Spontaneous Radiological Disappearance of a Large Staghorn Calculus in an Atrophic Kidney With One Percent Function

Staghorn calculi are usually managed with active intervention to prevent progressive renal damage, and spontaneous resolution is exceedingly rare. We report the complete radiological resolution of a large staghorn calculus in an atrophic kidney with negligible residual function. An 83-year-old man was found incidentally to have a 4.3 cm right staghorn calculus in an atrophic kidney with only one percent function on mercaptoacetyltriglycine (MAG3) renography. As the patient was asymptomatic, had minimal renal function, and significant comorbidities, conservative management with watchful waiting was chosen. Follow-up imaging one year later demonstrated complete disappearance of the calculus on plain radiography and non-contrast computed tomography, with no evidence of fragmentation, passage, or extrusion, while the contralateral kidney remained unchanged. Although rare, spontaneous resolution of staghorn calculi has been described previously, particularly in poorly functioning kidneys, and potential mechanisms include dissolution of struvite or carbonate-apatite stones in a sterile or treated urinary tract and progressive renal atrophy reducing stone viability. This case adds to the limited evidence suggesting that conservative management may be appropriate in carefully selected patients with staghorn calculi in non-functioning or minimally functioning kidneys, where radiological surveillance may be sufficient and routine active intervention may not always be necessary.