Retroperitoneal infection and abscess are relatively rare, with common pathogens including Escherichia coli, Staphylococcus aureus, Proteus vulgaris, Aerobacter, and Streptococcus. Occasionally, anaerobic bacteria, Mycobacterium tuberculosis, Brucella, Actinomyces, and amoebae may also be causative agents. The retroperitoneal space exhibits minimal reactivity to bacterial infections, making physical examination findings subtle and diagnosis challenging.

bubble_chart Etiology

The main disease causes of peritoneal membrane infection and abscess are shown in the table.

Table: Disease causes of peritoneal membrane infection and abscess

The retroperitoneal space can be simply divided into five regions based on anatomical location: ① perirenal space; ② upper retroperitoneal space; ③ pelvic space; ④ lower retroperitoneal space combined with pelvic space; ⑤ localized musculoskeletal space, to facilitate the analysis of factors affecting outcomes.

bubble_chart Pathological Changes

Infection or abscess is usually confined to a primary site but may spread to the contralateral side or from one space to another. In rare cases, it can also spread distally along fascial planes or penetrate membranes, such as beneath the deep pelvic peritoneum; the root of the mesentery; subcutaneous tissues of the thigh, hip, anterior abdominal wall, back, and flank; subphrenic, mediastinal, and thoracic cavities; or even lead to diffuse retroperitoneal infection, causing cellulitis and necrosis.

The main symptoms include fever, chills, night sweats, and pain in both sides of the abdomen or the lower back, which are prominent manifestations of this disease. Other symptoms include nausea, vomiting, anorexia, weight loss, and general exhaustion. Some patients exhibit few symptoms other than general exhaustion. Common signs include fever (38–39°C), tachycardia, and localized mild tenderness in the abdomen (28%). In some cases (38%), a tender mass can be palpated (sometimes requiring rectal or pelvic examination). Generally, there is no abdominal rigidity. Occasionally, tenderness in the costovertebral angle, flank swelling, scrotal swelling, and scoliosis may occur. With perinephric abscess, the costovertebral angle may bulge and be tender, accompanied by psoas muscle spasm. If the iliopsoas muscle is involved, scoliosis, flexion, internal rotation, and pain upon extension of the ipsilateral hip joint may occur. Leukocytosis is present, and severe cases may show toxic granules and anemia. Rare manifestations include sinus tract formation, subcutaneous abscess, abscess rupture into the abdominal cavity, small intestine, colon, vagina, pleura, mediastinum, bronchus, pericardium, or blood vessels, with corresponding symptoms.

bubble_chart Auxiliary Examination

1. B-ultrasound examination

can detect the echo of a fluid dark area in a certain region behind the peritoneum and determine its size and location. It is easy to operate and can be repeated, with high diagnostic value, making it the preferred examination method.

2. X-ray

By comparing abdominal plain films and lateral films, the fat lines of both sides of the peritoneum, the shadows of the psoas muscles, and the spine can be observed. Soft tissue masses, clear renal outlines, and changes in the shape of the psoas muscles can be detected.

3. CT and magnetic resonance imaging (MRI)

have a high diagnostic rate. CT can provide the exact location of the abscess and show its relationship with surrounding organs.

4. Puncture and aspiration of pus

Fine-needle aspiration of pus can be performed under the guidance of CT or B-ultrasound. The aspirate can be examined pathologically, bacteriologically, and for generation and transformation. Contrast agents can also be injected to measure the size of the abscess, and catheter drainage can be performed simultaneously, which further improves diagnostic and therapeutic outcomes.

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This disease is often misdiagnosed, and many cases are only confirmed postmortem. Diagnosis should be based on symptoms such as abdominal pain, back pain accompanied by chills, fever, and local signs like scoliosis. Laboratory tests may reveal an elevated total white blood cell count with increased neutrophils. Urinalysis is mostly normal, but pyuria and proteinuria may occur with perinephric abscesses. Blood cultures sometimes identify pathogenic bacteria. Diagnostic aids include B-mode ultrasound, CT scans, and abdominal X-rays.

bubble_chart Treatment Measures

1. Non-surgical therapy

1. The rational use of antibiotics has significantly improved the prognosis of retroperitoneal abscesses following infection. Therefore, attention should be paid to the appropriate application of effective antibiotics in sufficient quantities.

2. Symptomatic treatment.

3. Supportive therapy: Depending on the presence of anemia and the patient's overall condition, adequate amounts of nutrients should be supplemented, along with blood transfusions and albumin supplementation.

4. Correct typical edema, electrolyte imbalances, and acid-base disturbances.

5. Puncture and aspiration of pus or catheter drainage under B-ultrasound guidance.

2. Surgical therapy

For patients with severe conditions, large abscesses, or poor response to non-surgical treatment, timely surgical incision and drainage should be performed.

The main approaches for retroperitoneal drainage are: ① Retroperitoneal drainage via the lumbar region; ② Presacral drainage; ③ Combined transthoracic and transdiaphragmatic incision and drainage; ④ Transabdominal drainage.

The first three drainage methods are more commonly used, while the latter is less effective and more prone to complications.