Acute appendicitis

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Key Recommendations

History and physical examination form the initial approach in the evaluation of a patient with possible appendicitis. It is routine practice in the US to request a computed tomography (CT) scan for patients presenting to the emergency room with features of acute appendicitis.[29]

Validated clinical decision tools such as the Alvarado score demonstrate high sensitivities and are useful for excluding appendicitis, but lack specificity.[30][31][32]

Ultrasound or magnetic resonance imaging (MRI) of the abdomen are recommended if the patient is pregnant.[7][33] Women of childbearing age should have a pelvic examination to rule out other pelvic pathology.[34]

History

The typical picture of central pain migrating to the right iliac fossa, associated with nausea, vomiting, and anorexia, occurs in less than half of presentations.[35] Abdominal pain is the most common presenting symptom. Pain typically starts at the mid-abdominal region and 1-12 hours later shifts to the right lower quadrant as the inflammation progresses.[36] Pain tends to be constant in nature, with intermittent abdominal cramps, and is usually worse on movement and coughing.

Location of the pain may vary depending upon the position of the appendix:[37]

Retrocecal appendix may cause flank or back pain
Retroileal appendix may cause testicular pain due to irritation of the spermatic artery or ureter
Pelvic appendix may cause suprapubic pain
A long appendix with tip inflammation in the left lower quadrant may cause pain to that region.

Anorexia is almost always present.[12] If the patient is hungry and wants to eat, this is reassuring and makes appendicitis less likely.[37] Nausea and vomiting are usually present in 75% of patients.[12] Absolute constipation is a late feature.[38]

Features that are significantly associated with appendicitis in pregnant patients are nausea, vomiting, and local peritonitis.[39]

Complicated appendicitis (perforation or intra-abdominal abscess) is more likely the greater the duration of symptoms and in older patients (>50 years).[40][41]

Children may present with nonspecific abdominal pain, anorexia, and vomiting.[8]

Physical exam

Usually, there are no significant changes in vital signs. Patients may have a low-grade fever.[2][37] In patients presenting with a high-grade fever, another diagnosis should be considered.[2] Tachycardia may be present (but this can also indicate a perforated appendix).[42]

A classic sign is right lower quadrant abdominal tenderness (McBurney sign) and localized rebound tenderness, if appendix is anterior. There may also be pain in the right lower quadrant after compressing the left lower quadrant (Rovsing sign).[35] In retrocecal appendicitis, pain may be elicited in the right lower quadrant with the patient lying on their left side and slowly extending the right thigh to cause a stretch in the iliopsoas muscle (psoas sign) or by internal rotation of the flexed right thigh (obturator sign).[12] However, Rovsing and obturator signs are of limited diagnostic value for acute appendicitis.[35][38][43]

Classic abdominal findings may not be present if the appendix is in an atypical position.[35]

Patients with perforation may present acutely ill with hypotension, tachycardia, and a tense, distended abdomen with generalized guarding and absent bowel sounds.[37]

A palpable mass may be felt with appendiceal perforation that has been contained by the omentum, resulting in a periappendiceal abscess.[7]

In children, pain with coughing and hopping can support the diagnosis.[9] Analgesia may be useful to facilitate abdominal exam if pain limits the examination. Analgesia does not lead to missed diagnoses in children.[44][45] See Evaluation of abdominal pain in children.

The diagnosis of appendicitis in pregnant women should not be made based on history and exam only. Blood tests, including inflammatory markers, should be ordered.[7]

Appendicitis is the most common nonobstetric surgical condition during pregnancy.[46] A delay in diagnosis and treatment may result in perforation, which is associated with significant maternal and fetal mortality.[46] In pregnant women, atypical pain such as right upper quadrant or right flank pain may occur after the first trimester due to displacement of the appendix by the gravid uterus.[42]

A collateral history should be taken if communication presents a challenge (e.g., when there is a language barrier, or in patients who are very young, have dementia, have a mental health diagnosis, or have a learning difficulty).[35] Appendicitis should be suspected if there is a history of becoming withdrawn or less active, or having reduced oral intake.[35]

Investigations

Blood tests

All patients with abdominal discomfort should have a complete blood count taken. Mild leukocytosis (10,000-18,000/microliter) with increased neutrophils is usually present. In children, CRP level on admission ≥10 mg/L and leukocytosis ≥16,000/microliter are strong predictive factors for appendicitis.[7]

