis. The diagnosis is ultimately confirmed by a positive urine culture.
The most common bacteria associated with acute pyelonephritis are E. coli, Klebsiella species, Proteus and Enterobacter species. Staphylococcus aureus, gram-positive bacteria, including GBS and P. mirabilis are less frequently isolated.
- Inpatient management – for at least 12 to 24 hours, or until urine culture results are available at which time antibiotics can be tailored to the specific bacteria.
- Empiric treatment – with broad-spectrum third generation cephalosporin (Ceftriaxone) should be started as soon as a presumptive diagnosis is made
3. Addition of an aminoglycoside can be considered for patients not responding to the initial empiric treatment. Prolonged use has been shown to cause ototoxicity in the fetus and should not be first line treatment.
4. IV antibiotics continue until the patient has been afebrile x 24-48 hours. Switching to PO antibiotics at that time is acceptable, assuming the patient is tolerating a PO diet.
5. PO antibiotics should continue for a total of 10-14 days (IV + PO).
6. Fluoroquinolones should be avoided in pregnancy, unless no alternative antimicrobial agent is available.
7. Acetaminophen to keep temperature below 100 F (38 C).
8. Careful monitoring of renal function, urinary output, and respiratory status, including pulse oximetry.
9. Fluid resuscitation with an isotonic crystalloid (LR or normal saline) to maintain adequate urine output (30-50 cc/hour)
10. Blood culture, if sepsis is suspected or if initial therapy fails
- Imaging of the urinary tract – if symptoms persist after 24-48 hours of treatment.
- Chest x-ray – if lung exam is suspicious for pneumonia or pulmonary insufficiency/ARDS or for patient with tachypnea or dyspnea . ICU admission is warranted in these cases for airway management.
- Antibiotic suppression – for the duration of the pregnancy after completion of treatment. Nitrofurantoin 100mg PO qHS and Cephalexin 500mg PO qHS are acceptable treatments.
- Urine cultures – obtained each trimester (or as necessary for symptoms) for the duration of the pregnancy
- Usually inpatient management is necessary for the first few days of treatment.
- For the patient who is deemed ready for discharge prior to the availability of culture and sensitivity results, a bactericidal cephalosporin is the optimal treatment. Appropriate PO cephalosporins include:
– cephalexin (Keflex) 500mg/6-12 hours. Cost $176.00/30 tabs (500mg)
– cefuroxime axetil (Ceftin) 500mg/12 hours. Cost $360.00/20 tabs
– ceftibutin (available only as brand name Cedax) 400mg/day. Cost $75.00/20 capsules. Also available as a suspension
– cefixime (Suprax) 400mg PO q day, ideally divided into 2 doses of 200mg/12-hours (dispensed as a suspension, 100 mg/5mL). Cost $294.00/ 100mL
– cefpodoxime (Vantin) 400mg/12 hours. Cost $195.00/20 tabs (200mg)
It is essential that culture and sensitivity results be reviewed and antibiotics adjusted accordingly for these patients.
- Maternal-Fetal Medicine, online ed. Creasy RK, Resnik R, Iams JD, Lockwood CJ, Moore TM. Ch 38, “Maternal and fetal infections”, ©2011, Elsevier Inc.
- Obstetrics: Normal and Problem Pregnancies, 5th ed. Gabbe SG, Niebyl JR, Simpson JL. Ch 36, pp 966-967, ©2002 Churchill Livingstone.
- Hooton TM. “Urinary tract infections and asymptomatic bacteriuria in pregnancy”. UpToDate version 19.2, 4/27/2011.
- Critical Care Obstetrics, 4th ed. Dildy GA. Ch 27, p 375. ©2004, Blackwell Science.