Ureteroscopic management of lower-pole stones in a pediatric population

PURPOSE: We report our experience with ureteroscopy to treat lower-pole calculi in children. PATIENTS AND METHODS: A retrospective review was conducted of all ureteroscopic procedures for lower-pole stone disease at a pediatric institution from 2000 through 2005. A total of 13 girls and 8 boys with a mean age of 15 years (range 1-20 years) underwent flexible ureteroscopy for lower-pole calculi. The mean stone burden was 12 mm. Stone-free status was defined by postoperative abdominal radiography, CT, or ultrasonography. RESULTS: Ureteral stenting was performed preoperatively in 38% and postoperatively in 71% of the patients. Ureteral-access sheaths were placed in 43%. There were no intraoperative or postoperative complications. With a mean follow-up of 11 months, 76% of the children were stone-free. The success rate for stones <15 mm was 93% v 33% for stones > or =15 mm (P = 0.01). CONCLUSION: Ureteroscopy and laser lithotripsy are safe and effective in children with lower-pole calculi. Ureteroscopy can be considered a primary treatment option for children with lower-pole calculi <15 mm.     

Prospective long-term followup of patients with asymptomatic lower pole caliceal stones

PURPOSE: The intervention time of asymptomatic lower pole calculi remains controversial. In this prospective study we evaluated the natural history and progression rate of asymptomatic lower pole stones. MATERIALS AND METHODS: Patients were followed every 6 months. Computerized tomography in even years, ultrasound scan in odd years after initial visit and abdominal plain films between these visits were evaluated. The largest diameter was measured for each calculus and the cumulative diameter was calculated for cases of multiple stones. Disease progression was defined as pain experienced during followup, stone growth or the need for intervention. RESULTS: A total of 24 patients, 14 male and 10 female, were followed for a mean of 52.3 months (range 24 to 72). Of the 24 patients 3 had bilateral lower pole stones. Mean cumulative stone diameter at presentation was 8.8 mm (range 2.0 to 26.0). Progression in stone size was demonstrated in 9 of 27 renal units (33.3%) with 2 (11.1%) requiring intervention. There was no need for intervention during the first 2 years of followup. Three stones passed spontaneously without any symptoms. Pain developed in 3 patients during followup, and 2 of them passed a stone and responded to the analgesics without further treatment. None of the patients had a pyelonephritic attack during followup. CONCLUSIONS: Our results showed that observation could be considered for patients with asymptomatic lower pole stones. However, patients should be counseled about the 33% disease progression and 11% intervention rates.     

Determination of stone composition by noncontrast spiral computed tomography in the clinical setting

OBJECTIVES: Several investigators have evaluated noncontrast computed tomography (NCCT) in predicting stone composition in vitro. We assessed NCCT in predicting stone composition in patients presenting to our emergency room with flank pain and stone disease. METHODS: One hundred twenty-nine patients presenting to our university hospital with flank pain underwent renal colic protocol NCCT scans at the request of the emergency room physicians. A General Electric, high-speed advantage CT scanner was used at 120 kV, 200 mA, and 1.4:1 pitch, with collimation varying between 3 and 5 mm. Ninety-nine patients with predominantly (greater than 50%) calcium oxalate or uric acid composition after either stone passage or stone removal were identified. Each scan was analyzed by one of two radiologists, who determined the predominant attenuation for each stone. Stones once passed or retrieved were analyzed by Urocor Laboratories. The attenuation and attenuation/size ratio (peak attenuation/size in millimeters) were compared with the results of the stone analysis. RESULTS: Eighty-two calculi predominantly composed of calcium oxalate and 17 calculi predominantly composed of uric acid were identified in 99 patients. The calculi ranged in size from 1 to 28 mm. A significant difference (P = 0.017, unpaired t test) was found between the Hounsfield measurement of uric acid calculi (mean 344 +/- 152 HU) and the Hounsfield measurement of calcium oxalate calculi (mean 652 +/- 490 HU). If only the Hounsfield units from stones 4 mm or larger were compared, the data were even more compelling (P = 0.002). However, using an attenuation/size ratio cutoff of greater than 80, the negative predictive value was 99% that a stone would be predominantly calcium oxalate. CONCLUSIONS: Using peak attenuation measurements and the attenuation/size ratio of urinary calculi from NCCT, we were able to differentiate between uric acid and calcium oxalate stones.     

