Preoperative evaluation of colorectal cancer using CT colonography, MRI, and PET/CT

Imaging studies are a major component in the evaluation of patients for the screening,staging and surveillance of colorectal cancer.This review presents commonly encountered findings in the diagnosis and staging of patients with colorectal cancer using computed tomography(CT)colonography,magnetic resonance imaging(MRI),and positron emission tomography(PET)/CT colonography.CT colonography provides important information for the preoperative assessment of T staging.Wall deformities are associated with muscular or subserosal invasion.Lymph node metastases from colorectal cancer often present with calcifications.CT is superior to detect calcified metastases.Three-dimensional CT to image the vascular anatomy facilitates laparoscopic surgery.T staging of rectal cancer by MRI is an established modality because MRI can diagnose rectal wall laminar structure.N staging in patients with colorectal cancer is still challenging using any imaging modality.MRI is more accurate than CT for the evaluation of liver metastases.PET/CT colonography isvaluable in the evaluation of extra-colonic and hepatic disease.PET/CT colonography is useful for obstructing colorectal cancers that cannot be traversed colonoscopically.PET/CT colonography is able to localize synchronous colon cancers proximal to the obstruction precisely.However,there is no definite evidence to support the routine clinical use of PET/CT colonography.

Laterally spreading tumors:Limitations of computed tomography colonography

AIM:To prospectively investigate the detection rate of laterally spreading tumors(LSTs)of the colorectum by computed tomography(CT)colonography(CTC).METHODS:Patients with LSTs measuring≥20 mm detected during colonoscopy were prospectively enrolled in the study.All patients underwent colonoscopy and subsequent CTC on the same day.CTC was performed using multi-detector CT without contrast in the prone and supine positions.Two radiologists blinded to the existence of LSTs read the virtual endoscopic images as well as 2-D images.LSTs were classified into granular and non-granular types based on colonoscopic appearance.RESULTS:Forty-seven pathologically proven LSTs were evaluated prospectively.Histology included adenomas in 19,mucosal cancers in 19 and T1 cancers in 9.The mean diameter of the LSTs was 35.1 mm.Twenty-eight(60%)LSTs were correctly identified by CTC,and the configuration was similar to the colonoscopic appearance in most cases.Detection rate for the granular type was significantly higher than that for the nongranular type(71%vs 31%,P=0.013).Detection rate of adenomas was significantly lower than mucosal cancers(32%vs 79%,P=0.008)and T1 cancers(32%vs 78%,P=0.042).CONCLUSION:The detection rate of LSTs by CTC,particularly the non-granular type was not acceptable.Practitioners should be aware of the relatively low detection rate when using CTC.

Recent trends in the prevalence and distribution of colonic diverticula in Japan evaluated using computed tomography colonography

BACKGROUND Computed tomography colonography(CTC)may be superior to colonoscopy and barium enema for detecting diverticula.However,few studies have used CTC to diagnose diverticula.AIM To evaluate the current prevalence and distribution of colonic diverticula in Japan using CTC.METHODS This study was conducted as part of the Japanese National Computed Tomographic Colonography Trial,which included 1181 participants from 14 hospitals in Japan.We analyzed the prevalence and distribution of colonic diverticula and their relationships with age and sex.The relationship between the diverticula and the length of the large intestine was also analyzed.RESULTS Diverticulosis was present in 48.1%of the participants.The prevalence of diverticulosis was higher in the older participants(P<0.001 for trend).The diverticula seen in younger participants were predominantly located in the right-sided colon.Older participants had a higher frequency of bilateral type(located in the rightand left-sided colon)diverticulosis(P<0.001 for trend).The length of the large intestine with multiple diverticula in the sigmoid colon was significantly shorter in those without diverticula(P<0.001).CONCLUSION The prevalence of colonic diverticulosis in Japan is higher than that previously reported.The prevalence was higher,and the distribution tended to be bilateral in older participants.