Utility of computed tomography and 18 F-fluorodeoxyglucose with positron emission tomography/computed tomography for distinguishing appendiceal mucocele caused by mucinous adenocarcinoma from other pathologies.

AIM: Differentiating appendiceal mucocele with mucinous adenocarcinoma from other pathologies before surgery is difficult. The objective of this study was to evaluate the utility of CT and 18 F-fluorodeoxyglucose (FDG) with positron emission tomography (PET)/CT for differentiating mucinous adenocarcinoma of appendiceal mucocele from other pathologies. METHOD: The study included 25 patients who underwent surgery for clinically diagnosed appendiceal mucoceles detected on CT at the University of Tokyo Hospital. Among these patients, 19 underwent FDG-PET/CT preoperatively. We compared features of the CT imaging findings and maximum standard uptake values (SUVmax ) detected by FDG-PET/CT between mucocele with mucinous adenocarcinoma and other pathologies. RESULTS: A total of 13 men (52%) and 12 women (48%) were included in this study, with a median age of 65 years (range 34-83). There were six patients (24%) with pathologically confirmed mucinous adenocarcinoma, 15 patients (60%) with appendiceal mucinous neoplasm and four patients (16%) with simple mucocele caused by chronic inflammation. On the CT findings, wall irregularity was the only significant feature for the two groups in this study (83.3% vs 0.0%, P < 0.01). There was a significant difference in the SUVmax levels on PET/CT between the two groups (100.0% vs 20.0%, P < 0.01). CONCLUSION: Distinguishing between mucocele with mucinous adenocarcinoma and other pathologies using imaging modalities is challenging. Our results suggest that wall irregularity on CT and elevated SUVmax on PET/CT are useful factors that can be employed for such discrimination.

Effects of preceding endoscopic treatment on laparoscopic surgery for early rectal cancer.

AIM: Endoscopic treatment for rectal cancer, such as endoscopic mucosal resection and endoscopic submucosal dissection, causes inflammation, oedema and fibrosis in the surrounding tissue. However, little is known about the effect of these endoscopic therapies on salvage laparoscopic rectal surgery. The objective of this retrospective cohort study was to analyse the effect of preceding endoscopic treatment on the outcomes of laparoscopic surgery for rectal cancer. METHOD: We analysed 53 patients who underwent laparoscopic surgery for rectal cancer with clinical Tis or T1 at our department between May 2011 and June 2019. Data from 30 patients who underwent laparoscopic surgery after preceding endoscopic treatment (Group E + S) were compared with those of 23 patients who underwent laparoscopic surgery alone (Group S). RESULTS: There was no significant difference between the groups with respect to preoperative details. The mean operative time tended to be longer in Group E + S, and the volume of intra-operative blood loss was greater in Group E + S than in Group S (median 63 ml vs 10 ml, P = 0.049). There were no significant differences between the groups in other surgical parameters or oncological outcomes. CONCLUSION: Laparoscopic surgery after endoscopic treatment for rectal cancer may be difficult due to an increased risk of intra-operative bleeding. Long-term prognosis after surgery was not affected by preceding endoscopic treatment in rectal cancer.

Incidence of and risk factors for lymphocele formation after lateral pelvic lymph node dissection for rectal cancer: a retrospective study.

AIM: Pelvic lymphocele is a common complication that develops after pelvic lymph node dissection. The incidence of pelvic lymphocele formation has been reported to be 10.5-51% after gynaecological or urological procedures. However, no evidence has been reported thus far with regard to the development of pelvic lymphocele following lateral pelvic lymph node dissection (LPND) for low rectal cancer. The aim of this study was to investigate the incidence of and risk factors for lymphocele formation after LPND for low rectal cancer and to examine its clinical management. METHOD: We retrospectively analysed the incidence of and risk factors for pelvic lymphocele formation after LPND for rectal cancer in our hospital between January 2012 and December 2017. We also compared the size of the lymphocele between asymptomatic and symptomatic patients by using CT volumetry and examined its clinical management. RESULTS: A total of 30 out of 98 patients (30.8%) developed pelvic lymphocele after rectal LPND. The number of resected nodes was significantly higher in patients with a pelvic lymphocele (P < 0.01). The median volume was significantly higher in patients with symptomatic pelvic lymphocele (P = 0.011). Among the nine symptomatic patients, two underwent CT-guided drainage, one underwent transurethral ureteral stent placement and one underwent laparoscopic marsupialization. CONCLUSION: It is essential to keep in mind the possibility of pelvic lymphocele formation during follow-up of patients who undergo LPND, and to consider an appropriate treatment when these patients are symptomatic.

Vascular anatomy of the splenic flexure, focusing on the accessory middle colic artery and vein.

AIM: Recently, the accessory middle colic artery (AMCA) has been recognized as the vessel that supplies blood to the splenic flexure. However, the positional relationship between the AMCA and inferior mesenteric vein (IMV) has not been evaluated. Herein, we aimed to evaluate the anatomy of the AMCA and the splenic flexure vein (SFV). METHOD: Two hundred and five patients with colorectal cancer who underwent enhanced CT preoperatively were enrolled in the present study. The locations of the AMCA and IMV were evaluated, focusing on the positional relationship between the vessels and pancreas - below the pancreas or to the dorsal side of the pancreas. RESULTS: The AMCA was observed in 74 (36.1%) patients whereas the SFV was found in 177 (86.3%) patients. The left colic artery (LCA) was the major artery accompanying the SFV in 87 (42.4%) of patients. The AMCA accompanied the SFV in 65 (32.7%) patients. In 15 (7.8%) patients, no artery accompanied the SFV. The origin of the AMCA was located on the dorsal side of the pancreas in 15 (20.3%) of these 74 patients. Similarly, the destination of the IMV was located on the dorsal side of the pancreas in 65 (31.7%) of patients. CONCLUSION: The SFV was observed in most patients, and the LCA or AMCA was the common accompanying artery. In some patients these vessels were located on the dorsal side of the pancreas and not below it. Preoperative evaluation of this anatomy may be beneficial for lymph node dissection during left-sided hemicolectomy.

Obstruction is associated with perineural invasion in T3/T4 colon cancer.

AIM: Perineural invasion (PNI) is a risk factor for recurrence and metastasis and consequently leads to decreased survival in patients with various malignancies. Recent studies showed that stent placement in obstructive colon cancer increases the frequency of PNI. We hypothesized that mechanical stress including obstruction itself may be associated with PNI. METHOD: We retrospectively reviewed 496 patients with pathological T3 or T4 colon cancer who did not receive preoperative treatment. Data were collected from medical charts and pathological findings. The relationships between PNI and other clinicopathological factors were analysed using univariate and multivariate analyses. RESULTS: PNI was observed in 239 (48%) patients. Obstruction was markedly more frequent in PNI-positive cancer (39%) than in PNI-negative cancer (24%, P = 0.0003). Multivariate analyses identified obstruction as one of the significant factors associated with PNI (OR 1.68, P = 0.028). Moreover, in 414 patients without distant metastasis who underwent complete resection, PNI was an independent factor associated with poor recurrence-free survival (hazard ratio 2.35, P = 0.003). The coexistence of PNI and obstruction resulted in greater decreases in recurrence-free survival than PNI-negative and/or non-obstructive cases. CONCLUSION: Our results suggest that obstruction is associated with PNI and consequently contributes to an increased postoperative recurrence in colon cancer.