Renal Dysfunction in HIV-1-infected Patients

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.

Renal abnormalities among HIV-infected, antiretroviral naive children, Harare, Zimbabwe: a cross-sectional study

BACKGROUND

Data on the prevalence of renal and urine abnormalities among HIV-infected children in Sub-Saharan Africa are limited. We set out to determine the prevalence of proteinuria; low estimated glomerular filtration rate (eGFR), urinary tract infection and associated factors among HIV-infected antiretroviral therapy (ART) naive children, aged 2-12 years, attending the paediatric HIV clinic at a tertiary hospital in Harare.

METHODS

Consecutive ART naive children attending the clinic between June and October 2009 were recruited. Detailed medical history was obtained and a complete physical examination was performed. Children were screened for urinary tract infection and for significant persistent proteinuria. Serum creatinine was used to estimate GFR using the modified Counahan-Barratt formula. The Student's t-test was used to analyse continuous variables and the chi-square or Fisher's exact test was used to analyse categorical data. Logistic regression was performed to assess the relationship between study factors and urine abnormalities, persistent proteinuria and the eGFR.

RESULTS

Two hundred and twenty children were enrolled into the study. The median age was 90 months (Q1=65.5; Q3=116.5). The prevalence of urinary tract infection was 9.5%. Escherichia coli was the predominant organism. There was uniform resistance to cotrimoxazole. Persistent proteinuria (urine protein to creatinine ratio greater than 0.2, a week apart) was found in 5% of the children. Seventy-five children (34.6%) had mild to moderate renal impairment shown by a low eGFR (30 to <90 ml/min/1.73 m2). Persistent proteinuria was more likely to be found in children who were wasted, weight-for-height (WHZ) z-score <-2 (p=0.0005). Children with WHO clinical stage 4 were more likely to have a low eGFR than children with less advanced stages (OR 2.68; CI 1.24-5.80). Urine abnormalities were more likely to be observed in children with WHO clinical stages 3 and 4 (OR 2.20; CI 1.06-4.60).

CONCLUSION

There is significant renal impairment among HIV-infected, ART naive children aged 2-12 years attending the outpatient paediatric HIV clinic at Harare Central Hospital. The abnormalities are more likely to occur in children with advanced HIV/AIDS. Screening for renal impairment and urinary tract infections in HIV-infected children before initiation of ART and regularly thereafter would be helpful in their management.

KEYWORDS

HIV, renal disease, persistent proteinuria, glomerular filtration rate, urinary tract infection.

HIV-1 infection and the kidney: an evolving challenge in HIV medicine

With the advent of highly active antiretroviral therapy (HAART), the incidence of opportunistic infections has declined substantially, and cardiovascular, liver, and renal diseases have emerged as major causes of morbidity and mortality in individuals with human immunodeficiency virus (HIV). Acute renal failure is common in HIV-infected patients and is associated with acute infection and medication-related nephrotoxicity. HIV-associated nephropathy is the most common cause of chronic kidney disease in HIV-positive African American populations and may respond to HAART. Other important HIV-associated renal diseases include HIV immune complex kidney diseases and thrombotic microangiopathy. The increasing importance of non-HIV-associated diseases, such as diabetes mellitus, hypertension, and vascular disease, to the burden of chronic kidney disease has been recognized, focusing attention on prevention and control of these diseases in HIV-positive individuals. HIV-positive individuals who experience progression to end-stage renal disease and who have undetectable HIV-1 viral loads while receiving HAART should be evaluated for renal transplant. Emerging evidence suggests that HIV-positive individuals may have graft and patient survival comparable to HIV-negative individuals. Several studies suggest that HIV-1 can potentially infect renal cells, and HIV transgenic mice have clarified the roles of a number of HIV proteins in the pathogenesis of HIV-associated renal disease. Host factors may modify disease expression at the level of cytokine networks and the renal microvasculature and contribute to the pathogenic effects of HIV-1 infection on the kidney.

HIV and the kidney: a status report after 20 years

The first association between HIV-1 infection and kidney disease was made in 1984 and much has been learned over the past 20 years. In recent years, more effective therapies for HIV-1 infection and its associated opportunistic infections have led to improved patient survival. However, with prolonged survival, morbidity associated with renal disease has also increased. Among the multiple glomerulopathies that can affect patients with HIV, focal segmental glomerulosclerosis (FSGS) is most common and frequently leads to end-stage renal disease. Although the precise mechanisms of HIV-associated FSGS remain to be elucidated, it appears that host genetic susceptibility, direct infection of the renal epithelium, and toxicity of one or more viral accessory protein contribute. Therapy for HIV-associated FSGS includes control of blood pressure and the use of angiotensin antagonist therapy. A randomized trial of angiotensin receptor blocker will be initiated shortly. Drug-related nephropathies are also common, manifesting as acute renal failure, nephrolithiasis, and interstitial nephritis. Tenofovir, a newer nucleoside analogue, has recently been implicated in causing tubular toxicity, although the incidence is low. Appropriate screening for renal dysfunction can minimize the likelihood of progressive renal injury in all patients with HIV-1 infection.

