Solid Renal and Juxtarenal Lesions

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The majority of solid renal or juxtarenal lesions present either prenatally or as a palpable abdominal mass in childhood. The most common renal tumor in the neonate remains congenital mesoblastic nephroma (CMN). More than 80 % are diagnosed in the 1st month of life and essentially all are identified by 1 year of age (Geller et al. 1997). CMN usually presents as an asymptomatic abdominal mass; however, prenatal US has also demonstrated polyhydramnios, fetal hydrops, and premature delivery in affected fetuses (Lowe et al. 2000). CMN is believed to consist of a proliferation in meta-nephric mesenchyme and appears leiomyomatous on gross pathological analysis. Cross-sectional imaging is mandatory and demonstrates a solid intrarenal mass that may contain cystic, hemorrhagic, and necrotic regions (Fig. 8.9). Although benign in greater than 95% of cases, complete surgical excision is necessary as local recurrence, and even metastases, have been reported (Heidelberger et al. 1993). Significant hemorrhage or spontaneous tumor rupture may mandate urgent ne-phrectomy (Matsumura et al. 1993; Arensman and Bel-man 1980).

Neuroblastoma is the most common solid extracra-nial malignancy in childhood. It arises from primitive

sympathetic nerve cells and may occur anywhere sympathetic tissue is found. However, over 75% are intraabdominal, with 65 % of these arising from the adrenal glands (Chandler and Gauderer 2004). Neuroblas-toma is an unusual tumor characterized by its variability in presentation. Well-advanced lesions may regress spontaneously, whereas others may progress despite aggressive therapy.

Because of their biologically active nature, neuro-blastomas may secrete a significant amount of cate-cholamines and hence, patients may present with palpitations, tachycardia, hypertension, flushing, and sweating. Intractable diarrhea may result from the secretion of vasoactive intestinal peptide (VIP) (Gesundheit et al. 2004). Another unusual symptom is cerebel-lar ataxia and opsomyoclonus (dancing feet, dancing eyes; myoclonic encephalopathy of infants). This syndrome is rare, of unknown etiology, and is usually associated with thoracic lesions (Bousvaros et al. 1986). Malaise, pain, and anemia may be the presenting complaint in up to 60% secondary to metastatic disease.

Physical examination classically reveals a firm, fixed lesion that is nodular to palpation and may cross the midline (Fig. 8.10). Children with neuroblastoma typically look unwell, are pale and cachectic compared to their rather robust appearing counterparts with Wilms tumor. Other differentiating features are summarized in Table 8.3. Investigations include cross-sectional imaging, complete blood work, serum and urine catechol-amine levels including vanillylmandelic acid (VMA) and metanephrines, and bone marrow cytopathology. Surgical resection is the primary treatment for those with localized disease. Adjuvant chemotherapy and radiotherapy is added depending on disease stage and patient age. Overall, the prognosis is good; however, those with advanced disease tend to do poorly despite aggressive multimodal therapy (Haase et al. 1999).

Wilms tumor is the most common pediatric malignancy of renal origin, accounting for nearly 90 % of renal masses (Lowe et al. 2000). It typically presents between the 3rd and 4th year of life and over 80 % are diag-

Table 8.3. Characteristics of Wilms tumor and neuroblastoma

Wilms Tumor Neuroblastoma

Typical age at 3 - 4 years of age presentation

Clinical Robust, healthy appearance

50 % less than 1 year

Pale, anemic, cachectic, signs/symptoms of metastatic disease

Physical Smooth mass does Nodular, craggy examination not cross midline mass, crosses midline

Fig. 8.9. CT of a large right palpable renal mass found in a newborn female. Nephrectomy was carried out and the tumor was identified as congenital mesoblastic nephroma (CMN)

Imaging Intrarenal, com presses adjacent parenchyma, stippled calcification in 50%

Extrarenal, displaces kidney

Palpable Epigastric Mass
Fig. 8.10. MRI of a large right adrenal neuroblastoma found in a 2-year-old boy who presented with malaise, lethargy, and a large palpable abdominal mass
Focal Nodular Hyperplasia
Fig. 8.11. CT of a large right intrarenal mass found to be Wilms tumor on pathological analysis in a 3-year-old female. Note the compression and distortion ofthe surrounding normal parenchyma by the tumor

nosed prior to 5 years of age (Lonergan et al. 1998). Synchronous or metachronous bilaterality occurs in 4% -13 % (Lonergan et al. 1998). A number of associated conditions have been identified, including cryptor-chidism, hemihypertrophy, hypospadias, and sporadic aniridia (White and Grossman 1991). Other congenital disorders have also been implicated such as WAGR syndrome, Beckwith-Wiedemann syndrome, Denys-Drash syndrome, and neurofibromatosis (Bove 1999). These syndromes primarily result in somatic overgrowth and it is believed that abnormalities at two genetic loci, WT1 at 11p13 and WT2 at 11p15, are responsible for Wilms tumor development in these syndromes (Coppes et al. 1994; Ping et al. 1989).