Stone disease in the Hmong of Minnesota: initial description of a high-risk population

BACKGROUND AND PURPOSE: The Hmong are an ethically distinct refugee population from the highlands of Laos. Metropolitan Minneapolis-St. Paul, Minnesota is home to the largest population of Hmong ( 40,000) outside Asia. A clinical impression that the Hmong have a high rate of uric acid stone disease was evaluated. PATIENTS AND METHODS: A retrospective chart review was performed. All adult Hmong patients seen between January 1, 2000, and December 31, 2001, by a large urology group practice (N = 205) were compared with a similar number of non-Hmong patients (N = 204). RESULTS: Of these patients, 94 Hmong (46%) and 23 non-Hmong (11%) patients had stone disease (P < 0.001). After addition of 75 non-Hmong stone patients to create a suitable comparison group, a total of 86 Hmong and 88 non-Hmong stone patients had complete records. Sex (57% v 60% male) and mean age (47.9 v 47.3 years) were similar. Staghorn calculi were found in 21 Hmong (24%) and 0 non-Hmong patients (P < 0.001). Surgical treatments differed between Hmong and non-Hmong (P = 0.004): SWL (16 v 35), ureteroscopy (24 v 29), percutaneous nephrolithotomy (19 v 7), and nephrectomy (5 v 0). Treatment for staghorn calculi was refused by 9 Hmong patients (43%). Stone composition was available in 40 Hmong and 39 non-Hmong. Uric acid (>10%) was found in 50% of Hmong and 10% of non-Hmong stones (P < 0.001). CONCLUSIONS: Hmong patients who come to urologic attention tend to do so for stone disease and tend to have uric acid calculi. The frequent requirement for invasive therapy, including nephrectomy, in the Hmong is of concern.     

Metabolic risk factors and the impact of medical therapy on the management of nephrolithiasis in obese patients

PURPOSE: Previous studies have demonstrated that obesity can increase the risk of stone formation as well as recurrence rates of stone disease. Yet appropriate medical management can significantly decrease the risk of recurrent stone disease. Therefore, we analyzed our obese patient population, assessing the risk factors for stone formation and the impact of selective medical therapy on recurrent stone formation. MATERIALS AND METHODS: A retrospective chart review was performed to identify obese patients with stone disease from our Stone Center. Metabolic risk factors for stones were identified as well as patient response to medical therapy. A similar analysis was performed on a group of age and sex matched nonobese stone formers. RESULTS: Of 1,021 patients 140 (14%) were identified as obese (body mass index greater than 30). Of these patients complete metabolic evaluations were available in 83 with an average followup of 2.3 years. The most common presenting metabolic abnormalities among these obese patients included gouty diathesis (54%), hypocitraturia (54%) and hyperuricosuria (43%), which presented at levels that were significantly higher than those of the nonobese stone formers (p <0.05). Stone analysis was available in 32 obese patients with 63% having uric acid calculi. After initiating treatment with selective medical therapy obese and nonobese patients demonstrated normalization of metabolic abnormalities, resulting in an average decrease in new stone formation from 1.75 to 0.15 new stones formed per patient per year in both groups. CONCLUSIONS: Obesity, as a result of dietary indiscretion, probable purine gluttony and possible type II diabetes, appears to have a significant role in recurrent stone formation. Appropriate metabolic evaluation, institution of medical therapy and dietary recommendations to decrease animal protein intake can significantly improve the risk of recurrent stone formation in these often difficult to treat patients.     

