Kidney cancer forms when cells in the kidney begin to grow out of control. The most common kind in adults is called renal cell carcinoma, which usually starts in the outer part of the kidney. In young children, Wilms tumor is the kind of kidney cancer that is more likely to develop.

According to the American Cancer Society, “Kidney cancer is one of the 10 most common cancers in both men and women in the United States. It accounts for about 4% to 5% of all cancers”. Risk factors for kidney cancer include smoking, being overweight, having high blood pressure, and having a close relative who had the disease.

Kidney cancer often starts to grow quietly without clear symptoms. This can make it hard to notice until it becomes more serious. However, there are a few subtle signs that could suggest something is wrong. Learning about these signals early might help you seek medical care sooner, which may improve treatment results.

1. Blood in the urine

Blood in the urine, also called hematuria, can be a common sign of kidney cancer. Sometimes, you might see bright red streaks in your urine. Other times, it can look brownish or tea-colored, which can be harder to notice. Even a small amount of blood can signal trouble. If you see any color changes in your urine, talk to your doctor. Not all cases of blood in the urine mean you have cancer, but it’s important to find out the cause.

2. Lower back or side pain

Kidney tumors may grow large enough to press on nearby tissues, leading to pain in the lower back or side. This pain can be constant or come and go. Some people describe it as a dull ache, while others say it feels sharp. If the pain does not get better over time or grows worse, you should see a doctor. Pain in the lower back or side that happens along with blood in the urine or other symptoms needs prompt attention.

3. Unexplained weight loss

If you lose weight without trying, it can be an early warning sign of kidney cancer. Cancer cells sometimes change how your body uses energy, causing you to burn calories faster. A tumor might also affect hormone levels or press on your stomach, making it hard to eat. If you drop a noticeable amount of weight for no clear reason, call your healthcare provider. Other conditions can also cause weight loss, but it’s wise to rule out kidney cancer.

4. Persistent fatigue

Fatigue is more than just feeling sleepy. It is a deep tiredness that does not get better even if you rest. When someone has kidney cancer, the body may lose healthy red blood cells, which can lead to anemia. Without enough red blood cells, your tissues do not get the oxygen they need, and you feel drained. The cancer might also affect certain hormones that control energy. If you are too tired to do your normal activities and it lasts for a while, consider seeing a doctor—especially if you have other symptoms like pain or changes in your urine.

5. Low-grade fever

Sometimes, kidney tumors can cause a mild fever that appears and disappears for no clear reason. A fever is often the body’s way of fighting infection, but it can also happen because of immune reactions to a tumor. If you find yourself having these mild fevers along with any of the signs above, seek medical help. A doctor can check whether an infection, an autoimmune problem, or a tumor might be causing it.

Diagnosis and next steps

If you notice any of these signs, you should make an appointment with a healthcare professional. They might run blood tests, do imaging scans like an ultrasound or a CT, or suggest other tests. If they see a concerning lump, they could do a biopsy to find out if it is cancer.

Treatment options depend on how big the tumor is and whether it has spread. Surgery is common, but targeted therapy, immunotherapy, or a mix of treatments might be recommended. Staying in touch with your medical team helps you decide the best plan for your situation.

When to seek help

Early kidney cancer often has no strong signs. That is why you should watch for lower back or side pain that does not go away, blood in your urine, and weight loss without trying. Getting checked early can find a tumor before it becomes more serious.

If you are diagnosed with kidney cancer, remember there are effective ways to treat it. Thanks to new surgeries and targeted therapies, survival rates have improved. After treatment, follow-up appointments are important for keeping track of your overall health.