The kidneys are organs that are responsible for eliminating waste material from the blood by making urine. The kidneys also produce hormones, which regulate blood pressure and control red blood cell production. Located just above the kidneys are the adrenal glands, which produce several essential hormones. Adrenal hormones help to regulate metabolism, blood pressure, inflammation, and response to stress. The adrenal glands also produce small amounts of sex hormones (androgens and estrogens).The body can function perfectly well with one kidney and one adrenal gland if they are normal. This allows for the removal of one entire kidney and adrenal gland when necessary to remove a cancer localized to the kidney area. If patients have poor kidney function before developing cancer of the kidney, it may not be possible to remove one kidney and still have normal function.
Normal Anatomy: Most people have two kidneys. The kidneys produce urine, which drains through narrow tubes (called ureters) into the urinary bladder. The kidneys are located toward the back of the flank, with one kidney on either side. The kidney is contained within a fibrous sheath called Gerota’s fascia. Within this fascia is a layer of fat that surrounds the kidney. The capsule is a thin layer that covers the outer surface of the kidney (analogous to the red external layer of an apple). The primary vein that drains the kidney (renal vein) merges with the vein that takes blood to the heart (vena cava). The term “renal” means pertaining to the kidney. An adrenal gland is located above each kidney within Gerota’s fascia.
Several types of tumors both benign and malignant may occur in the kidney. A kidney tumor is an abnormal area within the kidney. The terms mass, lesion, and tumor are often used interchangeably. Tumors may be benign (not cancerous) or malignant (cancerous). The most common type of kidney tumor is a fluid-filled area called a cyst. Simple cysts are benign and have a typical appearance on imaging studies. Simple cysts do not progress to cancer and usually require no follow-up treatment. Complex cysts do not have the typical benign appearance and may contain cancer. When complex cysts are present, the need for treatment is determined on an individual basis. Another type of kidney tumor is a solid kidney tumor (i.e. not fluid-filled). Solid kidney tumors may be benign, but are usually malignant. In fact, more than 90% of solid kidney tumors are cancerous.
In the United States, kidney cancer accounts for about 4% of all cancers, with approximately 13,000 kidney cancer deaths each year. Kidney cancer occurs slightly more often in males and is usually diagnosed between the ages of 50 and 70, but can occur at any age. In adults, the most common type of kidney cancer is renal cell cancer.
Many kidney tumors go undetected due to the lack of symptoms and are incidentally detected during the medical evaluation of an unrelated problem. Kidney tumors can cause symptoms by compressing, stretching or invading structures near or within the kidney. Symptoms caused by these processes include pain (in the flank, abdomen or back) and blood in the urine (small amounts may not be visible). If cancer spreads beyond the kidney, symptoms depend upon which organ is involved. Shortness of breath or coughing up blood may occur when cancer is in the lungs; bone pain or fracture may occur when cancer in the bone; and neurologic symptoms may occur when cancer is in the brain. In some cases, the cancer causes associated clinical or laboratory abnormalities called paraneoplastic syndromes. These syndromes are observed in approximately 30% of patients with kidney cancer and can occur in any stage. Clinical symptoms include weight loss, loss of appetite, fever, sweats and high blood pressure. Laboratory findings include elevated erythrocyte sedimentation rate, low red blood cell count (anemia), high calcium level in the blood, abnormal liver function tests, elevated alkaline phosphatase in the blood, and high white blood cell count. In many cases, the paraneoplastic syndrome resolves after the cancer is removed.
Detecting Kidney Cancer
When a kidney tumor is suspected, a kidney imaging study is obtained. The initial imaging study is usually an ultrasound or CT scan. In some cases, a combination of imaging studies may be required to completely evaluate the tumor. If cancer is suspected, the patient should be evaluated to see if the cancer has spread beyond the kidney.
Determining the extent of the spread or the stage of the cancer requires a number of tests. Staging tests include X-rays, computerized tomography (CT) scans, ultrasonography or magnetic resonance imaging (MRI). Other tests include an intravenous pyelogram (IVP) and arteriography. Intravenous pyelogram involves the injection of dye into a vein to help visualize the kidneys, ureters and bladder. If the patient has bone pain, recent bone fractures, or certain abnormalities on the blood tests, a bone scan is also recommended. Additional tests may be obtained as needed. Kidney cancer has the propensity to grow into the renal vein and vena cava. The portion of the cancer that extends into these veins is called “tumor thrombus.” Imaging studies help determine if tumor thrombus is present. There are no blood or urine tests that directly detect the presence of kidney tumors. Arteriography involves the injection of dye into the blood vessels supplying the kidney. Staging is ultimately confirmed by surgical removal of the cancer and exploration of the area adjacent to the kidney. The surgeon will often remove regional lymph nodes for examination under the microscope. Examination of both kidneys is essential to assure that one is working normally. Sometimes, more progressed stages of the disease can be determined by such tests without the need for surgery.
In 40% of patients, renal cell cancer will be limited to the kidney and is treated exclusively by surgery, which is curative 90% of the time. In the 60% of patients with renal cell cancer that has spread outside the kidney, the disease is generally not curable with surgery and other specialists, such as medical oncologists and possibly even radiation therapists, are involved with treatment.
Following completion of all diagnostic tests and surgery, a final “pathologic” stage and grade will be given. All new treatment information concerning renal cell cancer is categorized and discussed by the stage. Tumor grade is a subjective measure of how aggressive the tumor looks under the microscope; therefore, it is determined from a surgical specimen. Grade cannot be determined from radiographic imaging (CT scans, MRI, etc.), blood tests or urine tests. Grade usually ranges from 1 to 4 with higher numbers indicating a more aggressive tumor. Thus, higher grade implies a worse prognosis.
The following are simplified definitions of the various stages of kidney cancer. Click on each for a stage by stage overview of the most recent information available concerning the comprehensive treatment of renal cancer.
Stage I: The primary cancer is 7 centimeters (about 3 inches) or less and is limited to the kidney, with no spread to lymph nodes or distant sites.
Stage II: The primary cancer is greater than 7 centimeters (about 3 inches) and is limited to the kidney, with no spread to lymph nodes or distant sites.
Stage III: The cancer has spread to the regional lymph nodes but not to distant sites in the body, and/or extends to the renal veins or vena cava (large vein returning blood to the heart located in the middle of the abdomen near the back).
Stage IV: The cancer has spread to distant sites or invades directly beyond the local area.
Recurrent Renal Cell Cancer: Renal cell cancer has returned after primary treatment.
Clinical stage is based on radiographic imaging before surgery, whereas pathologic stage is based on the analysis of surgically removed tissue. Staging the cancer helps predict prognosis and survival.
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