Ammonium acid urate calculi: a reevaluation of risk factors

PURPOSE: We reevaluate the demographic and metabolic risk factors for ammonium acid urate stones. MATERIALS AND METHODS: Since 1986, 23 women and 21 men ranging in age from 20 to 81 years (mean 48.7) were treated for stones partly composed of ammonium acid urate. Stone composition ranged from 2 to 60% ammonium acid urate (mean 24.1) of the total stone mass. No patient had a pure ammonium acid urate stone, although 11 (25%) had stones with ammonium acid urate as the predominant crystal. RESULTS: In the 44 patients 1 or more potential risk factors for ammonium acid urate were identified. Of the patients 11 (25%) had a history of inflammatory bowel disease with 10 (22.7%) having undergone ileostomy diversion, 6 (13.6%) admitted to a history of significant laxative use or abuse, 18 (40.9%) were morbidly obese, 16 (36.4%) had a history of recurrent urinary tract infections and 9 (20.5%) had a history of recurrent uric acid stones. CONCLUSIONS: Patients clearly at risk for stones with an ammonium acid urate component include those with a history of inflammatory bowel disease and ileostomy diversion or laxative abuse. Other factors that may potentially enhance ammonium acid urate stone formation include morbid obesity, recurrent uric acid calculi and recurrent urinary tract infection. A careful history followed by further metabolic evaluation is warranted in these patients.     

Detection of Proteus mirabilis Urease Gene in Urinary Calculi by Polymerase Chain Reaction

Background: Urea-splitting microorganisms cannot always be detected by stone or urine culture in patients with infection stones. Detection of genetic elements within the calculi by the polymerase chain reaction (PCR) may be a useful alternative. In this study, we assessed the usefulness of the PCR method in detecting the urease gene specific to Proteus mirabilis in urinary calculi.
Methods: Thirty-eight metabolic stones (calcium oxalate and/or calcium phosphate, uric acid, or cystine) and 49 struvite stones were examined. The PCR was applied with DNA extracted by boiling pulverized stone pieces.
Results: Of the 87 stones, PCR demonstrated the presence of the P. mirabilis urease elements ureC1 and ureC2 in 1 7, all of which were struvite. Stone culture and urine culture had been performed in 22 and 46 struvite stone cases, respectively, and the PCR was positive in all of the 10 culture-positive calculi and also in two calculi from which P. mirabilis was not isolated.
Conclusion: PCR was reliable and convenient for detecting P. mirabilis in desiccated struvite calculi. Study to detect other species such as Ureaplasma or Corynebacterium would be useful in elucidating the role of bacterial infection in the formation of these stones.     

Predisposing factors in bladder calculi. Review of 100 cases

One hundred patients, aged twenty to ninety-two years, underwent 111 procedures for removal of bladder calculi. Most patients (88) had some type of bladder outlet obstruction. Two types of stones were identified: those that had apparently formed in the upper tract and been trapped in the bladder (17 cases) and those that appeared to have formed in the bladder in the presence of various types of outlet obstruction. Stone analysis revealed uric acid stones in 50 percent, calcium oxalate stones in 19 percent, and stones of mixed composition in 31 percent. Five patients had metabolic abnormalities predisposing to stone formation; in 2 cases, these abnormalities were discovered during the evaluation for stone disease. Treatment depended on stone characteristics, associated pathology, and the general health of the patient. A review of the literature with regard to the morbidity and mortality of combining treatment of vesical calculi and bladder outlet obstruction secondary to prostatic obstruction is included.     

Piezoelectric shockwave lithotripsy of urinary calculi: comparative study of stone depth in kidney and ureter treatments

PURPOSE: The aim of this prospective study was to assess the relation between stone depth and the efficiency of piezoelectric extracorporeal shockwave lithotripsy (SWL). PATIENTS AND METHODS: A total of 150 patients presenting with 25 pelvic, 75 caliceal, and 25 upper and 25 lower ureteral calculi were treated using the EDAP LT02 lithotripter. All of the stones were easy to localize with sonographic and radiographic systems, and their largest diameter ranged from 4 to 25 mm (mean 8.5 mm). Renal and upper ureteral calculi were treated with the patient in the supine position and lower ureteral stones in prone position. On the basis of a meticulous stone localization and focusing, depth measurements were carried out under real-time ultrasonic guidance, the minimal distance between the cutaneous plane and the focal point being recorded only for definitely localized calculi. RESULTS: Ureteral calculi were significantly deeper than renal stones (p < 0.0001), but the distance from the cutaneous plane was statistically similar for upper and lower ureteral calculi. Stone depth was statistically affected by body mass index (BMI), patients with a BMI >25 having significantly deeper renal and ureteral calculi than subjects with a BMI < or =25 (p < 0.00001 and 0.01, respectively). Renal stones resisting SWL were significantly deeper than successfully treated calculi (p < 0.03). At the level of the ureter, the success rate after one SWL session was 85% for stones with a depth < or =110 mm and 57% for deeper stones, the difference being significant (p < 0.05). CONCLUSION: Stone depth has a significant influence on treatment outcome after piezoelectric SWL for both renal and ureteral calculi. We recommend particular attention be given to corpulent patients presenting with ureteral stones.     

