Urinary-tract stones resulting from the excretion of oxypurinol

Acute Tumor Lysis Syndrome: A Metabolic Emergency in Cancer Patients

Tumor lysis syndrome (TLS) can be a life-threatening complication that occurs following the onset of chemotherapy treatment, most commonly in association with high-grade lymphoproliferative pathologies such as acute lymphoblastic leukemia and Burkitt lymphoma. The massive cell lysis caused by cytotoxic therapy leads to the rapid release in the blood of intracelullary products and the onset of severe metabolic and electrolytic complications (hyperkalemia, hyperphosphatemia, hypocalcemia and hyperuricemia) upto the acute renal failure. This article describes the incidence and pathophysiological basis of TLS, focusing on the new therapeutic strategies implemented over the last few years, especially with regard to the treatment of hyperuricemia. In particular, it highlights the characteristics of a recent drug, Rasburicase, as a safe and effective alternative, compared to traditional allopurinol therapy, for prophylaxis and treatment of children with hyperuricemia induced by chemotherapy.

Drug-Induced Urolithiasis in Pediatric Patients

Drug-induced nephrolithiasis is a rare condition in children. The involved drugs may be divided into two different categories according to the mechanism involved in calculi formation. The first one includes poorly soluble drugs that favor the crystallization and calculi formation. The second category includes drugs that enhance calculi formation through their metabolic effects. The diagnosis of these specific calculi depends on a detailed medical history, associated comorbidities and the patient's history of drug consumption. There are several risk factors associated with drug-induced stones, such as high dose of consumed drugs and long duration of treatment. Moreover, there are some specific risk factors, including urinary pH and the amount of fluid consumed by children. There are limited data regarding pediatric lithogenic drugs, and hence, our aim was to perform a comprehensive review of the literature to summarize these drugs and identify the possible mechanisms involved in calculi formation and discuss the management and preventive measures for these calculi.

Metabolic syndrome and uric acid nephrolithiasis: insulin resistance in focus

Uric acid nephrolithiasis (UAN) is an increasingly common disease in ethnically diverse populations and constitutes about 10% of all kidney stones. Metabolic syndrome and diabetes mellitus are accounted among the major risk factors for UAN, together with environmental exposure, individual lifestyle habits and genetic predisposition. The development and overt manifestation of UAN appears to stem on the background of insulin resistance, which acts at the kidney level by reducing urinary pH, thus hampering the ability of the kidney to generate renal ammonium in response to an acid load. Unduly acidic urinary pH and overt UAN are both considered renal manifestations of insulin resistance. The mechanisms underlying increased endogenous acid production and/or defective ammonium excretion are yet to be completely understood. Although the development of UAN and, more in general, of kidney stones largely recognizes modifiable individual determining factors, the rising prevalence of diabetes, obesity and accompanying metabolic disorders calls for the identification of novel therapeutic approaches and intervention targets. This review aims at providing an updated picture of existing evidence on the relationship between insulin resistance and UAN in the context of metabolic syndrome and in light of the most recent advancements in our understanding of its genetic signature.

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.

Epidemiology, pathophysiology, and management of uric acid urolithiasis: A narrative review

An in-depth comprehension of the epidemiology as well as pathophysiology of uric acid urolithiasis is important for the identification, treatment, and prophylaxis of calculi in these patients. Persistently low urinary pH, hyperuricosuria, and low urinary volume are the most important factors in pathogenesis of uric acid urolithiasis. Other various causes of calculus formation comprises of chronic diarrhea, renal hyperuricosuria, insulin resistance, primary gout, extra purine in the diet, neoplastic syndromes, and congenital hyperuricemia. Non-contrast-enhanced computed tomography is the radiologic modality of choice for early assessment of patients with renal colic. Excluding situations where there is acute obstruction, rising blood chemistry, severe infection, or unresolved pain, the initial management ought to be medical dissolution by oral chemolysis since this method has proved to be effective in most of the cases.

Treatment of Burkitt lymphoma in adults

Since its initial description in 1958, Burkitt lymphoma has become a prototype for our understanding of the pathogenesis and optimal treatment of aggressive lymphomas. The evolution of the treatment of this disease is explored and current therapeutic approaches evaluated. Special issues in the treatment of Burkitt lymphoma will also be discussed, including considerations in patients infected with HIV and current views on prophylactic measures and treatment of tumor lysis syndrome.

