What Are the Clinical Presentations of Colorectal Cancer?

Colorectal cancer is a common malignant tumor, including colon cancer and rectal cancer. The incidence of colorectal cancer is highest in the rectum, followed by the sigmoid colon, cecum, ascending colon, descending colon, and transverse colon, with a trend of recent development towards the proximal (right half of colon). Its onset is closely related to lifestyle, genetics, and colorectal adenoma.

Colorectal cancer in the early stages is asymptomatic or with mild symptoms, such as discomfort, indigestion, and occult blood in the stool. As the tumor develops, symptoms gradually appear, manifested as changes in bowel habits, abdominal pain, rectal bleeding, abdominal masses, intestinal obstruction, with or without systemic symptoms such as anemia, fever, and weight loss. The tumor's metastasis and infiltration can cause changes in affected organs. Colorectal cancer shows different clinical symptoms and signs depending on its location.

Clinical manifestations of colorectal cancer: Right-sided colon cancer

The main clinical symptoms of the right colon include loss of appetite, nausea, vomiting, anemia, fatigue, and abdominal pain. Right-sided colon cancer leads to iron-deficiency anemia, manifested as fatigue, weakness, and shortness of breath. Because the right colon's lumen is large, abdominal symptoms only appear when tumors grow to a certain size, which is one of the main reasons for the late diagnosis of tumors.

Clinical manifestations of colorectal cancer: Left-sided colon cancer

The lumen of the left colon is narrower than that of the right colon, making left-sided colon cancer more prone to causing complete or partial intestinal obstruction. Intestinal obstruction leads to changes in bowel habits, such as constipation, rectal bleeding, diarrhea, abdominal spasms, abdominal bloating, etc. Rectal bleeding with fresh blood indicates that the tumor is located at the end of the left colon or rectum. The definitive diagnosis is often earlier than that for right-sided colon cancer.

Clinical manifestations of colorectal cancer: Rectal cancer

The main clinical symptoms of rectal cancer are rectal bleeding, changes in bowel habits, and obstruction. If the tumor is located in the lower part of the rectum with hard feces, it is easily caused by feces rubbing and bleeding, often appearing as fresh or dark red blood, not mixed with formed stools, or attached to the surface of stools, which is often misdiagnosed as bleeding from hemorrhoids. The secondary infection caused by stimulation of the lesion and ulceration of the tumor, constantly causing defecation reflexes, is often misdiagnosed as "colitis" or "bacillary dysentery." When the tumor grows in a ring shape, it causes intestinal lumen stenosis, which is manifested as a deformation of fecal columns in the early stages and incomplete obstruction in the late stages.

Clinical manifestations of colorectal cancer: Tumor infiltration and metastasis

The most common form of infiltration for colorectal cancer is local invasion, where tumors invade surrounding tissues or organs, causing corresponding clinical symptoms. Anal incontinence, continuous pain in the lower abdomen and sacrum are caused by rectal cancer invading the sacral plexus. Tumor cell implantation and metastasis to the abdominal pelvic cavity form corresponding symptoms and signs. Rectal digital examination can palpate a mass in the rectovesical or rectouterine pouch, and tumors widely spread and metastasize within the abdominal pelvic cavity to form ascites. The distant metastasis of colorectal cancer mainly occurs in two ways: lymphatic metastasis and hematogenous metastasis. Tumor cells can be transferred to lymph nodes through lymphatic vessels or to other parts of the body, such as the liver, lungs, bones, etc., through hematogenous metastasis.