Retroperitoneal abscess
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Ahmed Younes M.B.B.CH [2]
Overview
Retroperitoneal abscess is an unusual type of abscess in surgical practice. It is often underdiagnosed due to the insidious onset of symptoms and its location in the retroperitoneal space making it hard to be accessible for the regular abdominal examination. It is most often due to Genitourinary infection (like Pyelonephritis) or GI cause (like Inflammatory Bowel Syndrome). CT & MRI are the cornerstones for diagnosis. Treatment is usually focused on surgical drainage either through open or percutaneous approaches under the umbrella of IV antibiotics.
Classification[1]
Simplified Classification was suggested according to the location of the abscess in the retroperitoneal space into :
- Perinephric.
- Upper retroperitoneal.
- Pelvic.
- Combined retroperitoneal and pelvic.
- Lٍٍocalized Musculoskeletal.
Pathophysiology
Pathophysiology
Retroperitoneal abscess is usually secondary to spread from other primary site either hematogenous or by contiguous spread. The bacteria (6) causing the abscess depends on the primary site. When the bacteria invades the retroperitoneal tissue, toxins released from it destroy the Tissue & trigger an inflammatory response. As a result of the inflammatory response, White Blood Cells get recruited. They phagocytose the invading bacteria but at the same time they break down the infected tissue. The healthy tissues around enclose the area with a membrane surrounding the abscess. After pus evacuation, the membrane grows in to fill the cavity.
Microscopic Findings
Abscess consists of a mixture of inflammatory cells together with debris tissue. From the surrounding wall grows some capillaries to form granulation tissue. If body defenses are successful in eliminating the infection, the granulation tissue continues to grow and the abscess continues to shrink in size until it is only a scar. If the offending pathogen is not cleared, the process goes on and may even spread.
Causes[2]
The most common isolated bacteria are :
- E. Coli or Proteus spp (if primary is from the urinary tract)
- Multibacterial & [[anaerobes] (if GIT is the primary source)
- Staphylococcus aureus (if from distant septic focus)
- Tuberculosis Bacteria (if secondary to Pott’s disease)
Differentiating Retroperitoneal abscess from other Diseases
- Retroperitoneal Hematoma : primary bleeding source, more rapid onset.
- Retroperitoneal Tumors : CT & MRI should give you an idea about the nature of retroperitoneal tissue.
- Chronic Pancreatitis : Risk factors for pancreatitis (Alcoholism, gall stones) and the presence of steatorrhea, DM II .. etc.
Epidemiology, Demographics[3]
- Retroperitoneal abscess is far less common than Intraperitoneal abscesses.
Gender
Age
increased incidence between third and sixth decades (5).
Demographics
- Most common cause in developing countries is spread from distant septic focus.
- Most common cause in developed countries are Renal and GI causes [2].
Risk Factors
Any septic focus can - theoretically - lead to retroperitoneal abscess. These are the primary foci in order of frequency to cause retroperitoneal abscess.
- Renal infections : spread from the Urinary Tract is the most common cause.
- GI diseases : Spread from the GI is the second common cause like perforated appendix, perforated colon cancer, Diverticulitis and Crohn’s disease.
- Bone infection : tuberculous spine or osteomyelitis
- Hematogenous spread : from distant septic foci.
- Iatrogenic : following abdominal or pelvic surgery.
Any condition compromising the immune system is a risk factor for developing retroperitoneal abscess. The following were the risk factors in order of frequency in observed patients [1]
- Diabetes Mellitus
- Cirrhosis
- Malignancy
- Remote infection
- Glucocorticoids intake
- Chronic renal failure
Screening
No introduced program for screening of retroperitoneal abscess.
Natural History, Complications and Prognosis:
Natural History
If untreated, Retroperitoneal abscess may cause septicemia with very high incidence of morbidity & mortality.
Complications[1] :
Most complications result from septicemia come late in the disease
- Pneumonia and respiratory failure type 1 is the most common complication with very high mortality.
