Ultrasound

A Bowel Inside a Bowel: Intussusception

The Case

A 14 month-old female with no significant PMH who presented to the Emergency Department with vomiting. Per mom, patient was well yesterday, but today has been refusing food, crying and vomiting. Patient has had no known sick contacts and her vaccinations are up to date. A review of systems was performed and was otherwise negative.

Physical Exam

Vital signs were within normal limits. Patient was listless with decreased responsiveness, but not in distress. No evidence of respiratory compromise. Abdominal exam was unremarkable, with no focal tenderness and no guarding, rigidity or rebound. During the time the examiner was present in the room, the patient had one episode of crying inconsolably and then vomiting.

An abdominal ultrasound was performed and the diagnosis was revealed to be Intussusception

Ultrasound

Ultrasound has been shown to be 97.9% sensitive and 97.8% specific for diagnosing ileocolic intussusception. To evaluate for intussusception, start with the high frequency low penetration linear transducer. In most young children this transducer will provide adequate depth. In an older child, you may have to use the higher penetration curvilinear transducer. If available, use warm gel to minimize patient discomfort and thereby increasing your changes of obtaining clear images. Begin in the transverse plane and slide your probe up to the right upper quadrant, across, and then down the left side, interrogating for the intussusception (Figure 1).

Figure 1: Suggested path of the ultrasound transducer to evaluate for intussusception.  (https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/september-2018/pediatric-emergency-ultrasound-deep-dive-on-pocus-for-intussusception/)

Figure 1: Suggested path of the ultrasound transducer to evaluate for intussusception.

(https://www.acep.org/how-we-serve/sections/emergency-ultrasound/news/september-2018/pediatric-emergency-ultrasound-deep-dive-on-pocus-for-intussusception/)

Most of the intussusceptions will be found on the right hand side, and are described as a “target sign” when you are viewing the intestinal intussusception in transverse or the “sandwich sign” in long axis.  The “lawn-mower” approach can be used, similar to the approach for SBO, and graded compression along your path can help move bowel gas out of the way to better evaluate the intestine. The hyperechoic rings are the mucosa and muscularis and the hypoechoic portion is the submucosa.  

Case Discussion

Intussusception is the most common abdominal emergency in early childhood, with the majority of cases occurring in patients <2 years of age. It occurs when the bowel telescopes in on itself and gets stuck. The peristaltic waves of the bowel causes waves of pain in the patient. The classic triad is described as pain, vomiting and bloody stools. Ultrasonography is the preferred diagnostic modality to evaluate for intussusception, given the high sensitivity and specificity (97.9% and 97.8% respectively) when performed by a skilled clinician. Ultrasound also has a high negative predictive value (approaching 99.7%) and can rule out intussusception in a majority of patients. Intussusception presents on ultrasound as a peripheral hypoechoic ring surrounding a central echogenic focus described as either a "target sign” or a “doughnut sign.” (Figure 2a) The visualized doughnut represents the layers of the intestinal wall that have invaginated into themselves. Color doppler can be applied to evaluate for tissue ischemia. (Figure 2b) The most common type of intussusception, ileocolic (as in this case) is usually found in the right lower quadrant. There is usually associated focal tenderness in the right lower quadrant (though this patient was non-tender). Treatment of a non-perforated intussusception typically consists of reduction via air enema, but sometimes operative management is indicated.

Figure 2: Ultrasound image of intussusception

Figure 2: Ultrasound image of intussusception

Ultrasound Case of the Month: A Silent Killer

The Case:

A 72 year old male with no PMH presents to the emergency department (ED) for vague abdominal discomfort and fullness. The patient is hemodynamically stable on arrival and received a point of care ultrasound (POCUS) for evaluation of his abdominal pain. FAST performed was negative for free fluid, however, the renal ultrasound showed unilateral mild hydronephrosis on the right side. POCUS was then performed to evaluate the aorta, and a large abdominal aortic aneurysm (AAA) was seen, measuring 14cm at its largest diameter.

 

Introduction:

When performing a POCUS it is important to remember the differential diagnosis for hydronephrosis is broad, and not limited to renal colic. The ureter can be obstructed either internally from a stone, or externally from surrounding structures.  When renal colic is on your differential, and you find hydronephrosis, be sure to also consider alternative diagnosis such as a AAA. In older patients, consider performing a AAA evaluation in all patients with suspected renal colic, and/or hydronephrosis. 

In this case, the patient had compression of the ureter from the large AAA resulting in hydronephrosis, but if the aorta had not been evaluated, we may have missed the more dangerous diagnosis. In addition, please remember that a patient may have leaking or rupture from the AAA which is located retroperitoneally and may not be seen on POCUS.

