Appendicular abscess

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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.

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.
• In 1886, Fitz diagnosed and described appendicitis for the first time.
• In 1894, McBurney performed an appendectomy for the first time.

Classification

• No known classification of appendicular abscess exists.

Pathophysiology

• 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.
• Once these blood vessels are obstructed, appendiceal tissue starts to die and leak out its cellular components.
• This leads to an increase in endoluminal and intramural pressure, which can result in an occlusion of the venules in the appendiceal wall resulting in thrombosis and occlusion and stasis of blood and lymphatic flow.
• The stasis favors the bacterial growth leading to infection of the appendix .
• Inflammatory mediators along with various bacterial toxins and proteolytic enzymes from the neutrophils are released, resulting in the formation of abscess in appendix.

Transmission

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

Duration

• 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.

Gross Pathology

• The serosal surface of the appendix looks pale with rough edges and yellowish exudate along with hyperemia

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.

Causes

Natural gut flora which includes gram negative and anaerobic bacteria play a major role in the development of appendicular abscess.

Aerobic bacteria	Anaerobes bacteria
Enterococcus Escherichia coli Klebsiella pneumoniae Pseudomonas aeruginosa Staphylococcus aureus Proteus	Bacteroides fragilis Clostridium perfringens

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

Diseases	Clinical features					Diagnosis		Associated findings
	Symptoms				Signs	Laboratory fingdings	Radiological findings
	Fever	Abdominal pain	Nausea vomiting	Diarrhea
Psoas abscess	✔	Dull RLQ pain radiating to hip and thigh	✔	✘	Positive Psoas sign	↑ WBC ↑ ESR ↑ BUN	CT demostrates enhancing collection in the psoas muscle.	Associated with IV drug abuse and HIV Staphylococcus Aureus is the most common pathogen involved
Cellulitis of right thigh	✔	✘	✘	✘	Involved site is red, hot, swollen, and tender	↑ WBC ↑ ESR ↑ BUN	Ultrasonographic-guided aspiration of pus is both gold standard for diagnostic and therapeutic In early cellulitis: Diffuse increase in the thickening and echogenicity of the subcutaneous tissue Late cellulitis: Accumulation of fluid in the subcutaneous tissue	Severe infection is indicated by Lymphangitic spread Circumferential cellulitis Pain out of proportionon
Crohn's disease	✔	RLQ continuous localized pain	✔	Bloody	Fullness or a discrete mass may be appreciated, typically in the right lower quadrant of the abdomen Extra intestinal manifestations are present	[ASCA]) are found in Crohn disease	Transmural ulcerations are seen on colonoscopy	Endoscopic visualization and biopsy are essential in the diagnosis
Gastroenteritis	✔	Diffuse crampy intermittent abdominal pain	✔	Bloody/ watery	Rebound tenderness, rash	Antilisteriolysin O (ALLO) is positive for bacterial gastroenteritis Culture media used to isolate bacteria. In most cases of viral gastroenteritis,lab tests are not indicated.	No specific test
Primary peritonitis	✔	Abrupt diffuse abdominal pain	✔	Bloody/watery	Abdominal distension, rebound tenderness	Peritoneal fluid shows >500/microliter count and >25% polymorphonuclear leukocytosis.	X-ray abdomen identifies free air under the diaphragm CT demonstrates abscess or fluid in abdomen,	History of advanced cirrhosis or nephrosis Peritoneal fluid analysis confirms the diagnosis
Pyelonephritis	✔	Flank pain radiating to inguinal region	✔	✘	CVA tenderness	Urine microscopy and culture confirm presence of bacteria.	CT demonstrates round swollen kidneys with hypo-dense appearance Abscesses may or may not be seen	CVA tenderness H/o UTI
Ovarian torsion	✘	Sudden sharp pain	✔	✘	Unilateral, tender adnexal mass		Ultrasonography shows ovarian cyst and decreased blood flow	Ultrasound is gold standard in diagnosing
Testicular torsion	✘	Sudden sharp pain	✔	✘	Swollen, tender, high-riding testis with abnormal transverse lie Loss of the cremasteric reflex	Normal Blood test Normal Urine analysis	Absent or decreased blood flow in the affected testicle Hypervascularity with a low resistance flow pattern (after partial torsion-detorsion)	Testicular torsion is a clinical diagnosis.  Testicular Workup for Ischemia and Suspected Torsion (TWIST) is employed for determination of risk for torsion
Pelvic inflammatory disease	✔	Bilateral lower quadrant pain	✔	✘	Purulent discharge from cervical os. Cervical motion tenderness	Abundant white blood cells (WBCs) on saline microscopy of vaginal secretions Laboratory evidence of cervical infection with N gonorrhoeae or C trachomatis(via culture or DNA probe)	Transvaginal ultrasonographic scanning or magnetic resonance imaging (MRI) shows thickened, fluid-filled tubes with or without free pelvic fluid or tubo-ovarian abscess (TOA).	Laparoscopy helps in confirmation of the diagnosis
Ruptured ectopic pregnancy	✔	Diffuse abdominal pain	✔	✘	Unilateral or bilateral abdominal tenderness Abdominal rigidity, guarding On pelvic examination, the uterus may be slightly enlarged and soft, and cervical motion tenderness	HCG hormone level is high in serum and in urine	Ultrasound reveals presence of mass in fallopian tubes.	Triad of amenorrhea, abdominal pain and vaginal bleeding SIgns of hypotension Transvaginal ultrasound with BHCG levels are the gold standard for diagnosis

