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.
- Blood
- CBC 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 culture
- Urine
- Urinalysis may reveal pyuria, proteinuria, and hematuria.
- Urine culture
- Abscess cultures
- Aerobic, anaerobic, and fungal cultures
- Imaging
- CT 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 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
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 when
- Drainage is <10 mL/day or becomes serous.
- Resolution of abscess on imaging
- Patient 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 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
- 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.
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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