Low urine pH is associated with reduced indinavir crystalluria in indinavir-treated HIV-infected individuals.

Indinavir is a potent HIV-1 protease inhibitor included in current antiretroviral therapeutic regimens. It is associated with renal and urological complications ascribed to indinavir crystalluria. We have previously reported that indinavir crystalluria is frequently observed soon after initiation of therapy. In a cohort of 54 asymptomatic indinavir-naive HIV-1-infected individuals during their first year of treatment with indinavir, approximately 25% of urinalyses (U/A) contained indinavir crystals. Because the determinants of the crystalluria are unknown, we examined the relationship between urine specific gravity (SG) and pH, singly and in combination, and indinavir crystalluria in these subjects. A total of 579 U/A were obtained from the study subjects at their scheduled monthly outpatient medical assessments. The frequency of indinavir crystalluria was lower in U/A with lower pH, irrespective of the SG. Conversely, U/A with high pH (> or = 6.0) had a higher frequency of indinavir crystalluria, which was further influenced by the urine SG. As a result, nearly half of the U/A (46.7%) with high pH (> or = 6.0) and intermediate-high SG (> or = 1.015) contained indinavir crystals. In conclusion, the frequency of indinavir crystalluria in asymptomatic HIV-1 infected individuals during their first year of treatment with indinavir was markedly influenced by the urine pH and SG. Our findings suggest that low urine pH may have a protective effect against indinavir crystalluria across the entire range of urine SG.

Systemic amyloidosis involving the diaphragm and acute massive hydrothorax during peritoneal dialysis.

Hydrothorax secondary to trans-diaphragmatic fluid leakage through a peritoneo-pleural communication is an occasional, potentially serious complication of peritoneal dialysis. The etiology of this condition is not clear, being thought to be due either to congenital or acquired diaphragmatic fenestrations or acquired scarcity of muscle fibers in the tendinous part of the diaphragm which are compounded by increased intra-abdominal pressure during the dwell period of peritoneal dialysis. We report a 54-year-old woman who developed irreversible acute renal failure from adjuvant chemotherapy for ovarian cancer previously resected surgically. Three days after the onset of continuous ambulatory peritoneal dialysis, she developed acute respiratory distress associated with a massive right hydrothorax secondary to a peritoneo-pleural communication demonstrated by scintigraphy. At autopsy 2 weeks later, systemic amyloidosis was surprisingly found and histologic examination of the right hemidiaphragm showed the presence of amyloid, among sparse muscle fibers. This is the first case report of a distinct pathological process, i.e. amyloidosis, involving the diaphragm associated with a peritoneo-pleural communication causing massive hydrothorax at the onset of peritoneal dialysis.

Prospective study of urinalysis abnormalities in HIV-positive individuals treated with indinavir.

Indinavir is a potent protease inhibitor widely used in combination with reverse-transcriptase inhibitors to treat human immunodeficiency virus (HIV) disease. Individuals treated with indinavir are prone to develop urinary complications, including renal colic, renal calculi, lower urinary tract symptoms, and indinavir crystalluria. Although renal stones secondary to indinavir have been described and characterized, little is known about the onset, frequency, and significance of the crystalluria. To document the longitudinal characteristics of indinavir crystalluria and associated urine abnormalities, 54 asymptomatic indinavir-naive HIV-positive individuals had urinalysis testing initially weekly and then monthly during the first year of indinavir treatment. Six hundred eight urinalyses were performed (11 +/- 2 urinalysis/subject), including 579 microscopy examinations performed by a nephrologist (10 +/- 2 examinations/subject). Baseline urinalysis results were essentially normal. After the start of treatment, indinavir crystalluria was frequently observed (67% of subjects). After the first 2 weeks, indinavir crystalluria remained constant at a frequency of approximately 25% of urine sediments examined at each test point. Other urine abnormalities, principally leukocytes (>/=10/high-power field) and casts, were observed in 39% of subjects. These abnormalities were more severe in five subjects, with concomitant increasing serum creatinine levels in three of them. Additional urine findings include the predominance of low pH (/=1.025 in 66% of urinalyses). In conclusion, abnormal urinalysis results were noted frequently during the first year of treatment with indinavir. The main findings were the high proportion of subjects with crystalluria and the relatively high frequency of crystalluria observed consistently throughout. These findings may occasionally be associated with other urine abnormalities, presumably secondary to indinavir crystalluria.

Metabolic acidosis during urinary retention in a patient with an enterovesical fistula.

