INDINAVIR UROLITHIASIS: AN EMERGING CAUSE OF RENAL COLIC IN PATIENTS WITH HUMAN IMMUNODEFICIENCY VIRUS

PURPOSE: We evaluate the clinical, diagnostic and radiographic findings in patients on indinavir therapy who presented with renal colic, and propose appropriate treatment options for indinavir urolithiasis. MATERIALS AND METHODS: A total of 16 patients positive for human immunodeficiency virus on indinavir were evaluated for 18 episodes of severe renal colic requiring hospitalization. Laboratory evaluation was performed in all patients followed by an imaging study. Conservative treatment included intravenous hydration, narcotic analgesics and temporary cessation of indinavir. Intervention was elected only in patients with persistent fever or intractable pain. A month after hospital discharge an excretory urogram and metabolic stone evaluation were performed. Mean followup was 9.3 months and 2 patients had recurrent symptoms. RESULTS: All patients presented with nausea or vomiting and hematuria. Imaging studies confirmed obstruction in all patients with 13 radiolucent (indinavir) and 3 radiopaque (calcium oxalate) stones. Patients with radiolucent and radiopaque stones demonstrated significant differences in urinary pH (p = 0.002) and serum creatinine (p = 0.03). Conservative therapy was successful in 11 patients (68.8%) within 48 hours and 4 patients (25%) with radiolucent calculi required endoscopic stenting for persistent fever. Metabolic stone evaluation demonstrated significant hypocitruria (less than 50 mg./24 hours) in all patients with radiolucent calculi. CONCLUSIONS: The urologist should be familiar with this growing cause of renal colic in patients on indinavir therapy. Pure indinavir stones are radiolucent and have a soft, gelatinous endoscopic appearance. Conservative treatment is successful in most patients and if intervention is deemed medically necessary, endoscopic stent placement should be the procedure of choice.     

Indinavir urolithiasis

Indinavir sulfate is a protease inhibitor that has been found to be extremely effective in increasing CD4+ cell counts and in decreasing HIV-RNA titers in patients with HIV and AIDS. However, patients receiving indinavir also have been noted to have a significant risk for developing urolithiasis. Published reports of indinavir urolithiasis estimate its incidence at between 4 and 13%. Indinavir has a high urinary excretion with poor solubility in a physiologic pH solution. Consequently, patients develop urinary stones that are principally composed of indinavir or of a mixture of indinavir and other substances, such as calcium oxalate. Similar to other forms of urolithiasis, acute flank pain and hematuria are the typical symptoms of indinavir urolithiasis. Indinavir urolithiasis is unique in that computed tomography, which was once thought to be efficacious in identifying all urinary calculi, is not useful in imaging stones that are composed of pure indinavir. Indinavir urolithiasis generally responds to a conservative regimen of hydration, pain control, and the temporary discontinuation of the medication. Only a minority of patients need surgical intervention. Approximately 10% of patients ultimately need to discontinue indinavir therapy altogether. Indinavir is an antiviral agent that has a significant role in the treatment of AIDS. Although urolithiasis is a significant side effect of indinavir use, limiting its clinical application is not the answer. Rather, physicians need to know more about indinavir urolithiasis to help their patients cope with its potential complications.     

Urolithiasis associated with protease inhibitors.

OBJECTIVE: We evaluated the radiographic characteristics as well as the clinical management of urolithiasis induced by systemic therapy with indinavir sulfate, a protease inhibitor utilized in the treatment of HIV infection. PATIENTS AND METHODS: Fifteen consecutive HIV-positive male patients (average age 41.3 years) who presented with urolithiasis while being treated with indinavir sulfate (average time 11.1 months) were studied. RESULTS: All patients presented with flank pain, and eight had gross hematuria. All but one patient had microscopic hematuria. The location of the stones was the kidney in three, the proximal ureter in four, and the distal ureter in nine. One patient had both a renal and a proximal ureteral stone. The stones were radiolucent on CT imaging in five patients and could not be seen in five. In the five cases in which a stone was not definitely identified, a diagnosis of urolithiasis was established on the basis of ureteral obstruction and periureteral/renal streaking noted on CT. Treatment included observation with hydration in eight patients, ureteral stent placement in two patients, ureteroscopy in three patients, and extracorporeal shockwave lithotripsy in two patients. Stones were analyzed in five patients and proved to be 100% indinavir in three and a mixture of indinavir, calcium oxalate monohydrate, and calcium oxalate dihydrate in two. CONCLUSIONS: Urolithiasis is a recognized complication of treatment with indinavir sulfate. Pure indinavir stones cannot be seen on CT unless intravenous contrast medium is utilized. Mixed calcium and indinavir stones can occur and may be radiopaque. The majority of HIV-positive patients with symptomatic urolithiasis can be treated conservatively with hydration. Metabolic evaluation of these patients with identification and correction of factors predisposing to stone formation may minimize future recurrences. Administration of this effective medication thus can continue uninterrupted.     

