[Rectal Cancer: Optimal Preoperative Diagnostics].

Preoperative diagnostics for rectal cancer aim to determine the extent of local and systemic spread. Local staging includes rectoscopy with accurate height localisation, histological confirmation, MRI of the pelvis and, particularly in the case of localised tumours, endosonography. In addition to tumour height and possible infiltration of adjacent organs, MRI findings should include minimum tumour distance from the mesorectal fascia and MR morphological criteria for extramural vascular invasion. In the case of lower rectal cancer, the relationship to the various components of the sphincter muscle is important in planning the surgical strategy; in the case of upper rectal cancer, the MRI findings should include possible infiltration of the peritoneal fold. As outlined in the German guidelines, the basic diagnostic tests required to detect or exclude distant metastases are a chest X-ray and an abdominal ultrasound. If unclear findings are observed, these should be supplemented by a chest and abdominal CT. In addition to the carcinoembryonic antigen (CEA) test, which is primarily used for follow-up, a complete colonoscopy should be performed to rule out a second malignancy in the colon. If this is not possible due to an obstructive tumour, the colonoscopy should be performed three months postoperatively. Additionally, a preoperative CT or MR colonoscopy can reliably detect larger polyps and carcinomas.