Appendicitis

History

Appendix described as early as 1500's
Appendicitis recognized as early as 1700's
McBurney vs Rockey-Davis appendectomy became standard of care in early 1900's
Laparoscopic appendectomy became standard of care in 1980's
Antibiotics alone appropriate for select cases as of 2020

The appendix has been described by anatomists as early as the 1500's, and appendicitis was increasingly recognized after multiple autopsy studies throughout the 1700's. However, it's clinical relevance was not initially recognized in part due to surgical dogma but also because the therapeutic implications were not clear. This mindset began to shift after the 1886 inaugural meeting of the Associotion of American Physician where pathologist Reginald Fitz, MD of Harvard presented on appendicitis, emphasizing early surgical removal. Claudius Amyand performed the first known appendectomy in 1735 on an 11-year-old boy as part of surgical repair of a longstanding scrotal hernia. An increasing number of case reports and series were published throughout the 1800s. American surgeons rapidly accepted appendectomy for acute appendicitis by the turn of the 20th century. Open approaches involved an oblique right lower quadrant muscle-splitting or "grid iron" incision, today referred to as a McBurney incision after Charles McBurney, MD of New York popularized it in a 1894 Annals of Surgery article. Surgeons A. E. Rockey of Portland and Gwilym G. Davis of Philadelphia separately described a transverse muscle-splitting incision, described today as a Rockey-Davis incision. Management of the appendiceal stump was initially controversial, but most surgeons eventually settled on a combination of ligating and amputating the base followed by burying the stump with serosal imbricating sutures. An increasing understanding of the pathophysiology of acute appendicitis, to include the importance of fluid resuscitation and early interruption of peritoneal contamination eventually dropped mortality rates, with the advent of antibiotics in the 1940-1950s substantially aiding in this. Death from appendicitis today is rare and is most common in extremes of age or immunocompromise.¹ Laparoscopic appendectomy gradually became the standard treatment for appendicits since, compared to open appendectomy, it is associated with less post-operative pain, faster recovery, earlier hospital discharge, and faster return to normal state of health. Recent clinical trials have suggested it is feasible and effective to treat acute uncomplicated appendicitis non-operatively with antibiotics alone.²

Williams GR. Presidential Address: A History of Appendicitis: With Anecdotes Illustrating Its Importance. Annals of Surgery. 1983;197(5):495-506.
Moris D, Paulson EK, Pappas TN. Diagnosis and Management of Acute Appendicitis in Adults: A Review. JAMA. 2021;326(22):2299. doi:10.1001/jama.2021.20502.

Epidemiology

MC 20-30 y/o
Male-to-female 1.4:1

Acute appendicitis is most frequent during the second and third decades of life, whereas children 9 years or younger have the lowest incidence. Appendicitis is more common among men (malefemale ratio, 1.4:1), who have a lifetime incidence of 8.6% compared with 6.7% for women. People with a higher income ($44 691 vs $30 027) and education (college-educated vs noncollege-educated patients) have a lower incidence of acute appendicitis. The incidence of perforated appendicitis has been increasing despite a decline in the overall incidence of acute appendicitis. Men are more likely to have perforated appendicitis than women (31 vs 25 per 100 000 person-years).¹

Moris D, Paulson EK, Pappas TN. Diagnosis and Management of Acute Appendicitis in Adults: A Review. JAMA. 2021;326(22):2299. doi:10.1001/jama.2021.20502.

Pathophysiology

Appendiceal outlet obstruction progresses to wall inflammation
Increasing pressure produces localized ischemia and eventually perforation
Perforation may be contained (abscess) vs generalized (peritonitis)

Appendiceal outlet obstruction has been proposed as the primary factor that initiates appendicitis. Acute appendicitis begins with inflammation of the appendiceal wall that is followed by localized ischemia, perforation, and the development of a contained abscess or generalized peritonitis. The obstruction of the appendiceal lumen leads to increased luminal and intramural pressure, resulting in thrombosis of small vessels in the appendiceal wall and lymphatic flow stasis. As lymphatic and vascular compromise progress, the wall of the appendix becomes ischemic and eventually necrotic. As the appendix becomes dilated and congested, the T8-T10 visceral afferent nerves are stimulated, leading to vague periumbilical abdominal pain. Irritation of the surrounding parietal peritoneum stimulates somatic nerves, which is clinically manifest as right lower quadrant pain.¹

Moris D, Paulson EK, Pappas TN. Diagnosis and Management of Acute Appendicitis in Adults: A Review. JAMA. 2021;326(22):2299. doi:10.1001/jama.2021.20502.