We report a patient known to have an enterovesical fistula who presented severe acute metabolic acidosis during an episode of urinary retention. The enterovesical fistula which had been intermittently symptomatic for 4 years, had developed after several intestinal surgical procedures and related intraperitoneal sepsis following resection of colon cancer 21 years previously. The patient who had a total colectomy and ileostomy, was admitted for hip replacement with the routine placement of a Foley bladder catheter. Three weeks post-operatively, the patient developed acute urinary retention following removal of the urinary catheter. The output from his ileostomy was immediately markedly increased, presumably from bladder urine diverted into the intestines through the enterovesical fistula. Within a few days he presented a normal anion gap metabolic acidosis with raised urea and stable creatinine; his clinical status deteriorated markedly with profound obtundation. These metabolic abnormalities were readily corrected by re-insertion of the Foley catheter with restoration of normal urine flow and immediate corresponding fall in the ileostomy output. Radiographic studies showed the presence of the enterovesical fistula originating from the jejunum. This is the first report of acute metabolic acidosis in association with an enterovesical fistula; the severe metabolic disturbances were triggered by the development of urinary retention resulting in the diversion of urine into the small bowel through the fistula.

Acquired cystic kidney disease: rapid progression from small to enlarged kidneys simulating adult polycystic kidney disease.

A 57-year-old man on chronic hemodialysis presented marked bilateral renal enlargement due to acquired cystic kidney disease (ACKD). He had been on hemodialysis for less than 3 years only (14 months prior to receiving a functional renal transplant which lasted 8 years, followed by 18 additional months of dialysis), before the diagnosis of ACKD was made following an episode of flank pain with gross hematuria. The marked changes in kidney appearance during this 11-year period were documented by serial ultrasound examination showing the kidneys to be of near-normal size before the start of dialysis (> or =10 cm in 1986), then shrunken and contracted 5 years later while having a functioning renal transplant (<5 cm in 1991), and markedly enlarged reaching the size of adult polycystic kidney disease after returning to dialysis (>13 cm in 1997). Since the risk of ACKD increases with duration of dialysis, we sought additional predisposing factors in this unusual case and found that 2 years after renal transplantation, the patient was diagnosed with breast cancer for which he was treated with surgical excision and tamoxifen. Based on ultrasound evidence that the tamoxifen treatment preceeded the appearance of the renal cystic changes, we wonder whether this drug may have played a role in the rapid development of ACKD.

The natural history of leukocyturia associated with indinavir treatment in HIV+ individuals.

Urinary complications observed during indinavir treatment of HIV disease are often attributed to indinavir crystalluria. In a prospective study of urinalysis during the first year of indinavir therapy, 5 of 54 asymptomatic HIV+ individuals presented severe leukocyturia (> or =100 cells/HPF) usually accompanying indinavir crystalluria. The clinical course of these 5 individuals, successfully treated for HIV and monitored for an second follow-up year, suggests that recurrence of severe leukocyturia may be an indicator of renal damage, likely tubulointerstitial disease caused by indinavir crystalluria. This is in contrast to the remaining 49 subjects, including those presenting mild leukocyturia, who did not demonstrate any evidence of renal disease. Regular urinalysis is therefore recommended in the clinical management of indinavir-treated individuals to detect early renal damage secondary to indinavir crystalluria and to prevent further renal impairment.

Erythrocytosis after renal transplantation represents an abnormality of insulin-like growth factor-I and its binding proteins.

BACKGROUND: Secondary erythrocytosis is classically defined by an increase in erythropoietin (EPO) production. Despite increased levels of EPO often seen in secondary erythrocytosis, some of these forms such as that seen after renal transplantation remain undefined. Our group has recently investigated the in vivo function of insulin-like growth factor-I (IGF-I) in erythropoiesis both in humans and in a murine model of chronic renal failure. These data, and the recently recognized role of IGF-I in polycythemia vera, suggested that IGF-I might be involved in secondary erythrocytosis. METHODS: Renal transplant recipients who developed erythrocytosis after transplantation were compared to normal individuals and to renal transplant recipients without erythrocytosis. We measured fasting serum EPO and IGF-I in all three groups. Because binding proteins may modify IGF-I function, IGF-I-binding proteins (IGFBP) 1 and 3, major binding proteins of IGF-I, were also measured. RESULTS: Renal transplant recipients have significantly elevated serum of IGF-I and IGFBP3 compared to normal individuals. When transplant recipients with and without posttransplant erythrocytosis were compared, similar levels of IGF-I were found; however, the group with erythrocytosis had significantly elevated IGFBP1 and IGFBP3. No other significant differences including EPO levels were found between the groups. CONCLUSIONS: Erythrocytosis after renal transplantation represents an anomaly of both IGF-I and its major binding proteins. Further studies are under way to better define this dysregulation and determine whether IGF-I can play a more generalized role in secondary forms of erythropoiesis.

