Crossed fused renal ectopia (CFRE) is an uncommon developmental anomaly of the genitourinary system whereby the two kidneys are located on the same side of the body and joined together, while the ureter of the ectopic kidney still enters the bladder in its normal side. CFRE has variable clinical presentations and usually discovered incidentally when patients are investigated for abdominal complaints. Treatment may be conservative when renal function is preserved with no associated symptomatic urological complications. Highlighted here is the unusual presentation of left-to-right CFRE with acute pyelonephritis as an appendix mass in a 19-year-old female.