Imaging

Some form of imaging is usually warranted. Most nonpregnant patients presenting to the emergency room with abdominal pain suggestive of appendicitis will have a CT scan of the abdomen and pelvis.[7][33] Preoperative imaging with a CT scan of the abdomen (ultrasound or MRI for pregnant women) now forms the usual standard of care. Women and children, in particular, may benefit from preoperative imaging.[9][29][47]

Choice of imaging modality

Although CT scan has greater sensitivity and specificity than ultrasound in diagnosing appendicitis, the latter is readily available, rapid, and able to be performed at the bedside.[7][48][49][50] Ultrasound has a sensitivity of 71% to 94% and specificity of 60% to 98% for acute appendicitis; if ultrasound is unequivocally positive for appendicitis, ultrasound has comparable accuracy to a positive CT or MRI for ruling in appendicitis.[51][52] If, on ultrasound, a normal appendix is visualized in its full length, then acute appendicitis can be excluded. However, this is rarely the case, and the greatest utility for ultrasound is to detect an alternative cause of abdominal pain that excludes appendicitis.[7]

Appendiceal CT scan is increasingly used as the initial diagnostic test for acute appendicitis, and it is routine practice in the US to request a CT for patients presenting to the emergency room with features of acute appendicitis.[29] The Infectious Diseases Society of America (IDSA) offers a conditional recommendation for abdominal CT as the initial imaging modality to diagnose acute appendicitis.[53] A CT is also indicated in atypical presentations.[33][54] However, delayed surgery subsequent to CT scan for presumed appendicitis is associated with an increased rate of appendiceal perforation.[55] Intravenous contrast is usually appropriate whenever a CT is obtained in adults with suspected acute appendicitis; however, CT without intravenous contrast also has high diagnostic accuracy in detecting acute appendicitis and may be appropriate.[33][53] Intravenous contrast-enhanced CT scan with or without oral contrast has up to 100% sensitivity compared with 92% sensitivity in nonintravenous contrast-enhanced CT scan.[56][57][58][Figure caption and citation for the preceding image starts]: CT abdomen - thickened appendix.Nasim Ahmed, MBBS, FACS; used with permission [Citation ends]. The IDSA recommends to consider observation and supportive care, with or without antibiotics, if CT is negative but clinical suspicion for acute appendicitis persists.[53] If clinical suspicion is high, consider surgical intervention.[53] Laparoscopy may also be reasonable if there is diagnostic uncertainty.

In pregnant women presenting with features of appendicitis, an abdominal sonogram should be performed to identify the appendix.[53] If the sonogram examination is inconclusive, an abdominal MRI (particularly in early pregnancy) may be appropriate.[33][53][54] MRI has been proven to be a highly accurate diagnostic test for acute appendicitis, with a sensitivity of 0.96 and specificity of 0.97 in pregnant women.[59] However, a negative or inconclusive MRI does not exclude appendicitis and surgery should still be considered if clinical suspicion is high.[7][59]

In children, point-of-care ultrasound is the most appropriate first-line diagnostic tool, if an imaging investigation is indicated based on clinical assessment.[52][53] In children, if there is diagnostic doubt and ultrasound results are inconclusive, a second-line imaging technique (i.e., CT or MRI) should be used based on local availability and expertize.[7][53] Low-dose CT is preferred if ultrasound is negative.[7]

Tests to exclude other causes

A urinalysis should be performed to exclude possible urinary tract infection or renal colic. Sexually active women of childbearing age should have a urinary pregnancy test.

Venepuncture and phlebotomy: animated demonstration

How to take a venous blood sample from the antecubital fossa using a vacuum needle.

Novel biomarkers

Several novel biomarkers may be of value in the diagnosis and severity assessment of acute appendicitis. These are not routinely used or recommended in established guidelines, and require further investigation.

Neutrophil-to-lymphocyte ratio. The simple ratio between neutrophils and lymphocytes measured in peripheral blood has been shown to have moderate predictive power for acute appendicitis and may be a useful adjunctive tool for diagnosis.[61]
Hyponatremia. Several studies have shown a link between hyponatremia and acute appendicitis, and as a predictor of complicated appendicitis.[62][63]
Pentraxin 3.[64]
Serum amyloid A. One systematic review and meta-analysis showed that serum amyloid A has a sensitivity and specificity for acute appendicitis of 0.87 and 0.74 respectively.[65]
Platelet indices. Studies suggest that low mean platelet volume is a marker of acute appendicitis.[66][67]

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