Migrating Staghorn Calculus Secondary to a Renocolic Fistula: A Case Report and Review of the Literature.

Background: Staghorn calculi are large renal stones which occupy most of the renal pelvis and are commonly associated with chronic or recurrent upper urinary tract infections (rUTIs). They often require more aggressive management, such as percutaneous nephrolithotomy (PCNL) or nephrectomy, although conservative management may be a safer option for select patients, particularly those with significant comorbidities. The presence of chronic stones or recurrent infections in the kidney increases the risk of complications, including fistula and abscess formation. Case Presentation: A 68-year-old female presented to the emergency department with signs of urosepsis. Computed tomography (CT) imaging revealed a left-sided staghorn calculus with concurrent smaller renal calculi. Due to worsening kidney function during hospitalization, repeat imaging was done, which revealed a staghorn calculus in the rectum. The staghorn calculus migrated to the colon through a renocolic fistula, and the patient subsequently passed the large staghorn through the rectum spontaneously. Conservative management was pursued due to her high surgical risk. Several months after discharge, she represented with signs of infection, and a large left-sided psoas abscess was identified. Conclusion: As the patient had severe comorbidities, our options to manage the staghorn calculi were very limited. She responded well to conservative management initially, but then was found to have another complication associated with the staghorn. It is acceptable to manage uncomplicated staghorn calculi conservatively in a small selection of patients, who are not good candidates for more invasive procedures, though in healthier and younger people, aggressive management is recommended to prevent further complications or deterioration. It is crucial to highlight the importance of early recognition and individualized treatment for renocolic fistulas, as timely intervention can significantly improve patient outcomes.