Appendicular abscess overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
Appendicular abscess is defined as a collection of pus resulting from necrosis of the tissue superimposed with infection in an inflamed appendix. It is unusual and rare entity and a life threatening complication of acute appendicitis. It is seen in 2-7% of population presenting with appendicitis. When the appendix become inflamed (appendicitis), complications arise if it is not treated promptly. When the abscess develops it remains limited by the walls of cavity formed by the inflamed coils of intestine and usually forms in the right lower abdomen. The abscess can spread to pelvis leading peritonitis if the wall is ruptured. In most of the patients the intestinal coils and omentum in the abdominal cavity tend to cover the inflamed appendix forming an appendicular mass. [1]
Historical perspective
Appendicitis was first officially described by Reginald J. Fitz of Harvard University in 1886. He also coined the term appendix. Since then, the appendectomy has become one of the most common surgical procedures. The laparoscopic appendectomy was invented in the 1980s, and has led to reduced length of hospital stay a decreased risk of infection, and a reduction in post-operative pain.
Classification
No known classification of appendicular abscess exists.
Pathophysiology
An appendicular abscess is a complication of acute appendicitis. It is resulted due to the invasion of the appendix by bacteria following an obstruction. The appendix exists at the junction of the small and large intestine and is a natural habitat of wide variety of bacteria. It is therefore prone to develop complications when blocked and coupled with an infection, acute appendicitis can be life threatening and can lead to gangrene, masses, rupture and general peritoneal infections when it gets ruptured. Obstruction of the tubular space inside the appendix is the main inciting event, this initial problem leads to the inflammation of the appendix, obstruction of the blood vessels supplying it, and finally infection. Inflammatory mediators along with various bacterial toxins and proteolytic enzymes from the neutrophils are released, resulting in the formation of abscess in appendix.
Causes
Microbiology responsible for appendicualr abscess includes a mixture of aerobic and anaerobic organisms that are natural habitat of gut. The most commonly isolated aerobic organism is Escherichia coli, and the most commonly observed anaerobic organism is Bacteroides fragilis. The type and density of aerobic and anaerobic bacteria isolated from appendicular abscesses depends upon the organism that dominate the habitat and degree of obstruction.
Differential Diagnosis
Appendicular abscess should be diagnosed early and treat promptly not only to reduce morbidity and mortality, but it is also important to differentiate from other abdominal diseases presenting with RLQ pain , fever, nausea and vomiting such as psoas abscess, cellulitis, torsion of testis and ovaries, ectopic pregnancy etc as the un-drained abscess carries high risk of mortality
Risk factors
Identifying risk factors that predict the likelihood of complications of appendicitis is a crucial step in managing appendicular abscess. Appendicitis is most common risk factor of developing abscess and it is more common among people in the age group of 10 to 30 years old. Appendicitis is one of the medical emergency that need proper attention than any other abdominal causes if symptoms are not conclusive or neglected abscess can develop and can lead to death.
Screening
According to the Guidelines by the Surgical Infection Society and the Infectious Diseases Society of America, there is insufficient evidence to recommend routine screening for appendicular abscess.
Natural history, Complications and Prognosis
Without treatment, the patient will likely develop symptoms of diffuse abdominal pain, which is different from typical appendicitis pain, starting centrally (in the periumbilical region) before localizing to the right iliac fossa in the right lower quadrant of the abdomen. During the final stage of the untreated disease process, the appendix will rupture, and this may eventually lead to death if peritonitis develops.[2]. Complications that can develop as a result of the untreated appendicular abscess include:septicemia, rupture, peritonitis, hemorrhage and death. Prognosis of the abscess is good with antibiotics and percutaneous drain and resolves without the need for appendectomy, but it is recommended to follow and appendicular abscess by interval appendectomy after 8-12 weeks to prevent recurrence.
Diagnosis
History and Symtoms
The key to an efficient and accurate diagnosis is a detailed and thorough history. The onset, location, radiation, and duration of pain, aggravating or relieving factors, severity of pain (constant or intermittent), characteristics of the pain should be obtained in helping out the cause of abdominal pain. Symptoms of appendicular abscess are mostly atypical compared to appendicitis and include include high grade fever, constant pain in the right iliac fossa, prolonged diarrhea associated with nausea and vomiting and increased micturition and tenesmus.
Physical Examination
Physical examinations mostly focus on abdominal findings. The patient may appear toxic with diffuse abdominal pain and high grade fever and tachycardia. Even minimal pressure on the abdomen can elicit a marked response from the patient due to pain. Typical signs of appendicitis may not be elicited.
Laboratory findings
Common electrolyte and biomarker indicators of appendicitis include leukocytosis and a shift to the left in the segmented neutrophils.
Abdominal X-ray
Plain abdominal radiography is not the most useful tool in making a diagnosis of appendicular abscess.
Ultrasound
In general, whenever available, CT scans are preferred over ultrasounds for diagnosing appendicular abscess. Ultrasound imaging presents the least amount of radiation and is therefore the investigation of choice for young patients. Findings include fluid collection (hypoechoic) in the appendicular region which may be well circumscribed with dilated appendicular wall
Abdominal CT
CT scans are the diagnostic test of choice for detecting appendicular abscess. They can provide critical information regarding the size of the abscess. CT scans are preferred over ultrasounds for the detection of abscess but is contraindicated in children due to risk of exposure. Findings include Appendiceal wall thickening (wall ≥ 3mm), appendiceal wall hyperenhancement, mural stratification of the appendiceal wall
MRI
Magnetic resonance imaging (MRI) has become the common technique for diagnosing abscess in children and pregnant patients. On an MRI, a periappendiceal stranding appears as an increased fluid signal on the T2 weighted sequence
Treatment
Medical therapy
No universal standard treatment exists for appendicitis complicated by abscess. The mainstay of treatment includes abscess drainage along with empiric antibiotics. Antibiotics should be started immediately once the diagnosis of abscess is made. The duration of treatment with intravenous antibiotics ranges from 5 to 10 days, until fever resolves. Monotherapy with a beta-lactam/beta-lactamase inhibitor is the preferred choice of drugs. Combination third generation cephalosporins plus metronidazole is also employed. Percutaneous drainage can be performed under ultrasound or CT guidance, using either the Seldinger or trocar technique. When an abscess is deep in the pelvis, depending on the specific location of the fluid collection, access may be obtained via transgluteal, transvaginal, or transrectal approaches.
Surgical Therapy
Following drain and antibiotics an interval appendectomy is recommended for patients after six to eight weeks, it is done to prevent recurrence of appendicitis and to exclude neoplasms as a cause (such as carcinoid, adenocarcinoma, mucinous cystadenoma, and cystadenocarcinomas). The surgical approach can be either laparoscopic or open (laparotomy)
Prevention
There are no primary preventive measures available for appendicular abscess.
References
- ↑ Williams, Norman (2013). Bailey & Love's short practice of surgery. Boca Raton, FLa: CRC Press. ISBN 978-1444121285.
- ↑ Appendicitis. Wikipedia (2016). http://schools-wikipedia.org/wp/a/Appendicitis.htm Accessed on February 4, 2016