Appendicitis classically presents as RLQ pain, fever, vomiting without diarrhea, a high WBC and normal UA. But pattern recognition is a great way to miss appendicitis–especially in children, women and the elderly–as the following studies makes clear.
The implications of missed opportunities to diagnose appendicitis in children. Acad Emerg Med 2013 Jun;20(6):592-6. In this retrospective analysis of 816 children undergoing appendectomies, 39 (about 5%) were missed at initial presentation. Not surprisingly this resulted in increased length of stay and higher rates of perforation, abscess and obstruction.
Here were their characteristics of those with a missed diagnosis of appendicitis
- History: 13% RLQ pain, 36% fever, 70% emesis, 26% diarrhea
- Evaluation: 20% CBC, 36% UA, 3% CT, 5% US, 8% surgery consult
- Discharge diagnosis: 44% gastro, 10% constipation, 10% emesis, 18% abdo pain NOS, 18% other (URTI, UTI, pharyngitis)
Misdiagnosis of Acute Appendicitis in Children Attending the Emergency Department: The Experience of a Large, Tertiary Care Pediatric Hospital. Eur J Ped Surg 2016. Similar results: of 400 cases of pediatric appendicitis 3.75% were initially misdiagnosed, a quarter of whom were labelled “gastro.”
There are a number of lessons here
- Don’t rely on a classic history of RLQ pain and fever, and don’t discard appy because of diarrhea. RLQ tenderness is appy until proven otherwise, and can begin as periumbilical pain
- Know the limitations of tests: CBC can give falsely-reassuring WBC; appendiceal irritation of the ureters can give urine WBC misdiagnosed as UTI; US and even CT are not 100% sensitive
- Before writing the discharge diaganoses of “gastro”, “constipation”, “vomiting” or “abdo pain”, consider the appendicitis score (see below)
- For patients with acute abdo complaints, provide clear discharge instructions of when to return or schedule a reassessment in the emergency department or with their primary health provider.
Misdiagnosis of appendicitis in non-pregnant women of childbearing age. J Emerg Med 1995;13(1):1-8. This study from 20 years ago found a misdiagnosis rate of 33%. While this doesn’t seem to correspond to experience, the lessons are still helpful
- Symptoms leading to misdiagnosis: bilateral lower abdo pain/tender, cervical motion tenderness, right adnexal tenderness
- Most common misdiagnoses: PID, gastro, UTI
This again highlights the potential of misdiagnosing appy as gastro if there is loose stool, or UTI if there is pyuria–and in women there is additional potential misdiagnosis of PID which can share symptoms and signs. In an effort to help distinguish PID from appy there’s been a clinical decision rule: Clinical prediction rule to distinguish pelvic inflammatory disease from acute appendicitis in women of childbearing age. Am J Emerg Med 2007 Feb; 25(2): 152-7. They found a 100% sensitivity in ruling out appendicitis from PID if three criteria are met: 1) no migration of pain, 2) no nausea or vomiting, 3) bilateral abdominal tenderness
Elderly patients also have higher rate of delayed diagnosis and higher complications of appendicitis.
CLINICAL DECISION RULE
The Alvarado appendicitis score was developed to integrate history/physical/lab tests to help risk stratify patients presenting with potential appendicitis–using the MANTRELS acronym:
- Migratory: +1
- Anorexia: +1
- Nausea/vomit: +1
- Tender RLQ: +2
- Rebound: +1
- Elevated temp: +1
- Leuk >10: +2
- Shift: +1
Of note, the CBC contributes a minority of points, and there are no loss of points for diarrhea or leukocytes in the urine.
In a recent review of the utility of the score, What Are the Most Clinically Useful Cutoffs for the Alvarado and Pediatric Appendicitis Scores? A Systematic Review in Annals of Emergency Medicine 2014, the authors found the following likelihood ratios
- for adults: 0.03 for <4 points, 0.01 for <5 points, 0.42 for 4-6 points, 0.98 for 5-8 points, 3.4 for >6 points, 6.7 for >8 points
- for children: 0.02 for <4 points, 0.04 for <5 points, 0.27 for 4-6 points, 1.2 for 5-8 points, 4.2 for >6 points, 8.5 for >8 points
So the score is helpful is altering your pre-test likelihood if it’s low or high, but not helpful in the middle.
In conclusion, consider appendicitis with any abdominal complaint, including in the presence of loose stool and pyuria. Consider appy before diagnosing children with gastro, women with UTI/PID, and elderly patients with constipation or non-specific abdo pain. Beware test limitations, especially of WBC but also US/CT. Consider the MANTRELS score to risk stratify patients, and provide clear discharge instructions