Bacteruria, UTI, and Pyelonephritis

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Today, we’re going to review all the iterations of urine culture abnormalities in pregnancy. We screen urine cultures in the first trimester and many times again later on in pregnancy, and urinary symptoms are a common complaint.

Asymptomatic bacteriuria is when high levels of bacteria are in urine without associated symptoms. This occurs in 2-7% of pregnant women and typically occurs early in pregnancy.

Urinary tract infections can be broken down into two sub-categories:

  1. Lower UTI, or acute cystitis is basically an infection of the bladder, with symptoms of dysuria, urinary frequency, and urgency. They occur in 1-2% of pregnant women.

  2. Upper UTI, or acute pyelonephritis may have symptoms of simple cystitis, but include systemic symptoms of infection: flank pain, fevers, chills, nausea/vomiting and costovertebral angle (CVA) tenderness. They occur in 0.5-2% of pregnant women, and more commonly in the 2nd and 3rd trimesters.

Non pregnant women can experience asymptomatic bacteriuria as well as pregnant women. In the non pregnant patient, ASB can be quite prevalent, particularly as we age — over 20% in patients >80 years old. Multiple studies have shown that treatment of asymptomatic bacteriuria in the general, nonpregnant population does not reduce frequency of symptomatic infection or prevent adverse outcomes. Importantly, adhering to this principle helps with antibiotic stewardship.

Pregnant women, however, are different story. As many as 20-35% of pregnant women with asymptomatic bacteriuria will develop symptomatic cystitis or pyelonephritis if untreated, and risk is reduced by 70-80% with treatment. Asymptomatic bacteriuria is not only associated with pyelo, but also associated with adverse pregnancy outcomes, like preterm birth and low birth weight infants. Thus, versus other populations, ASB treatment is imperative in pregnancy.

The most common organisms implicated in these urinary infections include: 

  • E. coli - about 70% 

  • Klebsiella  - about 3% 

  • Enterobacter - about 2% 

  • Gram positive organisms (like GBS) = 10% 

Diagnosis and Screening Recommendations for ASB, Cystitis, and Pyelonephritis:

  • Asymptomatic bacteriuria 

    1. Finding high-level bacterial growth on urine culture without symptoms consistent with a UTI.

    2. Recommendation per Infectious Disease Society of America to screen all pregnant women for asymptomatic bacteriuria at least once in early pregnancy (usually 12-16 weeks).

    3. Diagnostic criteria:

      1. Isolation of same bacterial strain greater than or equal to 10^5 colony-forming units/mL in two consecutive voided urine samples, or

      2. A single catheterized specimen with one bacterial species isolated in >/= 10^2 cfu/mL 

  • Acute Cystitis 

    1. Symptoms as described above (dysuria, etc) with pyuria seen on urinalysis.

    2. Should be confirmed with urine culture, but with typical symptoms and pyuria, should start treating without the culture coming back.

    3. Cystitis should NOT involve systemic symptoms.

  • Pyelonephritis 

    1. Can have all of the above (though dysuria may not always be present).

    2. Fevers, chills, flank pain, nausea/vomiting, CVA tenderness.

    3. Pregnant women can become VERY sick 

      1. Estimated that as many as 20% of pregnant women with pyelonephritis develop complications like septic shock syndrome or variants like ARDS.

      2. One study of 32,282 pregnant women in the general obstetric population with pyelo → 23% had anemia, 17% had bacteremia, 7% had respiratory insufficiency, and 2% had renal dysfunction.

    4. Diagnostic evaluation can include:

      1. Urinalysis, urine culture.

      2. CBC

      3. Possibly blood cultures and lactic acid if patient presents with sepsis.

      4. Imaging not routine, but in patients who are severely ill or who have symptoms of renal colic, diabetes, prior urologic surgery, immunosuppression, urosepsis, or repeated pyelo, imaging can help identify other complicating factors, ie. infected stone, renal abscess.

      5. Can consider CT, but ultrasound preferred due to decreased radiation exposure in pregnant women.

Treatment 

  • Asymptomatic bacteriuria 

    1. Basic principle is to treat with antibiotics tailored to culture results and then follow up cultures to confirm sterilization of the urine.

    2. Possible antibiotics to consider include beta-lactams, nitrofurantoin, or fosfomycin.

    1. A short course is usually effective in eradicating asymptomatic bacteriuria,  although a single-dose regimens may not be as effective as slightly longer regimens. However, optimal duration of therapy is uncertain.

