Acute Acalculous Cholecystitis Secondary to Acute Pyelonephritis in a Young Woman: A Diagnostic Pitfall in the Emergency Department.

Acute acalculous cholecystitis (AAC) is typically observed in critically ill patients, making its diagnosis in otherwise healthy individuals a significant clinical challenge. We present a rare case of a 29-year-old woman initially suspected of having AAC based on clinical assessment and ultrasonography. While initial imaging fulfilled the sonographic criteria for acalculous cholecystitis, subsequent contrast-enhanced computed tomography revealed right-sided acute pyelonephritis with secondary reactive gallbladder changes. The patient was successfully managed conservatively with intravenous followed by oral antibiotics, resulting in complete recovery without surgical intervention. This case underscores the potential for renal pathology to mimic primary biliary disease and highlights the critical role of advanced imaging in preventing unnecessary invasive procedures in the emergency department.