[False interpretations of computed tomograms in malignant lymph node diseases of the pelvis and abdomen]

In the presence of a retroperitoneal mass with loss of normal aortic and caval contours no distinction can be made by CT between metastases or malignant lymphoma and primary sarcoma or retroperitoneal fibrosis if a primary tumour is not known. A false diagnose is quite possible if intestinal loops or vessels are considered as enlarged lymph nodes. These pitfalls can be avoided by intravenous application of contrast medium and by filling of all intestinal loops with orally administered contrast medium, in special cases even via a gastric tube. Pitfalls in post-therapeutic changes, like haematoma, scar tissue or lymphocele, are confounded with tumour recurrence of recent metastases and are give false-positive results in follow-up examinations. If no regression of lymph node enlargement after therapy is observed, a distinction between active metastases and nodal induration is impossible. False-negative results are due to metastatic, but not enlarged lymph nodes and cannot be avoided by CT.