Sandbox:pancreatic abscess

Overview

Pancreatic abscess is an unusual and rare, but life threatening complication of acute pancreatitis. It develop 5 weeks after the onset of pancreatitis and after onset of symptoms and subsidence of the acute phase of pancreatitis. Most of the pancreatic abscesses are developed from the progressive liquefaction of necrotic pancreatic and peri-pancreatic tissues, but some arise from infection of peripancreatic fluid or collections elsewhere in the peritoneal cavity. It is the most dangerous complication and the most common cause of death for acute pancreatitis.

Definition

Pancreatic abscess is defined as a localized collection of pus surrounded by a more or less distinct capsula in inflamed pancreas.

Causes

Common Causes

Common organisms causing pancreatic abscess are as follows:

Aerobic bacteria

• Enterococcus
• Escherichia coli
• Klebsiella pneumoniae
• Pseudomonas aeruginosa
• Staphylococcus aureus
• Proteus

Anaerobic bacteria

• Bacteriodes fragilis
• Clostridium perfringens

Differentiating Pancreatic Abscess from other Diseases

Pancreatic abscess should be diagnosed early and treat promptly not only to reduce morbidity and mortality, but also it is important to differentiate from other pancreatic disesases such recurrent pancreatitis, pancreatic psuedocysts etc. as the undrained abscess carreies high risk of mortality.

• Recurrent pancreatitis

Pancreatic necrosis CT findings: Well marginated zones of non-enhanced pancreatic parenchyma Pancreatic abscess CT findings: Absent or limited necrosis Infected pseudocyst

Characteristics	Pancreatic abscess	Infected pancreatic pseudocyst	Infected necrotic pancreas	Recurrent pancreatitis
Definition	Pancreatic abscess is defined as a localized collection of pus surrounded by a more or less distinct capsula in inflamed pancreas.	Pancreatic pseudocyst is defined as a collection of pancreatic juice enclosed by a non-epithelialized wall, that developed as a complication of acute pancreatitis, pancreatic trauma, or chronic pancreatitis.	Necrotic pancreas defined as a diffuse bacterial inflammation of necrotic pancreatic and peripancreatic tissue, but without any significant pus collections
Presentation	Present after onset of symptoms and after subsidence of the acute phase of pancreatitls	Present after 5 weeks of acute pancreatitis	clinically evident during the early phase of acute pancreatitis with signs of sepsis
Pathology	Pancreatic abscess contains pus with viable bacteria or fungi and little or no pancreatic necrosis. This pathology differentiates abscess from infected necrosis.	Presence of well-defined wall composed of granulation or fibrous tissue that distinguishes a pseudocyst from an acute fluid collection (cyst). The fluid is usually rich in pancreatic enzymes and is most often sterile.	Pathology shows areas of devitalized pancreatic parenchyma and peri-pancreatic fat necrosis.
Laboratory Findings	Hyperamylasemia Hypocalcemia <8 mg/dl Blood glucose >200 mg/dl LDH >350 units/liter		LDH >350 units/liter Hypocalcemia <8 mg/dl Blood glucose >200 mg/dl
Prognosis			Mortality is high compared to pancreatic abscess

Epidemiology and Demographics

Incidence

Incidence of pancreatic abscess is unknown, but McClave et al reported it as 2-5% among patients hospitalized for pancreatitis.

Case Fatality Rate

Mortality rate of pancreatic abscess is varies depending upon the severity of pancreatitis with range of 10-59%.

Risk Factors

• History of alcoholic pancreatitis who fails to respond to medical therapy

Natural History, Complications and Prognosis

Complications

Common complications	Respiratory complications	Gastric complications	Colon complications	Other complications
Intra abdominal sepsis Peritonitis Septicemia Pancreatic fistula	Pleural effusion Bronchopneumonia Atelectasis Pulmonary embolus	GI bleeding Gastric outlet obstruction	Colonic fistula	Pancreaticocolocutaneous fistula Wound infection Duodenal fistula Renal failure Hepatic failure

Prognosis

Prognosis of pancreatic abscess depends on the time of diagnosis and treatment. Outcome of pancreatic abscess is generally based on the severity of the infection. It is however a severe complication which may result in the death of the patient if the appropriate treatment is not administered. Patients are at risk of sepsis and multiple organ failure and in patients with delay in surgery to remove infected abscess, the mortality rate can get to 100%.\

Poor prognostic factors

• Delayed diagnosis

Association

• Biliary tract disease
• Alcohol addiction
• Carcinoma
• Peptic ulcer
• Trauma
• Polyarteritis nodosa

Diagnosis

As the clinical presentation of pancreatic abscess is variable or even obscure, it should be considered in any febrile patient even 2 weeks after an attack of acute pancreatitis, even in the absence of other symptoms.

History and Symptoms

Common Symptoms

Presenting symptoms of pancreatic abscess are vague and variable, but common symptoms include:

• Abdominal pain
• Back pain
• Nausea and vomiting
• Weight loss

Less common symptoms

• Melena
• Diarrhoea

Vital signs

• High grade fever (greater than 37.8°C)
• Upper abdominal pain
• Failure to thrive

Physical Examination Findings

• Abdominal tenderness
• Palpable abdominal mass
• Abdominal distention

Lab Findings

Blood Tests

• CBC with differential: Leukocytosis (range between 10,500 to 35,00O/mm³)
• Blood culture: Low sensitivity to diagnose causative organism in pancreatic abscess as shows positivity in few cases, but it helps to distinguish abscesses from sterile pseudocysts and provide guidance for selection of antibiotics.

Imaging

Imaging studies are crucial in the diagnosis and treatment of pancreatic abscess. Both ultrasonography and computed tomography (CT) can be helpful with the diagnosis and localization of pancreatic abscesses, which may extend from the pancreas anywhere (e.g. retroperitoneum, mesentery, mediastinum, and even the neck or genitalia).

X-ray

• Shows extraluminal (pancreas or lesser sac) gas bubbles suggesting abscess
• Disclosed pleural effusion
• Diaphragmatic elevation
• Basilar atelectasis

Ultrasound

• Shows fluid filled sac suggesting abscess

CT

CT had a sensitivity of 74%, compared with 35% for ultrasound in the diagnosis of pancreatic abscess.

Fine Needle Aspiration

Advantages

• Fine needle aspiration can distinguish sterile inflammation from infection and it is the procedure of choice in the verification of bacterial infection.
• High sensitivity of 90% to 100%
• Low complication rate
• It aid in the early diagnosis of infectious complications of pancreatic abscess and to avoid unnecessary laparotomy.

Treatment

Surgical Therapy

Surgical therapy is the traditional method of treatment of pancreatic abscesses, usually by inserting one or more non-traumatic drains through transperitoneal or throguh flank or retroperitoneum into the abscess cavity. Failure of the surgical drainage might be due to the reluctance to expose the cavity widely and to debride the necrotic components aggressively.

Endoscopic Drainage

Indications

• Patients who are unfit for surgical drainage.

Advantages

• Less invasive
• Potentially safe