A ruptured abdominal aortic aneurysm (AAA) is a vascular catastrophe responsible for 1-3% of deaths in men from the age 65-85 in developed countries. Rupture from an AAA is the 10th leading cause of death in males over 50, the mortality rate of a ruptured AAA approaches 90% and the incidence of AAA continues to increase. Therefore, it is essential for the EM physician to diagnose a AAA in a timely manner. (1) The minority of patients with a ruptured AAA (<25%) will present with the classic triad of hypotension, back pain and a pulsatile abdominal mass.  This results in a delay in diagnosis, or misdiagnosis. Patients may present with referred pain to the scrotum, buttocks, thighs, shoulders, and/or chest and can be misdiagnosed as having renal colic, diverticulitis or MSK pain.

Indications:

The current indications by ACEP for obtaining POCUS to detect AAA include:

Presence of syncope, shock, hypotension, abdominal pain, abdominal mass, flank pain or back pain- especially in patients >50 years old.(3) Currently, the U.S. Preventive Service Task Force recommends that men from the age of 65-75 years who have ever smoked be screened for an AAA sonography.(4)

Utility of bedside ultrasound for AAA in the ED?

While CTA is considered the surveillance study of choice(5),  research suggests that the sensitivity of point of care bedside ultrasound approaches 99% for abdominal aortic aneurysm (AAA). With such a excellent sensitivity and a high prevalence of AAA in specific patient populations (10-15% in men who smoke >65), providers should consider performing this scan at the bedside for an expedited diagnosis.(6)

Performing the scan:

  • The probe of choice is the 3.5 MHz curvilinear probe

  • Start just caudal to xyphoid process

  • Measure the aorta proximally, mid and distally in the transverse plane with the probe marker to the patient’s right (should be <3cm from outer to outer wall)

  • Measure the iliac arteries after the bifurcation in transverse (should be <1.5cm)

  • Evaluate the aorta distally in the longitudinal view with the probe marker to patient’s head as most aneurysms will be located infrarenally

  • Identify vertebral body as relevant landmark

  • Aorta is anterior to vertebral body

  • IVC is anterior & right (patient’s right) of vertebral body

Vertebral body: horseshoe shaped with hyperechoic anterior &amp; posterior shadowing

Vertebral body: horseshoe shaped with hyperechoic anterior & posterior shadowing

Tips and Tricks

  • Aorta and IVC can be confused in longitudinal view:

    • Aorta is rounder, less compressible, & has brighter thicker walls

  • Bowel gas & body habitus can make imaging difficult:

    • Apply steady pressure to move gas

    • Jiggle the probe to move bowel aside

    • Flex patients hips & knees to relax abdominal muscles

    • Lower probe frequency to improve sound wave penetration

Conclusion

POCUS scanning for AAA enables timely diagnosis of a condition with high mortality which is frequently misdiagnosed, or suffers a delay in diagnosis. AAA POCUS has high sensitivity and specificity that can be easily learned and performed in ED. In a patient with hydronephrosis, consider also AAA evaluation, even if renal colic is high on your differential diagnosis.

Faculty Reviewer: Dr. Kristin Dwyer

References:

  1. Sakalihasan N, Limet R, Defawe OD. Abdominal Aortic Aneurysm. Lancet 2005;365:15577-89.

  2. Fink HA, Lederle FA, Roth CS, Bowels CA, Nelson DB, Haa MA. The Accuracy of physical examination to detect abdominal aortic aneurysm. Arch Intern Med.2000;160(6):833-6.

  3. American College of Emergency Physicians. Policy Statement. 2001: Emergency Ultrasound Guidelines.

  4. U.S. Preventive Services Task Force. Screening for abdominal aortic aneurysm: recommendation statement. Ann Inter med. 2005;142(3):198-202.

  5. Cantisani V, Ricci P, Grazhdani H, et al. Prospective comparative analysis of colour-doppler ultrasound, contrast-enhanced ultrasound, computed tomography and magnetic resonance in detection endoleak after endovascular abdominal aortic aneurysm repair. Eur J Vasc Endovasc Surg. 2011;41:(2)186-92.

  6. Rubano, Elizabeth, Ninfa Mehta, William Caputo, Lorenzo Paladino, and Richard Sinert. Systematic Review: Emergency Department Bedside Ultrasonography for Diagnostic suspected Abdominal Aortic Aneurysm. Acad Emerg Med Academic Emergency Medicine 20.2 (2013): 128-38.

