Case 17 – The Beaver’s Tail

An Anomalous Incidental – and ode to #POCUS #FOAMed

Point of Care Ultrasound is based on the ability to answer binary, yes / no questions. Rapidly determining whether or not a patient has a particular pathology should aid in simplifying decision making.

Unfortunately ultrasound is not binary, but rather multiple shades of grey. While many cases are cut and dried, there are often anomalous and pathological incidental findings which can disrupt the POCUS binary mindset, confusing rather than simplifying clinical decision making.

Building a memory bank of normal and abnormal ultrasound findings is vital to help make sense of the unexpected. To this end, engaging with other ultrasound enthusiasts, sonographers and radiologists via social medial and other #FOAMed platforms is one way of building a mental database of ultrasound images. This can be especially helpful for those working in isolated or primary care environments, without the support of formal hospital ultrasound programs.

The following case describes an anomalous incidental finding during a FAST exam. It illustrates the dilemma a POCUS user may encounter when faced with the unexpected. It also highlights the benefit of exposure to a large volume of ultrasound images via #FOAMed, which in this instance, allowed the rapid identification of the image as a normal finding and avoided un-necessary acute referral for further investigation.

The Case

A young woman presented to the urgent care clinic following the onset of severe LUQ abdominal pain. It had started suddenly the previous evening when she had rolled over in bed. Two weeks prior she had been admitted to hospital for 4 days with hypotension, fever and abdominal pain related to acute EBV infection.

T = 36.2  HR 82  BP 113/70  RR 14  O2sat 98%. Abdomen – soft, moderately tender left upper quadrant. BHCG negative.

While a rare complication of  EBV, and certainly very unlikely given the clinical signs, the possibility of splenic haematoma or rupture was in the back of my mind.

The following LUQ ultrasound images were obtained as part of a FAST exam…

Focusing on the sub diaphragmatic region.

Discussion

At first glance there appears to be no free fluid, however the spleen looks heterogeneous, with the sub-diaphragmatic portion being relatively hypoechoic. Could this represent organised subcapsular haematoma? Splenic rupture and subcapsular haematomas are rare but potentially fatal complications of acute EBV. (1)

I then recalled a recent thread on Twitter. Maybe it’s not subcapsular haematoma, or even the spleen, but instead an elongated left lobe of the liver extending over to the LUQ (the beaver tail liver) (2)

Daniela explains…

You can tell it’s liver because the bright white little lines are portal veins in cross section, hepatic veins also visible, do not see this with blood https://t.co/cEzL6AqFdX

— Daniela Bonin (@DanielaDecibel) August 28, 2018

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This CT shows left lobe of liver extending to spleen so if you have US probe on LUQ you see both at same time, not typical but do see it occasionally pic.twitter.com/ZpqKExoa14

— Daniela Bonin (@DanielaDecibel) August 29, 2018

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Confusing a beaver tail liver for a subcapsular splenic haematoma is not as silly as it seems. Someone once got a laparotomy for the sake of a beaver tail misdiagnosed as a haematoma on CT!! (3)

But thanks to some #FOAMed powered image recognition, a false-positive FAST interpretation was averted. The patient was spared an un-necessary referral to the emergency department, for an even more un-necessary CT scan, and was instead discharged home.

thanks, FOAMed!

References

(1)   Won AC, Ethell A. Spontaneous splenic rupture resulted from infectious mononucleosis. International journal of surgery case reports. 2012; 3(3):97-9. [pubmed]

(2)  https://radiopaedia.org/articles/beaver-tail-liver

(3)  Cholankeril JV, Zamora BO, Ketyer S. Left lobe of the liver draping around the spleen: a pitfall in computed tomography diagnosis of perisplenic hematoma. The Journal of computed tomography. 1984; 8(3):261-7. [pubmed]