Colon Cancer Signs and Symptoms: What to Watch For

Diagnosed with colon cancer or a large polyp?

Meet Dr. Murtaza Shakir, board certified in General Surgery and Complex General Surgical Oncology, in Katy or Sugar Land to review your results and options. Call (713) 955-9191, or send your details and our team will call you back.

THE SHORT ANSWER

The most common signs of colon cancer are a change in bowel habits lasting more than a few weeks, blood in or on the stool, narrower stools, ongoing abdominal discomfort, unexplained fatigue from anemia and unintended weight loss. Early colon cancer often causes no symptoms at all, which is why screening from age 45 matters.

What Are the Early Signs of Colon Cancer?

Early colon cancer often causes no symptoms. When symptoms do appear, they tend to be subtle and easy to blame on diet, hemorrhoids or stress. The changes that most often turn out to be significant are:

A change in bowel habits that lasts more than a few weeks: new constipation, new diarrhea or alternating between the two
Narrower stools than usual, sometimes described as pencil-thin
Blood in or on the stool, which may be bright red or make the stool look dark or black
A feeling that the bowel does not empty completely, or an urge to go that does not ease afterward
Ongoing abdominal discomfort: cramps, gas, bloating or a dull ache
Unexplained fatigue or weakness, often from slow blood loss and anemia
Unintended weight loss

None of these is specific to cancer. The American Cancer Society notes that infections, hemorrhoids and irritable bowel syndrome can cause the same symptoms. What should prompt evaluation is persistence: symptoms that last beyond two to three weeks, or keep coming back, should be checked rather than watched. Our guide to abdominal pain and stomach discomfort covers other common causes.

Do Colon Cancer Symptoms Depend on Where the Tumor Is?

Yes. The colon changes in width and stool changes in texture along its length, so a tumor’s location shapes the first symptoms.

Right-sided (ascending) colon: the colon is wide and stool is still liquid, so tumors can grow large without blocking anything. They often cause slow, hidden bleeding and iron-deficiency anemia. The first clue may be fatigue, shortness of breath with exertion or a low blood count on a routine test, with no visible blood.
Left-sided (descending and sigmoid) colon: the colon is narrower and stool is formed, so tumors here are more likely to change bowel habits, narrow the stool and cause visible bright red blood, cramping or a feeling of incomplete emptying.
Rectum: rectal cancers commonly cause bright red bleeding, a persistent urge to pass stool and changes in stool shape.

Because rectal bleeding is so often caused by hemorrhoids, it is frequently dismissed. Bleeding that is new or persistent, or that occurs in someone over 40, should be evaluated even when hemorrhoids are present.

Which Colon Cancer Symptoms Need Emergency Care?

Symptoms that suggest a tumor is blocking the bowel or has caused significant blood loss need prompt care. Go to the emergency department, or call 911 if you feel faint, for:

Severe or worsening abdominal pain with bloating
Inability to pass stool or gas, with nausea or vomiting
Heavy rectal bleeding or passing large clots
Black, tarry stools
Dizziness, a rapid heartbeat or fainting, which can signal anemia or bleeding

Rapid, unexplained weight loss is not an ER problem on its own, but it deserves a prompt appointment with your doctor.

Who Is at Higher Risk for Colon Cancer?

Anyone can develop colon cancer, but several factors raise the likelihood:

Age: risk rises with age, and the American Cancer Society notes colorectal cancer has been rising in adults younger than 50.
Personal history of colorectal polyps, especially adenomas, or a previous colorectal cancer.
Family history of colorectal cancer or advanced polyps in a parent, sibling or child, especially when diagnosed at a young age or in several relatives.
Inherited syndromes such as Lynch syndrome or familial adenomatous polyposis (FAP).
Inflammatory bowel disease: long-standing ulcerative colitis or Crohn’s colitis.
Lifestyle factors: a diet high in red and processed meat and low in fiber, obesity, physical inactivity, smoking and heavy alcohol use.
Type 2 diabetes.

