Sandbox:Aditya

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Synonyms and keywords:

Overview

An appendicular abscess is unusual and rare entity and a life threatening complication of acute appendicitis. It is seen in 2-7% of population presenting with appendicitis.

Historical Perspective

• During the late 1600s, Lorenz Heister was the first surgeon to perform post-mortem sections of appendicitis and gave an unequivocal description of a perforated appendix and abscess.
• Fitz described and diagnosed appendicitis in 1886 for the first time.
• McBurney performed an appendectomy in 1894 for the first time..

Pathophysiology

• Obstruction of the tubular space inside the appendix is the main inciting event , this initial problem is compounded into a cascade of events that lead to the inflammation of the appendix, the obstruction of the blood vessels supplying it, and infection. Once these blood vessels are obstructed, appendiceal tissue starts to die and leak out its cellular components leading to inflammation of the appendix .
• This leads to an increase in endo-luminal and intramural pressure, which can result in an occlusion of the venules in the appendiceal wall resulting in filling with mucus and distends.
• This increase in pressure leads to thrombosis and occlusion of the small vessels, and stasis of lymphatic flow.
• This favours the bacterial growth if left medically unattended.

Transmission

• The abscesses usually contain a mixture of aerobic and anaerobic bacteria from the gastrointestinal tract.

Incubation

• The risk of perforation or abscess formation is negligible within the first 12 h of untreated symptoms, but then increases to 8.0% within the first 24 h.

Microscopic findings

• A focally necrotic appendiceal debris is seen in the mucosal wall. Intravascular fibrin is seen in medium-sized blood vessels.
• Clusters of neutrophils are seen on the serosal aspect.

Differentiating appendicular abscess from other abscess

Disease	Differentiating Signs and symptoms	Specific Lab tests
Acute mesenteric adenitis	Usually presents in children with a recent history of upper respiratory infection. Diffuse abdominal pain with tenderness not localized to the right lower quadrant. Guarding without rigidity Generalized lymphadenopathy is present.	Relative lymphocytosis in WBC differential counts is suggestive. Negative ultrasound or CT findings help exclude other diagnoses.
Intussusception
Crohn's disease
Viral gastroenteritis	Common in children; caused by viruses, bacteria, or toxin. Characterized by profuse watery diarrhea, nausea, and vomiting. Crampy abdominal pain often precedes the diarrhea, and no localizing signs are present. Typhoid fever, with intestinal perforation may cause localized abdominal pain and/or generalized and rebound tenderness, associated maculopapular rash, inappropriate bradycardia, and leukopenia will differentiate from appendicular abscess
Meckel diverticulitis
Peptic ulcer disease
Cholecystitis
Urinary tract infection
Right side ureteric stone
Pelvic inflammatory disease
Ectopic pregnancy
Ovarian torsion

Epidemiology and Demographics

The lifetime risk of appendicitis is 8.6 % for males and 6.7 % for females; however, the risk of undergoing appendectomy is much lower for males than for females (12 vs. 23 %) and it occurs most often between the ages of 10 and 30, with a male:female ratio of approximately 1.4:1.

Diagnosis

History

The key to an efficient and accurate diagnosis is a detailed and thorough history. The following information should be obtained:

• Onset, location, radiation, and duration of pain;
• Aggravating or relieving factors;
• Severity of pain (constant or intermittent);
• Characteristics of the pain;
• History of the pain;
• Association with nausea, vomiting, anorexia, or diarrhea;
• Time of last bowel movement; and
• Recent use of analgesics, narcotics, or antibiotics.

Laboratory findings

Leukocytosis with a shift to the left in the segmented neutrophils is the most common electrolyte and biomarker indicators of appendicular abscess. Other inflammatory markers like ESR and CRP are also elevated but are not specific to abscess.