Epidemiology and Demographics

Prevalance

The lifetime risk of appendicitis is 8.6 % for males and 6.7 % for female of which only 2-7% develops abscess.

Incidence

Annual incidence of appendicitis in united states is 9.38 per 100,000 persons.

Age

It occurs most often between the ages of 10 and 30.

Gender

Males are more commonly affected with appendicular abscess than females. The male to female ratio is approximately 1.4 to 1.

Race

• Appendicitis usually affects individuals of the white race.Non white individuals are less likely to develop Appendicitis.

• Appendicitis rates were 1.5 times higher for whites than for nonwhites, highest (15.4 per 10,000 population per year) in the west north central region, and 11.3% higher in the summer than in the winter months.

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

Natural history

• The symptoms of appendicular abscess typically develop when the inflamed appendix gets complicated due to decreased blood flow.
• 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.
• They will also experience loss of appetite, diarrhea, High gradefever, nauseua, and vomiting.
• During the final stage of the untreated disease process, the appendix will rupture, and this may eventually lead to death if peritonitis develops.

Complications

Complications that can develop as a result of the untreated appendicular abscess include:

• Septicemia
• Rupture
• Peritonitis
• Hemorrhage
• Death

Prognosis

• Most patients with appendicular abscess recover quickly with drain and IV antibiotics, but complications can occur if treatment is delayed or if peritonitis occurs.

• It usually takes between 10 and 28 days to recover completely.
• Typical Abscess responds quickly to antibiotics and percutaneous drain and resolves spontaneously.
• If abscess resolves, interval appendectomy should be performed 8-12 weeks after to prevent recurrent episodes.
• Atypical presentation(when the patient presents with fever, abdominal pain not typical to appendicitis, diarrhea) is more difficult to diagnose and is more apt to be complicated.
• In such condition prompt diagnosis, and treatment with emergent appendectomy yield the best results with full recovery usually occurring in two to four weeks.
• Mortality and severe complications are unusual but do occur in some cases, especially if peritonitis develops and is left untreated.

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.

Symptoms

Symptoms of an appendicular abscess include that of appendicitis with late presentation and can overlap. Typical symptoms of appendicitis may or may not be present but patient presents with

• Fever >38.5 C
• Generalized abdominal pain
• Vomiting
• Prolonged diarrhea
• Increased micturition due to irritation of the bladder wall by the inflamed appendix.
• Tenesmus can be also be noticed.

Physical Examination

Physical examinations mostly focus on abdominal findings. The patient may appear in pain with a fever and mild tachycardia. Even minimal pressure on the abdomen can elicit a marked response from the patient due to pain.

Vitals

• Fever
• Tachycardia
• Hypotension if the abscess is ruptured and associated with hemorrhage.
• Tachypnea.

Skin

• Diaphoresis
• Pallor
• Cold extremities.