影响第二次冲击波碎石术治疗上尿路结石患者成功的因素分析

目的 探讨影响第二次冲击波碎石术（extracorporeal shock wave lithotripsy, ESWL）治疗上尿路结石患者成功的因素。方法 回顾性分析2008年1月至2012年12月来本院接受第二次ESWL治疗的上尿路结石患者120例。根据患者上尿路结石有无完全排出分为成功组（n=80）和失败组（n=40）。回顾性分析所有患者的病历资料,相关因素分析包括性别、年龄、病程、BMI、结石侧别、结石位置、结石长度、结石宽度、结石数目、肾绞痛、血尿、肾积水程度、非增强螺旋CT值、冲击次数、冲击能量等指标。应用单因素、多因素非条件Logistic回归分析上尿路结石患者第二次ESWL治疗成功与否的危险因素分析。结果 120例上尿路结石患者临床特征显示,两组在病程、BMI、结石长度、结石宽度、结石数量、肾绞痛、肾积水程度、CT值、冲击次数方面差异有统计学意义（P＜0.05）,在性别、年龄、结石侧别、结石位置、血尿、冲击能量方面差异无统计学意义（P＞0.05）。经单因素、多因素 Logistic 回归分析结果显示,BMI偏高、结石长度＞2 cm、存在肾绞痛、肾积水程度严重、CT值＞750 HU会增加上尿路结石患者第二次ESWL治疗失败的风险（P＜0.05）。结论 临床医师利用ESWL第二次治疗上尿路结石患者过程中,应格外注意患者BMI、结石长度、肾绞痛、肾积水程度、CT值等关键指标。     

Increased prevalence and analysis of risk factors for indinavir nephrolithiasis

PURPOSE: Indinavir is a protease inhibitor used for treating HIV-1. The drug is lithogenic and was thought to cause a 3% incidence of kidney stones. We evaluated a cohort of patients positive for HIV on indinavir to determine the incidence of indinavir nephrolithiasis and identify risk factors for indinavir stone formation. MATERIALS AND METHODS: Our cohort study of the prevalence of indinavir nephrolithiasis included 155 patients with HIV for 5,732 patient-weeks. The same cohort was then used for a retrospective chart review to assess patient age, weight, duration of drug use, time to stone formation, CD4 count, creatinine, alanine transaminase, and urinary pH and specific gravity as risk factors for stone formation. RESULTS: We estimated the cumulative incidence of indinavir stone formation by the Kaplan-Meier product limit estimator method. At 78 weeks 43.2% of patients had stones (95% confidence interval [CI] 0.292 to 0.543). Increasing age was the only variable that was a statistically significant predictor of indinavair urolithiasis (relative risk 0.955, 95% CI 0.918 to 0.993, p = 0.0159). The mean duration plus or minus standard deviation of indinavir use was statistically the same in each group (42.5 +/- 27. 2 and 40.3 +/- 27.1 weeks in those without and with stones, respectively) despite the observed mean time to stone formation of 23.0 +/- 19.8 weeks. CONCLUSIONS: The clinical prevalence of indinavir nephrolithiasis is much greater than initially reported. Nephrolithiasis during indinavir use does not appear to induce patients to withdraw from the drug.     

Indinavir and renal lithiasis

Indinavir is a new specific and potent drug that inhibits, like other antiretroviral agents, the protease of immune deficiency virus (HIV) or acquired immune deficiency syndrome (AIDS), an enzyme necessary to maduration and replication of the virus. Indinavir has the capacity to bind the active site causing a decrease in plasma of HIV1-RNA and an increase of T-CD4 helper lymphocytes. The aim of this work is to study in HIV and/or AIDS patients treated with indinavir the crystalluria and the formation of renal calculi due to the clearance of this drug. Two out of nine patients studied in this work presented abundant crystalluria and one of them presented spontaneously passed renal stone. Urinary crystals were studied under polarized-light microscopy and renal stone was analyzed by infrared spectroscopy.     