X-Ray

• Plain abdominal radiography (PAR) is not the most useful tool in making a diagnosis of appendicular abscess.
• Plain abdominal films may be useful for the detection of ureteral calculi, small bowel obstruction, or perforated ulcer, but these conditions are rarely confused with appendicitis.
• An opaque fecalith can be identified in the right lower quadrant in less than 5% of persons being evaluated for appendicitis.

Ultrasound

• Ultrasound is the first investigation advised to evaluate a suspected appendicular pathology.
• Findings of an appendicular abscess include:
• Fluid collection (hypoechoic) in the appendicular region which may be well circumscribed and rounded or ill-defined and irregular in appearance

appendix may be visualised within the mass.

CT

• CT is significantly more sensitive than US for the diagnosis of appendicitis, but that US should be considered in children
• Fluid collection is seen in the appendicular region with or without air within. Many times an appendicolith may be visualized.

Treatment

No universal standard treatment exists for appendicitis complicated by abscess. The preferred treatment includes non-operative management such as drainage and broad spectrum IV antibiotics followed by interval appendectomy with high success rates up to 97% and low incidences of complications.

Medical Therapy

Antibiotic therapy must have broad spectrum activity towards both gram-negative and anaerobic pathogens.

Empiric therapy

Monotherapy with a beta-lactam/beta-lactamase inhibitor:

• Ampicillin-sulbactam :3 g IV every six hours
• Ticarcillin-clavulanate :3 g IV every four hours
• Piperacillin-tazobactam :3 g or 4.5 g IV every six hours

Combination third generation cephalosporins PLUS metronidazole

• Ceftriaxone  : 1 g IV every 24 hours (plus)
• metronidazole : 500 mg IV every eight hours.

Alternative empiric regimens

Combination fluoroquinolone◊ PLUS metronidazole:

• Ciprofloxacin (or) : 400 mg IV every 12 hours
• Levofloxacin (plus) : 500 or 750 mg IV once daily
• Metronidazole  : 500 mg IV every eight hours

Monotherapy with a carbapenem

• Imipenem-cilastatin : 500 mg IV every six hours
• Meropenem  : 1 g IV every eight hours
• Doripenem  : 500 mg IV every eight hours
• Ertapenem  : 1 g IV once daily

Surgery

Emergency appendectomy Indicated in the treatment of

• Perforated appendicitis, especially in patients with life-threatening signs of peritonitis,
• In patients with a large appendiceal abscess,
• In patients with an extraluminal appendicolith.

Percutaneous drainage

• Percutaneous drainage can be performed under US or CT guidance, using either the Seldinger or trocar technique.
• US is limited if the abscess is small, obscured by other structures, or if precise placement is required because of nearby vessels or organs. In these cases, CT is the optimal imaging modality.<ref>
• 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.
• If the fluid collection is sterile, a transgluteal approach is preferred because it allows for sterile technique.<REF>
• Most common locations include

Antero-superior to the bladder

• The patient is first placed supine on the CT table for a percutaneous anterior approach to the abscess.
• Localization scan using CT allows us for selecting a safe window of access into the collection.
• A coaxial micropuncture introducer set is advanced into the abscess under CT guidance.
• An Amplatz guidewire as advanced through the sheath and coiled within the abscess.
• After serial dilatation of the tract with a dilator, an pigtail drain is advanced over the guidewire and deployed.
• A final CT scan confirmed appropriate positioning of the catheter.

Abscess between the bladder and rectum

• The patient is placed in the prone position on the CT table for a posterior transgluteal approach.
• The micropuncture introducer set was advanced as medially as possible within the greater sciatic foramen to avoid vessels and the sciatic nerve.
• An pigtail drain was advanced into the abscess by employing the same technique for the anterior abscess.

Interval Appendectomy

Following drain and antibiotics an interval appendectomy is recommended for patients six to eight weeks, it is done to :

• Prevent recurrence of appendicitis.
• Exclude neoplasms (such as carcinoid, adenocarcinoma, mucinous cystadenoma, and cystadenocarcinomas)