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Retroperitoneal Abscess

- Percutaneous drainage should not be delayed especially in high-risk surgical patients. - Surgical drainage is performed when - Percutaneous drainage is not possible. - Failure of percutaneous drainage attempt - Multiple or multiloculated abscesses - Purulent material is too thick to drain. - Persistence of fever after 48 " 72 hours of appropriate antibiotic coverage - If the primary cause must be addressed surgically, such as urinary tract stone, perforated bowel, malignancy

- Treatment with antibiotics alone is associated with a 100% mortality rate (1). - Treatment with surgical drainage alone is associated with a 31% mortality rate (1). - Treatment with surgical drainage plus broad-spectrum antibiotic coverage is associated with a 16% mortality rate (1). - Mortality rate is higher with - Sepsis - Higher temperature (>104 °F) - Presence of underlying disease process, such as diabetic ketoacidosis - White blood cell (WBC) count >25,000 cells/ ΌL - High BUN - Positive blood cultures - Diagnostic delay

para>Consider necrotizing enterocolitis as an etiology in newborns (3).

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
  • Diverticulitis
  • Immunosuppression
  • Inflammatory bowel disease
  • Malignancy (GI or GU)
  • Osteomyelitis of the spine or ribs
  • Pelvic inflammatory disease
  • Renal insufficiency
  • Retroperitoneal hematoma
  • Surgery (GI or GU)
  • Urinary tract infections

Diagnosis

History

  • Insidious onset of nonspecific symptoms of infection including fever, chills, weight loss, nausea/vomiting, flank pain, low back pain, abdominal pain or groin pain, lethargy, and altered bowel habits (4)
  • History of GU, GI, female reproductive tract surgery or instrumentation, recent GI or GU infection, malignancy, osteomyelitis of a vertebral body, epidural abscess, inflammatory bowel disease, TB
  • Associated conditions: diabetes, renal insufficiency, immunosuppression

Physical Exam

  • Chronically ill-appearing patient with intermittent spiking fever, tachycardia
  • Tenderness to palpation of the lower abdomen, flank, groin, proximal thigh, costolumbar sensitivity ± rigidity and fullness or can be nonspecific, nonlocalized abdominal pain
  • Mass is potentially palpable in the abdomen, flank, thigh, groin, or scrotum.
  • Pleuritic pain may occur due to diaphragmatic irritation.
  • If there is pressure on adjacent nerves, referred pain may be felt in the groin, thighs, or knees (4).Check for psoas sign: pain elicited by hyperextension or flexion of the hip (5)

Differential Diagnosis

  • Appendicitis
  • Diverticulitis
  • Epidural abscess
  • Intra-abdominal infection
  • Malignancy
  • Necrotizing fasciitis
  • Osteomyelitis
  • Pancreatitis
  • Pelvic inflammatory disease
  • Perforated bowel
  • Psoas abscess
  • Pyelonephritis
  • Retroperitoneal hematoma
  • TB

Diagnostic Tests & Interpretation

Initial Tests (lab, imaging)

  • Laboratory findings are often nonspecific and variable.BloodCBC usually reveals leukocytosis with a shift to the left and possibly anemia (1).ESR is elevated.BUN and creatinine may present azotemia.Gram stain and blood cultureUrineUrinalysis may reveal pyuria, proteinuria, and hematuria.Urine cultureAbscess culturesAerobic, anaerobic, and fungal cultures
  • ImagingCT scan of the abdomen and pelvis is the diagnostic modality of choice (2).Gas within a low density mass is pathognomonic for an abscess.MRI show abscesses are more visible on T1-weighted images (2).Kidney, ureter, bladder (KUB) may reveal an absent psoas shadow, scoliosis, loss of renal outline, or soft tissue mass (1).Chest x-ray (CXR) may reveal an elevation of the ipsilateral diaphragm, pleural effusion, basilar atelectasis, or lower lobe infiltrate.Ultrasound (US) can show fluid collections but can have false positives (2).Radionuclide imaging has high radiation exposure and may reveal false positive with pyelonephritis, acute tubular necrosis, and neoplasms (1).

Diagnostic Procedures/Other

  • Percutaneous drainage via CT, MRI, or US of the abscess cavity
  • Specimens should be sent for aerobic, anaerobic, and fungal cultures.

Follow-up tests & special considerations

  • Require close observation for signs of sepsis.
  • Serial CT scanning to confirm drainage

Treatment

General Measures

Drainage of the abscess cavity plus empiric (IV) antibiotics

Medication

Broad-spectrum antibiotic coverage against facultative and aerobic gram-negative organisms, obligate anaerobic organisms, and enteric gram-positive streptococci

  • For suspected GI source, single-agent therapy (ertapenem, ticarcillin/clavulanate) or combination therapy (quinolone or cephalosporin + metronidazole) can be used empirically (6)[B].
  • Routine use of aminoglycosides is not recommended unless evidence of resistant organisms due to potential toxicity (6)[B].
  • Ampicillin/sulbactam is not recommended secondary to high resistance rates in community-acquired E. coli (6).
  • Empiric coverage for methicillin-resistant Staphylococcus aureus (MRSA) is only recommended for health care " associated infections and in those known to be colonized (6)[B].
  • Empiric coverage for yeast is not recommended (6)[B].
  • Quinolone-resistant E. coli are common in some areas (6)[B].
  • For suspected GU source (i.e., renal or perinephric abscesses), the organism in the urine culture typically parallels the bacteriology of the abscess.
  • If cultures are positive, narrow antibiotic coverage based on the results.
  • Duration of treatment is based on clinical improvement.