Effect of chronic renal failure on the expression of erythropoietin message in a murine model.

The anemia of chronic renal failure (CRF) is largely due to decreased production of erythropoietin (EPO) by the kidney. A small amount of EPO also originates from extra-renal sources, and this would be expected to assume a more important role in maintaining erythropoiesis when renal production is impaired. In this study, we examined the production of EPO mRNA by RT-PCR in kidney, liver, and bone marrow tissues isolated from normal mice, mice rendered acutely anemic by phlebotomy, and from mice with surgically induced CRF. The induction of acute anemia results in an expected increase in the expression of EPO mRNA in renal and hepatic tissue. In contrast, while the expression of EPO mRNA was expectedly reduced in the kidney from CRF mice, it was completely absent in the liver of these same animals. EPO mRNA expression was also absent in the bone marrow in both states of acute anemia and CRF. These results show that CRF can directly or indirectly can suppress the extrarenal production of EPO by the liver and that this effect may further aggravate the anemia of CRF.

Subtherapeutic erythropoietin and insulin-like growth factor-1 correct the anemia of chronic renal failure in the mouse.

Chronic renal failure (CRF) is associated with a hyporegenerative anemia, which is caused primarily by inadequate production of erythropoietin (EPO) by the diseased kidneys and is responsive to exogenous EPO administration. Little is known about compensatory mechanisms that might supervene in anemia with low levels of EPO. Multiple investigations in vitro suggest an important role for insulin-like growth factor-1 (IGF-1) as well as EPO in erythropoiesis. Recently, both EPO and IGF-1 in vitro have been found to stimulate erythroid colony forming units in the mouse. However, no studies have examined the effect of IGF-1, singly and in combination with EPO, in CRF in vivo. This study examined mice with surgically-induced renal failure of six weeks duration that were treated for three weeks with the combination of subtherapeutic doses of both EPO and IGF-1. The single administration of each cytokine caused no significant change in hemoglobin in all CRF mice. In marked contrast the combined administration of the two cytokines produced a striking rise in hemoglobin, resulting in anemia correction in the majority of animals. The response to the combination therapy was comparable to the maximal response obtained with a single EPO dose (10 U) in a dose-finding study. Although the data are limited to utilizing one dose of each cytokine and one preparation of IGF-1, the large increase in hemoglobin observed with the combination therapy indicates that these two cytokines work in concert to stimulate erythroid precursors in CRF. In addition, untreated CRF mice showed markedly increased serum levels of low molecular weight binding proteins for IGF-1, potentially reducing the bioavailability of IGF-1. These findings taken together suggest that the anemia of CRF may represent both an EPO and a functional IGF-1 deficient state.

Anemia of chronic renal failure: characterization in the mouse and correction with human recombinant erythropoietin.

Anemia is a cardinal feature of chronic renal failure (CRF) which contributes significantly to the clinical syndrome of chronic uremia. We have conducted a detailed examination of the hematological changes in CRF in the inbred mouse strain C57BL/6J. As in the human situation, CRF mice presented major hematological changes affecting primarily the erythroid cell series. Despite the presence of abundant iron stores in the bone marrow, the CRF mice developed a hypoproliferative anemia of a severity commensurate with the degree of renal impairment. The levels of circulating erythropoietin (EPO) in CRF mice were not significantly different from those in normal control littermates and were therefore inappropriately low for the degree of anemia. In contrast acutely bled control mice with normal renal function showed a significant inverse correlation between the serum EPO level and hemoglobin concentration, indicating an appropriate response to anemia. The chronic administration of recombinant human EPO raised the hemoglobin concentration of CRF mice, a therapeutic effect which was independent of the initial degree of anemia. These observations suggest that this animal model has wide applicability for the study of anemia secondary to CRF.

Possible role of mevalonate in the hypercholesterolemia seen in experimental chronic renal failure.

Hypercholesterolemia may contribute to the pathogenesis of atherosclerosis associated with chronic renal failure (CRF). The mechanism underlying CRF-induced hypercholesterolemia, however, is still unknown. Mevalonate is the direct product of the rate-limiting step in cholesterol synthesis which is catalyzed by 3-hydroxy-3-methylglutaryl coenzyme A reductase. We studied the changes in mevalonate metabolism in a mouse model of CRF in which serum total cholesterol levels are directly correlated with the degree of severity of the disease as measured by serum urea levels. The results of these experiments indicated that in CRF mice, the urine mevalonate levels were significantly lower, while serum mevalonate and total cholesterol levels were significantly higher than in normal mice. We believe that by restricting the normal urinary excretion of mevalonate CRF results in more of this precursor being available for direct cholesterol synthesis. In addition, an increase in circulating mevalonate may upregulate the shunt pathway of mevalonate metabolism in the liver and peripheral tissues, thus providing increased levels of the substrates acetoacetate and acetyl coenzyme A for cholesterol synthesis.