Tumour lysis syndrome: implications for cancer therapy

The tumour lysis syndrome (TLS) is a group of metabolic abnormalities caused by rapid and unexpected release of cellular components into the circulation as a result of massive destruction of rapidly proliferating malignant cells. It usually develops in patients with hematologic malignancies like acute lymphoid leukemia, non-Hodgkin and Burkitt's lymphoma after initiation of chemotherapy or may, rarely, occur spontaneously. Though TLS is seldom observed in relation to solid tumours, there have been reports of connections with examples such as lung, liver, breast, gastric carcinomas. The clinical manifestations of TLS include hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcemia. These indications if untreated lead to life-threatening complications such as acute renal failure, cardiac arrhythmias, seizures, and eventually death due to multiorgan failure. Therefore early detection of TLS is of vital importance. This can be accomplished by identification of high risk patients, implementation of suitable prophylactic measures and monitoring of the electrolyte levels in patients undergoing chemotherapy.

Recommendations for the evaluation of risk and prophylaxis of tumour lysis syndrome (TLS) in adults and children with malignant diseases: an expert TLS panel consensus

Tumour lysis syndrome (TLS) is a life-threatening oncological emergency characterized by metabolic abnormalities including hyperuricaemia, hyperphosphataemia, hyperkalaemia and hypocalcaemia. These metabolic complications predispose the cancer patient to clinical toxicities including renal insufficiency, cardiac arrhythmias, seizures, neurological complications and potentially sudden death. With the increased availability of newer therapeutic targeted agents, such as rasburicase (recombinant urate oxidase), there are no published guidelines on the risk classification of TLS for individual patients at risk of developing this syndrome. We convened an international TLS expert consensus panel to develop guidelines for a medical decision tree to assign low, intermediate and high risk to patients with cancer at risk for TLS. Risk factors included biological evidence of laboratory TLS (LTLS), proliferation, bulk and stage of malignant tumour and renal impairment and/or involvement at the time of TLS diagnosis. An international TLS consensus expert panel of paediatric and adult oncologists, experts in TLS pathophysiology and experts in TLS prophylaxis and management, developed a final model of low, intermediate and high risk TLS classification and associated TLS prophylaxis recommendations.

Guidelines for the management of pediatric and adult tumor lysis syndrome: an evidence-based review

PURPOSE

Tumor lysis syndrome (TLS) has recently been subclassified into either laboratory TLS or clinical TLS, and a grading system has been established. Standardized guidelines, however, are needed to aid in the stratification of patients according to risk and to establish prophylaxis and treatment recommendations for patients at risk or with established TLS.

METHODS

A panel of experts in pediatric and adult hematologic malignancies and TLS was assembled to develop recommendations and guidelines for TLS based on clinical evidence and standards of care. A review of relevant literature was also used.

RESULTS

New guidelines are presented regarding the prevention and management of patients at risk of developing TLS. The best management of TLS is prevention. Prevention strategies include hydration and prophylactic rasburicase in high-risk patients, hydration plus allopurinol or rasburicase for intermediate-risk patients, and close monitoring for low-risk patients. Primary management of established TLS involves similar recommendations, with the addition of aggressive hydration and diuresis, plus allopurinol or rasburicase for hyperuricemia. Alkalinization is not recommended. Although guidelines for rasburicase use in adults are provided, this agent is currently only approved for use in pediatric patients in the United States.

CONCLUSION

The potential severity of complications resulting from TLS requires measures for prevention in high-risk patients and prompts treatment in the event that symptoms arise. Recognition of risk factors, monitoring of at-risk patients, and appropriate interventions are the key to preventing or managing TLS. These guidelines should assist in the prevention of TLS and improve the management of patients with established TLS.