Wilms tumor most commonly initially manifests as an asymptomatic abdominal mass; however, associated coincidental trauma is present in up to 10% (Lonergan et al. 1998). Other signs and symptoms include abdominal pain, gross hematuria and fever. Tumor rupture causing severe abdominal pain and hemodynamic instability secondary to intraperitoneal hemorrhage has been reported in up to 3% (Godzinski et al. 2001). Atypical presentations such as varicocele, hepatomegaly, ascites, and congestive heart failure can occur in 10 % secondary to renal vein and inferior vena cava tumor extension (Ritchey et al. 1988). Acquired von Willebrand disease has been identified in 8 % of cases (Coppes et al. 1992).

Appropriate metastatic evaluation includes complete blood work as well as cross-sectional imaging including the thorax. CT or MRI usually reveals a large intrarenal mass with a pseudocapsule and distortion of the renal parenchyma and collecting system (Fig. 8.11). The majority of children with unilateral disease can safely undergo radical nephrectomy; subsequent adjuvant therapy is based on specific tumor stage and subtype. Bilaterality or tumor in a solitary kidney is initially treated by needle biopsy and neoadjuvant chemotherapy (Fig. 8.12 a, b). This usually results in signifi-

Vincristine Syringe
Fig. 8.12. a CT demonstrating multiple bilateral renal masses found on percutaneous needle biopsy to be Wilms tumor. b Follow-up CT in same patient after three courses of actinomycin-, vincristine-, and doxorubicin-based chemotherapy
Wilms Tumor And Child With Nephrectomy
Fig. 8.13. a Intraoperative photograph of a large central Wilms tumor in a 4-year-old girl with a solitary right kidney. b Intraoperative photograph in the same patient following tumor resection prior to reconstruction of the renal parenchyma. Note the tumor bed with Tissel gel to aid in hemostasis
Wilms Tumor Urine Analysis

Fig. 8.14. CT of a very large left renal mass in a 9-year-old boy. Fig. 8.15. US of a newborn femalewhopresentedwith gross he-The patient underwent radical nephrectomy; pathological maturia showing left RVT. Note the hyperechoic clot in the re-analysis demonstrated clear cell renal cell carcinoma (RCC) nal vein located in the renal sinus

Fig. 8.14. CT of a very large left renal mass in a 9-year-old boy. Fig. 8.15. US of a newborn femalewhopresentedwith gross he-The patient underwent radical nephrectomy; pathological maturia showing left RVT. Note the hyperechoic clot in the re-analysis demonstrated clear cell renal cell carcinoma (RCC) nal vein located in the renal sinus cant tumor shrinkage, enabling a subsequent nephron-sparing approach in the majority (Fig. 8.13 a, b).

Renal cell carcinoma (RCC) is rare in the pediatric population, accounting for only 7 % of all primary renal tumors in the first 2 decades of life (Lack et al. 1985). It is associated with von Hippel-Lindau syndrome and this disease must be ruled-out in patients presenting with RCC in the pediatric age group. Children with RCC tend to present later in life and are more apt to manifest signs and symptoms of disease. At the Hospital for Sick Children in Toronto, Canada, review of 15 patients treated over a 25-year period revealed the mean age at presentation to be over 7 years and that nearly 75 % presented with signs or symptoms of disease such as gross hematuria, abdominal pain, or polycythemia. CT demonstrates a typical enhancing renal mass (Fig. 8.14). Treatment is similar to adults, with radical extirpative surgery providing the best outcomes.

Renal vein thrombosis is rarely responsible for a palpable abdominal mass in the neonate. Venous throm bosis leads to vascular congestion and enlargement of the kidney and is marked clinically by hematuria, pro-teinuria, hypertension, and consumptive thrombocy-topenia. It is associated with dehydration, sepsis, maternal diabetes, birth asphyxia, and coagulopathies (Lowe et al. 2000). Doppler US is the best imaging modality, as it can demonstrate renal vein and vena cava extension (Fig. 8.15). Unilateral disease is best treated conservatively, with rehydration and correction of predisposing factors; however, bilateral thrombosis requires more aggressive treatment such as systemic anticoagulation or thrombolysis and is associated with a worse prognosis (Nuss et al. 1994).

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