Rare case of spontaneous renal calyx rupture due to vesicoureteral junction stone in a horseshoe kidney.

A 50-year-old patient with a prior history of chronic smoking presented to the emergency department with diffuse abdominal pain, primarily localized to the right hypochondrium and epigastric region, along with nausea, but without fever, vomiting, or urinary symptoms. Laboratory tests were largely unremarkable except for isolated hematuria and a mildly elevated CRP. Given the atypical clinical presentation, a 3-phase abdominal CT scan (without contrast, portal, and delayed phases) was conducted, revealing a horseshoe kidney with an obstructing 4 mm stone at the right ureteral meatus.