Computed tomography (CT) scan of the pelvis unreliably detects metastases to lymph nodes from rectal carcinoma. Alternative features of tumor spread visualized on pelvic CT scan may aid preoperative evaluation. Two patients in a series had thickened perirectal fascia due to tumor involvement. The perirectal fascia was recently described by others from CT scans of the pelvis. The extent of the perirectal fascia shown on CT scan correlated with descriptions of Waldeyer's fascia that stress its expansive nature enveloping internal iliac vessels and lymphatics. The perirectal fascia and Waldeyer's fascia are proposed to be synonymous, and lymphangitis carcinomatosa is proposed to account for a thickened perirectal/Waldeyer's fascia in rectal carcinoma. The fascial thickening also is found in inflammatory pathology of the rectum (probably due to inflammatory lymphangitis), and fascial thickening on pelvic CT scan is thus not an absolute indicator of carcinoma.