Implications of disorders of purine metabolism for the kidney and the urinary tract

The spectrum of kidney and urinary tract disorders related to purines comprises acute hyperuricosuric nephropathy, chronic urate nephropathy and urolithiasis. Two factors in the development of acute hyperuricosuric nephropathy are increased uric acid concentration and low pH in the tubular fluid. Chronic urate nephropathy still possess several problems: incidence (although this seems to be decreasing, presumably owing to effective prevention), the source of interstitial urate, the cause of the interstitial deposition of urate, and the role of urate deposits in the pathogenesis of the interstitial nephropathy. The relation of the experimental nephropathy to the pathogenesis of chronic urate nephropathy in the human is not yet clear but a model is proposed according to which interstitial urate derives from two sources: hyperuricaemic plasma and hyperuricosuric tubular fluid. Urolithiasis related to purines leads to uric acid-urate stones, xanthine stones, 2,8-dihydroxyadenine stones, iatrogenic xanthine and oxipurinol stones, and possibly calcium stones. Pathogenetic factors in uric acid lithiasis are hyperuricosuria (whether due to an inborn enzyme abnormality or of unknown aetiology) and low urinary pH; oliguria is a contributory factor. There remain several open questions about uric acid lithiasis: incidence, the shift of its location from lower to upper urinary tract, the interplay of pathogenetic factors, and the role of compounds which inhibit crystallization.

Tumor lysis syndrome in elderly

The majority of cancers occur in adults over the age of 65, with about 70% of all cancer deaths in this population. Tumor lysis syndrome (TLS) is a complication of hematological and others malignancies, caused by massive tumor cell lysis due to chemotherapy, immunotherapy, radiotherapy. TLS can determine an alteration of the body's normal homeostatic mechanisms and cause hyperuricemia, hyperkaliemia, hyperphosphatemia, hypocalcaemia and uremia. Aggressive fluid administration has been recommended in all patients presumed to be at risk of this syndrome. Hyperkaliemia has to be correct with hypertonic glucose, resins and dialysis. Initial treatment of hyperphosphatemia includes phosphate binders. The cornerstone of prevention and treatment of hyperuricemia includes both inhibiting the formation of uric acid as well as increasing its renal clearance through urinary alkalinization, allopurinol, rasburicase. Conventional management to prevent acute renal failure consists of intravenous hydration, diuretic therapy and urinary alkalinization. The management of TLS in elderly patients is often complicated by the renal and the heart senescence and by the presence of multiple co morbid conditions, polypharmacy and difficulties with adherence to complex medication and dietary regimens.

Simultaneous treatment with citrate prevents nephropathy induced by FYX-051, a xanthine oxidoreductase inhibitor, in rats

The possible mechanism of the underlying nephropathy found in the rat toxicity study of FYX-051, a xanthine oxidoreductase inhibitor, was investigated. Rats received oral treatment of either 1 or 3 mg/kg of FYX-051, with and without citrate for four weeks to elucidate whether nephropathy could be caused by materials deposited in the kidney. Furthermore, analysis of the renal deposits in rats was also performed. Consequently, interstitial nephritis comprising interstitial inflammatory cell infiltration, dilatation, basophilia and epithelial necrosis of renal tubules and collecting ducts, deposits in renal tubules and collecting ducts, and so forth was seen in six of the eight rats and in all eight rats in the 1 and 3 mg/kg FYX-051 alone groups, respectively, with the intensity in the 3 mg/kg group being moderate to severe. In the simultaneous treatment with citrate group, however, no alterations were observed in the kidney, except for minimal interstitial nephritis in one instance in the 3 mg/kg FYX-051 + citrate group along with an increased urinary pH, leading to an increase in xanthine solubility. Analysis of intrarenal deposits showed that the entity would be composed of xanthine crystals. The present study, therefore, showed that nephropathy in rats occurring after the administration of FYX-051 was a secondary change caused by xanthine crystals being deposited in the kidney, and no other causes could be implicated in this kidney lesion.

Simultaneous determination of 16 purine derivatives in urinary calculi by gradient reversed-phase high-performance liquid chromatography with UV detection