The etiology of urolithiasis in HIV infected patients

PURPOSE: It is commonly thought that urinary lithiasis in HIV infected patients on protease inhibitor therapy is composed primarily of the protease inhibitor itself. Since many HIV infected patients on protease inhibitors presenting to our institution had nonprotease inhibitor stones, we investigated potential underlying metabolic abnormalities that may account for the lithogenesis. MATERIALS AND METHODS: We retrospectively reviewed all HIV infected patients on protease inhibitors with renal colic and evidence of nephrolithiasis who presented to our institution between June 1996 and January 2001. Patients were evaluated for stone composition and metabolic abnormalities of blood and urine when possible. RESULTS: A total of 24 patients were identified, and all were or had been on protease inhibitors (indinavir 14, ritonavir 3, nelfnavir 2, unspecified 5). Of the 14 patients on indinavir only 4 (28.6%) had indinavir containing stones. The remaining stones in this group and in those not on indinavir contained various amounts of calcium oxalate monohydrate and dihydrate, ammonium acid urate and uric acid. Of 10 patients who underwent 24-hour urine collection for metabolic evaluation 8 (80%) had abnormalities, including hypocitraturia in 5, hyperoxaluria in 4, hypomagnesuria in 4, hypercalciuria in 3, increased supersaturation of calcium oxalate in 3 and hyperuricosuria in 2. Abnormalities in the levels of urinary phosphate and sodium were also observed. CONCLUSIONS: HIV infected patients form many types of stones, which probably are attributable to underlying metabolic abnormalities rather than the use of protease inhibitors. A complete metabolic evaluation is warranted in these patients, as a means of guiding treatment to prevent future stone episodes, while avoiding the need to alter antiretroviral regimens.     

复杂性肾结石的早期诊断及预防

目的通过分析复杂性肾结石病史,结石成分等临床特点,为其诊疗及预防提供帮助。方法回顾性研究2009年8月至2010年5月于北京大学人民医院进修期间118例复杂性肾结石病例,对患者病史、既往史、结石化学成分及尿常规、肾功能等临床资料进行总结分析。结果118例患者中,7例(5.9%)接受过定期规律体检,97例(82.2%)从未曾接受过健康体检,64例(54.2%)曾有结石病史,86例(72.9%)以疼痛、血尿及发热等不适症状为主诉,92例(78.0%)伴有泌尿系感染,18例(15.3%)伴有肾功能不全,结石成分中含钙结石94例(79.7%),感染石55例(46.6%),含尿酸结石28例(23.7%)。结石以混合成分为主,其中感染石与草酸钙的混合成分所占比例最大,共51例(43.2%)。结论应通过定期规律体检提高早期诊断比例,控制结石进展,根据不同结石成分,采取有针对性的预防措施,同时必须重视抗感染治疗,以减少患者损伤,降低结石复发率。     

Low-dose computed tomography for the evaluation of flank pain in the pregnant population

BACKGROUND: Evaluation of the pregnant patient with suspected renal colic is complex. Fetal irradiation concerns have traditionally prohibited the use of CT in this population. We report our institution's experience using low-dose CT in the evaluation of pregnant patients with refractory flank pain. PATIENTS AND METHODS: A retrospective review of all patients who underwent low-dose CT evaluation of the urinary tract for suspected urinary tract stones was performed. Data obtained included gestational age, urinalysis and ultrasonography results, CT findings, and calculated fetal radiation exposure. RESULTS: Between April 2004 and December 2006, 20 patients with an average gestational age of 26.5 weeks presented to our institution with acute, refractory flank pain consistent with a diagnosis of urolithiasis. All patients underwent renal ultrasonographic evaluation before unenhanced CT of the abdomen and pelvis using a low-dose protocol. The average radiation exposure was 705.75 mrads (range 210-1372; SD +/- 338.66 mrads). Of the 20 patients, CT demonstrated urinary stones (1-12 mm) in 13. Of those patients with documented stones, 4 were treated conservatively, 2 underwent intrapartum stent placement, 5 had ureteroscopy with stone extraction, and 2 were treated postpartum. CONCLUSION: Low-dose CT is highly sensitive and specific for the detection of urinary calculi in the pregnant population. CT confers a low risk of fetal harm and can improve patient care when used judiciously.     

