The accuracy of X-ray examination for colorectal cancer

X-ray examination is a common method for diagnosing colorectal cancer, but it does not have a high diagnosis rate for all types of colorectal cancer. Rectal cancer is easily missed due to its low position and wide rectum. Cecal cancer is difficult to differentiate and is also prone to misdiagnosis. The specific reasons are as follows.

1. The scope of early colorectal cancer lesions is relatively limited, and the examination of lesions smaller than 1 cm is not detailed.

2. Improper preparation for cleansing enema may also affect the examination. For example, retained fecal matter may cover up smaller tumors, or may mistake small tumors for fecal matter.

3. Excessive use of barium masked the tumor

4. The sigmoid colon and the liver and spleen flexures are too long and overlap each other, covering up the tumor.

5. The cecum is filled with cancer but is mistakenly believed to be full, resulting in missed diagnosis.

In addition, the accuracy of X-ray diagnosis varies greatly depending on the location of the cancer. In general, the accuracy of X-ray diagnosis of the cecum and rectum is lower than that of the middle section. For example, among Alleock's 43 cases of cecal cancer, only 35% were diagnosed, and the misdiagnosis rate was 65%. Cooley pointed out the misdiagnosis rate of different parts through research. The false negative rate of cecal cancer was 27%, the false negative rate of sigmoid colon cancer was 8%, and the false negative rate of rectal cancer was as high as 49%. The diagnoses of the ascending, transverse, and descending colon in the middle section were all correct. Among all 130 cases of cancer above the rectum, the correct diagnosis was about 90%.