Retroperitoneal fibrosis and bilateral hydronephrosis secondary to gastric cancer: A case report

Rationale: Retroperitoneal fibrosis (RPF) is a rare fibroinflammatory condition that can lead to ureteral obstruction and renal dysfunction. While most cases are idiopathic, secondary causes including malignancies should be considered. RPF secondary to gastric cancer is extremely rare, with only a few cases reported. Patient concerns: A 56-year-old woman presented with generalized edema, decreased urine output, and nausea that had begun 7 days prior. Laboratory tests revealed acute kidney injury, and imaging showed bilateral hydronephrosis. Diagnoses: Further evaluation through abdominal-pelvic computed tomography and esophagogastroduodenoscopy revealed a depressed ulcerative gastric lesion. Histopathological examination confirmed poorly differentiated gastric adenocarcinoma. Intraoperative biopsy of retroperitoneal fibrotic tissue showed malignant cell infiltration, confirming RPF secondary to gastric cancer. Interventions: The patient underwent subtotal gastrectomy and bilateral percutaneous nephrostomy for urinary diversion. Antibiotics were administered postoperatively for urinary tract infection. She was discharged with a plan for adjuvant chemotherapy. Outcomes: Urine output and renal function normalized following percutaneous nephrostomy insertion. The patient’s infection resolved with antibiotic therapy, and she remained clinically stable at discharge. Lessons: This case illustrates a rare presentation of gastric cancer manifesting as malignancy-associated RPF. Clinicians should maintain a high index of suspicion for occult malignancy in patients with bilateral ureteral obstruction of unclear cause. Early imaging and histological evaluation are critical for diagnosis and appropriate management.