Acute appendicitis

Essentials

  • Appendicitis is a common disease. Its typical main symptom is pain moving into or mainly felt in the right lower quadrant (RLQ) of the abdomen.
  • The diagnosis is usually confirmed by ultrasonography or computed tomography (CT).
  • Uncomplicated appendicitis in patients aged between 18 and 60 can usually be treated by antimicrobial medication or surgery, according to local practice.
  • Surgery should be used if the appendicitis is complicated or if the patient is a child or a pregnant woman.

Prevalence

  • Appendicitis is most common in younger age groups but it is encountered in older people as well.
  • Appendicectomy is still one of the most common emergency surgical operations.

Symptoms and findings

  • The classic history consists of upper abdominal pain followed by right lower quadrant (RLQ) pain at the McBurney point (picture (McBurney's point and the position of the appendix)).
  • The patient may be febrile, nauseous and/or vomiting.
  • A physical examination shows RLQ tenderness to palpation.
    • Rebound tenderness and pain on percussion
    • If the peritoneum becomes irritated, the abdominal wall muscles feel tense (guarding) on palpation.
  • If the appendix ruptures (bursts), either a periappendicular abscess contained by the surrounding tissues or peritonitis will develop.
  • In more elderly people, the clinical picture may be vague and the probability of tumours increases.
  • The location of the appendix may vary (picture (McBurney's point and the position of the appendix)).
    • In pregnant women, as pregnancy advances, the growing uterus pushes the caecum, and hence also the appendix, upwards, and consequently the pain of appendiceal inflammation moves upwards and laterally.
    • Patients with retrocaecal appendicitis present with pain that is higher and closer to the back than in classic appendicitis. The pain is due to tension of the psoas muscle, which lies behind the caecum.
    • Inflammation of an appendix that lies more within the pelvis produces somatic pain lower than the McBurney point in the upper pelvic region. The pain can be elicited by contracting the obturator muscle (flexion and internal rotation of the right hip).

Diagnosis

  • Diagnosis is based on the clinical picture.
    • If appendicitis is suspected, basic blood tests should be done (basic blood count, platelets and neutrophils, CRP, sodium, potassium, creatinine).
    • The probability of acute appendicitis can be estimated by the Adult Appendicitis Score https://www.appendicitisscore.com/. If the probability is low, discharging the patient without carrying out further investigations or giving antimicrobial treatment is probably safe.
  • Vital signs (blood pressure, heart rate, temperature, oxygen saturation) should be taken.
  • The diagnosis should be verified by imaging.
    • Ultrasonography is often the primary investigation in patients below 35–40 years and those of normal weight, if conservative treatment is not considered. Ultrasonography cannot exclude complicated appendicitis or a tumour.
    • Abdominal CT is often used to diagnose appendicitis [Evidence Level: A]. CT can distinguish between cases of complicated and uncomplicated appendicitis.
    • In complicated appendicitis, a faecalith can be seen inside the appendix, the appendix is gangrenous or perforated or a periappendicular abscess may have developed after perforation.
  • Appendicitis recurring after conservative treatment should be treated by appendicectomy.
    • If appendicitis was previously diagnosed by CT, repeat imaging is not necessary if symptoms recur and no other cause is suspected.
  • For differential diagnosis, see table T1.
Table 1. Differential diagnosis of appendicitis
Differential diagnosis Clinical signs
Gastroenteritis (mesenteric lymphadenitis) Symptoms of intestinal infection, lymphadenopathy and appendix no more than mildly dilated on CT
Urinary tract infection Pyuria and bacteriuria
Right-sided urinary tract stone Microscopic haematuria and colicky pain
Gynaecological infections Abnormal discharge and pain during gynaecological examination
Ectopic pregnancy Positive pregnancy test, often decreased haemoglobin and a positive Kehr sign
Ovarian causes Rupture of an ovarian cyst usually causes mild symptoms, torsion produces more severe pain
Diverticulitis with perforation If the sigmoid colon is long, pain in mid/right lower abdomen
Cholecystitis A low-lying gallbladder in an elderly patient

Treatment

  • Uncomplicated appendicitis may be treated by antimicrobial medication if the patient is aged 18–60.
    • The criteria and practices of conservative treatment vary by hospital.
    • Conservative treatment can be started if the diagnosis of appendicitis has been confirmed and complications have been excluded by CT. This is why appendicitis should still be treated in specialized care.
  • Complicated appendicitis is usually treated by laparoscopic appendicectomy [Evidence Level: A]. Appendicectomy is also used to treat appendicitis in children, pregnant women and patients over 60.
  • Treatment of cases where a periappendicular abscess has already developed varies by hospital.
    • In patients older than 40, an abscess is associated with an increased tumour and cancer risk. Therefore, to the extent possible, surgery should only be performed later.
    • If necessary, an abscess can be drained or punctured at the hospital.
    • Colonoscopy should be readily performed before appendicectomy in patients older than 40.

References

1. Salminen P, Sippola S, Haijanen J, et al. Antibiotics versus placebo in adults with CT-confirmed uncomplicated acute appendicitis (APPAC III): randomized double-blind superiority trial. Br J Surg 2022;109(6):503-509  [PMID:35576384]
2. Sippola S, Haijanen J, Grönroos J, et al. Effect of Oral Moxifloxacin vs Intravenous Ertapenem Plus Oral Levofloxacin for Treatment of Uncomplicated Acute Appendicitis: The APPAC II Randomized Clinical Trial. JAMA 2021;325(4):353-362  [PMID:33427870]
3. Salminen P, Tuominen R, Paajanen H, et al. Five-Year Follow-up of Antibiotic Therapy for Uncomplicated Acute Appendicitis in the APPAC Randomized Clinical Trial. JAMA 2018;320(12):1259-1265  [PMID:30264120]
4. Salminen P, Paajanen H, Rautio T et al. Antibiotic Therapy vs Appendectomy for Treatment of Uncomplicated Acute Appendicitis: The APPAC Randomized Clinical Trial. JAMA 2015;313(23):2340-8.  [PMID:26080338]
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