Question
What is the role of imaging studies in pediatric patients with suspected appendicitis in the emergency department?
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Response from Robert Glatter, MD Attending Physician, Department of Emergency Medicine, Lenox Hill Hospital, New York, NY |
A frequent diagnostic dilemma in the emergency department (ED) is a child with an abdominal examination suspicious for appendicitis. Overall, appendicitis is the most common condition requiring intra-abdominal surgery in infancy and childhood. Although it commonly occurs, accurate diagnosis of appendicitis remains a clinical challenge.
According to one study, acute appendicitis may be missed at initial clinical examination in up to 57% of children aged 12 years and younger and in nearly 100% of children under the age of 2 years. Based on current data, missed appendicitis is the most frequent successful malpractice claim against ED physicians.
Diagnosing appendicitis in younger children (< 5 years old) can be especially challenging. Clinical presentations can be confusing, and the diagnosis is often delayed or missed, resulting in a higher frequency of complications such as appendiceal perforation and formation of a phlegmon or abscess. In addition, many typical features of appendicitis, such as localized right lower quadrant pain, fever, and leukocytosis, may be minimal or absent in younger children.
Although appendicitis has traditionally been a clinical diagnosis made after a thorough history, physical examination, and applicable laboratory studies, many patients are found to have normal appendices at surgery. The misdiagnosis of appendicitis has led to the inappropriate removal of a normal appendix in up to 30% of patients. A rate of unnecessary removal as high as 20% has traditionally been considered "acceptable" in the surgery literature.
However, misdiagnosing a patient with appendicitis will lead to needless surgery, and increases hospital costs and patient morbidity without addressing the underlying cause of the patient's symptoms. As a result, many pediatric surgeons believe that negative laparotomy rates can be further reduced if modern diagnostic methods (graded compression ultrasound and abdominal/pelvic computed tomography [CT] scanning) are used to confirm or exclude acute appendicitis.
Over the past 2 decades, graded compression sonography has emerged as a useful imaging technique for the evaluation of suspected appendicitis, especially in children. Sonography is a noninvasive, rapid, widely available, and relatively inexpensive technique. Most importantly, sonography does not involve the use of ionizing radiation from CT scanning, a key consideration when imaging otherwise healthy pediatric patients, who are up to 10 times more sensitive to the effects of ionizing radiation than middle-aged and elderly adults.
The main concern with sonography is that it is operator-dependent, requires a high level of skill and expertise, and may be technically limited by some clinical situations (severe pain, overlying gas). Moreover, sonography frequently does not allow the detection of normal or perforated appendices, and therefore may be of limited value in evaluating patients at the extremes of the disease spectrum. The reported diagnostic accuracy of graded compression sonography varies widely; the reported sensitivity of sonography in children ranges from 44% to 94%, and specificity ranges from 47% to 95%.
Based on pooled data from a meta-analysis by Doria and coworkers, CT scanning has been shown to be approximately 94% sensitive and 95% specific for acute appendicitis in young children. The overall accuracy has been shown to be approximately 97%, with a false-negative rate for the diagnosis of appendicitis between 2% and 3%. Advantages of CT include the ability to image the entire abdomen; locate perforations, abscesses, and phlegmons; and make alternative diagnoses. Disadvantages include exposure to radiation and the need for oral/intravenous contrast based on certain protocols.
Based on a recent study by Tsao and colleagues involving more than 1078 patients, the positive predictive value (PPV) of CT scanning for appendicitis was 96.4 % vs 90.8% based on history and physical examination alone. From this study, the authors concluded that the correct preoperative diagnosis of appendicitis is statistically more accurate with CT scanning compared with history and physical examination alone (P < .045).
The management of complicated (perforated) appendicitis has evolved significantly in the current era of CT scanning. In the past, preoperative imaging was reserved for ambiguous or equivocal cases after a thorough history and physical examination. With the wider use of CT scans to evaluate children for acute appendicitis, the ability to identify complicated (perforated) appendicitis has allowed for non-operative management (antibiotics with or without percutaneous drainage and interval appendectomy up to 3 months later), which is associated with a lower mortality/complication rate.
This trend toward non-operative management for complicated (perforated) appendicitis has influenced pediatric surgeons to consider CT scanning (after an inconclusive graded compression ultrasound) increasingly more valuable in the evaluation of complicated appendicitis in younger (age < 5) pediatric patients.
Although a number of pediatric surgeons may elect to go to the operating room based on a "straightforward" case of appendicitis (right lower quadrant tenderness, fever, and leukocytosis), a CT scan should be highly considered (after an inconclusive graded compression ultrasound) in cases where there is suspicion for perforated appendicitis (amenable to nonsurgical management) because there is a lower false-negative rate (2%-3%) with CT compared with history and physical examination alone. An interval appendectomy may then be performed approximately 3 months later.
Conclusion
1. In pediatric patients whose examination is equivocal for acute appendicitis (and in whom graded compression ultrasound is inconclusive), CT scanning should be strongly considered because it has the potential to change management from operative to non-operative. The lower false-negative rate associated with CT scanning (as opposed to history and physical examination alone) as well as the higher positive predictive value argue for strong consideration for CT scanning in patients with an equivocal examination and suspicion for appendicitis.
2. In pediatric patients who are clinically stable and in whom there is a strong suspicion for complicated appendicitis (perforation/abscess), CT scanning is indicated to evaluate for abscess or phlegmon, potentially changing initial management to non-operative (intravenous antibiotics plus or minus percutaneous drainage), with a subsequent interval appendectomy.
3. Concerns regarding radiation associated with CT scanning should be discussed with parents when they are making decisions regarding imaging modalities for their child.