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

Case # 13: What Lies Beneath

A 30 year old male presents to the emergency department after blunt trauma to the face from an altercation. He notes he was punched several times in the face but did not pass out. His exam is notable for significant right periorbital ecchymosis and edema with inability to open his eye. You are unable to perform a direct eye exam given the significant periorbital swelling.  A CT maxillofacial is performed which shows an isolated right inferior orbital wall fracture.

Vitals: T 98.6 HR 85 BP 142/81  RR 14 O2 98% on RA

Prior to ENT consultation, a bedside ultrasound of the orbits is performed.  In spite of being unable to open the eye, what can you tell your consultant regarding your exam?

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Answer and Learning Points

Answer

Using ultrasound as an adjunct to your exam, you are able to tell the consultant that there is a normal appearing, reactive pupil and that the extra-ocular movements of the eye are intact. The consultant is appreciative over the phone and is happy to come in and see the patient whom after evaluation is discharged home with close outpatient follow up.

Learning Points

It is often the case where a patient suffers such significant facial trauma that a complete physical exam of the orbit due to periorbital swelling is not possible. Ultrasound can be a critical tool in these cases to provide useful information to assess for multiple potential pathologies. Previous studies have shown the ability of ocular ultrasound in trauma to detect elevated intracranial pressure (via optic nerve sheath diameter), retinal detachment, vitreous hemorrhage, and retrobulbar hematoma. It can also be used for early detection of muscular entrapment in the case of an orbital wall fracture, as well as performed serially for pupillary response in patients with significant neurological injury at risk for deterioration and potential herniation.

  • To evaluate extraocular movements:
    • Prepare the patient by laying the bed backwards and having their face parallel to the ceiling,  supporting the patient's head and neck with a pillow or blanket.
    • (Optional) Place a tegaderm over the eye. If you do, ensure there is no air between the tegaderm and the eyelid.
    • Place a small amount of ultrasound gel on the closed eyelid  and prepare the linear probe with the gain turned almost all the way up.
    • Stabilize your hand on the patient's nasal bridge or zygoma, with the probe marker to your left, and place the probe transverse on the orbit with minimal pressure being applied directly to the eye. This is very important in trauma as the area is likely painful and theoretically the patient could have a ruptured globe.
    • Adjust the depth to ensure the optic nerve is just visualized at the bottom of the screen. The anterior chamber and lens should be used as visual landmarks to ensure you are in proper location.
    • Next, have the patient look left and right, then turn the probe to a sagittal orientation and have the patient look up and down. During these maneuvers you should be evaluating for symmetric movements of the orbit in each direction.
    • If you do not appreciate symmetric movements of the orbit in all directions then you may have entrapment of an extraocular muscle.
  • To evaluate for pupillary response and shape:
    • Be sure to dim the lights in the room prior to performing this exam to allow for an adequate pupillary response.
    • Gently apply the linear probe with gel in a transverse plane just inferior to the eye, angling superiorly towards the patient's head (Depending on the location of the swelling around the eye, you can also place the probe superior to the eye, angling inferiorly towards the patient's feet).
    • Keep flattening out your probe angle relative to the skin until you have a cross section of the pupil and iris in view.
    • The pupil should be evaluated for symmetry as an asymmetric or oblong pupil could suggest globe rupture. You can then shine a light in the affected or non-affected eye (consensual light reflex) and observe the pupil for constriction.

 

Author

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

References

    1. Blaivas M. Bedside emergency department ultrasonography in the evaluation of ocular pathology. Acad Emerg Med 2000;7:947-50.
    2. Blaivas M, Theodoro D, Sierzenski P. A study of bedside ocular ultrasonography in the emergency department. Acad Emerg Med 2002;9(8):791-9.
    3. Kimberly HH, Shah S, Marill K, Noble V. Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure. Acad Emerg Med 2008;15(2):201-4.
    4. Tayal VS, Neulander M, Norton HJ, et al. Emergency department sonographic measurement of optic nerve sheath diameter to detect findings of increased intracranial pressure in adult head injury patients. Ann Emerg Med 2007;49(4):508-14.
    5. Harries A, et al. Ultrasound assessment of extraocular movements and pupillary light reflex in ocular trauma. Am J Emerg Med 2010 28(8):956-9.