Issues for Referral

  • Diagnostic delay and postponed treatment increase mortality rate.
  • In patients requiring surgical drainage and are high-surgical risk, CT-guided percutaneous drainage as a temporary measure is suitable.

Surgery/Other Procedures

  • Percutaneous drainage should not be delayed especially in high-risk surgical patients.
  • Surgical drainage is performed whenPercutaneous drainage is not possible.Failure of percutaneous drainage attemptMultiple or multiloculated abscessesPurulent material is too thick to drain.Persistence of fever after 48 " 72 hours of appropriate antibiotic coverageIf the primary cause must be addressed surgically, such as urinary tract stone, perforated bowel, malignancy

Ongoing Care

Follow-up Recommendations

Close observation for signs of sepsis

Patient Monitoring

  • Reimage depending on clinical progress.
  • Close monitoring of drains and irrigated appropriately
  • Remove drain whenDrainage is <10 mL/day or becomes serous.Resolution of abscess on imagingPatient is clinically improved.

Prognosis

  • Treatment with antibiotics alone is associated with a 100% mortality rate (1).
  • Treatment with surgical drainage alone is associated with a 31% mortality rate (1).
  • Treatment with surgical drainage plus broad-spectrum antibiotic coverage is associated with a 16% mortality rate (1).
  • Mortality rate is higher withSepsisHigher temperature (>104 °F)Presence of underlying disease process, such as diabetic ketoacidosisWhite blood cell (WBC) count >25,000 cells/ ΌLHigh BUNPositive blood culturesDiagnostic delay
  • Marked reduction in mortality with early diagnosis, immediate drainage, and antibiotic coverage

Complications

  • Abscess may cross the midline into another space.
  • Atelectasis
  • Bleeding
  • Deep vein thrombosis (DVT)
  • Empyema
  • Fistula formation to stomach, small bowel, duodenum, lung
  • Flank abscess
  • Organ failure
  • Osteomyelitis
  • Perforation through diaphragm
  • Pneumonia
  • Rupture into peritoneum
  • Sepsis

References

1.Tunuguntla A, Raza R, Hudgins L. Diagnostic and therapeutic difficulties in retroperitoneal abscess. South Med J. 2004;97(11):1107 " 1109.

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2.Hammond NA, Nikolaidis P, Miller FH. Left lower-quadrant pain: guidelines from the American College of Radiology appropriateness criteria. Am Fam Physician. 2010;82(7):766 " 770.

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3.Brook I. Intra-abdominal, retroperitoneal, and visceral abscesses in children. Eur J Pediatr Surg. 2004;14(4):265 " 273.

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4.Crepps JT, Welch JP, Orlando R III. Management and outcome of retroperitoneal abscesses. Ann Surg. 1987;205(3): 276 " 281.

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5.Jakab F, Egri G, Faller J. Clinical aspects and management of a retroperitoneal abscess [in Hungarian]. Orv Hetil. 1992;133(37):2335 " 2339.

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6.Armstrong C. Updated guideline on diagnosis and treatment of intra-abdominal infections. Am Fam Physician. 2010;82(6):697 " 709.

Additional Reading

  • Tunuguntla A, Raza R, Hudgins L. Diagnostic and therapeutic difficulties in retroperitoneal abscess. South Med J. 2004;97(11):1107 " 1109. []

Codes

ICD09

  • 567.38 Other retroperitoneal abscess
  • 998.59 Other postoperative infection
  • 567.31 Psoas muscle abscess
  • 590.2 Renal and perinephric abscess

ICD10

  • K68.19 Other retroperitoneal abscess
  • K68.11 Postprocedural retroperitoneal abscess
  • K68.12 Psoas muscle abscess
  • N15.1 Renal and perinephric abscess

SNOMED

  • 32362007 Retroperitoneal abscess (disorder)
  • 2471009 Postoperative intra-abdominal abscess (disorder)
  • 266463007 Iliopsoas abscess (disorder)
  • 80640009 Perirenal abscess (disorder)

Clinical Pearls

  • Rare condition in which perirenal abscesses are more common
  • CT scan of the abdomen and pelvis is the diagnostic modality of choice.
  • Insidious onset of nonspecific symptoms
  • Close observation for signs of sepsis
  • Marked reduction in mortality with early diagnosis, immediate drainage, and antibiotic coverage