Pharmacologic treatment of uric acid calculi

Uric acid stone disease is dependent on three pathogenetic factors: acid urine pH, low urine volume, and hyperuricosuria. The management of nonobstructing uric acid calculi should include maintenance of an alkaline urine, an increase in urine volume, and reduction in urinary uric acid excretion. It appears that potassium alkali may avoid the complication of calcium stone formation in patients with uric acid stones. In patients with obstructing uric acid calculi, more rapid dissolution may be accomplished with intravenous alkalinization or direct irrigation of the stone with an alkaline solution.     

GERIATRIC UROLITHIASIS

Purpose

We define the differences between geriatric patients with urinary stone disease compared to a younger cohort.

Materials and Methods

A data base, including serum biochemical profiles, 24-hour urinalyses and standardized questionnaires, was retrospectively evaluated from more than 6,000 consecutive patients with urinary stone disease.

Results

Geriatric stone formers comprised 12% (721) of all stone patients. Two-thirds of these elderly patients had aberrant urinary values and 29% had isolated hypocitraturia compared to 17% in the younger group. Of geriatric stone forming patients 76% had recurrent urinary stones (mean 3.5 stone episodes), which was similar to the younger comparable group (77%, mean 3.3 stone episodes). The severity of urinary stone disease was similar between the 2 groups based on the need for urological intervention. Geriatric stone patients, in general, experienced the first stone episode later in life (after age 50 years) compared with younger patients. Elderly patients had an increased incidence of uric acid stones, but had a similar incidence of struvite calculi. Geriatric stone patients underwent parathyroid surgery more frequently (2.7 versus 0.7%). Geriatric stone forming patients rarely had renal failure.

Conclusions

The incidence, recurrence and severity of recurrent urinary stone disease were similar between geriatric and younger stone forming patients. Geriatric stone patients had an increased incidence of isolated hypocitraturia, uric acid calculi and previous parathyroidectomy. The geriatric stone population is not merely an extension of younger stone forming patients presenting at an older age. Rather, geriatric patients commonly experience the first symptomatic stone episode later in life.     

Childhood urolithiasis in north-western Libya

The study reviews causes of urolithiasis and its manifestations in North-West (NW) Libya. Libyan childhood urolithiasis accounted for 3.6% of nephrology out-patient work load. There were 59 children with urolithiasis, including 34 boys and 25 girls with a mean age of 2.8 ± 2.42 years. Urolithiasis was more common among younger age groups (P = 0.001) and in boys with primary oxaluria and infective etiology. The causes of urolithiasis included metabolic stones in 64%, infective in 26%, and it was idiopathic in 10%. Overall, family history of renal stone disease was elicited in 59%; it was 92% in patients with primary oxaluria. The main presenting features were abdominal pain (27%), gross hematuria (22%), associated urinary tract infection (UTI; 24%), and stone release in 19%. Stone location was bilateral in 64%, multiple in 68%, and in the upper tract in 93% (P = 0.05). Important complications encountered included chronic renal failure (13%), hydronephrosis (34%), systemic hypertension (8%), and rickets in 17%. Calcium oxalate was the most prominent constituent, seen in 41% of the calculi, followed by struvite (21%), uric acid (10%), carbapatite (7%), and cystine (3.5%). Diagnostically helpful findings were family history, age at presentation, UTI by urease producing organisms, rickets, imaging and chemical analysis of calculi. Early detection and prompt treatment helps in preventing long-term sequelae in patients with urolithiasis.     

