12 Hallmark Symptoms of Rectal Cancer

Rectal cancer is a type of cancer that affects the rectum, which is the last part of your digestive system. When you eat, food moves through your stomach, passes through the small intestine, and enters the colon before reaching the rectum and allowing you to pass a bowel movement (poop). However, when cancer cells develop in the rectum, it can cause symptoms like changes in bowel movements, bloody poops, unintentional weight loss, fatigue, and anemia.

Rectal cancer is often grouped with colon cancer as "colorectal cancer" because they share many similarities. According to the American Cancer Society, about 46,220 people in the United States will learn they have rectal cancer in 2024.

Colorectal cancer rates have decreased annually since 2011 due to better screening, but cases in young adults under 50 have been rising each year since the mid-1990s. Therefore, knowing the warning signs is important.

Rectal cancer often starts with small growths called polyps. A rectal polyp is a tiny bump on the inside lining of your rectum. Most polyps are harmless, but some can turn into cancer if they're not removed. 

You might not notice any symptoms when you have polyps or early-stage rectal cancer. However, as the tumor grows, you may notice some symptoms start developing.

Blood in Stool

Painful Bowel Movements

People with rectal cancer may feel pain during bowel movements. This may feel like a sharp pain, a burning sensation, or general discomfort. If bowel movements start to hurt when they didn't before, it's a good idea to talk to your healthcare provider about it, as this may be an underlying sign of cancer or a digestive disorder.

Changes in Bowel Habits

A tumor in the rectum can interfere with normal bowel function, potentially leading to changes in how often you have a bowel movement or what your stool looks like. For example, you might have constipation (hard stools that are difficult to pass) if the tumor is partially blocking the rectum. You may also experience diarrhea (very loose, watery stools). 

Sometimes, your stool might look thinner than usual, like a pencil. You might also feel a sudden urge to have a bowel movement. This can occur if the tumor reduces the rectum's ability to hold stool in your body.

Incomplete Bowel Emptying

After a bowel movement, you might feel like you haven't completely pooped. However, when you try to have another bowel movement, nothing comes out. This sensation is called tenesmus and can be caused by the tumor taking up space in the rectum.

Progressive Symptoms

As rectal cancer advances, you may experience additional symptoms. These are often called progressive symptoms because they tend to develop as the cancer grows or spreads.

Unexplained Weight Loss

You might notice that you're losing weight without trying. This can happen for several reasons when you have rectal cancer. Cancer cells use up a lot of your body's energy, especially glucose, which is a type of sugar your body uses for fuel. When cancer cells use up so much glucose, your body has to work harder to make more sugar. To do this, it starts breaking down your fat and muscle for extra energy. This process can lead to weight loss.

At the same time, your body is trying to fight the cancer by releasing substances called cytokines that cause inflammation. This inflammation, along with the cancer itself, changes how your body handles food and energy. These changes can make you lose more weight.

The growing tumor can also affect your eating habits. It might make you feel full quickly or reduce your appetite, so you eat less than usual. Some people with rectal cancer have ongoing diarrhea, which can cause weight loss because your body doesn't absorb all the nutrients from your food as it is supposed to. You may also feel nauseous or have stomach pain, which can make reduce appetite and cause weight loss.

Anemia

Rectal cancer can cause small amounts of blood loss over time, even if you don't see the blood. This ongoing blood loss can lead to anemia, a condition where you don't have enough healthy red blood cells in your body to deliver oxygen to your organs and tissues. Symptoms of anemia include feeling weak, short of breath, or dizzy.

Fatigue

Many people with rectal cancer experience fatigue (extremely tired), even if they’re getting enough rest. A cancerous tumor can cause fatigue in several ways, such as by using up your body's energy, disrupting your ability to take enough nutrients through food, and potentially causing anemia (low red blood cell count).

Abdominal Pain or Cramping

As a tumor grows, it can press on surrounding tissues and organs, causing abdominal pain. You might feel cramping in your lower abdomen that doesn’t go away, bloating, a feeling of fullness, or gas.

