Faculty Bibliography

The kidney is able to rapidly eliminate many water-soluble xenobiotics (exogenous chemicals). However, in the face of extraordinary serum concentrations of these xenobiotics or renal dysfunction, alternative elimination techniques often become necessary. Extracorporeal removal (ECR) techniques are used to increase the clearance of xenobiotics. These techniques include hemodialysis (HD), charcoal hemoperfusion (HP), and modalities grouped under the heading of continuous renal replacement therapy (CRRT): continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodiafiltration (CVVHDF). Extracorporeal removal is limited to patients with significant or potentially significant clinical poisoning because the resources required to perform ECR are great. Therefore, most patients who are treated with these techniques are being cared for in intensive care units (ICUs). Our goal in this review is to discuss the properties that make xenobiotics amenable to removal by ECR and the advantages and disadvantages of the individual techniques. We discuss xenobiotics that constitute clear indications for ECR, including the toxic alcohols, salicylates, and lithium. We review the use of CRRT, a modality for which clear indications for treatment of poisonings are currently lacking

Mammalian urine contains a range of macromolecule proteins that play critical roles in renal stone formation, among which Tamm-Horsfall protein (THP) is by far the most abundant. While THP is a potent inhibitor of crystal aggregation in vitro and its ablation in vivo predisposes one of the two existing mouse models to spontaneous intrarenal calcium crystallization, key controversies remain regarding the role of THP in nephrolithiasis. By carrying out a long-range follow-up of more than 250 THP-null mice and their wild-type controls, we demonstrate here that renal calcification is a highly consistent phenotype of the THP-null mice that is age and partially gene dosage dependent, but is gender and genetic background independent. Renal calcification in THP-null mice is progressive, and by 15 mo over 85% of all the THP-null mice develop spontaneous intrarenal crystals. The crystals consist primarily of calcium phosphate in the form of hydroxyapatite, are located more frequently in the interstitial space of the renal papillae than intratubularly, particularly in older animals, and lack accompanying inflammatory cell infiltration. The interstitial deposits of hydroxyapatite observed in THP-null mice bear strong resemblances to the renal crystals found in human kidneys bearing idiopathic calcium oxalate stones. Compared with 24-h urine from the wild-type mice, that of THP-null mice is supersaturated with brushite (calcium phosphate), a stone precursor, and has reduced urinary excretion of citrate, a stone inhibitor. While less frequent than renal calcinosis, renal pelvic and ureteral stones and hydronephrosis occur in the aged THP-null mice. These results provide direct in vivo evidence indicating that normal THP plays an important role in defending the urinary system against calcification and suggest that reduced expression and/or decreased function of THP could contribute to nephrolithiasis

INTRODUCTION: Uremic syndrome consists of nitrogenous waste retention, deficiency in kidney-derived hormones, and reduced acid excretion, and, if untreated, may progress to coma and eventual death. Previous experience suggests that oral administration of a probiotic formulation of selected microbial strains may extend renoprotection via intraintestinal extraction of toxic waste solutes in patients with chronic kidney disease (CKD)stages 3 and 4. This report presents preliminary data from a pilot study. METHODS: This was a 6-month prospective, randomized, double-blind, placebo-controlled crossover trial of a probiotic bacterial formulation conducted in four countries, at five institutions, on 46 outpatients with CKD stages 3 an nd 4: USA (n=10), Canada (n=113), Nigeria (n=115), and Argentina (n=8). Outcomes were compared using biochemical parameters:blood urea nitrogen (BUN), serum creatinine, and uric acid. General well-being was assessed as a secondary parameter by a quality of life (QQOL) questionnaire on a subjective scale of 1-10. RESULTS: Oral ingestion of probiotics (90 billion colony forming units [CFUs]/day) was well tolerated and safe during the entire trial period at all sites. BUN levels decreased in 29 patients (63%, P<0.05), creatinine levels decreased in 20 patients (43%, no statistical significance), and uric acid levels decreased in 15 patients (33%, no statistical significance). Almost all subjects expressed a perceived substantial overall improvement in QOL (86%, P<0.05). CONCLUSION: The main outcomes of this preliminary trial include a significant reduction of BUN, enhanced well-being, and absence of serious adverse effects, thus supporting the use of the chosen probiotic formulation for bowel-based toxic solute extraction. QOL and BUN levels showed statistically significant differences in outcome (P<0.05) between placebo and probiotic treatment periods at all four sites (46 patients). A major limitation of this trial is the small sample size nd elated inconsistencies

