Definition:
Wilms tumor is the most common tumor of the kidney in infants and children. It is not painful and is usually found when the parent or pediatrician feels a large mass in the abdomen or flank. This tumor may involve just one or both kidneys. The kidneys are organs located on either side of the spine near in the upper abdomen. They function by removing waste products from the blood and they make urine, which is then passed through tubes called ureters to the bladder, where it is then emptied from the body.

A Wilms tumor is a malignant tumor (cancer) which means it has the ability to grow and spread.  The places it usually spreads to include the lungs, liver and nearby lymph nodes.

Wilms tumor has been associated with a number of genetic syndromes or birth defects which include : WAGR (a constellation of syndromes including Wilms tumor, Aniridia, ambiguous Genitalia, and mental Retardation); Beckwith-Wiedemann Syndrome (a condition of very large babies who may have large tongues and large internal organs, abdominal wall defects and a predisposition to Wilms tumors); Denys-Drash syndrome (characterized by kidney failure before age 3, abnormal development of sexual organs and Wilms tumor); Undescended testicles (also known as cryptorchidism, when one or both of the testicles fails to descend in it’s normal path from the abdomen to the scrotum); Hypospadius (a condition in which the urethra (the tube in the penis where urine comes out of) doesn’t open on the end of the penis, but opens in a spot underneath the penis) Children born with these genetic syndromes or birth defects should be screened for Wilms tumor with an ultrasound exam every 3 months until they are 8 years old.

Diagnosis:
A history and physical exam of your baby by your physician is the most likely place in which the diagnosis of a Wilms tumor will be made. If one is suspected your physician will order a number of tests. These are at the discretion of your physician, but may include the following:

• Urinalysis: a sample of urine will be examined for blood, sugar, protein and bacteria
• Blood tests: a sample of blood will be drawn and the following tests will be ordered from it:
  • Complete blood count to look for anemia and infection as well as platelet count
  • A blood chemistry to measure electrolytes and certain substances in the blood produced by the kidneys
  • Liver function tests to measure substances made by the liver that are measured in the blood. High levels of certain substances can indicate that the liver is not working appropriately
  • Bleeding and clotting studies to determine if there are any abnormalities in the ability of the blood to clot appropriately
• Radiology studies: (all or just some of these studies may be ordered at the discretion of your physician):
  • Ultrasound of the abdomen. This is a test which uses sound waves to create an image of the abdomen. It is useful in diagnosing a kidney tumor.
  • CT scan of the abdomen and chest. This test makes detailed pictures of the body using contrast by vein and X-rays. It is very useful in diagnosing a kidney tumor as well as evidence of spread of the tumor to other organs.
  • X-ray of the abdomen
• Biopsy: a procedure in which a sample of tissue is taken (usually by a needle) from the kidney. For a Wilms tumor, this is usually performed by a radiologist with local anesthesia. The sample is then sent to the pathologist who will examine it closely under a microscope to check for cancer.

Treatment:
Because a Wilm’s tumor is a cancer, you will meet with a pediatric oncologist (medical cancer doctor) as well as a pediatric surgeon. They will discuss the treatment options with you and work to answer all of your questions. Once the tumor is found and the extent of the tumor is estimated by the preoperative tests, surgery is usually the next step. In certain circumstances, chemotherapy before surgery is recommended. This usually depends on the anatomy of the kidney as well as the extent of the tumor on diagnosis.

If surgery is recommended as the first step, your pediatric surgeon will explain the procedure, risks, and benefits in detail and answer all of your questions. The procedure will be performed under general anesthesia (your child will be asleep). An incision will be made on the abdomen, either under the ribcage on the side with the tumor, or in the middle of the abdomen up and down. The abdominal cavity will then be explored for metastases to the liver and peritoneum (lining of the abdomen) and the non-affected kidney will be examined. The kidney with the tumor will then be removed, along with the ureter (the tube that connects the kidney to the bladder). In certain circumstances, the surgeon may feel that it is best to remove just a portion of the kidney. Lymph nodes surrounding the kidney will also be removed. All of the surgical specimens will be examined by a pathologist to determine the extent of the cancer. The incision will be closed using stitches that are dissolvable, your child awakened from the anesthesia, and sent to the recovery room where he will be closely monitored.

After surgery, your child will be kept in the hospital and given pain medicine and fluids by vein. Once his intestines start working (usually 2-3 days), he wiil be started on a clear liquid diet, which will be advanced to a regular diet as tolerated. Your child will be monitored closely with physical exams and blood tests while in the hospital. He will be able to resume activity when they feel ready and will be released from the hospital once his pain is well-controlled with pain pills, he is eating a regular diet and he is stable from your surgeon’s standpoint.

Usually after surgery, your oncologist (medical cancer doctor) will recommend chemotherapy for a certain amount of time. You will likely meet with your oncologist again to discuss the timing of the chemotherapy.

Prognosis:
The prognosis, or chance of recovery, is determined by a number of factors. These include :

• How different the tumor cells are from normal kidney cells.
• The stage of the cancer. This is the extent of the cancer in the body, determined by the extent of the tumor, invasion of other organs and metastases (spread of tumor to distant sites).
• The type and size of the tumor.
• The age of the child.
• Whether the tumor can be completely removed in surgery.
• Whether the cancer has just been diagnosed or has recurred (come back).
• Whether there are any abnormal chromosomes or genes.
• Whether the patient is treated by pediatric experts with experience in treating patients with Wilms’ tumor.

Further reading:
http://www.nlm.nih.gov/medlineplus/wilmstumor.html – provides links to information on Wilms tumor from the American Cancer Society and the National Institute of Health