Acute appendicitis is one of the most common atraumatic surgical emergencies. It can affect patients at any age, however the incidence peaks around the second and third decades. Reports of male to female predominance are conflicting, with some sources citing either sex with a slight majority. In children over 1 year of age acute appendicitis is the most common cause of atraumatic abdominal pain, and in pregnancy it is the most common non-obstetric surgical emergency. Although the incidence peaks earlier in life, consider the diagnosis in all ages with atraumatic abdominal pain. Especially consider the atypical presentation.
Upon completion of this module, the student will be able to:
Identify patients with suspected appendicitis
Describe the classic history and physical exam findings in appendicitis, as well as the atypical presentation
Discuss the roles of laboratory tests and imaging in the diagnosis of appendicitis
Describe the management options for appendicitis
A classic presentation of appendicitis occurs as follows:
Vague epigastric or periumbilical pain.
Nausea, vomiting and anorexia.
Abdominal tenderness, migrating then localizing to the right lower quadrant.
This classic presentation though, is highly variable especially at extremes of age and anatomical location of the appendix. A retrocecal appendicitis may present a variety of ways including low back pain, left sided pain and even right upper quadrant pain.
Right lower quadrant pain and guarding generally have a high sensitivity (81%) for appendicitis, but poorly specific (53%). Abdominal rigidity is highly specific (83%) with a low sensitivity (27%). The classic Psoas, Obturator and Rosving’s signs are all relatively poor predictors of appendicitis. No single exam finding should be used to rule in or rule out the disease.
Atypical presentations can occur in any patient, but more are more likely in extremes of age, and pregnant patients. Children can be more of a diagnostic challenge due to communication barriers and vague symptoms. In children less than four years old perforation rates can be as high as 90%.
Another high-risk population includes elderly patients presenting with subtle signs and significant comorbities. They too can often present late. Immunosuppressed patients will likely have a decreased inflammatory response and may have more subtle signs, like the elderly population.
Maintain a high level of suspicion for appendicitis, but do not forget to consider a broad differential. Do not forget the genital exam in both sexes. Females of childbearing age require special attention rule out gynecologic pathology that can be misdiagnosed as appendicitis, such as ectopic pregnancy, ovarian torsion, and TOA. The pregnant patient can also have atypical complaints secondary to a gravid uterus.
Male patients with a classic presentation of appendicitis including acute abdominal pain that has migrated from the umbilicus to right lower quadrant along with McBurney’s point tenderness, anorexia and fever will sometimes be taken to the OR without additional workup. Most often, however a workup including lab tests and imaging is required.
There is no single lab test specific for the diagnosis of appendicitis. Many patients with appendicitis will have a leukocytosis, however 10-20% of patients will have normal white blood cell count. The converse is also true many patients with a leukocytosis will not have appendicitis. Since many other pathologies cause an elevated WBC. Another inflammatory marker, C-reactive protein, can be used along with the WBC for supporting or ruling out appendicitis. CRP alone cannot be used to rule in or rule out the disease. Both an elevated CRP and WBC have a combined sensitivity of 98%, and if both labs are within normal limits the diagnosis is less likely.
Urinalysis should be obtained. It is useful for determining pregnancy, and evaluating for infection and hematuria. Pyuria without bacteria present can be cause by inflamed appendix in close proximity to the ureter or bladder. Hematuria without other findings could suggest a ureteral stone as the cause of pain. Again, UA in isolation cannot rule out appendicitis.
Ultrasound is quickly becoming a more popular diagnostic tool in the Emergency Department. It is the preferred imaging modality in children and pregnant patients with suspected appendicitis due to absence of radiation. One multicenter cohort study found ultrasound is 72.5-86% sensitive to 96% specific for appendicitis in children. The diagnostic accuracy is variable depending on the skills of the sonographer and size of the patient. Ultrasound is typically much less sensitive in adults than children. A normal appendix on ultrasound is typically less than 6 mm and compressible. An appendix greater than 6-7 mm in diameter and noncompressible is indicative of appendicitis. Other findings that support the diagnosis are increase wall thickness, fecalith, and increased vascularity. Doppler flow can be used to demonstrate the increased vascularity of an inflamed appendix. An excellent resource for learning this skill is the Ultrasoundpodcast.com. Here is their video link on using ultrasound for diagnosing appendicitis:
CT is the preferred imaging study for evaluating acute appendicitis in adult males and nonpregnant females. CT of the abdomen/pelvis is also more useful for discovering the alternatives on your differential diagnosis list, and diagnosing complications of appendicitis (perforation, abscess, etc.). As with ultrasound and enlarged appendix over 6-7 mm, increased wall thickness, fecalith and periappendiceal stranding can support the diagnosis. The overall sensitivity for contrast enhanced CT ranges from 95-100%, which is considerably better than ultrasound. Specificity similarly is around 96%. One study showed that non–contrast CT (90 % sensitivity and 86% specificity) was inferior to CT with rectal only administered contrast (93% sensitivity and 95% specificity) and CT with both IV and oral contrast (100 % sensitivity and 89% specificity). IV contrast is recommended for evaluation of suspected appendicitis, but non-contrast CT still has excellent sensitivity, ranging from 89.5%-96% depending on the study. The ability to accurately use non-contrast CT studies is helpful in patients with contraindications, such as renal insufficiency and contrast allergy. Non-contrast CT scans are also faster to obtain. For those patients that do not have a contraindication to IV contrast, but cannot tolerate oral contrast due to pain or vomiting, rectal contrast may be used. Administration of rectal contrast is just as sensitive as oral contrast, and allows the CT to be obtained faster than with oral contrast.
