[Radiological diagnostics and follow-up of rectal carcinoma]

Rectal carcinoma is one of the most frequent malignant tumors in adulthood. Not only after total resection but also after partial resection of the tumor with postoperative radiochemotherapy a sufficient follow-up is necessary to diagnose recurrent rectal cancer as early as possible. Various guidelines suggest different intervals for physical examinations and diagnostic methods depending on the initial tumor stage. In addition to routine examinations, the physician can choose between CT, MRI, endosonography and functional imaging techniques such as PET and immunoscintigraphy for further evaluation if a recurrent rectal cancer is suspected. Multiple studies and meta-analyses show the differences in the specificity and sensitivity of the diagnostic methods in the detection of lymph nodes, metastases, and local tumor infiltration. Endosonography and endorectal MRI show very good results in staging local tumor infiltration. However, obstructive lesions can inhibit an adequate examination. CT provides prompt and convincing results in the evaluation of the metastases. Most of the time the tumor can be identified but the lack of detailed imaging makes it hard to perform sufficient staging. Additionally image-guided biopsy can be performed. Immunoscintigraphy and PET have a high specificity because they take advantage of the tumor's metabolism. The introduction of the PET-CT has eliminated the disadvantage of low image resolution. In addition to the detection of small nodular pulmonary metastases, MRI with its "phased-array" coils is another excellent tool for the diagnosis of recurrent rectal cancer and search for metastases. This review shows the advantages and disadvantages of each diagnostic method in the visualization of recurrent rectal cancer.