The “infected stone” is a urologic emergency. Patients with nephrolithiasis causing obstruction and fever / concern for concomitant urinary tract infection you should obtain urine and blood cultures, and initiate antibiotic therapy. Other useful labs include CBC with differential and a renal profile (chem-7). Empiric antibiotic therapy is based on local resistance patterns and whether or not the patient has had a previous UTI. Proteus, Providencia, Klebsiella, Pseudomonas, and enterococci are commonly seen bacteria. Ceftriaxone is a good first choice for many patients, but you may need broader agents like Piperacllin/Tazobactam. Boys are more likely to have obstructive uropathy; 80% of stones + UTI are male.

Urosepsis is a rare, but life treating complication of obstructing kidney stones. Urology will perform emergent drainage of the affected kidney by placing either a ureteral stent of percutaneous nephrostomy tube – this lowers the intrarenal pelvic pressure due to stone-induced obstruction. Staged removal of the calculi follows.

Non-obstructing stones can also be associated with UTIs that are difficult to clear. Start antibiotics empirically and consider calling Urology in the ED or arranging follow up in the next day or two. The threshold to remove the stone in the face of a UTI is very low.

References

Barreto L, Jung JH, Abdelrahim A, et al. Medical and surgical interventions for the treatment of urinary stones in children. Cochrane Database Syst Rev 2018; 6:CD010784.

Yoshimura K, Utsunomiya N, Ichioka K, Ueda N, Matsui Y, Terai A. Emergency drainage for urosepsis associated with upper urinary tract calculi. J Urol. 2005 Feb;173(2):458-62. doi: 10.1097/01.ju.0000150512.40102.bb. PMID: 15643207.