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Emergency Ultrasound

Cases That Count: McBurney’s Point Tenderness: Is this always appendicitis?

By Manon Loonis, MS4 & Meghan Kelly Herbst MD

 

Questions:

  1. What pathology is demonstrated in these clips (clip 1 & clip 2)?
  2. What are the ultrasound criteria for this pathology?
  3. What are the potential pitfalls of this Point-of-Care Ultrasound (PoCUS) study?

Case:

A 40 year-old male with a past medical history of hypertension and diabetes presented to the ED complaining of two to three days of gradual onset, worsening right lower quadrant pain, associated with nausea, one loose stool, and subjective fevers and chills. He works with heavy machinery but couldn’t recall whether his symptoms began while using the equipment, or any specific incident that provoked his symptoms. He denied vomiting, black or bloody stools, chest pain, shortness of breath, trauma, dysuria, or any other concerns.

On presentation, he was awake, lying still on the stretcher, calm and cooperative. Exam yielded right lower quadrant tenderness over McBurney’s point. Palpation of the left lower quadrant also elicited pain in the right lower quadrant. However, he did not exhibit guarding, rebound, or pain with backward right thigh flexion.

POCUS was performed using a high-frequency linear transducer to assess for appendicitis using the peritoneal line, psoas muscle, and iliac vessels as landmarks. Instead of visualizing a non-compressible, blind-ended fluid-filled tubular structure consistent with appendicitis, a partial view of a larger air-filled segment of bowel with a 7mm thickened wall and surrounding inflamed fat was appreciated (clip 1). Visualizing the same area with a low frequency convex transducer allowed for the entire area to be seen and a diagnosis was made (clip 2). The patient had an elevated white blood cell count to over 18,000 cells per microliter and for this reason had a computed tomography (CT) scan, which confirmed the diagnosis of diverticulitis involving an elongated sigmoid loop located in the right lower quadrant. He also had a small contained perforation, for which he was admitted to the surgery service.

Role of POCUS in the Evaluation of Right Lower Quadrant Abdominal Pain

There is a broad differential for patients presenting to the ED with right lower quadrant abdominal pain, including but not limited to right ureterolithiasis, testicular torsion, ovarian torsion, ovarian cyst rupture, small bowel obstruction, hernia, appendicitis, and right-sided diverticulitis. Clinical context and physical exam will help prioritize items on the differential, but POCUS findings such as the presence or absence of hydronephrosis, blood flow to the affected testicle, a large ovary or ovarian mass, free fluid in the pelvis, dilated loops of small bowel with alternating peristalsis, a loop of bowel outside the peritoneal space, or visualizing an inflamed appendix or diverticulum has the potential to rule in or out the pathology of concern. An “ultrasound-first” approach has been described and adapted by providers in different abdominal pain settings for this reason, with a positive impact on real-time decision making.1-3

The first study using bedside ultrasound for the diagnosis of diverticulitis dates back to 1997, demonstrating that surgery residents with limited training in ultrasound could diagnose diverticulitis with an accuracy of 88%.4 About ten years later the first case report of diverticulitis diagnosed by POCUS in the hands of an emergency physician was published, recommending the development of a protocol for its use, suggesting this may decrease CT use in some (well-appearing) patients.5 In experienced hands, sensitivity and specificity of ultrasound for diverticulitis approach 100%.6 Complications such as perforation may decrease the sensitivity.7 Findings such as bowel wall thickening, pericolic inflammation, and inflamed diverticula carry sensitivities ranging from 33-78%, and specificities approaching that of CT in the mid 90s. CT has improved sensitivity ranging from 50-100% but more importantly can look for complications such as perforation and abscess formation.8-10 While more research needs to be done on the feasibility of emergency physician performed POCUS for diverticulitis, visualization of an air-filled loop segment of bowel that has a thickened wall and peri-colonic inflamed fat over the area of maximal tenderness supports this pathology, and may preclude the need for CT imaging.

Answers:

1. What sonopathology is demonstrated in these clips?

Diverticulitis

2. What are the ultrasound criteria for this pathology?

 A non-compressible air-filled diverticulum with wall thickening greater than 4mm, surrounded by hyperechoic inflamed fat.6,11 The hypoechoic wall surrounding a hyperechoic center has been referred to as a “target sign” or “pseudokidney sign.”12

3. What are the potential pitfalls of this Point-of-Care Ultrasound (PoCUS) study?

While PoCUS can identify a diverticulitis with high accuracy and specificity, it does not necessarily identify complications of this disease. For this reason, if diagnostic data or the physical exam suggests perforation or abscess, a CT scan should be performed to assess for these complications.

References

  1. Ramarajan N, Krishnamoorthi R, Barth R, et al. An interdisciplinary initiative to reduce radiation exposure: evaluation of appendicitis in a pediatric emergency department with clinical assessment supported by a staged ultrasound and computed tomography pathway. Acad Emerg Med. 2009; 16(11): 1258-1265
  2. Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med. 2014; 371(12): 1100-1110.
  3. Bassler D, Snoey ER, Kim J. Goal-directed abdominal ultrasonography: impact on real-time decision making in the emergency department. J Emerg Med. 2003: 375-378.
  4. Zielke A, Hasse C, Nies C, et al.Prospective evaluation of ultrasonography in acute colonic diverticulitis. Br J Surg. 1997; 84: 385-388.
  5. Baker JB, Diku M, Swadron SP. Diagnosis of diverticulitis by bedside ultrasound in the emergency department. J Emerg Med. 2006; 30(3): 327-329.
  6. Schwerk WB, Schwarz S, Rothmund M. Sonography in acute colonic diverticulitis. Dis Colon Rectum. 1992; 35:1077–1084.
  7. Hollerweger A, Macheiner P, Rettenbacher T, et al. Colonic diverticulitis: diagnostic value and appearance of inflamed diverticula-sonographic evaluation. Eur Radiol. 2001; 11 (10) 1956-1963.
  8. Lembcke B. Diagnosis, differential diagnoses, and classification of diverticular disease. Viszeralmedizin. 2015; 31: 95-102.
  9. Oudenhoven LFIJ, Puylaert JBCM, Koumans RKJ. Right colonic diverticulitis: US and CT findings – new insights about frequency and natural history. Radiology. 1998; 208: 611-618.
  10. Puylaert JBCM. Ultrasound of colon diverticulitis. Dig Dis. 2012; 30: 56-59.
  11. Mazzei MA, Cioffi Squitieri N, Guerrini S, et al. Sigmoid diverticulitis: ultrasound findings. Crit Ultrasound J. 2013; 5(Suppl 1):S5.
  12. Anderson DR. The pseudokidney sign. Radiology. 1999;21:395–397.

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