People with a strong family history, an inherited syndrome or long-standing inflammatory bowel disease usually need earlier and more frequent screening, which is worth discussing with a physician before any symptoms appear.

When Should You Start Colon Cancer Screening?

Adults at average risk should start screening at age 45. The U.S. Preventive Services Task Force (USPSTF) recommends screening from 45 through 75, with individualized decisions from 76 to 85. Most colon cancers begin as a polyp that takes years to turn cancerous, and the National Cancer Institute notes that finding and removing polyps can prevent colorectal cancer. Screening also finds cancers at an early, curable stage.

Colonoscopy every 10 years if normal. It examines the whole colon and allows polyps to be removed at the same time.
Stool tests: a fecal immunochemical test (FIT) every year, or a stool DNA-FIT test every one to three years. A positive result must be followed by a colonoscopy.
CT colonography every 5 years, or flexible sigmoidoscopy every 5 years, or every 10 years with a yearly FIT.

The best test is the one that actually gets done. If you are 45 or older and have never been screened, that is the single most useful step you can take, regardless of symptoms.

Have a Positive Screening Test or Biopsy?

Dr. Murtaza Shakir reviews colonoscopy, pathology and imaging results and explains surgical options for patients in Katy and Sugar Land. Call (713) 955-9191 to arrange a visit.

Request a consultation → (713) 955-9191

How Do Doctors Diagnose and Stage Colon Cancer?

Colonoscopy with biopsy is the definitive test when symptoms or a positive screening test raise concern. A flexible camera examines the full length of the colon, and any suspicious area is sampled to confirm whether cancer is present and what type.

Blood tests: a complete blood count checks for anemia. A CEA (carcinoembryonic antigen) level is often measured as a baseline; it is not a screening test, but it helps with follow-up after treatment.
Imaging: a CT scan of the chest, abdomen and pelvis shows whether cancer has spread to lymph nodes, the liver or the lungs. For rectal cancer, a pelvic MRI or endorectal ultrasound shows how deeply the tumor has grown.
Stage: together these tests set the stage, from stage 0 and I, where cancer is limited to the inner layers of the bowel wall, through stage III, where it has reached nearby lymph nodes, to stage IV, where it has spread to distant organs. The stage guides treatment.

How Is Colon Cancer Treated?

Surgery is the main treatment for most colon cancers that have not spread widely. The operation, a colectomy, removes the segment of colon containing the tumor along with its blood supply and nearby lymph nodes, then reconnects the healthy ends. Depending on location this may be a right, left, sigmoid or extended colectomy. Most colectomies can be performed laparoscopically or robotically through small incisions, which typically means less pain and a faster recovery than open surgery. Some very early cancers within a polyp can be removed entirely during colonoscopy.

Chemotherapy: recommended after surgery for many stage III and some higher-risk stage II cancers to lower the chance of recurrence, and used as the main treatment when cancer has spread to distant organs.
Radiation therapy: used mainly for rectal cancer, often with chemotherapy before surgery to shrink the tumor.
Targeted therapy and immunotherapy: options for certain advanced cancers, chosen based on the tumor’s genetic features.

Colon cancer that has spread to the liver can sometimes still be treated with the goal of cure, by removing or ablating the liver tumors as well as the primary cancer. This is where a surgeon trained in both colorectal and liver surgery is particularly valuable. Learn more on our liver cancer and surgical oncology pages.

What Is Recovery Like After Colon Cancer Surgery?

After a laparoscopic or robotic colectomy, most patients stay in the hospital for about two to four days, walking from the first day and returning to a light diet as bowel function recovers. Open surgery generally means a longer stay.

Desk work is often possible within two to three weeks
Heavy lifting is usually limited for about six weeks
Bowel habits may take several weeks to settle
Some rectal cancer operations need a temporary or, less commonly, permanent stoma, which is discussed in detail beforehand

Follow-up after treatment includes regular visits, CEA blood tests, CT scans and a repeat colonoscopy, typically at one year and then at intervals, to catch any recurrence or new polyps early. Our pre-operative and post-operative care pages cover general preparation and recovery.

