Pathophysiology and Management of Infectious Staghorn Calculi

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The American Urological Association Nephrolithiasis Guidelines Panel recently conducted a critical meta-analysis of the existing literature to determine the optimal management for staghorn calculi. This article briefly discusses the pathophysiology of staghorn calculi and, based on the panel's recommendations, examines the alternative medical treatments (eg, chemolysis) and surgical treatments (eg, shock wave lithotripsy, open surgery, ureteroscopy, and percutaneous nephrolithotomy) available for staghorn patients. Considering the various modalities for staghorn disease, percutaneous nephrolithotomy should be the first-line treatment for most patients based on its superior efficacy and low morbidity.

Section snippets

Pathogenesis

Struvite calculi have plagued man since the beginning of civilization, dating back approximately 7000 years ago to the era of the ancient Egyptians [2]. In 387 BC Hippocrates first documented an association between urinary tract infections and urinary stones [3]. Over 2000 years later in 1845, a Swedish geologist named Ulex discovered magnesium ammonium phosphate in bat guano and named the substance “struvite” after his mentor, the Russian diplomat Baron H.C.G. von Struve. Struvite calculi are

Clinical manifestations, diagnosis, and natural history

As previously mentioned, struvite stones may grow rapidly over a period of weeks to months and, if left untreated or inadequately treated, may progress into staghorn calculi. Unlike patients with small calcium stones, infection calculi tend to be insidious and chronic in formation and typically do not present with the acute renal colic frequently seen with an obstructing ureteral stone. Instead, staghorn calculi usually develop in the renal collecting system and remain there until a diagnosis

Treatment

Staghorn calculi are primarily managed surgically with complete stone clearance as the goal of treatment. In selected patients who are otherwise poor surgical candidates, dissolution therapy remains an alternative. Dissolution therapy may also be useful following surgical therapy for treatment of residual fragments. Currently, several surgical treatment options exist for staghorn calculi, including SWL, ureteroscopy, PCNL, open surgery, and combination therapy. Herein the authors describe these

Dissolution therapy

Chemolysis, or dissolution therapy, of struvite stones has been around for over 70 years. In 1932 Keyser attempted dissolution of stones by retrograde infusion [14], and in 1938 Hellstrom dissolved a renal stone using boric acid and permanganate [5]. Subsequently in 1943 Suby and Albright developed Suby's solution, which was later modified to Suby's solution G, consisting of citric acid, magnesium oxide, and sodium carbonate [15]. The addition of magnesium decreased mucosal irritability and

Shock wave lithotripsy

While SWL is the most common treatment for renal calculi, it is not usually used as monotherapy in the treatment of staghorn calculi because of low stone-free rates, which range from 18% to 67% [19], [20], [21], [22], [23]. Additionally, SWL for staghorn calculi may be associated with significant potential morbidity, including steinstrasse, renal colic, sepsis, and perinephric hematoma. However, SWL is the least invasive of the stone treatments and should be considered in combination with other

Prevention

Following primary surgical treatment of staghorn calculi, medical management may be useful in preventing stone recurrence. Strategies include dietary modification and oral therapies that acidify the urine (pH < 7.19), inhibit ammonia production (urease inhibitor), and sterilize the urine.

Cost-effectiveness

In the modern era of health care cost containment, urologists must examine the various treatment options for staghorn calculi from a cost-effectiveness standpoint. Chandhoke [61] developed a cost-effectiveness index to estimate the average cost of rendering one patient stone-free and found that PCNL monotherapy and combination sandwich therapy were each more cost-effective than SWL monotherapy. Taking stone surface area into account, this study suggests more specifically that combination

Summary

Staghorn calculi are large stones that fill the renal pelvis and extend into the majority of the calices. These stones are usually composed of pure struvite or struvite in combination with calcium carbonate apatite. Staghorn stones are strongly associated with urinary tract infection caused by urease-producing bacteria. Untreated staghorn calculi are likely to destroy the kidney and thus an aggressive therapeutic approach is clearly warranted. According to the AUA Nephrolithiasis Guidelines

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