Magnetic Resonance Imaging
MRI is typically reserved for pregnant patients with a nondiagnositic ultrasound. MRI has a similar diagnostic accuracy compared to CT, however emergent MRI often has limited availability, is expensive and more time consuming. As with ultrasound, MRI avoids radiation exposure however, the contrast medium used in the study, IV gadolinium, is potential teratogen. Similar to using IV contrast with CT, IV gadolinium cannot be used in patients with renal insufficiency.
How do I make the Diagnosis?
As mentioned above most cases of suspected appendicitis require lab test and imaging.
In adults, complete blood count, basic metabolic panel, CRP, and urinalysis are a good starting point of the workup. Urine pregnancy should be obtained for all females of childbearing age.
If the patient is a male or a nonpregnant female a CT scan would be the imaging modality of choice.
If the patient is child, pregnant or you have a high suspicion for gynecologic disease, then ultrasound would be a more appropriate initial imaging modality.
For low risk pediatric and pregnant patients with an indeterminate ultrasound observation for serial exams is warranted to avoid radiation and/or contrast. Another reasonable option in a low risk patient would be to have them return to the emergency department in 12 to 24 hours for a repeat examination. This option to return is also applicable to patients with negative CT scans and persistent symptoms.
All patients discharged home after a negative workup should be counseled on return precautions. No diagnostic test is perfect.
Clinical decision tools, such as the Alvarado score can be useful when considering the diagnosis. A calculator for the Alvarado score can be found here. A low score, <1-4, has approximately 96% sensitivity for ruling out appendicitis. In a meta-analysis the Alvarado score was inconsistent in children and tended to over predict appendicitis in women. The score was well calibrated in adult males. In general though, the Alvarado score is poor at ruling in the disease.
Acute appendicitis is traditionally a surgical disease. Prompt appendectomy is the treatment. Certain complicated cases like perforation with a walled off abscess will require drainage by interventional radiology. This should be done in conjunction with your surgical collegues.
Once the diagnosis is confirmed the patient should be made NPO and IV antibiotics should be started in the emergency department. Examples of appropriate antibiotics for uncomplicated appendicitis include ampicillin-sulbactam, or cefoxtin, or a combination of metronidazole and ciprofloxacin.
For complicated appendicitis (perforation, abscess, immunocompromise, etc.) a carbapenem, such as meropenem or imipenem, can be used or an extended spectrum penicillin with a beta-lactamase inhibitor, such as piperacillin/tazobactam.
Do not forget IV fluid resuscitation, pain control and antiemetics. Analgesia with reasonable doses of opioids has not been shown to alter the abdominal exam.
Emergency Department Disposition
OR for appendectomy
Interventional Radiology for percutaneous drainage of abscess
Observation in hospital for serial examinations
Return in 24 hours for a repeat examination
Pearls and Pitfalls
Maintain a broad differential diagnosis
An afebrile patient with a normal WBC does not rule out appendicitis
There is no single sign, symptom, or lab that completely rules out appendicitis
Urinalysis with pyuria or hematuria can be appendicitis due to an inflamed appendix next to the bladder and hematuria may represent nephrolithiasis. .
The localization of pain can be atypical due to the anatomic position of appendix and referred pain.
Ultrasound should be used as the first imaging study in children and pregnant females
Extremes of age have atypical presentations necessitating a high index of suspicion
In females presenting with RLQ pain and tenderness, make sure gynecologic diseases have been appropriately considered including ectopic pregnancy, ovarian torsion, or tuboovarian abscess.
Check the testicles! Do not miss torsion.
Every patient discharged home after a negative workup should receive appropriate return precautions. No test is perfect.
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Mittal, MK et al. Performance of ultrasound in the diagnosis of appendicitis in children in a multicenter cohort. Acad Emerg Med. 2013 Jul;20(7):697-702. doi: 10.1111/acem.12161
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