Detection of renal tubular lesions after abdominal aortography and selective renal arteriography by quantitative measurements of brush-border enzymes in the urine

Urinary Protein Excretion following Intravenously Administered Ionic and Non-Ionic Contrast Media in Man

Urinary protein excretion following intravenous administration of the radiographic contrast media (CM) diatrizoate (ionic) and iopromide (non-ionic) was examined in 20 patients with normal renal function. Neither of the two CM had any effect on the 24-h urinary excretion of albumin (a marker of glomerular proteinuria). The 24-h urinary excretion of the retinol-binding protein (a marker of low molecular weight or tubular proteinuria) and the folate binding protein, a protein localized in the brush-border membranes of the proximal tubular cells, showed a statistically significant transient increase the day after diatrizoate injection, whereas no increase was observed after iopromide. Thus, only a minimal and temporary disturbance of the renal proximal tubular function was observed after diatrizoate injection in patients with normal renal function.

Systemic, Pulmonary and Renal Haemodynamic and Renal Morphologic Effects of Intravenously Infused Iodixanol

The systemic, pulmonary and renal haemodynamic effects following an intravenous infusion (1 ml/s, 4 ml/kg) of a non-ionic iso-osmolar contrast medium (iodixanol) were investigated in 8 pigs. Histopathologic changes occurring after infusion of iodixanol were studied by repeated renal biopsies. Iodixanol caused a significant increase of cardiac output, mean right atrial pressure, mean pulmonary arterial pressure, mean pulmonary arterial occlusion pressure and mean arterial pressure. There was a decrease of the systemic and pulmonary vascular resistances. Most renal biopsies showed no pathologic findings after infusion of iodixanol but in 3 specimens proteinaceous content was observed 15 min after infusion.

In Vivo Fluorescence Microscopy of Microcirculation in the Renal Cortex of Mice

In vivo fluorescence microscopy was used in experimental studies of renal cortical microcirculation in mice. The effects of i.v. infusions of mannitol and iohexol were studied in normal and obese/hyperglycemic mice and in mice with streptozotocin-induced diabetes mellitus. All infusions produced marked effects on the distribution and velocity of cortical blood flow with no differences between iohexol and mannitol. The renal cortical blood flow was inhomogeneous regarding different capillaries and there was an initial rise in the number of capillaries with increased blood flow after infusions of both mannitol and iohexol. The infusions of contrast medium were initially followed by a significantly larger number of capillaries with decreased blood flow in the obese/hyperglycemic mice (p < 0.05) than in the diabetic and nondiabetic mice. The variations in obese/hyperglycemic groups were, however, large. The effects were the same in normal and diabetic animals.

Nicardipine infusion for hypotensive anesthesia during orthognathic surgery has protective effect on renal function

PURPOSE

Hypotensive anesthesia may adversely affect renal function. The purpose of this study was to evaluate the renoprotective effect of nicardipine in patients undergoing orthognathic surgery under hypotensive anesthesia.

MATERIALS AND METHODS

In this double-blinded randomized controlled study, healthy patients undergoing orthognathic surgery were enrolled to evaluate renal function during and after hypotensive anesthesia. The predictor variable was the agent, nicardipine vs remifentanil, used to maintain mean arterial pressure at 50 to 65 mm Hg. Primary outcome variables were renal function markers and secondary outcome variables were hemodynamic data, which were measured before hypotension, 2 hours after hypotension, 1 hour postoperatively (t3), and 24 hours postoperatively. Linear mixed model was used to analyze repeatedly measured data.

RESULTS

Forty-six patients were randomly allocated to receive remifentanil (R group; n = 23) or nicardipine (N group; n = 23). The renal tubular function marker, urinary N-acetyl-1-β-D-glucosaminidase (NAG), was lower at t3 in the N group than in the R group (P = .014). In the N group, fractional excretion of sodium was significantly higher at t3 compared with baseline (P < .0001). The 2 groups did not show any differences in estimated creatinine clearance and serum cystatin C.

CONCLUSION

Subclinical and reversible renal dysfunction appears during hypotensive anesthesia in patients undergoing orthognathic surgery. Continuous infusion of nicardipine attenuated the increase in NAG, which is a marker of renal tubular injury, during hypotensive anesthesia with desflurane and remifentanil.