      1. The only exception is fosfomycin - a single dose can successfully treat bacteriuria.

    1. Follow up 

      1. Up to 30% of women fail to clear asymptomatic bacteriuria after short course therapy, so repeat culture is recommended about a week after finishing antibiotics.

      2. However, there isn’t a lot of data about if we should repeat another culture later on for repeat screening after treatment, or if this is even necessary.

      3. Similarly, not a lot of data about treating again if repeat culture is positive and for how long, though general consensus is to treat.

  • Acute cystitis 

    1. Treatment is usually empiric because it’s hard to make someone wait until cultures are back.

    2. Same antibiotic treatment options as for asymptomatic bacteriuria.

    3. Again, treatment time is uncertain, but usually 3-7 day course as long as there are no symptoms/signs of pyelo (except fosfomycin, which is single-dose regimen).

    4. Follow-up repeat culture 7 days after antibiotic completion, as with ASB.

    5. If a woman has 2 or more episodes of recurrent cystitis in pregnancy, it is reasonable to start antibiotic prophylaxis:

      1. Cephalexin 250-500mg qHS or nitrofurantoin 50-100mg qHS depending on susceptibility of organisms on previous cultures.

  • Pyelonephritis 

    1. Pregnant people need to be admitted because they are WAY more likely to get super sick compared to nonpregnant women.

    2. Parenteral antibiotics initially, then converted to oral antibiotics when woman has been afebrile for 24-48 hours.

    3. Empiric antibiotics:

      1. Broad spectrum beta-lactams - ie. ceftriaxone 

      2. If someone has ESBL (extended spectrum beta-lactamase) bacteria, can consider a carbapenem.

      3. Avoid fluoroquinolones and aminoglycosides in pregnancy.

    4. Oral antibiotics:

      1. Should usually be beta-lactams, or if second trimester, can consider trimethoprim-sulfamethoxazole (Bactrim).

      2. Do not use nitrofurantoin or fosfomycin because they do not achieve adequate levels in the kidney.

    5. Suppression/Prophylaxis:

      1. Should consider preventative therapy for the duration of pregnancy because recurrent pyelo during pregnancy occurs in 6-8% of women.

      2. Some practices continue antibiotic prophylaxis for six weeks postpartum, but the data is unclear to the benefit of this.


Obstetrical Ultrasound

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Sonographic nomenclature breaks down into three main types of ultrasound:

  1. Limited US: for a specific, singular purpose (i.e., viability, placental location, presentation, cervical length).

  2. Standard US: A more thorough examination, which requires a number of elements including:

    • Fetal presentation and number 

    • Amniotic fluid volume

      1. AFI (normal 5-25) or DVP (normal 2-8)

      2. SMFM recommends using DVP over AFI to diagnose oligo in the third trimester as using AFI leads to more interventions without improving perinatal outcomes 

    • Fetal Heart Rate / Rhythm

    • Placental location 

      1. Previa covers cervical os, either partially or wholly.

      2. Low lying placental edge is within 2cm of os.

        1. Partial or marginal previa is unfavored terminology.

      3. Suspicion for abnormal placentation for previa in setting of history of cesarean. With previa, history of 

        1. 1 prior cesarean = 3% risk of PAS

        2. 2 prior cesarean = 11% risk of PAS

        3. 3 prior cesarean = 40% risk of PAS

        4. 4 prior cesarean = 61% risk of PAS

    • Fetal biometry/anatomic survey.

    • Cervix and adnexa when clinically appropriate and when technically feasible. 

  3. Specialized US: A highly technical ultrasound that focuses on particular organ systems or uses dynamic measures.

    1. Examples include level 2 ultrasounds which provide further anatomic detail than a standard US, or fetal doppler ultrasonography, biophysical profiles, or fetal echocardiograms.

Important Facts for Ultrasound, by Trimester:

First Trimester: Know the absolute and relative criteria for early pregnancy failure, from SRU’s publication in NEJM:

(c) NEJM, 2013

2nd / 3rd Trimester: Know components of a basic growth scan by the Hadlock formula. Some representative photos are here! Images courtesy of www.fetalultrasound.com. Be sure to check out The OBG Project 2nd Trimester Ultrasound Atlas if you’re a chief resident with access to OBG First!

Appropriate plane for BPD and HC measurements

Appropriate plane for fetal abdominal circumference.

Appropriate plane for fetal abdominal circumference.

Appropriate plane and landmarks for fetal femoral length measurement.

