Incomplete sagittal septum of the bladder with cystolithiasis

INTRODUCTION: Incomplete sagittal septum of the urinary bladder is an extremely rare congenital anomaly and one of the variations in bladder duplication. Herein, we report a case of incomplete sagittal septum of the bladder with cystolithiasis. CASE PRESENTATION: A 20‐year‐old man was referred to our department for examination and treatment of symptomatic cystolithiasis and a suspected giant ureterocele on the left side. Cystoscopy and urography performed under general anesthesia revealed anatomical structures suggestive of the sagittal septum of the bladder. Subsequently, transurethral septostomy and cystolithotripsy were performed. The detrusor muscle was microscopically identified, leading to the diagnosis of an incomplete sagittal septum of the bladder. CONCLUSION: Although extremely rare, an incomplete sagittal septum of the bladder may be difficult to differentiate from a ureterocele, and should be considered when a large cystic lesion is found in the bladder.