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Surgery of Pediatric Malignant Abdominal Tumors
WilmsÂ’ Tumor and Neuroblastoma

Wilms' tumor is an embryonal (primitive cells similar to those seen in the embryo) tumor of renal (kidney) origin and the most common kidney tumor in children. Approximately 400 cases occur each year in the United States. It is more common in African American children. Its highest incidence is between 2-5 years of age. It is one of the most curable of all childhood tumors. Associated anomalies are common. A multimodality approach utilizing surgery, radiation, and chemotherapy are routinely used in treatment.

Anatomy and Physiology

  • The kidneys are a pair of bean shaped reddish-brown organs that lie on either side of the spinal column and just below the diaphragm. They are about 5 inches (12.5 cm.) long and 3 inches (7.5 cm.) wide (Figure 1)
  • On the medial (facing the spine) border the kidney is notched at the hilus, the point where the major artery to the kidney enters and vein leaves
  • The ureter also leaves from the hilus
  • The kidney is made up of over a million renal tubules (nephrons). All the nephrons together form the cortex . The nephrons filter the blood of waste products that pass into the urine
  • The urine passes from the nephrons into collecting tubes called calyxes and then into the renal pelvis (the dilated upper portion of the ureter) and into the ureter, which conducts the urine into the urinary bladder
    1. The wall of the renal pelvis and ureter are composed three layers. The inner layer called the mucosa is lined with cells called transitional cells
    2. The middle layer is composed of muscle
    3. The outer layer is composed of fibrous tissue and is called the adventitia
  • Two kidneys are not necessary for survival. In fact, less than one kidney is all that is necessary
  • On the upper surface of each kidney lies the adrenal gland, a small pyramid shaped tissue that produces steroid hormones and adrenaline
  • A capsule of thin tissue encloses each kidney
  • The renal fascia (Gerota's fascia) is a membrane layer that encloses the kidney and adrenal gland. It is separated from the capsule of the kidney by the perinephric space, which contains fat
Figure 1 - Anatomy of the kidney. The upper portion of the kidney is cut away to expose the cortex, calyxes and renal pelvis. The renal artery and ureter enter and the renal vein leaves the kidney at the hilus. The adrenal gland rests on the upper pole of the kidney. © N. Gordon

Pathology

  • These tumors often have more than one tissue present. Muscle, cartilage and fatty tissue may be present In addition to the nephrogenic (kidney) tissue
  • These tumors are large and bulky that invade surrounding tissues and involve local lymph nodes and blood vessels
  • They have a rapid growth pattern
  • Staging is as follows::
    1. Stage I - the tumor is limited to the kidney and completely excised
    2. Stage II - the tumor extends beyond the kidney but is able to be completely removed. The capsule of the kidney may be invaded and the tissues surrounding the kidney may be involved
    3. Stage III - Tumor confined to the abdomen and blood vessels not involved. Includes tumor rupture (or biopsy) or implants of tumor in the peritoneum (lining of the abdomen. Lymph nodes are involved.
    4. Stage IV -Metastasizes (spreads) to distant organs (lung, distant lymph nodes, brain)
    5. Stage V - Both kidneys involved

History and Exam

  • These tumors usually present as a bulky abdominal mass felt by a parent or pediatrician
  • Blood may be present in the urine
  • Hypertension (elevated blood pressure) may be present
  • A large upper abdominal mass is readily felt

Tests

  • Several tests are used to diagnosis and stage the tumor
  • Intravenous Urography (also called Intravenous Pyelogram or IVP). An iodine containing X-ray 'dye' that is injected into a vein (intravenous contrast) is removed by the kidney. The dye accumulates in the calyxes, renal pelvis, ureter and urinary bladder and outlines any abnormality in these areas
  • Abdominal Ultrasound. The transducer (sound producer and receiver) is placed over the kidney and a picture of the kidney and any abnormality is produced on a monitor screen
  • Computerized Tomography (CT scan). The combination of an X-ray beam and computer produces a picture of the kidney and any tumor. It can readily tell the difference between a kidney tumor and a benign kidney cyst. Accuracy of determining between benign and malignant tumors is improved by giving intravenous contrast before the scan
  • Magnetic Resonance Imaging (MRI). The combination of a large magnet, radiofrequency waves and computer produce a picture of the kidney and any tumor. It is the best non invasive method of demonstrating blood vessels in and about the kidney
  • Additional imaging may be done to identify metastatic disease before surgery
    1. Liver scan - radioactive isotope study to evaluate liver for metastatic disease
    2. Bone Scan - radioactive isotope study to evaluate bone for metastatic disease
    3. Chest x-ray - to evaluate the lung for metastatic disease
  • Before surgery the function of the liver and kidney are evaluated as well as the ability of blood to clot. Hemoglobin level in the blood is determined

Indications for Surgery

  • Surgery provides the best chance for cure
  • Advanced cases may be considered for chemotherapy before surgery

