[Diagnosis of recurrent rectal cancer: Comparison of CT and MR]

For the assessment of local recurrence after surgical treatment of rectal carcinoma the results of MR and CT examinations in 29 patients were analyzed. Diagnosis was confirmed by surgery, by multiple biopsies and by follow-up examinations. CT yielded in only 11 cases clearly positive or negative findings. There were 4 false positive and 2 false negative results; in 12 cases the diagnosis remained uncertain. On the other hand, a clear differentiation was possible by MR in 23 cases with characteristically prolonged T2 in recurrent tumour and low signal intensities in fibrosis. Difficulties in differentiation were found only in early fibrotic reactions after surgery, inflammation or radiotherapy and in rare fibrotic tumours.