Kidney (Renal) Mass

A renal mass is a growth on the kidney.

A renal mass, sometimes also called a kidney tumor, can be either benign or malignant.

Benign renal masses are non-cancerous and include cysts, angiomyolipomas, oncocytomas, fibromas, and hemangiomas. Malignant masses are cancerous. The most common malignant renal mass is renal cell carcinoma, a type of kidney cancer.

Learn more about kidney masses, including their definition, causes, symptoms, diagnosis, treatment, and potential risks and complications.

What is a kidney mass?

A kidney (renal) mass is an abnormal lump or growth on the kidney, which can be either benign (non-cancerous) or malignant (cancerous). Most kidney masses are discovered incidentally during imaging studies for other conditions. The primary goal is to determine whether the tumor is benign or malignant and to decide on an appropriate treatment strategy.

Types of kidney masses

Benign masses

• Renal cysts: Fluid-filled sacs that are often benign and asymptomatic.
• Angiomyolipomas: Benign tumors composed of blood vessels, muscle, and fat.
• Oncocytomas: Benign tumors that resemble renal cell carcinoma but have distinct cellular features.

Malignant masses

• Renal cell carcinoma (RCC): The most common type of kidney cancer, accounting for about 90% of cases.
• Transitional cell carcinoma (TCC): Cancer arising from the lining of the urinary tract, including the renal pelvis. Also called urothelial carcinoma.
• Wilms tumor: A rare kidney cancer that primarily affects children.
• Sarcomas of the kidney: Rare cancers originating from the kidney’s connective tissues.

Learn more about kidney cancer>>

Causes of kidney mass

Health care providers do not know exactly why kidney tumors happen. Researchers are studying kidney tumors to understand how and why they occur. You may be at increased risk of kidney tumors based on:

• Age: Increased risk with advancing age.
• Gender: More common in men than women.
• Smoking: Significant risk factor for renal cell carcinoma.
• Obesity: Increased body fat is associated with a higher risk of kidney cancer.
• Hypertension: Chronic high blood pressure can contribute to kidney cancer risk.
• Chronic kidney disease: Long-term kidney disease can increase the risk of renal cell carcinoma.

Genetic conditions or a family history of kidney tumors can also put you at higher risk for the condition.

Symptoms of kidney tumors

Many people do not have any symptoms of a kidney tumor. These masses are often found during tests for other conditions. Some people may experience symptoms including:

• Hematuria: Blood in the urine, which may be visible or microscopic.
• Flank pain: Pain or discomfort in the side or back.
• Weight loss: Unexplained loss of weight.
• Fatigue: Persistent tiredness or weakness.
• Fever: Intermittent fever without an obvious infection.

Diagnosis of kidney tumors

Because kidney masses often do not have symptoms, they are often detected during tests for other conditions. Diagnosing a kidney mass may include:

• Symptom assessment: Detailed inquiry about the presence, duration, and severity of symptoms such as hematuria, pain, or weight loss.
• Medical history: Review of risk factors, family history, and genetic predispositions.
• Physical examination: Comprehensive examination, including palpation of the abdomen and flank.
• Urinalysis: Testing urine for blood and abnormal cells.
• Blood tests: Assessing kidney function, liver function, and overall health.
• Imaging studies:
  • Ultrasound: Initial imaging to detect the presence and characteristics of the mass.
  • CT scan: Detailed cross-sectional imaging to evaluate size, location, and extent of the mass.
  • MRI: In-depth imaging, especially useful for characterizing complex cysts and vascular structures.
• Biopsy: In some cases, a needle biopsy is performed to obtain a tissue sample for histopathological analysis.
• Bone scan: To check for bone metastasis in cases of suspected advanced cancer.
• PET scan: To evaluate for metastasis and assess the activity of the mass.

Learn more about kidney health problems>>

How are kidney masses treated?

Treatment for kidney masses depends on several factors, including the size of the tumor and whether it is benign or malignant. Treatments may include:

Active surveillance

Monitoring small, asymptomatic masses with regular imaging and follow-up, particularly if they are likely benign.

Surgery

• Partial nephrectomy: Removing the tumor while preserving the rest of the kidney, suitable for small or localized masses.
• Radical nephrectomy: Complete removal of the affected kidney, typically for larger or more invasive tumors.
• Nephron-sparing surgery: Techniques to preserve kidney function by sparing as much kidney tissue as possible.

Ablation therapies

• Cryoablation: Freezing the tumor to destroy cancer cells.
• Radiofrequency ablation: Using heat from electrical currents to destroy cancer cells.

Medical treatments

• Targeted therapy: Medications that target specific pathways involved in cancer growth, used for advanced or metastatic renal cell carcinoma.
• Immunotherapy: Drugs that stimulate the immune system to fight cancer, particularly in advanced or metastatic cases.
• Chemotherapy: Less commonly used for renal cell carcinoma due to limited effectiveness, but may be used for transitional cell carcinoma.

Radiation therapy

• External beam radiation: Targeted radiation to destroy cancer cells, typically used for palliation in metastatic disease.
• Stereotactic body radiation therapy (SBRT): A highly focused form of radiation therapy for precise targeting of tumors.

Follow-up care

• Regular check-ups: Routine follow-up with imaging studies and laboratory tests to monitor for recurrence or progression.
• Monitoring for complications: Assessing kidney function and overall health after treatment.

Management of a kidney (renal) mass requires timely diagnosis and appropriate intervention to prevent complications and improve outcomes. Understanding the causes, symptoms, diagnostic methods, and treatment options is essential for effective management. If you or a loved one have been diagnosed with a kidney mass or are experiencing related symptoms, consulting with a health care provider and a specialized medical team will help develop a comprehensive treatment plan tailored to your specific needs and circumstances.