Incidence and etiology of acute renal failure among ambulatory HIV-infected patients

BACKGROUND

Acute renal failure (ARF) is a cause of renal dysfunction in human immunodeficiency virus (HIV)-infected patients. Its incidence and causes have not been studied since the introduction of highly active antiretroviral therapy (HAART) in HIV ambulatory patients.

METHODS

This is a prospective cohort study of 754 HIV patients, 18 years or older, seen at a university-based infectious disease clinic between 2000 and 2002. ARF was identified using proportional increases in serum creatinine from baseline and by chart review. Clinical conditions were assessed at the time of the ARF event. ARF incidence rates (IR) were calculated by dividing the number of events by person time at risk. To compare patients with and without ARF, t test or chi-square test were used.

RESULTS

Patient's mean age was 40 years; 68% were male and 61% were black. One hundred-eleven ARF events occurred in 71 subjects (IR 5.9 per 100 person-years; 95% CI 4.9, 7.1). ARF was more common in men, in those with CD4 cell count <200 cells/mm(3), and HIV RNA levels >10,000 copies/mL. These patients more often had acquired immunodeficiency syndrome (AIDS), hepatitis C infection (HCV), and have received HAART. ARF was mainly community-acquired, due to prerenal causes or acute tubular necrosis, and associated with opportunistic infections and drugs. Liver disease was a cause of ARF in HCV-infected patients.

CONCLUSION

ARF is common in ambulatory HIV patients. Immunosuppression, infection, and HCV are important conditions associated with ARF in the post-HAART era.

The clinical art and science of urine microscopy

PURPOSE OF REVIEW

The examination of urine sediment is a diagnostic test which is frequently neglected by nephrologists. With this review the authors wanted to demonstrate that it can provide useful and relevant information in a wide spectrum of clinical situations.

RECENT FINDINGS

The authors reviewed the main contributions dealing with urine sediment examination, published in international journals in the period from January 2002 to April 2003. After a section on methodological aspects, they described the importance of urine sediment examination in various diseases of the urinary tract. These included bladder B-lymphoma, systemic histoplasmosis, urate nephropathy, Fabry disease, myeloma cast nephropathy, giant cell arteritis, and lupus nephritis. The significance of 'decoy cells' in the urine as a marker of polyomavirus BK reactivation was also discussed, both in renal transplantation and other conditions such as solitary pancreas transplantation, chronic lymphatic leukaemia, and HIV infection. In the section devoted to urine sediment changes caused by drugs the authors dealt with leukocyturia induced by indinavir, and crystalluria, which can follow amoxycillin and acyclovir administration. Finally, they reported on the utility and limits of flow cytometry for the automated analysis of urine sediments.

SUMMARY

The review of the recent literature on urine sediment examination shows that this test has important clinical implications in a large spectrum of diseases. Therefore, it should be more widely used by nephrologists.

Trends in the epidemiology of focal segmental glomerulosclerosis

There is marked variation in the frequency of focal segmental glomerulosclerosis (FSGS) around the world. Recent studies of renal biopsy specimen archives from several institutions in the United States suggest that the incidence of FSGS has increased over the past 20 years. Indeed, FSGS has become the leading cause of idiopathic nephrotic syndrome in adults and has become increasingly common in children as well. Further, the data indicate that black individuals are at increased risk for developing idiopathic FSGS as well as FSGS in the setting of human immunodeficiency virus (HIV)-1 infection. Data from around the world suggest great variability in the proportion of glomerular disease that is attributed to FSGS, with recent increases seen in some countries and not in others. Epidemiologic data from the United States Renal Data Systems (USRDS) show that the incidence of end-stage renal disease (ESRD) owing to idiopathic FSGS has increased considerably, both as absolute numbers and as a fraction of the total ESRD incident population, with FSGS now accounting for 3.3% of incident ESRD cases. In the United States, the annual rate of incident FSGS ESRD cases is 7 per million for the general population, 20 per million for black individuals, and 5 per million for white individuals. The numbers of acquired immune deficiency syndrome (AIDS) nephropathy incident ESRD cases increased rapidly until reaching a plateau after 1995. The reasons for the recent increase in idiopathic FSGS and FSGS incident ESRD cases are complex, but these trends are likely caused, at least in part, by a real increase in the incidence of FSGS over the past 10 to 20 years.

HIV-associated nephropathy in African Americans

Human immunodeficiency virus-1 (HIV-1) infection is associated with several glomerular syndromes, the most prevalent of which is HIV-associated focal segmental glomerulosclerosis (FSGS). At present, HIV-associated FSGS may account for up to 30% of patients in the United States entering end-stage renal disease (ESRD) as a consequence of FSGS. The mechanisms responsible for HIV-associated FSGS are not well defined, but evidence has been presented in favor of direct infection of renal parenchymal cells and toxicity of HIV-1 accessory proteins. HIV-associated FSGS has a striking predilection for patients of African descent. This likely has a genetic basis, although the gene or genes responsible have not yet been identified. One approach is to examine candidate genes for polymorphisms that are associated with disease. Another approach uses a genome-wide scan, relying upon linkage disequilibrium between DNA markers and the disease gene, to identify the causal gene or genes. African Americans are an admixed population, with genetic contributions from African, European, and Native American populations. In admixed populations, linkage disequilibrium between disease genes and marker genes can be exploited to identify disease genes, using an approach termed mapping by admixture linkage disequilibrium (MALD).