Retroperitoneal abscess

　　1. Etiology

　　Generally secondary to the inflammation or perforation of retroperitoneal organs, particularly the gastrointestinal part within the anterior retroperitoneal space, some are secondary to hemogenous infection, and a few cases have unknown etiology.

　　1. Biliary tract perforation, the lower two-thirds of the common bile duct is located in the retroperitoneal space. Stone impaction and compression of the bile duct wall can lead to necrosis, or gallbladder removal, exploration of the bile duct for stone extraction can cause injury to the bile duct, leading to bile leakage and the formation of a biliary retroperitoneal abscess.

　　2. Duodenal injury or posterior wall ulcer perforation, as the majority of the duodenum is located posterior to the peritoneum, delayed diagnosis and treatment after injury or ulcer perforation can lead to the accumulation of large amounts of digestive fluids in the retroperitoneal space, secondary infection, and the formation of a retroperitoneal abscess. Misdiagnosis of duodenal injury or improper surgical management of duodenal rupture can lead to duodenal fistula and severe retroperitoneal space infection. In addition, minimally invasive trauma to the posterior side of the duodenum may occur during endoscopic examination or catheter insertion (including biliary drainage), especially during endoscopy when torsion and compression may occur, leading to varying degrees of duodenal trauma. Duodenal fluid may leak into the retroperitoneal space, causing retroperitoneal space infection.

　　3. Colitis, perforation of the ascending and descending colon located posterior to the peritoneum can cause retroperitoneal infection, often leading to the formation of a retroperitoneal abscess.

　　4. Appendicitis, especially when the appendix is located posterior to the mesentery of the ileocecal junction or posterior to the cecum, may present atypical symptoms, leading to delayed diagnosis and treatment, which can result in pericecal abscess formation, followed by extension to form a retroperitoneal abscess.

　　5、肾周炎，肾周脓肿扩散或肾外伤尿外渗等引起腹膜后感染，继而形成腹膜后脓肿。

　　6、急性坏死性胰腺炎胰腺及胰腺周围组织坏死继发感染后，极易向胰周侵犯，可到达小网膜囊，肠系膜根部，双侧肾周间隙，结肠后区，骼窝，乃至整个腹膜后间隙，是腹膜后脓肿最常见原因之一，雷道雄等报告在1993～2000年收治经B超或CT检查证实的腹膜后脓肿约23例，其中急性坏死性胰腺炎18例，约占78.3％。

　　致病菌多来自大肠和泌尿系，主要为大肠杆菌，变形杆菌，其次为葡萄球菌，链球菌，厌氧菌等感染。

　　二、发病机制

　　由于腹膜后间隙的解剖特点，腹膜后感染和化脓易于扩散，而且抵抗细菌的能力较腹膜腔为差，是腹膜后脓肿发生的生理因素，腹膜后间隙感染的途径归纳起来主要有3条。

　　1、直接侵入如肾痈，肾表面脓肿等直接侵入腹膜后间隙的周围组织导致的脓肿。

　　2、周围组织或器官感染的蔓延，如直肠感染引致的骨盆直肠间隙脓肿，可以沿腹膜后间隙向上蔓延。

　　3、经血行和淋巴途径扩散到腹膜后间隙的感染如败血症，但很少见。

　　由于腹膜后间隙部位深在，腔隙大，组织疏松，一旦发生感染病灶易于向潜在间隙蔓延扩散。

　　1、泌尿系统化脓性感染脓肿侵及肾脏，输尿管或膀胱时可出现尿急，尿频脓尿等泌尿系感染症状。

　　2、腹腔脏器和组织的弥漫性感染脓肿可破溃于胸腔，腹腔，纵隔，前腹壁，腰大肌，臀部或股部等，引起脓胸，腹膜炎等化脓性病变。

　　8. In cases of acute necrotizing pancreatitis complicated with retroperitoneal abscess due to extensive invasion by the pancreas posteriorly, the transverse colon, the root of the mesentery, and the perirenal space, etc., the retroperitoneal diffuse lesions contain a large amount of necrotic tissue, inflammatory exudates, and bacterial toxins. In addition to aggravating the condition of acute pancreatitis, it often leads to gastrointestinal bleeding and intestinal fistula.