Frequency of urolithiasis in individuals seropositive for human immunodeficiency virus treated with indinavir is higher than previously assumed

PURPOSE: Indinavir was approved by the Food and Drug Administration in 1996 as a human immunodeficiency type 1 protease inhibitor to treat human immunodeficiency virus infection. Prompted by the high number of patients receiving indinavir who present with renal colic at our institution, we performed a detailed investigation of the true frequency of urolithiasis during indinavir treatment. MATERIALS AND METHODS: We evaluated 105 patients with a mean age of 38.1 years who were treated with indinavir from 1996 to 1997. Before indinavir treatment was initiated all patients underwent renal ultrasonography, urinalysis, and determination of serum sodium, potassium, calcium, uric acid and creatinine. It was recommended that all patients drink 2 l of fluids daily, and all remained under continuous surveillance. RESULTS: Metabolic evaluation and ultrasonography showed no abnormality in any case. A stone episode occurred in 13 men (12.4%) as renal colic during observation. Colic recurred in 1 patient after 2 and 5 months, and in 1 after 2 months. Median duration of indinavir treatment until an acute stone episode was 21.5 weeks (range 6 to 50). A total of 12 stones passed spontaneously. Three patients underwent ureteroscopic calculous removal and 1 was treated with extracorporeal shock wave lithotripsy. CONCLUSIONS: Despite adequate patient information and compliance the rate of nephrolithiasis during indinavir therapy was 12.4%.     

Spontaneous thrombosis of the renal vessels. Rare entities to be considered in differential diagnosis of patients presenting with lumbar flank pain and hematuria.

We report 2 cases of spontaneous thrombotic occlusion of the main renal vessels presenting with acute lumbar flank pain and hematuria suspect of nephrolithiasis. Clinical and laboratory signs of blood hypercoagulability, generalized arterial embolism, nephrotic syndrome or glomerulonephritis were absent. Excretory urography, nephrosonography and retrograde ureteropyelography showed no evidence of upper urinary tract calculi or other causes of obstruction. Renal angiography and cavography demonstrated an acute renal vein thrombosis in 1 patient and a thrombotic occlusion of all but one of the segmental renal arteries in the other patient. These 2 cases demonstrate that thrombotic occlusion of the renal artery or renal vein has to be considered in patients who are presenting with lumbar flank pain and hematuria, in whom the excretory urogram shows severe malfunction of one of the kidneys, and stone disease can be excluded. Renal angiography and cavography as well as CT scan should be carried out in these patients. When the disease is diagnosed at an early stage, an intra-arterial thrombolysis can be attempted.     

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.     

A case of drug induced urolithiasis composed of acetyl sulphapyridine associated with ulcerative colitis]

A 26-year-old female visited our hospital complaining left flank pain and macroscopic hematuria. She had been suffering ulcerative colitis and administered salazosulphapyridine and predonisolone from 17-year-old. Intravenous urography showed radiolucent multiple stones in the left renal pelvis. Three sessions of extracorporeal shock wave lithotripsy were performed after ureteral stenting. Although disintegration and discharge of the stones were satisfactory, bladder stone induced by ureteral stent was complicated. The extracted bladder stone showed a yellowish brown color and the surface was granular shape. Composition of the stone was acetyl sulphapyridine which was a metabolite of salazosulphapyridine. After maintenance of the urinary pH ranges between 6.5 and 7.5 by medication of sodium bicarbonate, the patient remains free of stone for 3 years. Drug induced urolithiasis originated from salazosulphapyridine is extremely rare. Satisfactory oral fluid intake and urinary alkalization are important for prevention of sulpha drugs calculi of urinary tract.     

