Rectal cancer is a malignancy that develops in the rectum, the final section of the large intestine connecting the colon to the anus. People often search for visual information to understand the disease and what medical professionals see during diagnosis. This article describes the visual signs a person might observe and the detailed “pictures” that diagnostic tools provide to physicians to identify the tumor, determine its extent, and plan treatment.
Patient-Observed Visual Symptoms
The most common sign a person may observe is blood when passing stool. This blood can appear as bright red streaks coating the stool or toilet paper. Bleeding higher up in the digestive tract may cause the stool to appear dark, tarry, and black, a condition known as melena.
Another noticeable visual change is an alteration in the shape of the stool. The tumor mass can physically narrow the passage, causing the stool to emerge thin, sometimes described as pencil-like or ribbon-like. In advanced stages, the cancer may cause systemic changes visible on the body. This includes unexplained weight loss or a persistent pale appearance of the skin due to anemia caused by chronic internal blood loss.
Clinical Visualization During Diagnosis
Medical evaluation moves past external observation to internal visualization using specialized tools. Endoscopic procedures, such as a colonoscopy or sigmoidoscopy, provide a direct, high-resolution video feed of the rectal lining. Through the scope, a doctor can see the tumor as an irregular, often ulcerated mass that bleeds easily upon contact.
This visual image stands in contrast to a benign polyp, which typically has a smoother surface and a more regular shape, such as a stalked (pedunculated) or flat (sessile) growth. If a tumor is identified, further imaging scans provide “pictures” of the surrounding tissue. Magnetic Resonance Imaging (MRI) is preferred for local staging because it excels at showing soft tissue contrast.
On a T2-weighted MRI scan, the layers of the rectal wall are distinct, allowing doctors to measure the depth of tumor penetration. The tumor appears with an intermediate signal intensity against the hypointense line of the muscularis propria. Computed Tomography (CT) scans offer a broader view, creating cross-sectional images of the abdomen and chest. These images are less useful for seeing the rectal wall itself but are essential for visualizing potential spread to organs like the liver or lungs.
Interpreting Visuals of Cancer Progression
The detailed images from MRI and CT scans are used to classify the disease using the Tumor, Node, Metastasis (TNM) staging system. The T (Tumor) classification is determined by the MRI, which shows whether the tumor is confined to the rectal wall layers or has invaded the perirectal fat. A tumor extending beyond the muscularis propria into this fat is categorized as a T3 lesion.
The N (Node) classification relies on the visual characteristics of nearby lymph nodes seen on the scans. Nodes that are enlarged, have irregular borders, or show a heterogeneous internal structure are considered suspicious for containing cancer cells. The M (Metastasis) classification is determined by the CT or PET scan, which searches for cancer spread to distant organs. Liver metastases, the most common site of spread, typically appear on CT scans as hypoattenuated, or lower-density, lesions compared to the healthy liver tissue.
Lung metastases are visible as small, distinct nodules scattered throughout the lung fields on a chest CT. Oncologists often use these data points to create diagrams that illustrate the tumor’s size and its precise relationship to the mesorectal fascia, the boundary surrounding the rectum that is removed during surgery. Confirmation of these boundaries is a primary factor in determining the surgical approach and the need for pre-operative treatment.
Visual Realities of Post-Treatment Recovery
Following surgery, the most apparent visual sign of treatment is the presence of surgical scarring on the abdomen. A procedure called a Total Mesorectal Excision (TME) is often performed to remove the tumor and surrounding tissue, resulting in a midline or transverse abdominal incision scar. The recovery process may also involve an ostomy, which is a surgically created opening on the abdomen’s surface called a stoma.
A stoma is a pink or red, moist spout of tissue where the end of the intestine is brought out to redirect waste into an external pouching system. This necessity is visible for many patients, either temporarily or permanently. If radiation therapy was part of the treatment plan, the skin in the pelvic or perineal area may show irritation. This can range from mild redness, similar to a sunburn, to discoloration or dry peeling of the skin in the treated region.