Diagnosing acute appendicitis

In this video, we'll go through a foolproof approach to diagnosing this problem, why imaging is not always the answer, and what to do once you've diagnosed appendicitis.

Olutayo A. Sogunro, DO FACS FACOS
Olutayo A. Sogunro, DO FACS FACOS
6th Oct 2021 • 5m read

Acute appendicitis relies on clinical diagnosis, which means it can be easy to get it wrong. So how do you make sure your patient has acute appendicitis and not something else? In this video, we'll go through a foolproof approach to diagnosing this problem, why imaging is not always the answer, and what to do once you've diagnosed appendicitis.

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Video transcript

In this chapter we will discuss acute appendicitis. Acute appendicitis is inflammation of the vermiform appendix. It affects about 233 out of 100,000 people worldwide. It occurs most frequently in the second and third decade of life, with the highest incidence in 10 to 19 year olds. Males are slightly more affected than females within lifetime incidence of 8.6% in males, and 6.7% in females. So what causes appendicitis?

Appendicitis is thought to be caused by a source of obstruction, which leads to inflammation of the appendiceal wall. This causes localized ischemia and can lead to perforation which is a major complication of appendicitis. Other complications include abscess, and peritonitis. Some of the common causes of obstruction in the appendix are fecalets, or compacted fecal deposits, lymphoid hyperplasia, which occurs commonly in young patients, infection, and tumors.

The signs and symptoms of acute appendicitis include abdominal pain, the pain often starts in the periumbilical region and then migrates down to the right lower quadrant. The classic constellation of symptoms of appendicitis are right lower quadrant pain, nausea and vomiting, anorexia, fever, diarrhea, and malaise. Now let's work up acute appendicitis.

The physical exam is very important when diagnosing acute appendicitis. In addition to your history, it is the biggest tool that will help you determine if there is appendicitis or not. To learn how to perform a detailed physical exam of the abdomen, please refer to my Abdominal Examination Essentials Course available in the Medmastery course library.

A common finding in appendicitis is periumbilical pain that migrates to the right lower quadrant as we discussed previously, there can be rebound tenderness, tenderness to palpation at McBerney's point, obturator sign, psoas sign, and rovsing's sign. So what might you expect to see in the lab results of a patient with acute appendicitis? Mild leukocytosis or increased white blood cell count is present in most patients.

Approximately 80% of patients have a leukocytosis and a left shift, meaning an increase in the number of immature neutrophils or bands in the blood. The sensitivity and specificity of an elevated white blood cell count in acute appendicitis is 80% and 55%, respectively, in very early acute appendicitis, the white blood cell count might be normal.

The main white blood cell count in a patient with acute appendicitis is 14,500 cells per cubic millimeter of blood, or 14.5 international units. Remember that acute appendicitis is a clinical diagnosis. The Alvarado score is a clinical scoring system for determining the probability of appendicitis. It is based on the presence of, or absence of, six clinical findings and two laboratory findings. It gives each of these findings a weighted score, and the maximum total equals 10.

To interpret the score, the categories are based on low, moderate, and high probability. A score of 7 to 10 indicates a high probability of appendicitis. These patients have up to a 93% probability of acute appendicitis and usually requires surgical treatment or non operative definitive treatment with antibiotics. So what about imaging? Acute appendicitis is generally a clinical diagnosis, but diagnostic imaging is used mainly to increase the specificity of the diagnostic evaluation for appendicitis, and helps a decrease in negative appendectomy rate.

Imaging is not required in the diagnosis of acute appendicitis. However, when imaging is obtained in emergent or urgent care settings, computed tomography or CT scan imaging is a preferred imaging modality. CT scan with intravenous contrast demonstrates the highest diagnostic accuracy and visualization of the appendix.

A non diagnostic exam, one that does not visualize the appendix does not rule out acute appendicitis and continued evaluation is needed. CT scan imaging is particularly helpful to evaluate the complications of acute appendicitis such as preforation, abscess, and fistula formation. This is an axial slice of a CT scan of the abdomen and pelvis from a patient with acute appendicitis. There are several key features of acute appendicitis you can expect to see on CT scan. First is an enlarged appendix with a diameter greater than seven millimeters.

You may also see an appendicolith which will present as a bright and light colored lesion, representing compacted VCs. Here you can see the appendicolith in a coronel slice as well. You might also see wall thickening greater than two millimeters. You can also see some fluid around the appendix that we refer to as Periappendiceal fluid or free fluid, the dark gray area adjacent to the appendix.

Although not visible in this image, fat stranding around the appendix can also be seen as an acute appendicitis. Ultrasound can also be performed to look for appendicitis, while CT is generally the preferred imaging modality for acute appendicitis abdominal ultrasound that focuses on the right lower quadrant is the recommended imaging exam in children and pregnant women.

The main advantages of ultrasound include the lack of ionizing radiation, and intravenous contrast, as well as its availability as it can often be done at bedside. However, the major disadvantage is that it has a much lower diagnostic accuracy than CT scan or MRI. The rate of non diagnostic or indeterminant exams with the appendix are high with ultrasound. There are reports of 50 to 80% of normal appendencies not visualized on ultrasound.

To learn more about using ultrasound to diagnose acute appendicitis, please see Med Masteries Point of Care Ultrasound Masterclass. Magnetic Resonance Imaging or MRI is not the first line imaging in acute appendicitis. It is reserved for certain populations, particularly pregnant women in whom we suspect appendicitis and children who can cooperate with the exam. Let's discuss treatment of acute appendicitis.

The treatment for acute appendicitis can be medical or surgical. When using antibiotics, coverage of gram positive bacteria and anaerobes is generally sufficient. Regardless of the initial empiric regimen, the therapeutic regimen should be revisited once culture and susceptibility results are available. Bowel rest involves not taking anything orally. This allows the inflammatory process to cool down without any additional stimulation from the GI tract. Laparoscopic appendectomy is a gold standard surgical approach for appendicitis. It involves the minimally invasive removal of the appendix using surgical tools and a laparoscope performed by a general surgeon in the operating room under anesthesia.