Purpose or Case Report: Wilms tumor is a common malignant renal neoplasm in children and accounts for the vast majority of renal tumors in children. Modern treatment regimens have increased overall survival for Wilms tumor to over 90%[1]. Despite this, 10-15% of patients with favorable histology and up to 50% with anaplastic histology will experience primary progression or recurrence. The most common site of recurrence is to the lungs and the liver[2]. Peritoneal disease and recurrence has been described[3-4].
We present an interesting case of a 13-year-old female with extensive peritoneal recurrence of Wilms tumor. The patient initially presented at the age of 12 with a 3-day history of abdominal pain. CT revealed a 13 cm right renal mass with no other lesions in the chest, abdomen, or pelvis. She underwent right nephrectomy, during which she was upstaged to stage 3 when tumor rupture occured. Histology was favorable. She completed chemo and radiotherapy. CT CAP at 6 months follow-up showed no recurrent disease. Approximately 7 months later or 13 months after initial diagnosis the patient presented with constipation and abdominal pain. Initial non-contrast CT demonstrated filling of the abdomen and pelvis with a high density material(Figure 1). Given the patient’s history and concern about some nodularity to the density, MRI was performed and demonstrated extensive heterogeneous mass-like peritoneal disease filling the abdomen and pelvis(Figure 2). There were additional areas of peritoneal caking and thickening(Figure 3). Ultrasound guided biopsy was performed and the pathology was identical to that of the excised Wilms.
While unusual recurrent Wilms tumor should be included in the differetial diagnosis of massive intraperitoneal neoplasia

1. Metzger, M. L. (2005). Current Therapy for Wilms Tumor. The Oncologist, 10(10), 815-826. doi:10.1634/theoncologist.10-10-815
2. Dome, J. S., Rodriguez-Galindo, C., Spunt, S. L., & Santana, V. M. (2014). Pediatric Solid Tumors. In Abeloff's Clinical Oncology (5th ed.). Philadelphia: Churchill Livingstone/Elsevier.
3. Brisse, H. J., Schleiermacher, G., Sarnacki, S., Helfre, S., Philippe-Chomette, P., Boccon-Gibod, L., . . . Neuenschwander, S. (2008). Preoperative Wilms tumor rupture. Cancer, 113(1), 202-213. doi:10.1002/cncr.23535
4.Slasky, B. S., Bar-Ziv, J., Freeman, A. I., & Peylan-Ramu, N. (1997). CT appearances of involvement of the peritoneum, mesentery and omentum in Wilms tumor. Pediatric Radiology, 27(1), 14-17. doi:10.1007/s002470050053
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