Preventing the Primary Cesarean Section

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This mega-episode was inspired by a two-part Grand Rounds series written by our PGY-4 Brown OBGYN class. We’ll dive into some of the history of cesarean, the challenges and data with respect to deciding on cesarean delivery, and current evidence-based strategies to reduce the risk of primary cesarean in low-risk women.

Cesarean sections have been around for a long time, the very first of which was documented around 1750 BC. However, surgery was originally performed only on a dead or dying mom with the hope of saving the child, or so the infant could be buried separately from mom per religious edicts. And then for the first 3000 years of cesarean, the mortality rate for women was… 100%. And it stayed this way until the mid-18th century! Anesthesia was introduced in 1846 with the discovery of ether, and as the 19th century progressed sutures and antibiotics became live-saving measures that allowed women to survive cesarean.

With the urbanization of the western world through this time period, more women began to deliver in hospitals as cesarean became a viable alternative, rather than delivering at home. In the USA, by 1955, 99% of births occurred in hospital. The rate of cesarean in the US stayed low until the 1970s, which coincided with the introduction of electronic fetal monitoring. A cesarean rate of <10% prior to EFM increased to 17% by 1980, 25% by 1988, and 31.9% in 2016.

Now with the increased use of cesarean, we should expect some benefit to it. And there certainly are! There are life-saving implications for both mother and baby, and when needed, the surgery is absolutely a necessary tool for an obstetrician. That said, cesarean does not come without its own risks. For mothers, cesarean is associated with more risk of bleeding, infection, thrombosis, increased pain, worse satisfaction with the birth experience, and risks to future pregnancy such as increased risk of repeat cesarean and risk of placenta accreta spectrum (PAS) disorders. For infants, cesarean carries slightly higher risks of respiratory difficulty during the transition, breastfeeding difficulty, and intracranial hemorrhage (if laboring prior to cesarean; rates of IVH between SVD and non-laboring cesarean are about equal).

One of the criticisms of cesarean delivery are that its use does not seem standardized. There is a high level of variation between countries, and in the US, there is high variation between states, cities, and even hospitals in the same city! As an example, here are the nulliparous term singleton vertex (NTSV) cesarean rates between US states for 2016:

While no rate of cesarean has proven to be the “optimal” or “ideal” amount, some observational data may provide some clues. The WHO has compared countries’ rates of cesarean with respect to both maternal and neonatal mortality, and also attempted to normalize these countries’ resources by demonstrating their relative wealth. For both maternal and neonatal mortality benefit, the rate seems to sit around 20% — you can see these graphs from the WHO below.

In order to safely choose our use of cesarean delivery, there are evidence-based guidelines to recall. The ACOG/SMFM Obstetric Care Consensus #1 on safe prevention of the primary cesarean delivery is one such tool. In this document, there are three important thresholds to remember. This is nicely outlined in checklist format by the folks at the California Maternal Health Quality Collaborative (CMQCC):

The use of partographs also has some limited data to support their use to help monitor labor progress. While one version over another hasn’t been shown to be superior, in a before-and-after study, the presence of their use helped to reduce cesarean rates, likely because of the closer attention to normal labor progress that was effected by them.

We additionally came across some other exciting ways to try to help reduce cesarean rates or examine cesarean utilization. Some of these things include:

  • Open Access to Cesarean Data 

    • Beth Israel Deaconess’ NTSV rate was a target of a large, stepwise quality project, with a decrease from 35% to 21% over 8 years. However, their single best year of improvement was from 2014-2015, when cesarean data was fully unmasked and shared amongst all physicians who practiced there. Similar findings have been demonstrated in the CMQCC hospitals. Simply put, no one likes to be an outlier amongst their peers!

  • Cesarean Audit Committees

    • These committees meet to review all unplanned cesarean delivery, prepare and interpret data, and look for opportunities for improvement in terms of physician/midwife, nurse, or patient education.

      • These committees offer the advantage of individualized feedback for improvement of practice based on more nuanced classifications that adjust for risk in population than just “NTSV.” 

      • Meta-analyses have demonstrated reduced cesarean rates stemming from a cesarean audit in concert with multifaceted programs to reduce cesarean delivery.

  • Utilizing Labor Dystocia Checklists

    • Several quality collaborative groups use checklists, such as the one from CMQCC above; these are evidence-based, objective, and don’t call into question a provider’s interpretation of labor progress. 

      • Overall decrease PCS by preventing premature C/S for indications of labor dystocia. 

      • Some institutions have gone as far as to institute “double doctor” reviews for cesarean for labor arrest, allowing for a second opinion, particularly regarding the feasibility of operative vaginal delivery.