Urolithiasis in Okinawa, Japan: A relatively high prevalence of uric acid stones

AIM: The aim of the present study was to investigate the composition of urinary tract stones in patients from Okinawa, the most southern island group of Japan. METHODS: The study was conducted by 12 hospitals in Okinawa. A total of 1816 urinary tract calculi were obtained from 1816 patients (1323 males; 493 females). The patients had a mean age of 53 +/- 15.3 years (mean +/- SD). The calculi were examined to determine their chemical composition. Stone samples were analyzed by computed infrared spectrophotometer. RESULTS: Pure stones comprised 58.4% of the total, with calcium oxalate stones accounting for 40% (21% monohydrate [whewellite]; 6.6% dihydrate [weddellite]; and 12.4% combined monohydrate and dihydrate stones), uric acid/urate stones for 9.6%, calcium phosphate stones for 5.1%, and struvite stones for 3.7%. The other 41.6% of the stones consisted of calcium oxalate mixed with other components. The male-to-female ratio was 2.7:1. CONCLUSION: In our series, calcium oxalate stones accounted for 81.6% of the urinary tract calculi, while uric acid/urate stones accounted for 15.8%. Uric acid stones, predominantly the anhydrous and/or dihydrate forms, showed a relatively high prevalence. Calcium oxalate stones, predominantly in the form of whewellite, showed a high prevalence among pure calculi; while the predominant combinations among mixed calculi were weddellite + calcium phosphate and whewellite + uric acid/urate.     

Stone fragility: its therapeutic implications in shock wave lithotripsy of upper urinary tract stones

OBJECTIVE: To analyse the impact of stone composition on stone fragility (fragmentation) and clearance of upper urinary tract stones after shock wave lithotripsy (SWL). MATERIAL AND METHODS: Between 1st July 1998 and 31st July 2001, 300 renal and ureteric units of 290 patients (10 being bilateral) underwent SWL for upper urinary tract calculi. The degree of fragmentation was divided into four types: (I) Excellent, (II) Good, (III) Fair and (IV) No fragmentation. Stone composition was done by X-ray diffraction crystallography. A statistical comparison was made between degree of fragmentation, number of shock waves delivered, voltage setting, number of sessions required and requirements of adjuvant procedures according to the stone composition. RESULTS: Stone analysis revealed that 90% of the patients had calcium oxalate stones. Of these 80% were calcium oxalate monohydrate (COM) and 20% calcium oxalate dehydrate (COD). Struvite, apatite and uric acid stones comprised of 6%, 3% and 1% respectively. Type-I fragmentation was achieved up to 63.96%, 50% and 100% in COD, struvite and uric stones respectively as compared to 44.9% and 44.44% for COM and apatite stones. Type-III fragmentation was seen up to 8.79% and 33.3% respectively in COM and apatite as compared to 5.55% or less in other types of the stones suggesting that COM and apatite stones produce larger fragments. The mean number of shock waves, voltage and number of treatments was significantly higher for COM and apatite stones (p value < 0.005) with a stone free rate of only 65-66% and 65-68% respectively at three months (p value < 0.001). Similarly the number of adjuvant procedures required in COM alone was more, i.e. 31 as compared to 17 procedures in rest of the other kinds of stones (p value < 0.05). CONCLUSION: Stone composition in Indian subcontinent is different from the western world. Fragility of a stone varies with the composition of the stone and affects the therapeutic results.     

Outcomes of long-term follow-up of patients with conservative management of asymptomatic renal calculi

Study Type – Prognosis (cohort) Level of Evidence 4 What’s known on the subject? and What does the study add? Several small series studies have looked at the natural history of asymptomatic renal stones. The number of subjects in these studies ranged from 24 to 300 and duration of follow‐up ranged from 19.4 to 52.3 months. The reported incidences of spontaneous passage, progression and intervention were 3 to 15%, 33 to 77% and 7 to 26%. This study reports on the natural history of asymptomatic stones with an average size of 5.7 mm which were smaller in size than those reviewed in other series. The findings were that the incidence of spontaneous passage was higher than in other series at 20% and that the incidence of intervention was low at 7.1%. This study found that stones that were less than 5 mm in diameter were significantly more likely to pass spontaneously than stones that were larger and there were no other significant differences in the outcomes when stratified according to the initial size and location of stones.

OBJECTIVE

? To evaluate the long‐term outcomes of patients undergoing observation of asymptomatic renal calculi.

PATIENTS AND METHODS

? This is a retrospective review of 50 patients with 85 stones undergoing observation with annual imaging from January 2005 to December 2009. ? The incidences of spontaneous stone passage, stone progression and intervention were evaluated and assessed for statistical difference according to initial size and location of stone. ? Percutaneous nephrolithotomy, shock wave lithotripsy and ureteroscopy were performed when patients developed complications from the stones.

