Section I. Theoretical basis Retroperitoneal tumors occurring in the left upper abdomen have special characteristics in surgical diagnosis and treatment due to their anatomical location, and this chapter is a brief introduction with our hospital experience. Our hospital summarized the experience of diagnosis and treatment of 71 cases of retroperitoneal tumors in the left upper abdomen, age 0.5 to 76 years, average 39.1 years. The number of male and female cases was similar. The most common pathological types of retroperitoneal tumors in this area were liposarcoma, nerve sheath tumor, teratoma, smooth muscle tumor, ganglioneurofibroma, and neuroblastoma. Other types are paraganglioma, malignant lymphoma, malignant mesenchymal tumor, metastatic tumor, primitive neuroectodermal tumor, malignant fibrous histiocytoma, malignant hemangiopericytoma, synovial sarcoma, malignant Brenner’s tumor, and choriocapillary epithelial carcinoma. Clinically, left epigastric retroperitoneal tumor is mostly manifested as epigastric or left epigastric pain and discomfort, accompanied by left low back soreness and distension, abdominal distension, etc. The epigastric distension and pain can sometimes be relieved by right side lying, and the low back pain can radiate to left lower abdomen, and in a few cases, it can be accompanied by left shoulder discomfort, left upper limb numbness, or left thigh pain and numbness. Left upper abdominal distension may be obvious after meals, and sometimes it shows pressure feeling. Patients with left epigastric retroperitoneal tumor may also have fever, poor appetite, vomiting, weakness, emaciation, chest tightness and shortness of breath when lying on the back, and dyspnea. These manifestations are mostly caused by the tumor pressing on the surrounding organs, involving the nerves or growing into the left thoracic cavity. The tumor can reach up to the top of left diaphragm, which can lead to reactive pleural effusion. The tumor can infiltrate with the left diaphragm, and can also metastasize to the lower posterior mediastinum through the diaphragmatic fissure. The left lobe of the liver may be invaded, and the left kidney and adrenal gland are commonly extruded, encircled and invaded by the tumor in this area. If the tumor is of neurogenic origin, the vertebral body and intervertebral foramen may also be involved. The stomach, spleen and tail of the pancreas are mostly raised by the left epigastric retroperitoneal tumor, which may lead to difficulty in eating and splenomegaly. If the tumor in this area is accompanied by lymph node metastasis, the fused enlarged lymph nodes may be distributed around the abdominal cavernous artery and hepatic artery, all of which make the surgical treatment more difficult. About 20% of the retroperitoneal tumors in the left upper abdomen can be portal and mass, and sometimes patients seek medical attention because of the incidental discovery of left upper abdominal mass. Preoperative ultrasound, CT, MR and other imaging examinations can detect the lesion and provide information on tumor site, size, morphology, parenchymal characteristics, changes in surrounding organs, etc. The accuracy of localization and diagnosis is 100%. However, qualitative diagnosis is difficult, 11% in our hospital statistics, and mostly liposarcoma, teratoma and other tumors with strong characteristics. The choice of surgical incision for left upper abdominal retroperitoneal tumor is quite important for successful completion of resection. Most of them choose combined thoracoabdominal incision, such as reverse “L”, “L”, arc, “├óΓé¼”, etc. Longitudinal incision can be made through the middle of abdomen or through the rectus abdominis muscle, and thoracic incision can be made through the 6th intercostal space, 7th intercostal space, etc. The thoracic incision can be made through the 6th intercostal space, 7th intercostal space, etc. There are also options for a large roof-shaped incision under both rib margins, an oblique incision from the 11 thoracic eminence to the anterior superior iliac spine, and a large “ten” incision in the left upper abdomen. During the operation, the left lumbar position or the right lateral position can be adopted as needed. The key to complete resection of left epigastric retroperitoneal tumor is to be familiar with anatomy and good at joint organ resection. Due to tumor invasion, combined resection of the left kidney is common, especially for liposarcoma of perirenal fat capsule origin. The prerequisite for combined resection of the left kidney is that the preoperative examination confirms good function of the right kidney. If the tumor involves part of the renal cortex, partial nephrectomy can be performed. If the tumor involves only the renal vessels, only a section of the renal vessels can be removed. The artery can be bridged, and the vein can be anastomosed with the ovarian vessels or relying only on the side branch to return, or only repairing the ruptured vessels. If the diaphragm is invaded, partial resection is possible, or the diaphragm can be cut to remove the chest tumor, and closed drainage of the chest cavity must be placed after surgery. Other combined resection organs include part or all of the gastric wall, tail of the pancreatic body, spleen, left lobe of the liver, splenic flexure of the colon, left psoas major muscle, part of the vertebral body, left adrenal gland, etc. The rate of complete resection of left upper abdominal retroperitoneal tumor by the naked eye was 96% in 71 cases counted in our hospital, and the maximum bleeding was 6,000 ml, the maximum blood transfusion was 5,400 ml, and the longest operation time was 12 h. All 56 cases who obtained follow-up after the operation survived for more than 1 year, and all 15 cases of recurrence underwent reoperation, with a 3-year survival rate of 83%.