POCUS To Rule In Appendicitis Prior to CT Imaging

Written by Dr. Ben Araki (PGY2) , Dr. Nora McNulty (PGY4) and Dr. Nicole Del Valle

Chief Complaint: “The pain in my stomach is getting worse”

HPI:

A 29-year-old male with no past medical history presents with two days of gradually worsening, initially intermittent but progressively becoming more persistent, sharp pain diffusely in the generalized abdomen, now localized in the right lower quadrant (RLQ). Additionally, he reports pain in the left testicle accompanied by chills, nausea, anorexia, dysuria, and diarrhea. The patient used naproxen, experiencing some relief. He denies fever, vomiting, cough, bloody stool, trauma, constipation, or flank pain. There is no history of abdominal surgeries.

Vitals Signs: 

BP: 120/70 mmHg, HR: 79 bpm, Temperature: 98.7 F, RR: 18 bpm, SpO2: 98% on RA

Pertinent PE: 

Pertinent physical exam findings include RLQ tenderness to palpation, along with involuntary guarding. The McBurney’s and Psoas signs are positive. Additionally, there is minimal tenderness noted in the left testicle.

Pertinent Lab data:

Pertinent laboratory data include a white blood cell count (WBC) of 12.25 x 10^9/L and a neutrophil percentage of 76%.

Questions:

1. Based on the presented information, what is the most likely diagnosis?

2. If you were to perform specific diagnostic imaging, which ones would you prioritize and why?

Discussion:

In a relatively young male with no past medical or surgical history, presenting with RLQ abdominal pain that appears to have migrated from the generalized abdomen, an important diagnosis to consider is appendicitis. The location and pain pattern of migratory pain are textbook. The initially diffuse abdominal pain, resulting from visceral peritoneal irritation and perceived as generalized due to poor localization over the T8-T10 dermatomes, then localizes to the RLQ as it reaches the parietal peritoneum [1]. Another supporting piece of evidence is anorexia, also known as the hamburger sign [2]. The presence of diarrhea may also reflect ileal irritation from an inflamed appendix [3]. Physical findings, including tenderness at McBurney's point and a positive Psoas sign, are also helpful in supporting this diagnosis. Laboratory data with a white blood cell count above 10 x 10^9/L and neutrophil percentage above 70% are often associated as well [4]. Although rare, testicular discomfort and dysuria have been reported in association with acute appendicitis [5]; furthermore, the clinical picture is less suggestive of epididymitis, scrotal abscess, testicular torsion, or urinary tract infection.

Under a high index of suspicion for appendicitis, ultrasonography (US) should be the first-line imaging modality, especially in children and young adults, particularly reproductive-age women [6]. In the right clinical context with clear US evidence for the diagnosis, no further imaging is required. In the case of equivocal or unclear imaging results via US, further imaging with computed tomography or magnetic resonance imaging is indicated.

Then, what about POCUS? Studies have demonstrated mixed results. In one study, POCUS was shown to have moderate accuracy; however, it exhibited low sensitivity and specificity, rendering it inadequate as a definitive imaging modality for undifferentiated ED patients [7]. In contrast, other studies have reported a sensitivity of up to 86% and specificity of 91%, with positive and negative likelihood ratios of 9.24 and 0.173, respectively [8]. These findings suggest that in a clinical scenario highly suggestive of acute appendicitis, unequivocal results via ED POCUS could be definitive in confirming the diagnosis without requiring further imaging.

In this patient case, based on the high suspicion for acute appendicitis, bedside POCUS was performed, focusing over the site of pain indicated by the patient's finger. Our images show all signs classic for appendicitis on POCUS including:

Target sign (hypoechoic center surrounded by a hyperechoic ring surrounded by a hypoechoic ring in axial view),

Lack of peristalsis and lack of compressibility,

Outer appendiceal diameter of 6 mm or greater on cross-section,

and a possible "Ring of Fire" sign (increased wall vascularity; signs of inflammation) [9].

Ben's Pearls:

• The POCUS approach for appendicitis exhibits low sensitivity but high specificity, making it most effective in a population where there is a heightened suspicion of appendicitis (e.g., positive right lower quadrant tenderness, McBurney's sign, etc.) [8].

• A practical strategy for POCUS involves directly querying the patient about the location of pain, ideally having them point with one finger, and then placing the probe over that area [9]. 

• Theoretically, by utilizing clinical findings, laboratory testing, and POCUS, the surgical team could expedite the procedure without the need for a confirmatory CT scan, underscoring the significant advantages of utilizing POCUS in children and adults [10].

References:

1. Jones MW, Lopez RA, Deppen JG. Appendicitis. [Updated 2023 Apr 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493193/#

2. Alvarado, Alfredo. ‘Clinical Approach in the Diagnosis of Acute Appendicitis’. Current Issues in the Diagnostics and Treatment of Acute Appendicitis, InTech, 27 June 2018. Crossref, doi:10.5772/intechopen.75530.

3. Humes DJ, Simpson J. Acute appendicitis. BMJ. 2006 Sep 9;333(7567):530-4. doi: 10.1136/bmj.38940.664363.AE. PMID: 16960208; PMCID: PMC1562475.

4. Von-Mühlen B, Franzon O, Beduschi MG, Kruel N, Lupselo D. AIR score assessment for acute appendicitis. Arq Bras Cir Dig. 2015 Jul-Sep;28(3):171-3. doi: 10.1590/S0102-67202015000300006. PMID: 26537139; PMCID: PMC4737355.

5. Dienye PO, Jebbin NJ. Acute appendicitis masquerading as acute scrotum: a case report. Am J Mens Health. 2011 Nov;5(6):524-7. doi: 10.1177/1557988311415514. Epub 2011 Aug 3. PMID: 21816859.

6. Debnath J, George RA, Ravikumar R. Imaging in acute appendicitis: What, when, and why? Med J Armed Forces India. 2017 Jan;73(1):74-79. doi: 10.1016/j.mjafi.2016.02.005. Epub 2016 Mar 29. PMID: 28123249; PMCID: PMC5221358.

7. Becker BA, Kaminstein D, Secko M, Collin M, Kehrl T, Reardon L, Stahlman BA. A prospective, multicenter evaluation of point-of-care ultrasound for appendicitis in the emergency department. Acad Emerg Med. 2022 Feb;29(2):164-173. doi: 10.1111/acem.14378. Epub 2021 Sep 14. PMID: 34420255.

8. Benabbas R, Hanna M, Shah J, Sinert R. Diagnostic Accuracy of History, Physical Examination, Laboratory Tests, and Point-of-care Ultrasound for Pediatric Acute Appendicitis in the Emergency Department: A Systematic Review and Meta-analysis. Acad Emerg Med. 2017 May;24(5):523-551. doi: 10.1111/acem.13181. PMID: 28214369.

9. Riscinti, Matthew. “Bedside Ultrasound for Acute Appendicitis - Featuring Colorized Images.” TPA, TPA, 10 Jan. 2021, www.thepocusatlas.com/new-blog/appendicitis. 

10. Di Saverio, S., Podda, M., De Simone, B. et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World J Emerg Surg 15, 27 (2020). https://doi.org/10.1186/s13017-020-00306-3