RESULTS

? Patients were followed up for a mean of 46 months. Sixteen percent had bilateral stones and 38% had multiple stones. ? The average stone size was 5.7 mm and 31%, 26% and 43% of the stones were located in the upper, middle and lower pole respectively. ? Overall incidences of spontaneous passage, progression and intervention were 20%, 45.9% and 7.1% respectively. ? Stones measuring 5 mm or less were significantly more likely to pass (P= 0.006). ? There was no significant difference in the incidence of passage according to the initial location of the stone (P= 0.092). There was no significant difference in intervention or progression according to the initial size (P= 0.477 and 0.282 respectively) or location of stone (P= 0.068 and 0.787 respectively).

CONCLUSIONS

? Patients with asymptomatic renal stones may be managed conservatively in view of low risk of intervention (7.1%). ? Annual imaging should be performed as half of these stones will progress in size.     

Comparison of urinary stone and stent encrustation: biochemical analysis

PURPOSE: To compare biochemical analysis of stent encrustation with that of urinary stones from the same patient. PATIENTS AND METHODS: Any patient presenting from February to December 2000 with a symptomatic ureteral or renal calculus that necessitated stenting and delayed calculus retrieval was enrolled in the study. The stent and stone were sent to the same laboratory for qualitative and semiquantitative chemical analysis. A total of 50 stents and matched calculi were available for comparison; four stents were excluded because they had insufficient encrustation for analysis. RESULTS: Two patients had open ureterolithotomy; the remainder were treated by endoscopic or percutaneous means. Every stone containing calcium oxalate had a stent that was positive for calcium oxalate. Four uric acid stones were available for comparison, and three of the four matched stents tested positive for uric acid. CONCLUSION: Biochemical analysis of urinary stent encrustation is a good predictor of urinary stone composition, especially for calcium oxalate-containing stones. Uric acid stent encrustation is likely to occur in patients with uric acid stones.     

Metabolic abnormalities associated with calyceal diverticular stones

OBJECTIVE: To review the metabolic analyses of patients with calyceal diverticular stones who had surgical treatment of their calculi and to examine the effect of selective medical therapy on stone recurrence, as recent reports suggest that metabolic abnormalities contribute to stone development. PATIENTS AND METHODS: In all, 37 patients who had endoscopic treatment of symptomatic calyceal diverticular calculi were retrospectively reviewed. Stone composition and initial 24-h urine collections (24-h urinary volumes, pH, calcium, sodium, uric acid, oxalate, citrate, and the number of abnormalities/patient per collection) were compared with 20 randomly selected stone-forming patients (controls) with no known anatomical abnormalities. Stone formation rates before and after the start of medical therapy were calculated in the patients available for follow-up. RESULTS: Twelve of the diverticulum patients (five men and seven women) had complete 24-h urine collections, all of whom had at least one metabolic abnormality. Seven patients had hypercalciuria, four had hyperuricosuria and three had mild hyperoxaluria. The most common abnormality was a low urine volume; 11 of the 12 patients had urine volumes of <2000 mL/day (range 350-1950). Ten patients had hypocitraturia in at least one of the two 24-h urine samples; seven had low urinary citrate levels (172-553 mg/day) on both samples. The findings were similar in the control group. The diverticulum patients had 3.1 abnormalities/patient, and the controls had 2.9 abnormalities/patient (P > 0.05). No patients had gouty diathesis and none developed cystine stones. Stone analyses were similar in the two groups; both developed either calcium oxalate or mixed calcium oxalate/calcium phosphate stones. Six patients were followed for a mean of 23.1 months while on selective medical therapy; only one passed any additional stones, thought to be existing calculi, for a remission rate of five of six (83%). CONCLUSIONS: All patients with symptomatic calyceal diverticular stones who had comprehensive metabolic evaluation had metabolic abnormalities. There were similar abnormalities in the control random stone-formers. The abnormalities were corrected with selective medical therapy, as shown by the high remission rate. We recommend that, for patients with symptomatic calyceal diverticular calculi, a metabolic evaluation should be considered to determine stone forming risk factors.     

