Intra-Abdominal Infections

Jayalakshmi Kuseladass

Ashley Tyler

Christopher Trabue

INTRODUCTION

Intra-abdominal infections represent a common and diverse group of infectious diseases. Appendicitis alone accounts for more than 300,000 hospital discharges annually. They are the second most common cause of sepsis and sepsis-related mortality behind pulmonary infections. Identifying and controlling the source of such infections remains the cornerstone of management.

EPIDEMIOLOGY AND CLASSIFICATION

I. UNCOMPLICATED—CONFINED TO HOLLOW VISCUS OF ORIGIN, 80% OF CASES

II. COMPLICATED—EXTENDS BEYOND HOLLOW VISCUS OF ORIGIN WITH ABSCESS FORMATION OR PERITONITIS

III. “HEALTH CARE ASSOCIATED” IS DEFINED AS EITHER

a. Hospital onset (culture results >48 hours after hospital admission)

b. Community onset in a patient with one of the following risk factors:

i. Invasive device at the time of admission

ii. History of methicillin-resistant Staphylococcus aureus (MRSA) infection or colonization

iii. History of surgery, hospitalization, dialysis, or residence in a long-term care facility in past 12 months

IV. ETIOLOGY

a. Appendicitis

b. Pyogenic liver abscess

c. Biliary infection

i. Cholecystitis

ii. Cholangitis

d. Necrotizing pancreatitis

e. Diverticulitis

f. Health care-associated intra-abdominal infection (postoperative)

MICROBIOLOGY

I. COMMUNITY-ACQUIRED PATHOGENS

a. Enterobacteriaceae

i. Microbiologic characteristics

1. Gram-negative bacilli

2. Facultative anaerobes (i.e., can survive in both aerobic and anaerobic conditions)

3. Lactose fermenting

ii. Examples: Escherichia coli, Proteus mirabilis, Enterobacter species, Klebsiella species

b. Obligate anaerobic bacteria

i. Microbiologic characteristics: diverse

ii. Examples: Bacteroides fragilis, Clostridium species, Fusobacterium species, Peptostreptococcus species

c. Gram-positive aerobic cocci

i. Microaerophilic streptococci, including Streptococcus anginosus group bacteria

ii. Enterococcus species

d. Candida albicans

II. HEALTH CARE-ASSOCIATED PATHOGENS—INCLUDES THE FOLLOWING, IN ADDITION TO COMMUNITY-ACQUIRED PATHOGENS:

a. Lactose-nonfermentative gram-negative bacilli

i. Pseudomonas aeruginosa

ii. Serratia marcescens

b. S. aureus, including MRSA

c. Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae

d. Vancomycin-resistant enterococcus (VRE)

e. Non-albicans Candida species

CLINICAL MANIFESTATIONS

I. ABDOMINAL PAIN

a. Localization to site of infection

b. A less sensitive predictor in elderly patients who may have nonspecific symptomatology (i.e., fever, malaise, weight loss)

II. SYSTEMIC INFLAMMATORY RESPONSE SYNDROME (SIRS) →TWO OR MORE OF THE FOLLOWING:

a. Temperature >38.5°C or <35.0°C

b. Heart rate of >90 beats/min

c. Respiratory rate of >20 breaths/min or PaCO₂ of <32 mm Hg

d. WBC count of >12,000 cells/mL, <4,000 cells/mL, or >10% immature (band) forms

e. Sepsis → SIRS plus infection

III. MISCELLANEOUS SYMPTOMS

a. Abdominal distension

b. Nausea/vomiting

c. Malaise/fatigue

d. Weight loss

e. Constipation or obstipation

IV. SPECIFIC SYNDROMES

a. Appendicitis

i. Dull or vague periumbilical pain, followed by focal RLQ pain, followed by anorexia, nausea, and vomiting

ii. Shorter duration of symptoms (<24 hours)

b. Diverticulitis

i. LLQ pain in >70% of patients

ii. Longer duration of symptoms (>24 hours)

c. Cholecystitis

i. Epigastric pain and RUQ pain radiating to the right shoulder (tip of the scapula)

ii. Biliary colic—transient RUQ pain following gallbladder contraction (i.e., after a fatty meal)

DIAGNOSTIC EVALUATION

I. HISTORY AND PHYSICAL EXAMINATION

a. A thorough history and physical examination is usually sufficient to identify and in some cases localize an intra-abdominal infection.

b. In addition to the clinical manifestations noted above, it is essential to discern any history of recent or remote surgery.

c. Physical examination

i. Vital signs and general appearance

ii. SIRS manifestations

iii. Must include rectal and genitourinary/pelvic examination

iv. Abdominal examination

1. General appearance

a. Abdominal distension

b. Skin findings

i. Wound appearance, if applicable

1. Erythema

2. Dehiscence

3. Drainage and characteristics of drainage

a. Purulence

b. Blood

c. Presence of a surgical drain (i.e., Jackson-Pratt, Hemovac)

Table 50-1 Physical Examination Findings in Patients with Peritonitis

Sign	Finding	Association
Rebound tenderness	Worsening abdominal pain with release of palpation	Peritonitis
Psoas sign	Abdominal pain with extension of the right hip	Appendicitis with retrocecal appendix, psoas abscess
Obturator sign	Abdominal pain with internal rotation of the right thigh in flexion	Appendicitis with pelvic appendix
Rovsing sign	RLQ pain with palpation of the LLQ	Appendicitis
Murphy sign	Cessation or halting of breath with RUQ palpation, due to pain	Cholecystitis