Etiology

Appendicolith (MC in older adults)
Lymphoid hyperplasia (MC in young adults)
Benign or malignant tumors

Appendiceal outlet obstruction may be caused by appendicoliths, defined as the conglomeration of feces in the appendiceal lumen, calculi, lymphoid hyperplasia, infection, and benign or malignant tumors. In young adults, lymphoid follicular hyperplasia due to infection is thought to be the main cause of acute appendicitis, whereas in elderly patients, luminal obstruction by appendicolith or mass is more likely.¹

Moris D, Paulson EK, Pappas TN. Diagnosis and Management of Acute Appendicitis in Adults: A Review. JAMA. 2021;326(22):2299. doi:10.1001/jama.2021.20502.

Clinical Features

Diagnosis

Differential

Management

Antibiotics

Laparoscopic Appendectomy

Open Appendectomy

Complicated Appendicitis

6-7% lifetime risk in general population

peak incidence 2nd decade of life

Anatomy

small outpouching of cecum at 8 weeks gestation
elongated, tubular, rotates medially, fixed in RLQ
generous lymphatic tissue in submucosa
blood supply: SMA → ileocolic → appendiceal artery w/in mesoappendix
variable size (5-35 cm), average 8-9 cm in adults
base reliably identifed at convergence of taeniae at tip of cecum
appendix tip locations varies: 60% retrocecal, 30% pelvic, 7-10% retroperitoneal

Pathogenesis

luminal obstruction → ongoing mucus secretion & bacterial gas production elevates luminal pressure → venous drainage becomes impaired → mucosal ischemia → full-thickness ischemia → perforation → contained abscess vs diffuse peritonitis

Etiology

lymphoid hyperplasia (60% esp. children)
fecal stasis & fecaliths (35% esp. adults)
neoplasms (carcinoid, adenocarcinoma, mucinous)

Microbiology

Escherichia coli (64.6%)
Pseudomonas aeruginosa (16.4%)
Klebsiella pneumoniae (5.3%)
Enterococcus spp. (3.9%)
Streptococcus spp. (2.9%)
Citrobacter spp. (2.6%)
Enterobacter spp. (1.4%)

Clinical

retrocecal: classic migratory RLQ pain

retroperitoneal: back and/or flank pain

pelvis: suprapubic pain

Pediatric Considerations

fewer than 5% children w/appendicitis are less than 5-y/o

perforation rates:

neonates (83%)

< 5-y/o (50-100%)

5-12 y/o (11-32%)

> 12-y/o (10-20%)

Differential

mesenteric adenitis
acute gastroenteritis & ileitis: most commonly 2/2 acute self-limited bacterial infection (Yersinia enterolitica, Campylobacter, Salmonella, etc.); consider when there is prominent diarrhea
intussusception
Meckel diverticulitis: classically 2 ft from IC valve, but small bowel can migrate to RLQ and mimic appendicitis
Crohn's disease: consider when there is fatigue, prolonged diarrhea, weight loss, & fever
testicular torsion: a significant minority of patients report abdominal pain and not initially testicular pain
kidney stones: stones obstructing the renal pelvis or upper ureters will refer to the flank (ie CVA tenderness), but lower ureteral obstruction will radiate to the ipsilateral testicle or labium

FORAs

PID & TOA

ruptured ovarian cyst

mittleschmerz (mid-cycle abd pain 2/2 ovulation)

ovarian torsion

endometriosis

ectopic pregnancy

cecal diverticulitis (1.5% of all diverticulitis)

neutropenic enterocolitis (typhilitis) esp. if immunocompromised

Diagnosis

modified Alvarado score: ≥ 4 warrants imaging (consider alternative diagnosis for 1-3); a systematic review of 42 retrospective and prospective studies that included over 8300 patients w/suspected acute appendicitis and/or RLQ pain, overall, 99% of patients w/acute appendicitis had a score of > 4
- migratory RLQ pain (1 pt)
- anorexia (1 pt)
- nausea or vomiting (1 pt)
- RLQ tenderness (2 pts)
- RLQ rebound (1 pt)
- T > 37.5 C (> 99.5 F) (1 pt)
- WBC > 10 (2 pts)
CT-Abdomen/Pelvis w/IV Contrast: SN 95% vs SP 94-96%; a negative result visualizes a normal appendix (whereas inability to visualize the appendix, which occurs in 10-20% of cases, does not r/o appendicitis)
- appendiceal double-wall thickness > 6 mm
- appendiceal wall thickening > 2 mm
- periappendiceal fat stranding
- appendiceal wall enhancement
- fecalith
US-Abdomen: preferred in children and pregnancy; otherwise is an alternative to CT if not readily available due to high variability related to a combination of patient specific & operater-specific factors); 50-85% of exam fail to visualize the appendix
- appendiceal double-wall thickness > 6 mm
- non-compressible appendix
- focal pain over appendix w/compression
- periappendiceal fat hyperechogenicity
- fecalith
- RLQ fluid

Therapy

asdf

Complications

perforation with abscess

perforation with peritonitis

Miscellaneous

Amyand hernia: inguinal hernia containing appendix

First reported appendectomy 1735

first formal description of appendicitis 1886

McBurney's technique for muscle-splitting open technique 1894

Kurt Semm first lap appy 1982

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