Epidemiology of nephrolithiasis in France

Nephrolithiasis is a frequent disease that affects about 10% of people in western countries. The prevalence of calcium oxalate stones has been constantly increasing during the past fifty years in France as well as in other industrialized countries. Stone composition varies depending to gender and age of patients and also underlines the role of other risk factors and associated pathologies such as body mass index and diabetes mellitus. The decrease in struvite frequency in female patients is the result of a significantly improved diagnostic and treatment of urinary tract infections by urea-splitting bacteria. In contrast, the increasing occurrence of weddellite calculi in stone forming women aged more than 50 years could be the consequence of post-menopausal therapy. A high prevalence of uric acid was found in overweight and obese stone formers and in diabetic ones as well. Another important finding was the increased occurrence with time of calcium oxalate stones formed from papillary Randall's plaques, especially in young patients. Nutritional risk factors for stone disease are well known: they include excessive consumption of animal proteins, sodium chloride and rapidly absorbed glucides, and insufficient dietary intake of fruits and potassium-rich vegetables, which provide an alkaline load. As a consequence, an excessive production of hydrogen ions may induce several urinary disorders including low urine pH, high urine calcium and uric acid excretion and low urine citrate excretion. Excess in calorie intake, high chocolate consumption inducing hyperoxaluria and low water intake are other factors, which favour excessive urine concentration of solutes. Restoring the dietary balance is the first advice to prevent stone recurrence. However, the striking increase of some types of calculi, such as calcium oxalate stones developed from Randall's plaque, should alert to peculiar lithogenetic risk factors and suggests that specific advices should be given to prevent stone formation.     

螺旋CT扫描预测上尿路结石成分的体内研究

目的:研究螺旋CT对体内上尿路结石化学成分的预测价值。方法:2005年12月～2007年9月对157例上尿路结石患者在治疗前行螺旋CT平扫,测结石CT值。定量分析各种治疗方法所获取结石的化学成分。经统计学分析,找出不同成分结石的CT值范围。结果:一水草酸钙、尿酸、羟基磷灰石三种纯结石的软组织窗平均CT值分别为(851.50±188.74)HU、(446.92±47.20)HU和(835.53±110.58)HU。尿酸结石与一水草酸钙结石、尿酸结石与羟基磷灰石之间CT值的差异均有统计学意义。13例纯尿酸结石与144例尿酸含量小于70%的其他结石的CT值差异有统计学意义。以结石的软组织窗平均CT值500 HU为标准鉴别纯尿酸结石,其灵敏度为92.31%,特异度为96.53%,阳性预测值为70.59%,阴性预测值为99.29%。结论:结石的CT值可作为鉴别尿酸结石的一种方法,CT值小于500 HU的结石多考虑为尿酸结石。     

Effect of potassium citrate therapy on stone recurrence and residual fragments after shockwave lithotripsy in lower caliceal calcium oxalate urolithiasis: a randomized controlled trial

BACKGROUND AND PURPOSE: To evaluate the efficacy of potassium citrate treatment in preventing stone recurrences and residual fragments after shockwave lithotripsy (SWL) for lower pole calcium oxalate urolithiasis. PATIENTS AND METHODS: One hundred ten patients who underwent SWL because of lower caliceal stones and who were stone free or who had residual stone 4 weeks later were enrolled in the study. The average patient age was 41.7 years. All patients had documented simple calcium oxalate lithiasis without urinary tract infection and with normal renal morphology and function. Four weeks after SWL, patients who were stone free (N = 56) and patients who had residual stones (N = 34) were independently randomized into two subgroups that were matched for sex, age, and urinary values of citrate, calcium, and uric acid. One group was given oral potassium citrate 60 mEq per day, and the other group served as controls. RESULTS: In patients who were stone free after SWL and receiving medical treatment, the stone recurrence rate at 12 months was 0 whereas untreated patients showed a 28.5% stone recurrence rate (P < 0.05). Similarly, in the residual fragment group, the medically treated patients had a significantly greater remission rate than the untreated patients (44.5 v 12.5%; P < 0.05). CONCLUSION: Potassium citrate therapy significantly alleviated calcium oxalate stone activity after SWL for lower pole stones in patients who were stone free. An important observation was the beneficial effect of medical treatment on stone activity after SWL among patients with residual calculi.