Crystallization of L-cystine is a critical step in the pathogenesis of cystine kidney stones. Treatments for this disease are somewhat effective but often lead to adverse side effects. Real-time in situ atomic force microscopy (AFM) reveals that L-cystine dimethylester (L-CDME) and L-cystine methylester (L-CME) dramatically reduce the growth velocity of the six symmetry-equivalent {100} steps because of specific binding at the crystal surface, which frustrates the attachment of L-cystine molecules. L-CDME and L-CME produce l-cystine crystals with different habits that reveal distinct binding modes at the crystal surfaces. The AFM observations are mirrored by reduced crystal yield and crystal size in the presence of L-CDME and L-CME, collectively suggesting a new pathway to the prevention of L-cystine stones by rational design of crystal growth inhibitors

Gout is a chronic disease in which excessively high levels of serum urate (hyperuricemia) result in tissue depositions of sodium urate crystals and intermittent inflammatory attacks. Patients who have gout frequently experience a range of comorbidities, which complicates management and affects long-term prognosis. We review some of the more important of these comorbidities and consider the extent to which gout or hyperuricemia may be either a consequence or a cause of these related conditions. In addition, we briefly consider several neurological conditions in which the presence of gout or a high serum urate level may be associated with less disease, rather than more

We examined the effect of a controlled diet and two probiotic preparations on urinary oxalate excretion, a risk factor for calcium oxalate kidney stone formation, in patients with mild hyperoxaluria. Patients were randomized to a placebo, a probiotic, or a synbiotic preparation. This tested whether these probiotic preparations can increase oxalate metabolism in the intestine and/or decrease oxalate absorption from the gut. Patients were maintained on a controlled diet to remove the confounding variable of differing oxalate intake from food. Urinary oxalate excretion and calcium oxalate supersaturation on the controlled diet were significantly lower compared with baseline on a free-choice diet. Neither study preparation reduced urinary oxalate excretion nor calcium oxalate supersaturation. Fecal lactobacilli colony counts increased on both preparations, whereas enterococcal and yeast colony counts were increased on the synbiotic. Total urine volume and the excretion of oxalate and calcium were all strong independent determinants of urinary calcium oxalate supersaturation. Hence, dietary oxalate restriction reduced urinary oxalate excretion, but the tested probiotics did not influence urinary oxalate levels in patients on a restricted oxalate diet. However, this study suggests that dietary oxalate restriction is useful for kidney stone prevention

Cystinuria is a primary inherited aminoaciduria caused by mutations in the genes that encode the two subunits (neutral and basic amino acid transport protein rBAT and b(0,+)-type amino acid transporter 1) of the amino acid transport system b(0,+). This autosomal recessive disorder (in which few cases show dominant inheritance) causes a failure in the reabsorption of filtered cystine and dibasic amino acids in the proximal tubule. The clinical symptoms of this disease are caused by the loss of poorly soluble cystine, which precipitates to form stones. Although rare, the prevalence of cystinuria is sufficiently high that the disease results in a substantial contribution to pediatric renal lithiasis. A thorough understanding of cystine transport processes over the past 15 years and the genetic abnormalities responsible for the disease has led to a new classification of cystinuria and recognition that some cases result from an autosomal dominant etiology with incomplete penetrance. This Review examines the molecular and mechanistic effects of some of the mutations that cause cystinuria based on our current understanding of the structural and cellular biology of system b(0,+). This Review also describes the current treatments to prevent recurrent cystine lithiasis

Recent evidence suggests that targeting higher hemoglobin values with erythropoiesis stimulating agents (ESAs) may lack mortality benefits and may even result in adverse cardiovascular complications when used in chronic kidney disease patients. However, ESAs are frequently reported to result in improvements in health-related quality of life (HRQOL). The purpose of this review is to evaluate the magnitude and nature of ESA-associated improvements in HRQOL, as well as to understand how to interpret the clinical significance of HRQOL data. HRQOL findings should be analyzed not by statistical significance but rather by using a minimal clinically important difference approach, or, alternatively, a distribution-based approach (such as Cohen's effect size). HRQOL domains that are most improved with ESAs relate to physical symptoms, vitality, energy, and performance; domains of social functioning and mental health show modest improvement, whereas the domains of emotional functioning and pain show very little improvement. Additional domains not measured by commonly used instruments (such as the SF-36) that have been shown to improve with ESAs include sleep, cognitive functioning, and sexual functioning. The maximal increase in HRQOL per incremental increase in hemoglobin appears to occur in the range of 10-12 g/dl. Beyond this range, additional normalization of hemoglobin (to 12-14 g/dl) results in continued (albeit blunted) improvements in HRQOL.Kidney International advance online publication, 27 August 2008; doi:10.1038/ki.2008.414