Urolithiasis update: Evaluation and management

Urolithiasis is a worldwide disease which has affected humans from ancient eras to modern times. Recently, societal changes have altered the epidemiology of urinary calculi. The incidence of urolithiasis is higher in industrialized countries. Obese people are known to have a higher risk of stone formation. Metabolic syndrome has resulted in an increasing rate of nephrolithiasis among women. There are many useful tools for diagnosing urolithiasis, including conventional plain radiography, intravenous urography, ultrasonography, computed tomography (CT), and nuclear medicine. Nonenhanced CT has high sensitivities and specificities. It can be rapidly performed without intravenous administration of contrast material and can therefore be used in patients with severely impaired renal function. Beyond that, it can reveal extraurinary causes of flank pain. However, concerns about radiation exposure and costs remain. Since ancient times, hundreds of natural plant extracts and more recently, synthetic chemicals have been proposed to eliminate urinary calculi. Clinical trials demonstrated that calcium channel blockers and adrenergic antagonists are effective in enhancing stone passage. Shock wave lithotripsy (SWL) can successfully treat renal calculi. A meta-analysis study revealed that SWL is more effective in treating urinary calculi with a lower-frequency mode. Highly dense stones are more refractory to SWL. The stone composition can be evaluated by preoperative CT attenuation values. Patients with preoperative Houndsfield units (HUs) of >750 have a 10.5-times greater chance of needing three or more sessions of SWL treatment compared to patients whose HUs are <750. Ureteroscopy is a safe treatment for managing ureter stones when performed by experienced hands and ureteroscopy is preferred over SWL in patients with a larger upper-ureter stone, those who are pregnancy, and those with bleeding diathesis.     

Percutaneous nephrostomy for unusual complications occurring in patients with ureteral stones: a report of two cases

The first case is a 59-year-old man who had left flank pain and nausea. KUB, excretory urograms and CT scan showed a left ureteral stone at the ureterovesical junction associated with spontaneous rupture of the left renal pelvis. Percutaneous nephrostomy was performed. The ureteral stone was spontaneously discharged on the 4th postoperative day and extravasation of contrast medium from the left renal pelvis disappeared. The second case is a 42-year-old man who was admitted with bilateral flank pain, nausea and vomiting. KUB and excretory urograms showed bilateral hydronephrosis due to small bilateral ureteral stones. Serum BUN and creatinine had risen to 41 and 5.1 mg/dl, respectively, on the day after admission. Percutaneous nephrostomy to the left kidney was performed. BUN and creatinine were normalized immediately and the bilateral ureteral stones were spontaneously discharged by the 9th postoperative day. After the nephrostomy catheters were removed, no complications occurred in either case and KUB and excretory urograms showed normal findings.     

Pyuria in patients treated with indinavir is associated with renal dysfunction

BACKGROUND: Indinavir therapy is associated with a continuum of crystal-related syndromes, including nephrolithiasis, renal colic, flank pain without recognizable stone formation, dysuria and asymptomatic crystalluria. A frank nephropathy has been recognized recently as part of the spectrum. METHODS: A retrospective analysis of 72 HIV-infected individuals receiving indinavir was performed to identify the frequency and risk factors for indinavir-associated nephropathy and urinary complications. Individuals treated with nucleoside analogues alone served as controls. RESULTS: Mean serum creatinine levels rose from 1.03 +/- 0.16 mg/dl to 1.11 +/- 0.22 mg/dl at week 12 and 1.15 +/- 0.27 mg/dl at week 24 (both, p < 0.01). Thirteen individuals developed serum creatinine levels > or =1.4 mg/dl. Increased serum creatinine levels were found more frequently in women (p < 0.01) and were associated with pyuria and microhematuria (p < 0.01). Frank renal colic and/or nephrolithiasis (seven patients) and urinary pH were not associated with serum creatinine levels > or =1.4 mg/dl. The mean duration of indinavir treatment, until sterile pyuria occurred, were 22 weeks and 32 weeks until the first rise of serum creatinine levels to > or =1.4 mg/dl. Ten patients showed both findings, pyuria preceded the first rise in serum creatinine levels to > or = 1.4 mg/dl (18 vs. 27 weeks, p = 0.02). Renal biopsy, done in three patients, revealed tubulointerstitial disease with crystals in collecting ducts. In 21 patients, among them 11 with pyuria, indinavir was replaced for various reasons and pyuria disappeared in nine. In these patients mean serum creatinine levels decreased from 1.43 mg/dl at withdrawal of indinavir to 1.04 mg/dl three months later (p < 0.01). CONCLUSION: Indinavir therapy is associated with a decrease in renal function which is reversible after withdrawal. In addition, indinavir-associated tubulointerstitial disease does no in patients taking indinavir may help to identify patients being at risk for nephrotoxicity.     

