Penetrating peptic ulcers often lead to severe complications. The development of uretero-enteric fistulas is rare and can be challenging to diagnose and treat. Here, we present the case of a 41-year-old patient who previously underwent gastrojejunostomy for superior mesenteric artery syndrome and developed a peptic jejunal ulcer, leading to a uretero-jejunal fistula and finally causing acute pyelonephritis. The patient was managed with a multidisciplinary approach including medical therapy and endoscopic and radiologic interventions.