Non-urothelial carcinoma accounts for <5% of urinary bladder tumors, and primary bladder adenocarcinoma accounts for 0.5–2%, but the variant primary signet-ring cell is extremely rare. We present a rare case of a synchronous of dual primary malignancy from a rare variant of urinary bladder adenocarcinoma (signet-ring cell) with indolent prostate adenocarcinoma in a 61-year-old male. The patient presented with a rapidly progressive renal failure due to a non-dilated obstructive uropathy that formed a dilemma in the course of diagnosiswhich was relieved transiently by a high-dose methylprednisolone. Primary signet-ring cell adenocarcinoma of the urinary bladder is a very rare malignancy manifests as a high-grade, high-stage lesion, which takes a vague course and has a poor prognosis. It is often managed with radical cystectomy due to its aggressive nature.
Key messages Non-dilated urinary obstruction should be considered as a possible rare cause of rapidly progressive renal failure, and often, it is related to an indolent and progressive urinary malignancy.