Bicarbonates for the prevention of postoperative renal failure in endovascular aortic aneurysm repair: a randomized pilot trial

Purpose. Contrast-induced nephropathy (CIN) can contribute to acute kidney injury (AKI) in patients undergoing endovascular aortic aneurysm surgery. We evaluated the incidence of AKI together with the evolution of early biomarkers of renal injury in patients receiving bicarbonates or NaCl 0.9%. Methods. This study involved endovascular aortic aneurysm surgery patients. Group A (n = 17) received bicarbonates 3 mL/kg/h for 1 h before the procedure and then 1 mL/kg/h until 6 h after surgery, whereas group B (n = 17) received NaCl 0.9% using the same protocol. Biomarkers of renal injury from urine (interleukin-18 (IL-18), neutrophil gelatinase-associated lipocalin (NGAL), N-acetyl-β-D-glucosaminidase (NAG), and kidney injury molecule 1 (KIM-1)) and blood (NGAL, cystatin C) were measured at baseline and 3, 24, and 48 h postoperatively. Results. AKI occurred in 1 patient (2.9%), in the bicarbonates group. IL-18, NAG, NGAL, and KIM-1 significantly rose in both groups after the surgery. There was a greater rise in NGAL and IL-18 after 3 h in the bicarbonates versus NaCl 0.9% group: 1115% versus 240% increase (P = 0.03) and 338% increase versus 1.4% decrease (P = 0.01). Conclusions. Despite significant elevation in biomarkers of renal injury, we demonstrated a low rate of AKI following endovascular aortic surgery.

Cardiorenal syndrome: biomarkers linking kidney damage with heart failure

All the vital organs of the body share information by virtue of various biological mediators. Primary pathology of a major organ can lead to dysfunction of the other. Cardiorenal syndrome is an important example of such organ crosstalk. Primary dysfunction of the heart or kidney can lead to injury of the other organ. As molecular injury occurs prior to clinical dysfunction, effective interventions can be planned if one can detect this organ dysfunction at an earlier stage by virtue of some biological markers. Such biomarkers can be substances in urine, serum, imaging maneuvers or any other quantifiable parameters. Some currently available biomarkers are not sensitive enough to provide timely diagnosis of the disorder. An important research priority is the development of newer biomarkers or a panel of biomarkers for the early diagnosis of organ dysfunction, as well as nature of injury, guidance for therapeutic interventions and prognosis. Many newer biomarkers have been studied for both heart and kidney dysfunction. This article focuses on newer biomarkers for the cardiorenal syndrome.

Hypotensive anesthesia with propofol and remifentanil: protective effect of alpha-tocopherol on renal function

STUDY OBJECTIVE

To determine the effect of alpha-tocopherol in patients receiving hypotensive anesthesia with propofol-remifentanil.

STUDY DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENTS

66 ASA physical status I and II patients, aged 32 to 56 years, scheduled for nasal polypectomy.

INTERVENTIONS

Patients were allocated into two groups, the treatment and the control groups (T group and C group). T group received alpha-tocopherol 300 mg orally 5 to 6 hours before surgery.

MEASUREMENTS

Sampling times and measurements were done before hypotension (t0), 45 minutes after starting hypotension (t1), 90 minutes after starting hypotension (t2), 45 minutes after recovery of normotension (t3), and 24 hours after surgery (t4). Renal function was assessed by testing glomerular and tubular functions: glomerular filtration rate, fractional excretion of sodium (FENA); fractional excretion of urea (FEUN); and urinary N-acetyl-1-beta-D-glucosoaminidase (NAG) index (NAGi).

MAIN RESULTS

Glomerular filtration rate values remained unchanged in all patient populations. Fractional excretion of sodium was within reference ranges in both groups at times t0, t1, and t2. At time t3, a significant FE(NA) peak was observed. At this time, FENA was significantly higher in C group than T group (P < 0.001). FEUN time course was similar to the FENA trend. At time t4, FENA and FEUN returned to basal values. At time t3, NAGi was also increased without significant intergroup differences (P < 0.01, P < 0.001, and P < 0.01 vs times t0, t1, t2 in C group, respectively; P < 0.01, P < 0.01, and P < 0.001 vs times t0, t1, and t2 in T group, respectively).

