The abdomen and pelvis have been divided anatomically and clinically into peritoneal cavity and subperitoneal space by peritoneum. The subserosal areolar tissue which lines the inner surfaces of the peritoneum and the musculature of the abdomen and pelvis form the subperitoneal space. The surfaces of organs are covered by peritoneum, therefore, organs are located within subperitoneal space. Those organs that are deep to the posterior peritoneum are called extraperitoneal. Peritoneal reflections comprise the abdominal major ligaments and mesenteries. They contain the branches of the vascular, lymphatic, and nervous systems within subperitoneal space to supply the corresponding organs. Either the relationships of typical location and organ or the landmarks provided by major constituent vessels give a help to recognize ligaments and mesenteries on computed tomographic scans. The abdomen and pelvis may be visualized as unifying, anatomically continuous potential space by ligaments and mesenteries, which provide continuity of anatomic planes and permit the spread of diseases between intraperitoneal compartments, between extraperitoneal spaces, and between intraperitoneal and extraperitoneal localized sites. Understanding the anatomy of subperitoneal space would increase the capabilities to detect pathways of spread and localizing features of infections, malignancies, and traumas.

The abdomen and pelvis have been divided anatomically and clinically into peritoneal cavity and subperitoneal space by peritoneum. The subserosal areolar tissue which lines the inner surfaces of the peritoneum and the musculature of the abdomen and pelvis form the subperitoneal space. The surfaces of organs are covered by peritoneum, therefore, organs are located within subperitoneal space. Those organs that are deep to the posterior peritoneum are called extraperitoneal. Peritoneal reflections comprise the abdominal major ligaments and mesenteries. They contain the branches of the vascular, lymphatic, and nervous systems within subperitoneal space to supply the corresponding organs. Either the relationships of typical location and organ or the landmarks provided by major constituent vessels give a help to recognize ligaments and mesenteries on computed tomographic scans. The abdomen and pelvis may be visualized as unifying, anatomically continuous potential space by ligaments and mesenteries, which provide continuity of anatomic planes and permit the spread of diseases between intraperitoneal compartments, between extraperitoneal spaces, and between intraperitoneal and extraperitoneal localized sites. Understanding the anatomy of subperitoneal space would increase the capabilities to detect pathways of spread and localizing features of infections, malignancies, and traumas.

Objective:To explore CT imaging features related to disease-free survival (DFS) for gastric cancer (GC) patients with no clinical lymph node metastasis (cN0).Methods:From January 2005 to December 2018, 298 patients with GC were collected retrospectively in Peking University People′s Hospital. All the patients performed CT scanning before operation, and cT1-4N0M0 was defined by CT images. The clinical tumor stage (cT), extramural vessel invasion (EMVI), tumor morphological type, location and size were defined and recorded based on preoperative contrast-enhanced CT images. According to the pathological results, the patients were divided into pT1-2, pT3-4, pN0, and pN1-3 subgroups, with 148, 150, 135, and 163 cases, respectively. Progressive events and corresponding time were recorded during follow-up. DFS was defined as the time from radical operation to progressive events; if no progressive events occurred, DFS was defined as the time from radical operation to the last follow-up. The Kaplan-Meier curve and log-rank test were used to analyze the differences in cumulative DFS among patients with different CT imaging features, and Cox survival analysis was used to explore the independent CT imaging risk factors affecting DFS of cN0 patients. The log-rank test was used to test the effect of independent risk factors on cumulative DFS in different subgroups.Results:The follow-up time of enrolled patients was 36.0 (14.9, 59.3) months. The 3-year cumulative DFS rates of cT3-4 and cT1-2 GC patients were 61.2% and 85.6%, respectively, and the difference of DFS was statistically significant (χ 2=22.72, P<0.001). The 3-year cumulative DFS rate of EMVI-positive patients was 46.3%, which was lower than that of EMVI-negative patients (77.1%), and the difference was statistically significant (χ 2=21.34, P<0.001). There was no significant difference in 3-year cumulative DFS between different tumor locations and morphological types (χ 2=1.75, 1.73, P=0.189, 0.196). The difference in 3-year cumulative DFS between the tumor maximal diameter ≥3.4 cm and <3.4 cm groups was statistically significant (χ 2=17.58, P<0.001). On Cox survival analysis, cT (HR=5.203, P=0.001) and EMVI (HR=1.971, P=0.025) were independent risk factors for 3-year DFS in patients with cN0 GC. The results of subgroup analysis showed that the effect of EMVI on the 3-year DFS in pN0, pN1-3, pT1-2 and pT3-4 subgroups was statistically significant ( P<0.05). The effect of cT on the 3-year DFS was statistically significant in pN0, pN1-3, and pT1-2 subgroups ( P<0.05), but not in pT3-4 group (χ 2=2.58, P=0.108). Conclusion:cT and EMVI defined on preoperative CT examination are independently prognostic factors of 3-year DFS for patients with cN0 GC.