A reversed-phase high-performance liquid chromatography (HPLC) method with ultraviolet detection has been developed for the analysis of purines in urinary calculi. The method using gradient of methanol concentration and pH was able to separate 16 compounds: uric acid, 2,8-dihydroxyadenine, xanthine, hypoxanthine, allopurinol and oxypurinol as well as 10 methyl derivatives of uric acid or xanthine (1-, 3-, 7- and 9-methyluric acid, 1,3-, 1,7- and 3,7-dimethyluric acid, 1-, 3- and 7-methylxanthine). Limits of detection for individual compounds ranged from 0.006 to 0.035 mg purine/g of the stone weight and precision (CV%) was 0.5-2.4%. The method enabled us to detect in human uric acid stones admixtures of nine other purine derivatives: natural metabolites (hypoxanthine, xanthine, 2,8-dihydroxyadenine) and methylated purines (1-, 3- and 7-methyluric acid, 1,3-dimethyluric acid, 3- and 7-methylxanthine) originating from the metabolism of methylxanthines (caffeine, theophylline and theobromine). The method allows simultaneous quantitation of all known purine constituents of urinary stones, including methylated purines, and may be used as a reference one for diagnosing disorders of purine metabolism and research on the pathogenesis of urolithiasis.

Tumour lysis syndrome: new therapeutic strategies and classification

Tumour lysis syndrome (TLS) describes the metabolic derangements that occur with tumour breakdown following the initiation of cytotoxic therapy. TLS results from the rapid destruction of malignant cells and the abrupt release of intracellular ions, nucleic acids, proteins and their metabolites into the extracellular space. These metabolites can overwhelm the body's normal homeostatic mechanisms and cause hyperuricaemia, hyperkalaemia, hyperphosphaetemia, hypocalcaemia and uraemia. TLS can lead to acute renal failure and can be life-threatening. Early recognition of patients at risk and initiation of therapy for TLS is essential. There is a high incidence of TLS in tumours with high proliferative rates and tumour burden such as acute lymphoblastic leukaemia and Burkitt's lymphoma. The mainstays of TLS prophylaxis and treatment include aggressive hydration and diuresis, control of hyperuricaemia with allopurinol prophylaxis and rasburicase treatment, and vigilant monitoring of electrolyte abnormalities. Urine alkalinization remains controversial. Unfortunately, there have been few comprehensive reviews on this important subject. In this review, we describe the incidence, pathophysiological mechanisms of TLS and risk factors for its development. We summarise recent advances in the management of TLS and provide a new classification system and recommendations for prophylaxis and/or treatment based on this classification scheme.

Allopurinol induces renal toxicity by impairing pyrimidine metabolism in mice

We investigated the relationship between the toxic effect of allopurinol and pyrimidine metabolism in mice. Allopurinol-induced increases in plasma transaminase levels in dinitrofluorobenzene (DNFB)-sensitized mice were not affected by uridine. In contrast, plasma creatinine and BUN tended to decrease 18 hr after the last injection of uridine. Both plasma and urinary orotidine (OD) were detected in DNFB-sensitized mice after administration of a single dose of allopurinol. In contrast, TEI-6720, a newly synthesized xanthine oxidase/xanthine dehydrogenase inhibitor, caused neither pyrimidine metabolism abnormality nor renal impairment in DNFB-sensitized mice. Also, normal mice administered high doses of allopurinol showed abnormal pyrimidine metabolism together with renal toxicity which could be ameliorated by uridine, indicating that allopurinol essentially causes pyrimidine metabolism abnormality leading to renal impairment. In DNFB-sensitized mice, allopurinol increased urinary OD excretion to an extent similar to that in normal mice administered the same dose of allopurinol. However, renal impairment by allopurinol was more striking in DNFB-sensitized mice than in normal mice. Histopathological observations showed that allopurinol induced calculus formation in the collecting tubules and papillary duct. Calculus formation was increased by DNFB and decreased by uridine. These observations indicate that the enhancement of the renal toxicity of allopurinol by DNFB-sensitization may be due to some biological interactions between DNFB and allopurinol. In humans, it is possible that there are some biological interactions which serve to enhance the toxicity of allopurinol, resulting in the development of allopurinol hypersensitivity syndrome (AHS). In contrast, TEI-6720, had no effect on pyrimidine metabolism and showed no toxic effect.