- Recurrent Abscess after drainage.
- Renal Failure
- DVT
- Small Bowel Obstruction
- Arterial Thrombosis
- UTI
- Brain Abscess
- Empyema
- Osteomyelitis
Prognosis [1]
Poor prognostic factors include :
- Septicemia (Positive Blood Culture) : Not present in every patient. When present poor prognostic sign
- Number of days for fever to fade away after drainage : Persistence of fever more than 4 days carries a mortality more than 70%.
Diagnosis
History
Detailed history should be obtained from the patient presenting with insidious onset of abdominal pain. Common should be investigated (Kidney and GI diseases) especially in the presence of any of the risk factors (DM, corticosteroid intake).
Symptoms [1]:
Presentation is usually insidious and nonspecific besides that it’s unusual condition, this all delays the diagnosis.
- Fever is the most common complaint .. Usually more than 101 F.
- Constitutional symptoms : chills, malaise, anorexia and weight loss.
- Abdominal pain : Non localized due to the unusual site of the abscess.
- GI complaints which varied from case to case
- If abscess involves psoas major muscle, pain is usually referred to the hip, groin and knee.
Physical Exam[1]
General Appearance
The patient is usually fatigued & looking ill due to the preexisting risk factor. In advanced cases with septicemia, the patient may be drowsy with disturbed conscious level.
Vital signs
- Fever
- Tachycardia
- Tachypnea
- Hypotension (if shocked)
Abdominal Examination
- Abdominal tenderness is often present (localized)
- Positive psoas sign if the psoas muscle is involved.
- The classic signs of peritonitis is absent (making the diagnosis more difficult).
Lab Findings
- Classic lab findings of inflammation .. leukocytosis, high ESR, high CRP ,, etc.Leukocytosis is usually not very high (between 10.000 and 20.000 in most cases)
- Blood culture is not always positive (but carries a grave prognosis if +ve).Organism depends on the source of abscess as mentioned above in pathophysiology.
Radiological Findings
- CT & MRI are the 2 most important radiological diagnostic tools.
- CT shows fluid collection in the retroperitoneal space and may also show gas bubbles. It is also helpful in determining the primary source of the abscess.
Treatment[1]
Medical Treatment
- Intravenous antibiotics should be given in the light of results of the cultures.
- Initial empiric antibiotic therapy should consist of Aminoglycosides and Metronidazole (or clindamycin) .. If the source is pancreatitis, then imipenem should be added as it has bactericidal effect on the necrotic tissue[4].
- Drainage of the abscess is a must and uing medical treatment alone carries a mortality rate approaching 100 % in some studies.
Surgical Treatment [1]:
- Operative treatment is usually preferred unless in special cases when it is contraindicated.
- Retroperitoneal or pelvic approaches are much preferred than transperitoneal approach due to better outcomes and decreased probability of intraperitoneal spread.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Grollier G, Burucoa C, Bonnin M, de Rautlin de La Roy Y (1992). "Identification and susceptibility testing for obligate anaerobic bacteria using a semi-automated API ATB plus system". Ann Biol Clin (Paris). 50 (6–7): 393–7. PMID 1492717.
- ↑ 2.0 2.1 Winter BM, Gajda M, Grimm MO (2016). "[Diagnosis and treatment of retroperitoneal abscesses]". Urologe A. 55 (6): 741–7. doi:10.1007/s00120-016-0118-1. PMID 27220893.
- ↑ Vitale L, Kiss A, Drago GW (1994). "[Retroperitoneal abscesses: clinical and therapeutical aspects]". Minerva Chir. 49 (3): 163–5. PMID 8028724.
- ↑ Yamamichi F, Shigemura K, Kitagawa K, Arakawa S, Tokimatsu I, Fujisawa M (2017). "Should We Change the Initial Treatment of Renal or Retroperitoneal Abscess in High Risk Patients?". Urol Int. 98 (2): 222–227. doi:10.1159/000454887. PMID 28152534.