Surgery

  • Surgery is performed under general anesthesia with extensive monitoring in a warmed operating room
  • Initially the entire abdominal cavity is examined to identify all areas of involvement and to determine how much tissue needs to be removed. This is followed by a radical nephrectomy. This is the removal of the whole kidney from outside of the renal fascia including the fatty tissue around the kidney, attached adrenal gland and lymph nodes. This is the most common surgery performed for cancer of the kidney
    1. The surgery is carried out through either a bilateral subcostal or thoracoabdominal incision (Figure 2A). Usually the subcostal incision is used. The thoracoabdominal incision is preferred when the tumor is large and at the upper pole of the kidney
    2. After opening the abdomen, the colon is moved to expose the kidney (Figure 2B)
    3. Removal of the kidney begins with control of the renal artery and vein by tying these vessels with suture (Figure 2C)
    4. The kidney is then dissected from the surrounding tissues from outside of the renal fascia
    5. The ureter is then tied off and divided to allow removal of the kidney and adrenal gland (Figure 2D)
    6. The lymph nodes are then removed from the diaphragm to where the aorta (main artery in the body) divides into the arteries to the legs (Figure 2E)
    7. After removal, the incision is closed with sutures
Figure 2a - Surgical removal of the right kidney. Position of the bilateral subcostal and thoracoabdominal incisions. © N. Gordon Figure 2b - The colon is moved to expose the kidney. Note the position of the aorta, inferior vena cava and lymph nodes.© N. Gordon
Figure 2c - The renal blood vessels are dissected free and tied off and cut. © N. Gordon Figure 2d - After the renal fascia and kidney are freed up, the ureter is tied off and cut to remove the kidney. © N. Gordon
 
Figure 2e - The lymph nodes are then removed from the level of the diaphragm to the end of the aorta. © N. Gordon

Complications

  • The complications associated with any major operation can occur with a radical nephrectomy
  • Excessive bleeding is more important in the child because of the child's smaller amount of circulating blood
  • Injury to liver or spleen
  • Respiratory distress
  • Hypothermia (low body temperature)
  • Low urine output
  • Infection
  • Bowel obstruction

Post Operative Care

  • The child is cared for in a Pediatric Intensive Care Unit
  • The child may require ventilator support
  • Temperature and urine output are monitored
  • Intravenous fluids are given until the child can tolerate food
  • A tube is placed through the nose into the stomach (nasogastric tube) to relieve any pressure in the stomach
  • Antibiotics are given as necessary

Care After Discharge

  • These children are all considered for radiation and chemotherapy following recovery from surgery
  • At discharge, they are eating, drinking and eliminating
  • There is long term follow up with the surgeon, radiation oncologist for X-ray therapy, medical oncologist for chemotherapy and the pediatrician

Neuroblastoma

Neuroblastoma is an embryonic (primitive cells similar to those seen in the embryo) tumor that arise anywhere in the sympathetic nervous system (controls automatic bodily functions such as heart rate) from the neck to the pelvis. Seventy percent of these tumors arise from the adrenal medulla (inner most portion of adrenal gland) or lumbar (low back) sympathetic ganglia (a bulge in a nerve containing nerve cells). Treatment requires involvement of the pediatricians, surgeon, radiation oncologist and medical oncologists from the beginning.

Anatomy

  • The adrenal glands are located just above the kidneys (Figures 3 and 4). They are small triangular glands that have a cortex (outer layer of tissue) and inner medulla (central tissue core) (Figure 5). The cortex has three anatomical and functional zones:
    1. Zona glomerulosa- outer zone that secretes aldosterone (involved with regulation of sodium, potassium and chloride in the blood)
    2. Zona fasciculate - intermediate zone that secretes cortisone
    3. Zona reticularis - inner zone that secretes sex hormones
  • The medulla is centrally located and secretes catecholamines (adrenalin like chemicals)
  • The arterial inflow to the adrenal gland comes from:
    1. The inferior phrenic artery above
    2. The aorta medially (towards the midline)
    3. The renal artery below
  • The venous outflow is:
    1. The right central vein that drains into the vena cava
    2. The left central vein that drains into the left renal vein
Figure 3 - Anatomy of the right adrenal gland. The glad sits atop the right kidney and behind the duodenum. © T. Graves Figure 4 - The left adrenal gland lies atop the left kidney, behind the colon and surrounded by the pancreas and spleen.© T. Graves
 
