Tattooing the rectum just below the cancer

Using the colonoscope, the doctor went in and took a look above the cancer stricken zone, and immediately below. Once the scope was in position below the cancer, a needle injected black ink. Just in one spot, but quite lot. It then spread a little in the local area. No anaesthesia was needed, and it only made me uncomfortable when the scope was about 15 inches in. There it gave me a feeling of somebody pushing me on my stomach while having diarrhea.