Free Fluid in Morison’s Pouch on Bedside Ultrasound Predicts Need for Operative Intervention in Suspected Ectopic Pregnancy

Background

Vaginal bleeding and abdominal pain are common presenting symptoms to the emergency department (ED) in women in early pregnancy. While the majority of pregnant patients presenting with these symptoms are stable, a small subset of this group represents a ruptured ectopic pregnancy with a potential to rapidly decompensate, resulting in high rates of morbidity and mortality. Therefore it is critical for this diagnosis to be identified both accurately and rapidly.

The Focused Assessment of Sonography in Trauma (FAST) exam has been well studied in the acute trauma setting to identify internal bleeding however there is not much data on its use in the non trauma setting. In theory, it makes intuitive sense that it should perform similarly and be able to accurately identify significant non traumatic pelvic and intraperitoneal bleeding.

In a previous study, emergency physician (EP) performed bedside ultrasound (US) in suspected ectopic pregnancy was found to  decrease the time to both diagnosis and treatment [1]. The following study seeks to prospectively investigate the significance of positive fluid in Morison's pouch during transabdominal US examination performed by EPs in patients with suspected ectopic pregnancy. 

Free Fluid in Morison’s Pouch on Bedside Ultrasound Predicts Need for Operative Intervention in Suspected Ectopic Pregnancy‌

Clinical Question

Is EP performed US with identification of free fluid in Morison's pouch predictive of the need for operative intervention in suspected ectopic pregnancy?

Methods & Study Design

  • Design
    • Prospective observational study
  • Population
    • Conducted at Yale-New Haven Hospital, an urban Level 1 trauma center and teaching hospital
    • Pregnant women presenting to the ED in whom there was a suspicion of an ectopic pregnancy
  • Inclusion criteria
    • Female patients with positive pregnancy test who presented in first trimester with abdominal pain and/or vaginal bleeding and requiring further imaging or consultation
  • Exclusion criteria
    • No specific criteria
  • Intervention
    • EP performed transabdominal and transpelvic US evaluation for:
      • Free fluid in Morison's pouch (positive, negative or indeterminate)
      • Presence of intrauterine pregnancy (IUP), or no definitive IUP
      • Free fluid in the cul-de-sac (present, absent)
  • Outcomes
    • Follow up and chart review was performed by independent study investigators, blinded to ED US results, ultimately classifying the final outcome as ectopic or non ectopic pregnancy and further defining the management as operative or medical.

Results

Patient Flow Diagram 

Ultrasound Findings and Clinical Characteristics  of Patients

 

 

Strengths & Limitations

  • Strengths
    • Performed in ED based population
    • All ultrasound examinations performed by ED physicians making this applicable to point-of-care ultrasound
  • Limitations
    • Potential selection bias given that rate of ectopic pregnancy in study population was higher than most published rates
    • Not truly observational study as treating physicians were not blinded to ED US results
    • Some patients lost to follow up

Authors Conclusion

"Free intraperitoneal fluid found in Morison’s pouch in patients with suspected ectopic pregnancy may be rapidly identified at the bedside by an EP-performed US and predicts the need for operative intervention. Transabdominal pelvic US may show an IUP in more than one third of patients with suspected ectopic pregnancy."

Our Conclusion

While this paper does not have the methodological prowess of a multicenter randomized control trial, it accurately answers an important question with respect to positive fluid in Morison's pouch on ED US and the need for operative intervention in ectopic pregnancy. This study also highlights the niche of point-of-care ultrasound and why it is so critical to our practice as emergency medicine providers. Unlike radiological studies, which require increased time and may be difficult to obtain in critical patients, point-of-care ultrasound allows rapid identification of key findings that allow for early diagnosis and decision making.

Based on this study, the addition of positive fluid seen in Morison's pouch during ED US for suspected ectopic pregnancy now adds on a strong predictor for the need for operative intervention. This is especially important in unstable and hypotensive patients.

However, there are several caveats to understand when interpreting this data. First, all the patients in this study were enrolled after having a positive pregnancy test, therefore, prior to assuming that a young female with free fluid in her abdomen is from a ruptured ectopic pregnancy, a pregnancy must first be confirmed.  Second, not all free fluid in Morison's pouch in a pregnant woman is due to an ectopic pregnancy. In this data set, there was one patient that had a definitive IUP and free fluid in Morison's pouch which was found to be from a ruptured corpus luteal cyst. There are also case reports of splenic artery aneurysm rupture in pregnancy that could mimic a ruptured ectopic [2]. If an IUP is identified on transabdominal ultrasound, unless the patient is receiving advanced reproductive techniques, alternative explanations for the free fluid should at least be considered before a heterotopic pregnancy is presumed. Third, while this study demonstrates excellent specificity of positive fluid in Morison's pouch and the need for operative intervention in suspected ectopic pregnancy, it has very poor sensitivity. Therefore, ED US should be used as a rule in technique and does not replace formal ultrasound and obstetrical consultation if the diagnosis is not clear.

The Bottom Line

Free fluid found in Morison’s pouch in patients with suspected ectopic pregnancy can be rapidly identified at the bedside by emergency providers and predicts the need for operative intervention.

 

Authors

This post was written by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Rodgerson JD, Heegaard WG, Plummer D, Hicks J, Clinton J, Sterner S. Emergency department right upper quadrant ultrasound is associated with a reduced time to diagnosis and treatment of ruptured ectopic pregnancies. Acad Emerg Med. 2001; 8:331–6.
    2. Lynch MJ, Woodford NW. Rupture of a splenic artery aneurysm during pregnancy with maternal and foetal death: a case report. Med Sci Law. 2008;48:(4)342-5.
    3. Moore C et al. Free fluid in Morison's pouch on bedside ultrasound predicts need for operative intervention in suspected ectopic pregnancy. Acad Emerg Med. 2007; 8: 755-8

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