Figure 5 - The three zones of the adrenal gland. © T. Graves

Pathology

  • Neuroblastoma is the most common solid tumor under 1 year of age. Fifty percent of these tumors are seen in children less than 2 years of age
  • Approximately 500 neuroblastomas occur each year in the United States
  • These tumors present as firm, dark red lobulated (made up of lobes) masses
  • They infiltrate (invade) widely into adjacent structures and often grow around major blood vessels
  • They spread early into lymphatics and blood vessels
  • They are made up of primitive sympathetic ganglion cells
  • There is increased breakdown of norepinephrine (a normal adrenal medulla secretion) with increased urine levels of vanillylmandelic acid (VMA). Many patients will have increased urinary levels of homovanillic acid (HVA), a dopamine (chemical that raises blood pressure) breakdown product
  • The following staging is used:
    1. Stage I - Tumor is confined to the adrenal gland of origin and can be totally excised
    2. Stage II - Tumor extends beyond adrenal of origin but does not cross the midline. The regional lymph nodes may be involved
    3. Stage III - Tumor extends beyond the midline to tissues on the opposite side
    4. Stage IV - Metastasizes (goes) to other organs such as the skeleton, other organs, soft tissues and distant lymph nodes
    5. Stage V - Tumor localized to the adrenal gland of origin and not crossing the midline and with metastatic disease confined to liver, subcutaneous (under the skin) tissue and bone marrow (soft center of bone), but without evidence of bone cortex (hard portion of bone) involvement

History and Exam

  • Hypertension (high blood pressure) is present in 25% of cases
  • These children may have anorexia (not feel like eating), weight loss and anemia
  • In most instances, examination may show a firm mass that may be felt in the upper abdomen
  • Metastases to liver, lung, and bone marrow are frequently present at the time of diagnosis

Tests

  • Intravenous Urography (also called Intravenous Pyelogram or IVP). An iodine containing X-ray 'dye' that is injected into a vein (intravenous contrast) is removed by the kidney. The dye accumulates in the calyxes, renal pelvis, ureter and urinary bladder and outlines any abnormality in these areas
  • Computer Axial Tomography (CAT Scan) to assess the mass and involvement of other organs and tissues and to evaluate for liver and pulmonary metastases
  • Magnetic Resonance Imaging (MRI). The combination of a large magnet, radiofrequency waves and computer produce a picture of the tumor
  • Urine studies for VMA and HVA
  • Additional imaging may be done to identify metastatic disease before surgery
    1. Liver scan - radioactive isotope study to evaluate liver for metastatic disease
    2. Bone Scan - radioactive isotope study to evaluate bone for metastatic disease
    3. Chest x-ray - to evaluate the lung for metastatic disease

Indications for Surgery

  • The above tests help identify the group of children who will benefit with initial surgery
  • Survival is not enhanced by initial surgery that would only debulk (remove only part of) the tumor mass
  • If the tumor spreads to other structures or distant metastases are present, these children will often times be considered for radiation and chemotherapy before surgery. This combination preoperatively will often shrink the tumor to allow subsequent surgical removal

Surgery

  • Surgery is performed under general anesthesia with monitoring in a warmed operating room
  • A subcostal or transverse upper abdominal incision is used
  • An examination is performed to assess the extent of the disease
  • Left sided tumor-
    1. The stomach and left colon are moved away to enter the retroperitoneal (behind the peritoneum) space after which the tail of the pancreas and spleen are moved to expose the left kidney and adrenal gland
    2. The left central adrenal vein is tied and cut following which the adrenal gland with tumor is removed
  • Right sided tumor -
    1. The right colon is moved to enter the retroperitoneal space after which the right kidney and adrenal gland are exposed (Figure 6)
    2. The right central adrenal vein is tied and cut (Figure 7)
    3. The adrenal gland is separated from the surrounding tissues and any remaining blood vessels tied and cut following which the adrenal gland with tumor is removed (Figure 8)
  • Lymph nodes are removal on the involved side
  • Liver biopsy is frequently done
  • Any adjacent tissues that are involved are also removed when possible
  • The incision is closed with sutures
Figure 6 - The tumor of the right adrenal gland is exposed.© T. GravesFigure 7 - The right central adrenal vein is tied and cut as well as the feeding arteries. © T. Graves
 
Figure 8 - The adrenal gland containing the neuroblastoma is removed. © T. Graves

Complications

  • The complications associated with any major operation can occur with a radical nephrectomy
  • Excessive bleeding is more important in the child because of the child's smaller amount of circulating blood
  • Injury to liver or spleen
  • Respiratory distress
  • Hypothermia (low body temperature)
  • Low urine output
  • Infection
  • Bowel obstruction

Post Operative Care

  • The child is cared for in a Pediatric Intensive Care Unit
  • The child may require ventilator support
  • Temperature and urine output are monitored
  • Intravenous fluids are given until the child can tolerate food
  • A tube is placed through the nose into the stomach (nasogastric tube) to relieve any pressure in the stomach
  • Antibiotics are given as necessary

Care After Discharge

  • These children are all considered for radiation and chemotherapy following recovery from surgery
  • At discharge, they are eating, drinking and eliminating
  • There is long term follow up with the surgeon, radiation oncologist for X-ray therapy, medical oncologist for chemotherapy and the pediatrician