　　7. In cases of diffuse retroperitoneal lesions in ARDS and acute renal failure, the large absorption of necrotic tissue, inflammatory exudates, and bacterial toxins can trigger systemic coagulation, hemorrhage, renal failure, and even multiple organ dysfunction and other serious complications.

　　How to prevent retroperitoneal abscesses

　　1. What foods are good for retroperitoneal abscess patients

　　1. Supply easily digestible protein foods such as milk, eggs, fish, soy products, and so on.

　　2. Eat more foods rich in vitamin A, B-group vitamins, and vitamin C, such as oranges, apples, tomatoes, and other fruits and vegetables.

　　3. Provide sufficient nutrients for the patient, such as lean meat, chicken, pigeon soup, and so on.

　　2. What foods should not be eaten for retroperitoneal abscesses

　　Foods that are not conducive to wound healing, such as hog meat, fermented bean curd, scallion, chili, chive, and so on, should be avoided as they are prone to cause infection and hinder wound healing.

　　1. Surgical treatment:

　　1. Treat the primary disease.

　　2. Effective and sufficient abscess drainage is essential due to the formation of an abscess after retroperitoneal infection. The abscess cavity often contains a large amount of necrotic tissue, and the retroperitoneal space is a huge potential cavity with loose tissue and no obvious partitions, making infection easy to spread. If effective drainage is not performed or only antibiotics are used, the mortality rate can sometimes reach 100%. Therefore, once the diagnosis is confirmed, early and unobstructed drainage at the lower part of the abscess should be carried out. The drainage method can be puncture and catheter drainage under the guidance of B-ultrasound or CT, or surgical incision and exploration drainage, which should be determined according to the patient's overall condition, the location, size, and scope of the abscess.

　　3. Surgical incision and drainage

　　(1) Abdominal drainage: The traditional abdominal approach for drainage is suitable for initial surgical cases, such as retroperitoneal abscesses caused by appendicitis, duodenal or colonic injury perforation, which can be performed through abdominal drainage of gastrointestinal perforation or stoma surgery, and simultaneous abscess drainage, usually with multiple tube drainage.

　　(2) Retroperitoneal drainage via the posterior lumbar approach: This approach has the advantages of avoiding contamination of the abdominal cavity, faster recovery of gastrointestinal function after surgery, direct access to the retroperitoneal space, convenient operation, and conforms to the principle of lower bypass, with definite therapeutic effects. Therefore, some foreign scholars believe that retroperitoneal drainage should be avoided when the abscess has not ruptured into the abdominal cavity, and retroperitoneal drainage via the posterior lumbar approach is the best choice. During the operation, it is necessary to unblock the spaces of all abscesses and also perform effective drainage for abscesses spreading to the inguinal region and other parts.

　　4. Ultrasound or CT-guided puncture and catheter drainage via the posterior lumbar approach has many advantages compared to surgical drainage, such as less trauma, less blood loss, only requiring local anesthesia, and can be performed at the bedside under ultrasound guidance. It is especially suitable for patients with poor general condition who cannot tolerate surgical drainage. The efficacy of treatment is related to the characteristics of the abscess and its lesions; solitary, unilocular, and thin pus have good efficacy. The drainage of pus with semi-solid necrotic tissue inside may not be complete and requires repeated flushing. Some people propose that the method is not suitable for those with thick pus and semi-solid necrotic tissue inside. For patients with multiple abscesses or poor response to repeated puncture and catheter drainage, timely conversion to multiple tube drainage via posterior lumbar incision should be considered.

　　Secondly, drug treatment:

　　1. Select effective antibiotics based on the bacterial culture and drug sensitivity test of the pus.

　　2. Nutritional support therapy may cause intestinal paralysis due to retroperitoneal infection, resulting in intestinal dysfunction and affecting eating. Moreover, retroperitoneal abscesses are often delayed in diagnosis, and prolonged infection and consumption can lead to anemia, hypoproteinemia, and decreased immunity in patients. Therefore, nutritional support therapy should be strengthened to improve the nutritional status and immunity of patients, promote tissue healing, control and localize infection. Parenteral nutrition support should be used before the recovery of intestinal dysfunction, and after the control of infection and the recovery of intestinal dysfunction, gradually transition to enteral nutrition and resume normal diet.