Retroperitoneal Abscess

Reviewed 06/2017

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Subject: Retroperitoneal Abscess

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  • 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

      • Second and third 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



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

  • Slight male predominance (1)


Rare condition in which perirenal abscesses are more common (2


  • 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.

    • M. tuberculosis

    • Fungus

      • Candida sp.

Pediatric Considerations

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



  • 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)


  • Treatment of the primary disease

  • Prevention of infection, such as perioperative antibiotic prophylaxis

  • Prompt treatment of symptomatic infection


  • 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



  • 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)

    • Most common form of presentation is triad of fever, lumbar pain, and lumbar mass.

  • 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


  • 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)


  • Appendicitis

  • Diverticulitis

  • Epidural abscess

  • Intra-abdominal infection

  • Malignancy

  • Necrotizing fasciitis

  • Osteomyelitis

  • Pancreatitis

  • Pelvic inflammatory disease

  • Perforated bowel

  • Psoas abscess

  • Pyelonephritis

  • Retroperitoneal hematoma

  • TB



  • 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.

    • Ultrasound (US) can show fluid collections but not as precise as CT (6).

      • Abscesses appear as echoic masses with irregular walls. Can have poorly defined shadows and high refractive content is indicative of gas.

    • 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.

    • Radionuclide imaging has high radiation exposure, low diagnostic specificity, and technical difficulty and may reveal false positive with pyelonephritis, acute tubular necrosis, and neoplasms (1,6).


  • Percutaneous drainage via CT, MRI, or US of the abscess cavity

    • Contraindications: presence of coagulation disorders and calcified masses (can indicate benign cyst, renal artery aneurysm, renal neoplasm, hydatid cyst) (6)

  • Specimens should be sent for aerobic, anaerobic, and fungal cultures.

  • Require close observation for signs of sepsis.

  • Serial CT scanning to confirm drainage



Drainage of the abscess cavity plus empiric (IV) antibiotics 


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 (7)[B].

  • Routine use of aminoglycosides is not recommended unless evidence of resistant organisms due to potential toxicity (7)[B].

  • Ampicillin/sulbactam is not recommended secondary to high resistance rates in community-acquired E. coli (7).

  • Empiric coverage for methicillin-resistant Staphylococcus aureus (MRSA) is only recommended for health care–associated infections and in those known to be colonized (7)[B].

  • Empiric coverage for yeast is not recommended (7)[B].

  • Quinolone-resistant E. coli are common in some areas (7)[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.


  • 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.


  • 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 to 72 hours of appropriate antibiotic coverage

    • If the primary cause must be addressed surgically, such as urinary tract stone, perforated bowel, malignancy

    • Some secondary causes—that is, intestinal fistula, necrotic tumors, and osteomyelitis—tend to do better with surgery than percutaneous drainage.



Close observation for signs of sepsis 


  • 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 with absence of fever and improvement of leukocyte count.


  • 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/μL

    • High BUN

    • Positive blood cultures

    • Diagnostic delay

  • Marked reduction in mortality with early diagnosis, immediate drainage, and antibiotic coverage


  • 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


Tunuguntla A, Raza R, Hudgins L. Diagnostic and therapeutic difficulties in retroperitoneal abscess. South Med J.  2004;97(11):1107–1109.  [View Abstract]
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.  [View Abstract]
Brook I. Intra-abdominal, retroperitoneal, and visceral abscesses in children. Eur J Pediatr Surg.  2004;14(4):265–273.  [View Abstract]
Crepps JT, Welch JP, Orlando RIII. Management and outcome of retroperitoneal abscesses. Ann Surg.  1987;205(3):276–281.  [View Abstract]
Jakab F, Egri G, Faller J. Clinical aspects and management of a retroperitoneal abscess. Orv Hetil.  1992;133(37):2335–2339.  [View Abstract]
Capitán Manjón C, Tejido Sánchez A, Piedra Lara JD et al. Retroperitoneal abscesses—analysis of a series of 66 cases. Scand J Urol Nephrol.  2003;37(2):139–144.  [View Abstract]
Armstrong C. Updated guideline on diagnosis and treatment of intra-abdominal infections. Am Fam Phys.  2010;82(6):697–709.



  • K68.19 Other retroperitoneal abscess

  • K68.11 Postprocedural retroperitoneal abscess

  • K68.12 Psoas muscle abscess

  • N15.1 Renal and perinephric abscess


  • 567.38 Other retroperitoneal abscess

  • 998.59 Other postoperative infection

  • 567.31 Psoas muscle abscess

  • 590.2 Renal and perinephric abscess


  • 32362007 Retroperitoneal abscess (disorder)

  • 2471009 Postoperative intra-abdominal abscess (disorder)

  • 266463007 Iliopsoas abscess (disorder)

  • 80640009 Perirenal abscess (disorder)


  • 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