Sacral Meningoceles, ductal ectasia and pseudomeningoceles are all rare spinal defects that occur due to errors in collagen biosynthesis in the setting of Marfan's Syndrome. Meningoceles, which are extradural collections of cerebrospinal fluid, can form large pelvic collections which can compress local structures. In rare cases, this can lead to extrinsic ureteric obstruction, which can result in acute renal failure and urosepsis. We present a case of a 35-year old female with Marfan's syndrome, with one of the largest sacral meningoceles reported in the literature, causing acute ureteric obstruction, requiring urgent surgical intervention. •Meningoceles are rare and are associated with Marfan's syndrome due to errors in collagen biosynthesis.•Management of urinary tract obstruction secondary to external compression from a meningocele requires surgical decompression.•This can be in the form of ureteric stent placement or nephrostomy insertion.•Referral to a spinal surgeon for definitive management should also be undertaken.