When Should Patients in Katy, Sugar Land and Houston See a Surgeon?

See a surgeon once a cancer, or a polyp too large to remove during colonoscopy, has been found, or when you want to understand what an operation would involve before deciding on treatment. A primary care physician or gastroenterologist is usually the first stop for symptoms and screening.

Dr. Murtaza Shakir is board certified in both General Surgery and Complex General Surgical Oncology, with fellowship training at the University of Pittsburgh Medical Center that included colorectal and liver cancer surgery. He evaluates patients with newly diagnosed colon and rectal cancer at the Katy and Sugar Land offices and coordinates care with gastroenterologists and medical oncologists. Patients come from across Katy, Sugar Land, Richmond, Fulshear and West Houston.

Bring your colonoscopy and pathology reports and any CT or MRI results
Note any family history of colon, rectal or related cancers

See our colon cancer surgery page, learn what a surgical oncologist does, meet Dr. Shakir, read about general surgery, or call (713) 955-9191 to request a consultation.

Questions to Ask Your Surgeon About Colon Cancer

What stage is my cancer, and which tests still need to be done?
Which part of the colon will be removed, and how many lymph nodes will you check?
Can the operation be done laparoscopically or robotically?
Is there any chance I will need a stoma, and would it be temporary?
Will I need chemotherapy or radiation before or after surgery?
How long will I be in the hospital, and when can I return to work?
What follow-up tests will I need, and how often?

Frequently Asked Questions

Is blood in the stool always cancer?

No. Hemorrhoids and anal fissures are far more common causes. But new or persistent bleeding, especially after age 40, should be evaluated with a colonoscopy rather than assumed to be hemorrhoids.

Can young adults get colon cancer?

Yes. Most cases occur in older adults, but the American Cancer Society reports that colorectal cancer has been rising in people younger than 50. Persistent bowel changes or bleeding deserve evaluation at any age.

Can colon cancer be cured?

Yes. Found at an early stage, colon cancer is highly curable with surgery, and many stage III cancers are cured with surgery plus chemotherapy. Even some cancers that have spread to the liver can be treated with the goal of cure.

Is colon cancer surgery done laparoscopically?

Most colectomies today are performed laparoscopically or robotically through small incisions. Open surgery is used for very large tumors, emergencies or extensive prior surgery.

Will I need a colostomy bag?

Most colon cancer operations do not require a stoma. Some rectal cancer operations need a temporary stoma while the reconnection heals, and a small number need a permanent one. Your surgeon will explain what applies to you.

Who treats colon cancer near Katy and Sugar Land?

Dr. Murtaza Shakir, a board-certified general surgeon and surgical oncologist, evaluates and treats colon cancer at 410 W Grand Pkwy S, Suite 4D, Katy, TX 77494 and 17510 W Grand Pkwy S, Suite 320, Sugar Land, TX 77479. Request a consultation or call (713) 955-9191.

Key Takeaway

Colon cancer is common, usually slow-growing and very treatable when caught early. Get screened from age 45, and do not wait out bowel changes or bleeding that last more than a few weeks. If a cancer or large polyp is found, a surgical consultation clarifies the stage, the treatment plan and what surgery and recovery involve.

Sources and Further Reading

This article is general education, not personal medical advice. If you think you are having a medical emergency, call 911 or go to the nearest emergency room.

Meet the Surgeon

Dr. Murtaza Shakir is a board-certified General Surgeon and is board certified in Complex General Surgical Oncology. He earned his medical degree at Aga Khan University, completed General Surgery residency at Riverside Methodist Hospital in Columbus, Ohio, and a two-year Surgical Oncology fellowship at the University of Pittsburgh Medical Center. He sees patients at Surgical Associates of Southern Texas in Katy and Sugar Land.

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This page provides general information and is not a substitute for medical advice. For severe abdominal pain or other emergencies, call 911 or go to the nearest emergency room. Last updated October 16, 2026.