Struvite stones

Noncalcareous stones occur most commonly in the presence of urea-splitting organisms which create conditions in which magnesium ammonium phosphate (struvite) stones form. Urate stones form when urine is vmusually acid (pH < 5.5). 

Wang LP, Wong HY, Griffith DP. Treatment options in struvite stones. Urol Clin North Am 1997 24(l) 149-62. 

Joshi HB, Kumar PV, Timoney AG. Citric acid (solution R) irrigation in the treatment of refractory infection (struvite) stone disease is it useful Eur Urol 2001 39(5) 586-90. 

Another frequent phosphatic stone — found for 90 of 600 cases — was a mixture of apatite and struvite, while those containing brushite comprised only about 1.6% (Prien and Frondel, 1947). These apatite-struvite mixtures are said to occur usually in infected alkaline urine, and occur with all ratios of apatite to struvite. Stones of this type have been equated with the activity of E. coli, vvhich can produce ammonia — as also does Proteus mirabilis. Both of these organisms are pathogenic when present in the urinary tract. 

Struvite stones (also called triple phosphate or infection stones) are composed of magnesium ammonium phosphate hexahydrate. The formation of such stones requires urinary tract infection with urea splitting organisms and such stones are therefore more common in females and in certain patient populations (e.g, paraplegics), The risk of progression to CKD appears higher in patients who develop infection stones than in other forms of stone disease. 

Comparing 02 -microglobulin excretion in patients with calcium oxalate, uric acid, and struvite stones it can be seen that the patients with struvite stones have the highest values (fig 2). This can be taken as a result from a pyelonephritic tubular alteration. 

A number of known and potential urease inhibitors were screened as candidates fiir treating cellulose-based absorbent systems. Acetohydroxamk acid (AHA) was one die examples, This coDqmund is used clinically to dissolve struvite stones [5], An AHA molecule has a shape which fits very well to tlw active site of urease, therefore it can compete effectively against urea to form a stable complex with file em me. This inhibitor is watm -soluble and can be easily ai lied to a fiber-based substrate. Fw this purpose we chose Vizcnb 3905, a Buckeye-m airlaid nonwoven. The latter matoial contained SAP particles, had a basis weight of 2S0gfei and a web density of0.094 g/ca. ... 

Struvite stones composed of magnesium ammonium phosphate are of low radiopacity in their pure form. This material frequently forms a complex with calcium phosphate, which provides increased radiopacity and may produce a laminated radiographic appearance in the staghorn stone. 

Struvite stones are mainly seen in boys under the age of 5 years (Fig. 20.8). In one-third of patients there is a primary anomaly of the urinary tract, most often a ureteropelvic junction obstruction... 

In renal stones, apatite (Ca5(P04)3 OH, 1/2 C03) with a hexagonal shape has been observed however, this mineral is difficult to identify because of its cryptocrystalline appearance. Struvite (MgNH4P04 6 H20) orthorhombic, newberyte (MgHP04 3 H20) orthorhombic, whit-ockite (Ca3(P04)2) hexagonal, and also brushite have been reported to occur in renal stones82. ... 

In patients with a history of struvite kidney stones, consumption of 2 pints of cranberry juice daily for 9 years... 

Rat Studies. The computer calculations were tested by inducing the experimental formation of brushite/struvite bladder stones in rats. The inhibition of stone formation by the feeding of 5000... 

Approximately 10% of the human population (with regional differences indicating both genetic and environmental factors [33]) is affected by the formation of stones or calculi in the urinary tract. Urolithiasis is not only a painful condition, but also causes annual costs to the health system in the order of billions of dollars in the USA alone [34, 35]. Based on their composition, structure and location in the urinary tract, renal stones have been classified into 11 groups and their formation mechanisms have been discussed together with alterations in urinary parameters and metabolic risk factors for renal lithiasis [35]. Approximately 70% of these stones contain calcium oxalate monohydrate (COM) and dihydrate as major components, while other calculi are composed of ammonium magnesium phosphate (struvite), calcium phosphates (hydroxyapatite and brushite), uric acid and urates, cystine and xanthine. An accurate knowledge of the solubilities of these substances is necessary to understand the cause of renal or bladder calculi formation and find ways towards its prevention and treatment [36]. 

Fig. 20.8. A 5-month-old boy with recurrent urinary infection (Proteus mirabilis). Sonogram of the right kidney showing multiple stones (struvite 70%, carbonate-apatite 30%)...

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