Understand Childhood Cancers and Blood Disorders
The most common malignant tumor of the kidneys in children is Wilms Tumor. This is usually a cancer of young children, peaking in children who are 2-6 years of age, and very rare after the age of 10.
Most commonly the tumor presents as a mass that is felt in the child's abdomen that causes no symptoms. It is often discovered when a young child is being bathed and the parent feels a lump in the belly. At times the tumor may cause bloody urine, although this is often microscopic bleeding and would not be noticed. If the tumor ruptures, there is often complaints of abdominal pain, fever, and vomiting. At other times, the mass is very large and puts pressure on other adjacent structures - for example, it may push against the stomach, causing a child to quickly feel full when eating - it may even cause vomiting with enough pressure on the stomach.
There are a number of associated findings in some children with Wilms Tumor. A rare condition called aniridia - meaning absence of an iris - has a strong association with Wilms Tumors. Another unusual condition called hemihypertrophy - where one side of the child's body is larger and longer than the other - is also a, associated finding. Children born with the Beckwith-Wiedemann Syndrome - a disorder characterized by gigantism and a large tongue - or the Drash Syndrome have a high risk of developing Wilms tumors. Another situation that may be a forerunner to Wilms tumor is nephroblastomatosis, a situation where primitive kidney tissue that resembles fetal kidney tissue is present, and may ultimately progress into a true Wilms Tumor. In the presence of any of these conditions, surveillance sonograms would be in order for at least several years to diagnose a Wilms tumor at the earliest possible time.
Etiologies: Wilms tumors are usually sporadic events, with no predilection for any particular ethnic group. They are rarely inherited, but numerous parent/child cases have been reported. While parental occupation, particularly those who work with hydrocarbons or lead, were thought at one time to have a link with children developing Wilms Tumor, further studies showed no association. However, there have now been two genes (dubbed WT1 and WT2) identified on chromosome 11p that are involved with the development of Wilms Tumor in several patients.
Children with Wilms tumor overall have a very good outlook with a few exceptions. Children with the common pathologic pattern have an excellent outlook, even when distant metastatic disease is present on initial presentation. Most children will first undergo surgical removal of the kidney with the tumor, with careful attention to remove the mass without rupturing its outer wall. The disease is very sensitive to chemotherapy and radiation, with treatment depending on initial staging. Children with early stage disease are treated with a short course of chemotherapy only, with cure rates in excess of 95%. Those with evidence of spread outside of the kidney will be treated with more intense chemotherapy and low dose radiation, again with an excellent outcome. The outlook for children with clear cell or anaplastic variants of Wilms Tumor has not been as good, and the optimum treatment is still being investigated.
Two special presentations bear comment. Between 5 and 10% of Wilms tumors are bilateral, affecting both kidneys. In this situation, after just initial biopsy of the mass to confirm the pathology, chemotherapy will be used initially to shrink the disease. Following another evaluation to determine the areas and extent of residual disease, the patient will then undergo surgery to have removal of the portions of the kidney still containing tumor, and to render the child as disease-free as possible. This will then be followed by additional chemotherapy and sometimes with radiation as well.
Another occasional presentation that requires initial treatment with chemotherapy is one when the tumor grows out of the kidney, into the renal vein and into the inferior vena cava, the largest vein in the lower body. The tumor often extends all the way into the chambers of the heart, making a standard surgical approach impossible. In this situation, chemotherapy is used first to attempt to dissolve the tumor within these veins, following which an easier surgical approach can often be undertaken. At times the disease extending into the vena cava does not shrink appreciably, and in this situation, a surgical approach that includes possible cardiac bypass is often necessary to remove the tumor.