Urinary Symptoms

If the tumor grows large enough, it might press on your bladder, prostate, or urethra (the tube that carries urine out of your body). This can cause various urinary symptoms, such as urinating more frequently, having an urgent need to pee, or having trouble starting or stopping your urine flow. In some cases, you might experience pain when urinating, too.

In the advanced stages of rectal cancer, you may experience additional symptoms. These symptoms can occur when the cancer has metastasized (spread) to other parts of the body.

Jaundice

Jaundice occurs when your skin and the whites of your eyes turn yellow. It happens when there's too much of a substance called bilirubin in your blood.

With rectal cancer, jaundice happens if the cancer spreads to your liver. The liver processes bilirubin, but if cancer interferes with this process, bilirubin can build up in your body. Besides yellow skin and eyes, jaundice can cause dark urine and pale-colored stools.

Back Pain

As rectal cancer progresses, it can spread to nearby tissues and organs. If it spreads to the bones in your spine, you might feel pain in your back. This pain might be constant or come and go.

Back pain can have many causes, but if you have other symptoms of rectal cancer and develop new or worsening back pain, it's important to tell your healthcare provider so they can conduct a physical exam or order tests to reach a diagnosis.

Pelvic Pain

The pelvis is the lower part of your torso, between your hip bones. An advanced rectal tumor can press on nerves and other structures in your pelvis. This can cause dull aches, sharp pain, or discomfort. Some people describe this pelvic pain as pressure or heaviness.

Other Symptoms

Depending on where the cancer has spread, you may experience a variety of symptoms. For instance, if rectal cancer spreads to the abdomen, it could cause ascites, a fluid buildup that causes swelling and discomfort in your abdomen. If cancer cells spread to the lungs, you may develop shortness of breath or a persistent cough. Bone pain or swollen lymph nodes can also occur if cells spread to the lymphatic system.

Everyone's experience with rectal cancer is different. You may have some, all, or none of the symptoms. If you notice any unusual changes in your body, even if they're not on this list, it's always best to discuss them with your healthcare provider to get a proper diagnosis and start treatment (if needed) sooner rather than later.

Symptoms in Younger Adults 

Colorectal cancer used to be more common in people over age 50, but it has been increasing among people under the age of 50. Colon and rectal cancers diagnosed in people less than 50 years old are known as early-onset colorectal cancers (EO-CRCs). Since the early 1990s, the incidence of EO-CRCs has more than doubled among young adults.

Because of this trend, it's important for younger adults to not only get screened regularly via a colonoscopy starting at age 45 but also be aware of colorectal cancer symptoms. 

A study found that certain symptoms that appear three months to two years before diagnosis were linked to an increased risk of early-onset colorectal cancer. These symptoms include:

• Abdominal pain
• Rectal bleeding
• Diarrhea
  

The same study found that having one of these symptoms almost doubled the risk of early-onset colorectal cancer. Having two symptoms more than tripled the risk, and having three or more symptoms increased the risk by over six times. These associations were stronger in younger age groups and for rectal cancer specifically.

If you're a younger adult experiencing any of these symptoms, it's important to discuss them with your healthcare provider and get screened as soon as possible.

Contact your healthcare provider if you have symptoms of rectal cancer or may be at risk of the condition. Changes in your digestion or bowel movements can be due to other, less serious conditions. However, recognizing these symptoms and discussing them with your healthcare provider as soon as possible can make a significant difference in catching rectal cancer early, when treatment is most effective. 

Regular screening is a vital part of rectal cancer prevention and early detection. The American Cancer Society recommends that people at average risk start regular screening at age 45, often with a colonoscopy. If you have risk factors for rectal cancer, such as a family history of colorectal cancer or polyps, certain genetic conditions, or inflammatory bowel diseases, you may need to start screening earlier.

A Quick Review

The first signs of rectal cancer are blood in your poop and changes in your bowel habits. But as the cancer progresses, you may develop unintentional weight loss, fatigue, anemia, and abdominal pain. If the cancer metastasizes (spreads to other parts of the body), additional symptoms can occur.

Rectal cancer is typically more common in older adults, but the risk of younger people developing it is growing. If you're experiencing symptoms of rectal cancer or notice changes in your overall well-being, see a healthcare provider soon for diagnosis and treatment if needed.