Fall, 2013
Methods
Ultrasound investigation of the appendix should begin with the patient in the supine position. The sonographer would likely choose a high frequency linear or curvilinear transducer to evaluate the region of interest. In most cases, this region would consist of the right lower quadrant (RLQ), also known as the McBurney point; between the umbilicus and the anterior iliac crest.3 Frequently, the sonographer will ask the patient to point out the area of greatest pain. This may help the sonographer in determining the location of the appendix.

The appendix itself is a compressible, tube-like structure beginning at the base of the cecum and continuing distally.2 Due to its location in the abdomen, overlying bowel gas presents the greatest obstacle for ultrasound to overcome.4 Therefore, graded compressions are used to displace the bowel gas so that a scanning window can be obtained and the entire appendix can be visualized. An inflamed appendix will appear as a blind-ended tube that is non-compressible with a diameter measuring greater than 6 mm (from outer wall to outer wall).2,3 If suspected, a thorough investigation of the entire appendix should be done to try and identify any type of obstruction. Typically, an obstruction in the form of an appendicolith will appear as an echogenic structure located within the lumen of the appendix with posterior shadowing.2

Case Study
A 16-year-old patient presented to the emergency room with abdominal pain and tenderness. Urinalysis and other laboratory findings were negative. According to the patient, the pain began approximately four days prior in the area just above his umbilicus and radiated laterally to the patient’s RLQ. Ultrasound investigation of the area was ordered to rule out a possible appendicitis.
With the patient in the supine position, a high frequency linear transducer was used to investigate the region of interest. Upon sonographic examination of the RLQ, a non-compressible, blind-ended tubular structure was identified as the appendix. In the transverse plane, the diameter of the appendix measured 1.4 cm, which is more than double the normal measurement. Dual imaging was then used to demonstrate non-compressibility (Figure 1). Furthermore, in the transverse plane, the appendix demonstrated thickening of the wall consistent with appendicitis (Figure 2 and 3). A sagittal image of the proximal portion of the appendix shows an echogenic structure with posterior enhancement (Figure 4). This structure appeared suggestive of a possible blockage in the form of an appendicolith or fecalith. Together, with these sonographic discoveries and clinical findings, the diagnosis of acute appendicitis was made. The patient was scheduled for same-day surgery with a preoperative diagnosis of acute appendicitis without perforation. The operative report stated that a laparoscopic appendectomy was performed whereas the appendix was removed through a small incision in the umbilicus. According to the postoperative report, a confirmed diagnosis of appendicitis without perforation was made. The appendix measured 10.5 cm in length and 1.3 cm in diameter. The patient was discharged from the hospital two days later without any further complications reported.

Imaging Tip
Although power Doppler and color Doppler were not used during this particular study, the use of these two techniques can be valuable in the diagnosis of appendicitis; especially in cases where the appendix may appear normal or slightly abnormal with grayscale imaging.3 If the appendix appears normal or slightly abnormal and color Doppler demonstrates an increase of flow in the appendix, this may be indicative of appendicitis.3 When the appendix has a clearly abnormal appearance on grayscale imaging and the use of power Doppler displays very little or no flow one may suspect possible rupture or wall ischemia.3 Therefore, the use of color and power Doppler should be considered during any routine ultrasound of the appendix.

Discussion
The appendix, also referred to as the vermiform appendix, is a long, narrow, blind-ended tube often located within the right lower quadrant near the cecum.2 At present, the physiological significance of the appendix has not yet been determined.4 Acute appendicitis is a disorder of the appendix usually classified by some type of obstruction within the appendiceal lumen.2,3.4 Although statistics show a higher rate of cases of acute appendicitis among younger people ages 10 to 19, adults and young children are not immune. In fact, in cases of acute appendicitis in children under the age of 2, the rate of diffuse perforation of the appendix increases.5 This may be due to the fact that the omentum (layer of peritoneum of the abdominal organs) has yet to mature allowing perforation to occur more readily, or because these patients are incapable of conveying their clinical symptoms at the time of occurrence, consequently, delaying diagnosis and surgical intervention.5

In the past, cases of appendicitis were often diagnosed clinically and under observation without the use of alternative studies.3 Classic indications include periumbilical pain, nausea, vomiting, fever, and an elevated white blood cell count.2,3,4 However, due to the fact that these symptoms often mimic other gastrointestinal and gynecological issues, it was discovered that many individuals who underwent the appendectomy turned out to have a normal appendix.3

The use of diagnostic ultrasound imaging in suspected cases of acute appendicitis has proven to be an effective, inexpensive, and non-invasive alternative for identifying an inflamed appendix. The use of ultrasound regarding cases of acute appendicitis, has demonstrated a sensitivity and specificity of 78% and 83%, respectively.3,4 Although computed tomography (CT) is still considered the more superior imaging modality for its detection, patient exposure to potentially harmful radiation is still a concern with the use of CT. Nevertheless, CT still remains the standard due in large part to the limitations of investigating this region of the abdomen with ultrasound. Technically difficult patients and overlying bowel gas are the two main hindrances for sonographers to overcome. Also, given that ultrasound is user-dependent, evaluating this particular area can present a challenge to even the most experienced technician.

Currently, removal of the appendix is the most common treatment for those suffering from acute appendicitis.4 Normally, the surgical procedure of choice is a laparoscopic appendectomy wherein the entire appendix is removed through the patient’s umbilicus. Once removed, the patient will probably be placed on some form of antibiotic in order to avoid infection.4 The patient prognosis for this procedure is excellent with very few complications reported.

Conclusion
In conclusion, it should be considered that although computed tomography is still considered the best imaging method for evaluating the appendix, sonography has proven to be an effective alternative with less harmful effects to the patient. Despite certain limitations with ultrasound, abnormalities and conditions of the appendix, including cases of acute appendicitis, can be identified. In this particular study, the patient did not present with all the classic symptoms of acute appendicitis. However, with the use of sonography, a clear diagnosis was made without exposing the patient to the potentially harmful effects of ionizing radiation.






References
  1. Pickhardt, PJ; Lawrence, EM; Pooler, BD; and Bruce, RJ; Diagnostic Performance of Multidetector Computed Tomography for Suspected Acute Appendicitis. Annals of Internal Medicine 2011; 154 (12): 789-96.
  2. Penny, S; Examination Review for Ultrasound: Abdomen and Obstetrics and Gynecology. Lippincott Williams & Wilkins, 2011: 111.
  3. Kawamura, DM; and Lunsford, BM; Diagnostic Medical Sonography Abdomen and Superficial Structures. Lippincott Williams & Wilkins, 2012: 255-257.
  4. Ryan, C; Sonographic Evaluation of Acute Appendicitis. Journal of Diagnostic Medical Sonography 2012; 28 (6) 320-323.
  5. Wheeler, R; Appendicitis in Children and Young People. Clinical Risk, 2011; 17 (4): 126-129.
  6. All sonographic images were courtesy of Wayne Memorial Hospital Radiology, Department of Ultrasound.