  • Improved, transparent team communication 

    • Improved communication between physician or midwife, bedside nurse, patient, and support persons allows for appropriate expectations for labor or induction, and allows all members of the team to “be on the same page.”

    • At our institution, we are trialing using a whiteboard to document the partograph in the labor room; this allows the patient to compare patient to where they are on partograph compared to “standard labor progress.”

Have a technique you’re using at your hospital to help reduce primary cesarean delivery? Share it with us! We’d love to hear from you via email or the comments section of the website.

Chorioamnionitis and Endometritis

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Today we dive into intraamniotic infection (IAI), more commonly known as chorioamnionitis or endometritis. CO 712 reviews a lot of the surprisingly limited evidence on the management of IAI, and the essentials you need to know for your labor floor and for CREOGs.

IAI is an important topic because of its morbidity. 2-5% of term deliveries are complicated by chorioamnionitis. It is associated with acute neonatal morbidity, including things such as pneumonia, meningitis, sepsis, and death. Treatment intrapartum is associated with an over 10-fold decrease in GBS-neonatal sepsis. Maternal morbidities include dysfunctional labor curves that lead to further intervention, increased risk of postpartum hemorrhage due to atony, and peritonitis, sepsis, ARDS, and rarely death.

Risk factors for IAI include a longer length of labor and longer length of ROM. Additionally, it is thought that multiple digital vaginal exams in the setting of ROM  can increase risk. Other, less obvious risk factors include cervical insufficiency, nulliparity, meconium-stained fluid, use of internal fetal or uterine contraction monitoring, presence of genital tract pathogens (ie. STIs, GBS, BV), alcohol and tobacco use, and of course previous history of chorioamnionitis.

The gold standard diagnosis is made off of a gram stain or culture of amniotic fluid, but this is obviously problematic! So in reality, there are three categories of IAI or IAI-risk that help guide clinicians into deciding therapy:

  1. Isolated Maternal Fever: Single oral temperature of 39 C or greater OR an oral temperature of 38-38.9 C that persists when the temp is repeated after 30 minutes.

  2. Suspected intraamniotic infection: Based on clinical criteria, which includes maternal fever PLUS one of maternal leukocytosis, fetal tachycardia, or purulent or malodorous amniotic fluid. 

  3. Confirmed intraamniotic infection: Based on the gold standard of culture/gram stain.

Does every fever intrapartum need to be treated?

There are lots of things that can cause fever intrapartum or immediately postpartum other than chorioamnionitis, such as:

  • Misoprostol use and other types of drug fevers.

  • Epidural use.

  • Other sources of infection (ie. UTI, respiratory infection).

  • Also… being in a hot room (girl, labor is hard work)!

For isolated maternal fever of 38-38.9, CO 712 states that without other clinical criteria indicating infection and with/without persistent temperature elevation: 

  1. Few data exist to guide appropriate management of women with isolated intrapartum fever in absence of other clinical signs suggesting intra-amniotic infection.

  2. Consider antibiotics, but should definitely still communicate to pediatric team.

Our tendency is to treat persistent temperatures in this range in most cases.

Antibiotic Therapy: from CO 712:

ACOG CO 712

Once postpartum, antibiotics should not need to continue based on principle. Instead, antimicrobial therapy should be based on risk factors for postpartum endometritis:

  • Women who deliver vaginally may NOT require antibiotics postpartum as they are less likely to develop endometritis.

    1. However, give an additional dose if bacteremia or persistent fever are present.

  • Women undergoing cesarean deliveries should receive at least one additional dose of antimicrobial agents after delivery is recommended.

    1. One additional dose of chosen regimen + clindamycin 900 mg IV or metronidazole 500 mg IV.

Postpartum endometritis occurs when infection is not totally cleared out after delivery and affects the endometrium. Risk factors include chorioamnionitis, cesarean delivery, prolonged labor or ROM, manual placental removal, and all the chorioamnionitis risk factors above.

The diagnosis is based on the presence of postpartum fever, along with tachycardia, uterine tenderness, foul smelling lochia, and/or leukocytosis.

Treating endometritis occurs most commonly with clindamycin and gentamicin, with the addition of ampicillin (“triple therapy”) for GBS-positive patients. The patient should be treated until 24-48 hours afebrile. Additional oral antibiotic therapy after successful IV therapy is not required as RCTs have demonstrated no improved outcomes. And of course if someone isn’t looking better, consider source control measures (i.e., D&C for retained POCs) or a different source of infection.