Retroperitoneal fibrosis (RPF) encasing the ureters, is a rare cause of post-renal acute kidney injury. Fibrosis entraps the ureters, vessels and intestine leading to abdominal pain, ascites, pedal oedema and renal failure. It can be idiopathic or secondary to several factors including drugs or malignant diseases. Index case presented with abdominal distension and abdominal pain followed by oligo-anuria. Investigations revealed autoimmune thyroiditis and bilateral hydro-ureteronephrosis due to extensive RPF. Image guided biopsy from RPF showed metastases from adenocarcinoma, later confirmed to have primary signet-ring cell carcinoma in the stomach by endoscopy and histology. Retroperitoneal fibrosis and renal failure is an uncommon presentation for an occult gastric malignancy and vice versa.