Serial renal sonographic evaluation of patients with Lesch-Nyhan syndrome

The objective of this study was to review sequential renal sonograms of patients with Lesch-Nyhan syndrome obtained over several years to determine different sonographic patterns, the alterations in the patterns occurring over time and the relationship to management. Additional objectives were to evaluate the size of the kidneys, and to correlate the metabolic constituents of calculi with the therapeutic regimens and with the renal sonographic patterns. Serial sonograms of six patients with Lesch-Nyhan syndrome were reviewed for periods varying between 2 and 7 years with a mean of 4 years. The ages of the patients at the conclusion of the study were between 10 and 22 years. Three patterns of abnormal echogenicity were found; a punctate increase in echogenicity in the renal medullary pyramids, a diffuse increase in medullary pyramid echogenicity, and a pattern of increased echogenicity in the collecting system. These patterns were progressive but did not alternate on sequential scans, regardless of increasing or constant therapy. Analysis of calculi suggested patients were precipitating various metabolites concurrently; the incidence of metabolites appeared to be unrelated to therapy. Those patients with shadowing opacities, whether in the renal medulla or collecting system, were more likely to develop renal colic. Renal dimensions were small with renal function remaining normal.

Renal sonography in long standing Lesch-Nyhan syndrome

The Lesch-Nyhan syndrome is an x-linked defect of purine metabolism resulting in its classical form in major neurodevelopmental abnormality, hyperuricaemia, and hyperuricosuria. Uric acid calculi and crystalluria are common. Allopurinol is the main method of reducing serum and urinary uric acid levels, but results in xanthinuria and oxypurinoluria, both of which may cause crystal nephropathy and calculi. The variable ultrasonic appearances of multiple calculi and increased medullary echogenicity in four cases of long-standing treated disease and the nature of the renal disorder, which is at least partially iatrogenic, are described.

Etiopathogenesis of uncommon canine uroliths. Xanthine, carbonate, drugs, and drug metabolites

Metabolic disorders, medication, and diagnostic agents may be associated with urolithiasis in dogs. Examples of uroliths that have been uncommonly encountered in dogs include xanthine, dolomite, tetracycline, and sulfonamides. Detection of these and other apparently uncommon uroliths requires a high index of suspicion and proper methods of analysis.

Xanthine-containing calculi during allopurinol therapy

We report a case of urate overproduction owing to the Lesch-Nyhan syndrome (deficiency of hypoxanthine-guanine phosphoribosyltransferase). Urate crystalluria was controlled by allopurinol therapy but renal calculi developed, which contained a variety of purines, particularly the relatively insoluble xanthine, as well as oxypurinol and hypoxanthine. The potential hazard from the increased amounts of xanthine that are produced during allopurinol therapy for urate overproduction is stressed, as well as the importance of maintaining a high urine flow rate even during such therapy.

Xanthine calculi in the Lesch-Nyhan syndrome

Urinary tract calculi composed primarily of xanthine are rare in adults and children. However, there is risk of xanthine calculi formation in children with hereditary xanthinuria and children on xanthine oxidase inhibitor therapy for hyperuricemia. We describe the clinical presentation and management of 2 children with the Lesch-Nyhan syndrome (a congenital disorder of purine metabolism) and xanthine calculi. Little information has been available to direct the urologic management of such patients. We have based a plan for management upon our clinical experience with these children, as well as upon in vitro dissolution studies of the calculi. We have had some clinical success using an alternating acid/base dissolution therapy developed in the laboratory.

Prevention of recurrent uric acid and calcium oxalate stones by administration of the xanthine oxidase inhibitors Milurit 100 and Milurit 300

Disturbances in purine metabolism with hyperuricaemia and/or hyperuricosuria are a risk factor in uric acid and Ca oxalate stone formation. By way of a competitive xanthine oxidase inhibition, the formation of uric acid is reduced by allopurinol. In investigations on two groups of patients, Milurit could be demonstrated to decrease the uric acid levels in serum and urine. No differences could be seen in the dosages of 3 x 100 mg or 1 x 300 mg Milurit. Therefore, in stone recurrence prevention, the administration of Milurit 300 is recommended.

A distinct human variant of hypoxanthine-guanine phosphoribosyl transferase

A variant form of hypoxanthine-guanine phosphoribosyl transferase has been found in a neurologically normal pediatric patient who presented with hematuria an episodes of oliguria and azotemia. The level of erythrocyte enzyme activity was 3% of normal. Electrophoretic mobility was more rapid than normal. The Km for hypoxanthine was approximately ten times normal. Immunochemical analysis indicated that the variant enzyme cross reacted with antibody to normal HPRT. A system is described for the systematic characterization of a variant HPRT.