OBJECTIVETo investigate the value of preoperative abdominal contrast-enhanced multiple-row detector computed tomography (ceMDCT) in predicting the postoperative 1-year disease-free survival (DFS) for gastric cancer.

METHODSBetween January 2009 and December 2015, 237 gastric cancer patients at Peking University People's Hospital with complete preoperative clinical, image and follow-up data were enrolled in this retrospective study.

INCLUSION CRITERIA(1) primary gastric cancer was confirmed by pathology; (2) radical gastrectomy and D2 lymph node dissection were performed;(3) patients underwent preoperative ceMDCT. Patients with gastric stump cancer, concurrent metastasis, other malignancies, and undergoing neoadjuvant treatment were excluded. According to ceMDCT examination with or without ctEMVI (extramural venous invasion), patients were divided into ctEMVI-positive and ctEMVI-negative group. ctEMVI-positive was defined as that there was a continuous tubular and nodular soft tissue filling defect from the tumor to the adjacent blood vessel lumen in ceMDCT, suggesting the tumor directly invaded the blood vessels outside the muscularis propria of the gastrointestinal smooth muscle. Log-rank test was used to compare differences in 1-year DFS between ctEMVI-positive group and ctEMVI-negative group. According to the 8th edition of the American Joint Committee on Cancer (AJCC), the T staging in ceMDCT (ctT) and lymph node metastasis (lymph nodes with shorter diameter > 8 mm) were determined. The patients were subdivided into four subgroups, ctT4N(+), ctT4N(-), ctT1-3N(+), and ctT1-3N(-), to further compare the difference in postoperative 1-year DFS between ctEMVI-positive and -negative patients in each subgroups. Kaplan-Meier univariate analysis was performed on preoperative imaging data (ctT, ctN, ctEMVI, tumor location/growth pattern, and ctSize). Cox proportional hazard regression was used to find the independent risk factors of 1-year DFS rate. According to the number of independent risk factors, the patients were classified to different risk stratifications. The difference of 1-year DFS rate between different risk stratifications was compared.

RESULTSAccording to the results of ceMDCT, 72 patients (30.4%) were divided into the ctEMVI-positive group and 165 patients(69.6%) into the ctEMVI-negative group. The ctEMVI-positive group had significantly lower 1-year DFS rate (55.3%) than the ctEMVI-negative group (90.2%) (χ²=40.17, P<0.001). The 1-year DFS in the ctEMVI-positive ctT4N(+) subgroup was 34.5%, which was significantly lower than that of the ctMVI-negative ctT4N(+) subgroup (85.3%) (χ²=19.13, P<0.001). In the ctEMVI-positive ctT1-3N(-) subgroup, the 1-year DFS was 77.8%, which was also significantly lower than 98.5% of the ctEMVI-negative ctT1-3N(-) subgroup(χ²=15.09, P=0.003). In Cox proportional hazards regression analysis, ctT, ctN and ctEMVI were identified as independent prognostic factors of 1-year DFS with hazard ratio (HR) of 3.351(95%CI:1.249-8.986, P=0.017), 1.987(95%CI:1.085-3.637, P=0.027) and 3.398(95%CI:1.785-6.469, P<0.001), respectively. Risk classification was carried out according to the number of independent risk factors (ctT, ctN and ctEMVI). Grade 0 had no independent risk factors, grade 1 had one independent risk factor, grade 2 had two independent factors and grade 3 had 3 independent risk factors. The risk grading result showed that the numbers of patients form grade 0 to 3 were 71, 65, 68, 33, respectively, and the 1-year DFS rates were 98.5%, 82.1%, 79.0%, 34.5%, respectively(P<0.001). With the increase of the number of independent risk factors, 1-year DFS rate decreased gradually in patients with gastric cancer (P<0.001). Differences of 1-year DFS between grade 0 and grade 1(P=0.002), between grade 2 and grade 3(P<0.001) were both significant. Meanwhile the difference between grade 1 and grade 2 was not significant (P=0.578).

CONCLUSIONSctEMVI, ctT and ctN defined by preoperative ceMDCT are independent risk factors for the prognosis of gastric cancer. With the increase of risk factors, the 1-year DFS decreases gradually.

Disease-Free Survival ; Gastrectomy ; Humans ; Neoplasm Invasiveness ; Neoplasm Staging ; Prognosis ; Proportional Hazards Models ; Retrospective Studies ; Stomach Neoplasms ; diagnostic imaging ; surgery ; Survival Rate ; Tomography, X-Ray Computed