Abdomen

• The abdominal wall is very sensitive to mild palpation.
• Rebound tenderness (it cannot be elicited in most of the patients due to abscess formation)
• Abdominal guarding
• Rovsing's sign Deep palpation of the left iliac fossa may cause pain in the right iliac fossa.
• Psoas sign Occasionally, an inflamed appendix lies on the psoas muscle and the patient will lie with the right hip flexed for pain relief.
• Obturator sign If an inflamed appendix is in contact with the obturator internus, spasm of the muscle can be demonstrated by flexing and internally rotating the hip.This maneuver will cause pain in the hypogastrium.
• A digital rectal examination elicits tenderness in the rectovesical pouch in special cases of appendicitis.
• In case of a retrocaecal appendix even deep pressure in the right lower quadrant may fail to elicit tenderness.

Laboratory findings

Lab findings that are not specific but include leukocytosis with a shift to the left along with elevation of ESR and CRP

Electrocardiogram

There are no clear indications to obtain an ECG in patients with appendicular abscess.

X-Ray

• Plain abdominal radiography is not the most useful tool in making a diagnosis of appendicular abscess.

Ultrasound

• Ultrasound is the first choice of investigation 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 visualized within the mass.

US showing an area of high echogenicity measuring 5.2 X 6.7 cm in relation to the right hepatic lobe with echogenic rim.
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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 air fluid levels.

CT of abdomen showing an abscess in the retrocaecal location with an adjacent appendicolith with ascending colon being displaced anteriorly.

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 along with IV fluids followed by surgery which includes interval laparoscopic appendectomy. It has proved to have a high success rates up to 97% and low incidences of complications.

Percutaneous drainage

• Percutaneous drainage can be performed under USG or CT guidance, using either the Seldinger or trocar technique.
• USG 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.
• 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.
• Depending on the location of abscess,patient is placed in prone or supine position on the CT table
• Localization scan using CT allows in 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 is 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.

Medical Therapy

Antibiotics should be started immediately once the diagnosis of abscess is made. Preoperative antibiotics have been associated with lower rates of wound and intra-abdominal infections.

Empiric therapy

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

• Preferred regimen (1):Ampicillin-sulbactam 3 g IV q6h
• Preferred regimen (2):Ticarcillin-clavulanate 3 g IV q4h
• Preferred regimen (3):Piperacillin-tazobactam 3 g or 4.5 g IV q6h

Combination third generation cephalosporins PLUS metronidazole

• Preferred regimen (1): Ceftriaxone 1 g IV q24h AND Metronidazole 500 mg IV q8h OR 1500 mg q24h.
• Preferred regimen (2): Cefazolin 1–2 g IV q8h AND Metronidazole 500 mg IV q8–12 h OR 1500 mg q24h
• Preferred regimen (3): Cefuroxime 1.5 g IV q8h AND Metronidazole 500 mg IV q8–12 h OR 1500 mg q24h
• Preferred regimen (4): Cefotaxime 1–2 g IV q6–8 h AND Metronidazole 500 mg IV q8–12 h OR 1500 mg q24h

Alternative empiric regimens

Combination fluoroquinolone PLUS metronidazole:

• Preferred regimen (1): Ciprofloxacin 400 mg IV q12h AND Metronidazole 500 mg IV q8–12 h OR 1500 mg q24h
• Preferred regimen (2): Levofloxacin 750 mg IV q24h AND Metronidazole 500 mg IV q8–12 h OR 1500 mg q24h

Monotherapy with a carbapenem

• Preferred regimen (1): Imipenem-cilastatin 500 mg IV q6h OR 1 g q8h
• Preferred regimen (2): Meropenem 1 g IV q8h
• Preferred regimen (3): Doripenem 500 mg IV q8h
• Preferred regimen (4): Ertapenem 1 g IV q24h

Duration

The duration of treatment with intravenous antibiotics ranges from 5 to 10 days, until fever resolves, white blood cell count normalizes, and bowel function returns.

Surgery

Emergency appendectomy

Indications:

• When patients present with life-threatening signs of peritonitis
• large appendiceal abscess,
• In patients with an extraluminal appendicolith.

Interval Appendectomy

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

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

Complications of interval appendectomy

• Wound Infection (sepsis)
• Pelvic abscess
• Aspiration pneumonia

Late complication

• Abdominal adhesions
• Fecal fistula

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Prevention

Primary Prevention

There are no primary preventive measures available for appendicular abscess. Reducing the risk of appendicitis however, can help in the first place .Following a diet that includes fresh vegetables and fruit may lower the risk.

Secondary prevention

Peritonitis develops from the rupturing of the appendix and can lead to death is left untreated. Acute appendicitis that is evaluated and treated early with an appendectomy generally leads to no further complications and a patient's full recovery.