Use of double-pigtail stents in extracorporeal shock wave lithotripsy

Double-pigtail stents are placed commonly in patients before extracorporeal shock wave lithotripsy to prevent ureteral obstruction from steinstrasse. The use of double-pigtail stents in lithotripsy patients with a moderate stone burden was studied in a prospective randomized trial. Patients with unilateral renal stone(s) with at least 1 diameter between 7 and 25 mm. were eligible for the study. Fifty patients were randomized to a control or stented group. Double-pigtail stents with an attached suture were placed immediately before extracorporeal shock wave lithotripsy in the stented group. Stents were removed by the patients 1 week after lithotripsy. A survey on pain and associated symptoms was completed by patients at 1 and 14 days after treatment. There was no statistical difference in flank or abdominal pain, nausea, vomiting, temperature or use of analgesics at 1 and 14 days after extracorporeal shock wave lithotripsy in the control and stented groups. All patients in the stented groups complained of side effects attributable to the stent including urinary frequency and urgency, bladder pain, hematuria and flank pain with urination. Of 25 patients with stents 7 (27%) had early removal because of severe irritation, early migration or accidental removal. Among the patients with follow-up x-rays 1 month after treatment 17 of 21 (81%) in the control group and 12 of 19 (63%) in the stented group showed no evidence of remaining stones. The use of double-pigtail stents is not beneficial in patients with a moderate stone burden. Double-pigtail stents are associated with considerable patient discomfort but no decrease in symptomatic ureteral obstruction or final stone eradication rate.     

Clinical studies on childhood urolithiasis during the past 22 years

We have studied retrospectively 68 children who presented with urolithiasis between 1965 and 1986. Male to female ratio was 1.83 to 1 and the mean age was 9.5 years. Fifty four children (79%) had calculi in the upper urinary tract, 9 (13%) had in the lower, and 4 (6%) had calculi both in the upper and lower urinary tract. The most common presenting symptoms were gross hematuria (53%) and abdominal or flank pain (38%). Predisposing factors could be found only in 21 children (31%). Twenty four of the 68 patients (35%) had open surgery and 16 patients (24%) passed their stones spontaneously. Twenty one stones were analyzed by infrared spectroscopy. Infectious stone was more frequent than in adult cases. Among children five years old and younger, infectious stone was the most frequent. Among children over five years old, the number of idiopathic calcium stone has been on the increase with the years.     

Drug-induced urolithiasis

Drugs can cause renal stone formation either by raising excretion rates of naturally occurring stone components or by directly precipitating within the urinary tract. In large series of analysed renal stones, the overall frequency of drug-induced urolithiasis is less than 0.5%. Five clinical presentations of drug-induced crystallization in the kidneys can be recognized: asymptomatic crystalluria, symptomatic crystalluria; stone passage; obstructive uropathy and tubulointerstitial nephritis. In the current literature review, the protease inhibitors used for treatment of patients infected with the human immunodeficiency virus stand out as a new class of drugs that frequently causes crystallization within the urinary tract. The most widely used compound, indinavir, may lead to crystalluria and renal stone formation in up to 50% of patients, and occasionally also causes acute renal failure caused by obstructive uropathy or tubulointerstitial nephritis. On the other hand, ritonavir appears more often to induce (reversible) acute renal failure than stone formation.     

Urinary matrix calculi: our experience at a single institution

PURPOSE: Matrix stones are an uncommon form of urinary calculi and may be mistaken for tumors involving the renal collecting system, thereby presenting a diagnostic and therapeutic dilemma to the practicing urologist. MATERIALS AND METHODS: From 1980 to 2003 we identified 5 patients with urinary matrix stones referred to our tertiary medical center for evaluation and treatment. RESULTS: All 5 cases had complex clinical and radiographic features at presentation. We outline the clinical presentations, imaging findings and management, and review the literature of matrix stone disease. CONCLUSIONS: A high index of suspicion is required in diagnosing matrix calculi in addition to carefully selected radiographic imaging. Due to their variable appearance in standard radiological studies, the evaluation of matrix stones may require invasive techniques such as ureteroscopy for accurate diagnosis. Percutaneous removal is the primary treatment modality to render patients stone-free.