Types of Stones
Struvite

Struvite stones, commonly called infectious stones, are composed of magnesium, ammonium and phosphate. Struvite stones represent 7-31% of all renal calculi. Struvite stones are produced from urease-containing bacteria (i.e., Proteus, Klebsiella). Multimodal therapy includes percutaneous nephrolithotomy possibly followed by extracorporeal lithotripsy and chemolysis. For very large stones, anatrophic nephrolithotomy is performed. Medical management with antimicrobial therapy, chemolysis (hemiacidrin), urease inhibition (acetohydroxamic acid) and urinary acidification helps to prevent stone recurrence.

Struvite or infection stones account for 15% - 20% of all renal calculi. They occur more commonly in females with a female to male ratio of 2:1. The stones are composed of magnesium ammonium phosphate (struvite) and carbonate apatite (calcium carbonate and calcium phosphate) and often obtain staghorn proportions. These stones are always associated with urinary tract infections with urease splitting bacteria (Proteus, Klebsiella, Pseudomonas and less commonly, Staphylococcus aureus).

The indications for stone removal include urinary tract infection, progressive renal damage, urinary tract obstruction and persistent pain. Medical therapy is only an adjunctive roll in the management of these patients and is directed primarily at controlling the urinary tract infection prior to, during, and subsequent to surgical removal. Administration of Urease inhibitors (acetohydroxamic acid) may be useful in reducing the incidence of stone recurrence in patients with intractable urinary infections.

Suggested readings
Segura JW. Staghorn calculi. Urol Clin North Am 1997, 24:1:71-80.

Meretyk S, Gofrit ON, Gafni O, Pode D, Shapiro A, Verstandig A, Sasson T, Katz G, Landau EH. Complete staghorn calculi: Random prospective comparison between extracorporeal shock wave lithotripsy monotherapy and combined with percutaneous nephrostolithotomy. J Urol 1997, 157:3:780-786.

Wang LP, Wong HY, Griffith DP. Treatment options in struvite stones. Urol Clin North Am 1997, 24:1:149-162.

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