Retroperitoneal Abscess

Description

• A collection of purulent fluid located in the space between the peritoneum and transversalis fascia lining the posterior abdominal cavity
• Classified as primary if spread hematogenously or secondary if spread through infection of an adjacent organ
• The retroperitoneum can be further subdivided into three compartments:
  • Anterior pararenal space
    • 2nd and 3rd segments of the duodenum, pancreas, bile duct, portal and splenic veins, appendix, ascending/descending colon, transverse mesocolon
  • Perirenal space
    • Kidneys, renal vessels, adrenal glands
  • Posterior pararenal space
    • Contains no major organs and is filled with fat, blood vessels, and lymphatics
    • Bounded by renal fascia and the muscles of the posterior abdominal wall

Epidemiology

Incidence

• Most common in the 3rd to 6th decades (1)
• Slight male predominance (1)

Prevalence
Rare condition in which perirenal abscesses are more common (2)

Etiology and Pathophysiology

• Bowel perforation secondary to neoplastic disease, diverticulitis, pancreatitis, pancreatic cancer, retroperitoneal appendicitis, biliary tract disease, peptic ulcer disease, inflammatory bowel disease, peritonitis, colonoscopy following GI surgery, bowel infarction (1)
• Genitourinary (GU) extravasation secondary to obstruction, nephrolithiasis, pyelonephritis, urinary tract infection, urologic surgery, pelvic surgery, ovarian cancer
• Osteomyelitis of vertebral bodies or 12th rib, epidural abscess (1)
• Less common causes are trauma, hematogenous or lymphatic seeding from a distant infection, or postoperative complication (1).
• Infection seeds a confined space within the retroperitoneum.
• Can be a monomorphic or polymorphic predominance of organisms
• Typically consists of normal flora from adjacent organs (i.e., GI, GU, and female reproductive tract)
• Hypoxia and lack of appropriate blood supply limit effective immune response.
• Osmotic forces produce growth of abscess cavity.
• Mycobacterium tuberculosis was previously a common pathogen but is less common today.
• Most common pathogens
  • Staphylococcus aureus
  • Streptococcus sp.
  • Enterobacteriaceae
    • Citrobacter sp.
    • Escherichia coli
    • Klebsiella
    • Proteus sp.
    • Pseudomonas aeruginosa
    • Serratia
  • Anaerobes
    • Actinomyces
    • Peptostreptococcus
  • Bacteroides fragilis
    • Prevotella sp.
    • Clostridium sp.
  • Enterococcus sp.
  • Tuberculosis sp.
  • Fungus
    • Candida sp.

Pediatric Considerations
Consider necrotizing enterocolitis as an etiology in newborns.

Risk Factors

• Appendicitis
• Bowel perforation
• Chronic urinary retention
• Diabetes
• Diverticulitis
• Epidural infection
• GU tract obstruction
• Immunosuppression
• Inflammatory bowel disease
• Malignancy of the GU, GI, or female reproductive tract
• Osteomyelitis of the spine or ribs
• Pancreatitis
• Pelvic inflammatory disease
• Pregnancy
• Pyelonephritis
• Recent surgery of GU or GI
• Renal biopsy
• Tuberculosis (TB)

General Prevention

• Treatment of the primary disease
• Prevention of infection, such as perioperative antibiotic prophylaxis
• Prompt treatment of symptomatic infection

Commonly Associated Conditions

• Bowel perforation
• Diabetes mellitus
• Diverticulitis
• Immunosuppression (HIV, glucocorticoid use)
• Inflammatory bowel disease
• Malignancy (GI or GU)
• Nephrolithiasis
• Osteomyelitis of the spine or ribs
• Pelvic inflammatory disease
• Renal insufficiency
• Retroperitoneal hematoma
• Surgery (GI or GU)
• Urinary tract infections