What is that Hot Potato Voice? POCUS for the PTA

The Case:

A 25-year-old male with recurrent strep throat presents to the ED with sore throat, difficulty swallowing, and feeling as though his voice has changed.  His physical exam is significant for a left sided, bulging tonsil.  He is currently managing his own secretions, and his respiratory status is stable.  You are concerned that he has not been able to drink any fluids since the night prior.  He appears well hydrated, but you question if this is simple tonsillar cellulitis or a peritonsillar abscess (PTA).  You know that clinical diagnosis of PTA only has a reported sensitivity of 78% and a specificity of only 50% (Lyon et al, 2005) and want to do further diagnostic imaging.  Should this patient go to CT, or could you find an answer faster at the bedside with much less radiation? Can you drain this in the emergency department or does he need to proceed to the OR with ENT? He has gotten viscous lidocaine and his pain improved. His rapid strep was positive. You wheel out your bedside ultrasound and perform an intraoral ultrasound.

Using the endocavitary probe, you perform the following US of the peritonsillar region:

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Question:

What is the diagnosis?

Peritonsillar abcess
T - Tonsil, PTA - Abscess, Arrow - Carotid

T - Tonsil, PTA - Abscess, Arrow - Carotid

Point of Care PTA Ultrasound:

There are two techniques for performing an ultrasound of the tonsils - transcutaneous and intraoral.

Transcutaneous Ultrasound: This technique is useful in children, especially if performing a needle aspiration of the abscess, as it is less invasive and leaves spaces for aspiration equipment in the oral cavity.  Using the linear high frequency transducer, positioned under the mandible with your probe marker towards the patient’s earlobe on the same side, first identify the submandibular gland, and then the tonsil, immediately deep to the submandibular gland.

Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections."  Pediatric Radiology  46.7 (2016): 1059-067.

Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections." Pediatric Radiology 46.7 (2016): 1059-067.

Arrow - Vasculature (Carotid and IJ), SMG - Submandibular gland, T - Tonsil

Arrow - Vasculature (Carotid and IJ), SMG - Submandibular gland, T - Tonsil

Intraoral Ultrasound: As used in the case, this technique utilizes an endocavitary transducer after numbing the area with topical anesthetic for patient comfort. The transducer is placed intraorally abutting the area of suspected abscess with the probe marker facing the ipsilateral ear.

Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department."  Academic Emergency Medicine  12.1 (2005): 85-88.

Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department." Academic Emergency Medicine 12.1 (2005): 85-88.

The tonsil is identified by the irregular surface, representing tonsillar crypts. An isoechoic ring surrounding an anechoic region identifies an abscess with posterior enhancement.  Abscesses will develop in between the medial aspect of the tonsil and superior constrictor muscles.  Posterior and lateral to the tonsil is the important internal carotid artery, which can be seen with pulsatile flow on color Doppler.  It is important to identify this structure prior to draining of the abscess.  It will run anterior to the jugular vein within the carotid sheath.

T - Tonsil, PTA - Peritonsilar abscess, Arrow - Carotid  Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.”  Am J Emerg Med  (2015).

T - Tonsil, PTA - Peritonsilar abscess, Arrow - Carotid

Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.” Am J Emerg Med (2015).

Peritonsillar Abscess on Ultrasound:

  • Intraoral sensitivity ranges from 90-100%

  • Transcutaneous sensitivity ranges from 80-91%

  • Enlarged tonsils with:

    • Heterogenous, cystic, anechoic fluid

    • Well circumscribed with irregular margins

  • Usually along the posterolateral aspect of tonsil

  • Can save a patient from the radiation of a CT scan (where sensitivity is 100%, but specificity is 75%)

 

Back to our case:

Can you find an answer to your patient’s symptoms quickly, at the bedside?

  • Yes! You should think of ultrasound to help you diagnose a PTA, which in the published literature has a comparable sensitivity to CT (see above)

Do you need an ENT and to send this patient to the OR?

  • Case reports suggest that US assisted drainage can replace CT and operative drainage of abscesses (Todsen et al. 2018), but a true trial comparing the two modalities is yet to be completed

  • It never hurts to use your ultrasound to determine what you can see!

 

References:

  1. Bandarkar, Anjum N., Adebunmi O. Adeyiga, M. Taylor Fordham, Diego Preciado, and Brian K. Reilly. "Tonsil Ultrasound: Technical Approach and Spectrum of Pediatric Peritonsillar Infections." Pediatric Radiology 46.7 (2016): 1059-067.

  2. Lyon, Matthew, and Michael Blaivas. "Intraoral Ultrasound in the Diagnosis and Treatment of Suspected Peritonsillar Abscess in the Emergency Department." Academic Emergency Medicine 12.1 (2005): 85-88.

  3. McLario, David J., and John L. Kendall, eds. Case Studies in Pediatric Emergency and Critical Care Ultrasound. Cambridge: Cambridge UP, 2013. Print.

  4. Secko M, Sivitz, A. “Think ultrasound first for peritonsillar swelling.” Am J Emerg Med (2015).

  5. Todsen, Tobias, Stage, Mads G., Hahn, Christoffer H. “A Novel Technique for Intraoral Ultrasound-Guided Aspiration of Peritonsillar Abscess.” Diagnostics 8.3 (2018)