An assay to measure antibiotic efficacy against Staphylococcus epidermidis biofilms on implant surfaces.

Infection is a major limitation of implantable devices. Optimal antibiotic therapeutic regimes have not yet been defined. Implant-associated infections have a number of differentiating characteristics, which include the predominance of Staphylococcus epidermidis and other skin bacteria of normally low pathogenicity as the causative agents, together with a relative resistance to host defenses and to antibiotic therapy. These properties have been ascribed to the ability of the bacteria to exist on implant surfaces in the biofilm phase, which is protective. An assay of antibiotic activity using a standardized bacterial biofilm preparation of S. epidermidis is described. The assay is used to evaluate the relative efficacy of antibiotics to sterilize the biofilm, when they are used singly, or in double or triple combinations. The modulating effects of changing antibiotic concentrations and modifying the environment with CAPD variables (fresh and spent dialysis fluid, common PD solution additives) are also measured and the data summarized. It is hoped that, by using this and similar assays, individualized optimal therapeutic regimes of implant-associated infections may be logically planned.

The differential activity of aminoglycoside antibiotics with rifampin explored in a kinetic in vitro model of implant-associated infection (Staphylococcus epidermidis).

Implant-associated infections offer resistance to antibiotic treatment and possibly do so because the causative bacteria which reside on the artificial surface are enclosed in a protective matrix (biofilm) shielding the bacteria against the action of host defenses and antibiotic action. We have investigated in vitro the effect of various antimicrobial agents on biofilms of Staphylococcus epidermidis, which is the main organism responsible for implant-associated infections. Rifampin was found to exert superior activity, albeit incomplete, against S. epidermidis biofilms using an assay system which enabled the determination of the kinetics of antibiotic action over five days. In a large screening study looking for agents capable of completing the action of rifampin, gentamicin was unexpectedly found to be antagonistic to rifampin. The present study was undertaken to investigate further the activity of gentamicin and five other aminoglycoside antibiotics using a wider range of concentrations (2.5-20 micrograms/mL). The main findings were a marked synergy with rifampin demonstrated by streptomycin, producing a bactericidal outcome, which contrasted sharply with the indifference or antagonism shown by the other aminoglycosides. We then studied in further detail the effect of separate combinations of streptomycin and gentamicin with rifampin over a wider concentration range of each agent (1.25-40 micrograms/mL). Streptomycin showed strong rapid synergy with rifampin even at the lowest concentration of each antibiotic. Gentamicin demonstrated a concentration-related antagonism towards rifampin which was independent of rifampin concentration. The data support the conclusion that streptomycin, like cell-wall active antibiotics, exerts a potent synergy with rifampin against S. epidermidis biofilms, and that the other aminoglycosides, predominantly gentamicin, strongly antagonize rifampin action.(ABSTRACT TRUNCATED AT 250 WORDS)

Time-kill efficacy of antibiotics in combination with rifampin against Staphylococcus epidermidis biofilms.

Infections associated with implants are frequently resistant to conventional antibiotic therapy. This resistance has been ascribed to the presence of bacteria on the artificial surface within a protective glue-like matrix forming a bacterial biofilm. We have demonstrated that experimental biofilms of Staphylococcus epidermidis, the main pathogen associated with implantation, are exquisitely sensitive to the action of rifampin. This effect of rifampin is incomplete, however, with the emergence of rifampin-resistant survivors that readily repopulate the biofilm. Studies were therefore performed to determine the effect of combinations of 13 different antibiotics with rifampin against standardized S. epidermidis biofilm preparations in an in vitro assay enabling the kinetic measurement of antibiotic action over a five-day period. The antibiotic combinations with rifampin demonstrated unsuspected divergent patterns of antimicrobial activity against the biofilms: 1. rapid synergy with rifampin was observed with cell-wall active antibiotics (cloxacillin, cephalothin, cefazolin, and cefamandole), whereas slower synergy occurred with vancomycin, ciprofloxacin, tetracycline, and amikacin; 2. some antibiotics (tobramycin, erythromycin, clindamycin, fusidic acid) did not influence the outcome; 3. gentamicin unexpectedly showed marked antagonism to rifampin. These results are relevant to the design of optimal therapeutic regimens for the management of resistant implant-associated infections.