CONCLUSIONS

In patients without any renal disease, hypotensive anesthesia with propofol and remifentanil results in a transient tubular dysfunction, which appears to be minimized by the preoperative administration of alpha-tocopherol.

Biomarkers of acute kidney injury

The diagnosis of acute kidney injury (AKI) is usually based on measurements of blood urea nitrogen (BUN) and serum creatinine. BUN and serum creatinine are not very sensitive or specific for the diagnosis of AKI because they are affected by many renal and nonrenal factors that are independent of kidney injury or kidney function. Biomarkers of AKI that are made predominantly by the injured kidney have been discovered in preclinical studies. In clinical studies of patients with AKI, some of these biomarkers (eg, interleukin-18, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1) have been shown to increase in the urine before the increase in serum creatinine. These early biomarkers of AKI are being tested in different types of AKI and in larger clinical studies. Biomarkers of AKI may also predict long-term kidney outcomes and mortality.

Diagnosis, epidemiology and outcomes of acute kidney injury

Acute kidney injury is an increasingly common and potentially catastrophic complication in hospitalized patients. Early observational studies from the 1980s and 1990s established the general epidemiologic features of acute kidney injury: the incidence, prognostic significance, and predisposing medical and surgical conditions. Recent multicenter observational cohorts and administrative databases have enhanced our understanding of the overall disease burden of acute kidney injury and trends in its epidemiology. An increasing number of clinical studies focusing on specific types of acute kidney injury (e.g., in the setting of intravenous contrast, sepsis, and major surgery) have provided further details into this heterogeneous syndrome. Despite our sophisticated understanding of the epidemiology and pathobiology of acute kidney injury, current prevention strategies are inadequate and current treatment options outside of renal replacement therapy are nonexistent. This failure to innovate may be due in part to a diagnostic approach that has stagnated for decades and continues to rely on markers of glomerular filtration (blood urea nitrogen and creatinine) that are neither sensitive nor specific. There has been increasing interest in the identification and validation of novel biomarkers of acute kidney injury that may permit earlier and more accurate diagnosis. This review summarizes the major epidemiologic studies of acute kidney injury and efforts to modernize the approach to its diagnosis.

Urine proteomics: the present and future of measuring urinary protein components in disease

For centuries, physicians have attempted to use the urine for noninvasive assessment of disease. Today, urinalysis, in particular the measurement of proteinuria, underpins the routine assessment of patients with renal disease. More sophisticated methods for assessing specific urinary protein losses have emerged; however, albumin is still the principal urinary protein measured. Changes in the pattern of urinary protein excretion are not necessarily restricted to nephrourological disease; for instance, the appearance of beta-human chorionic gonadotropin in the urine of pregnant women is the basis for all commercially available pregnancy kits. Similarly, microalbuminuria is a clinically important marker not only of early diabetic nephropathy but also of concomitant cardiovascular disease. With the emergence of newer technologies, in particular mass spectrometry, it has become possible to study urinary protein excretion in even more detail. A variety of techniques have been used both to characterize the normal complement of urinary proteins and also to identify proteins and peptides that may facilitate earlier detection of disease, improve assessment of prognosis and allow closer monitoring of response to therapy. Such proteomics-based approaches hold great promise as the basis for new diagnostic tests and as the means to better understand disease pathogenesis. In this review, we summarize the currently available methods for urinary protein analysis and describe the newer approaches being taken to identify urinary biomarkers.

Diagnostic Potential of Urine Proteome: A Broken Mirror of Renal Diseases

This brief overview of studies into the urine proteome illustrates its potential value for diagnostic, prognostic, and pathophysiologic discovery. Hypothesis-targeted investigations of individual proteins as well as proteome-wide searches for urinary biomarkers of various diseases and their progression are reviewed. The majority of urine proteins appear as cleavage products that are found not only as free solutes but also in secreted membrane vesicles called exosomes. Described are several recent examples of important diagnostic findings using urine proteomics along with the idea that signature profiles of injury to individual nephron segments can be measured by this technology. Shared are some thoughts on the most challenging step: Integration of seemingly unrelated findings of various protein fragments into a rational pathogenetic pathway(s). The future chance that the centuries-old technique of uroscopy will reveal its secrets using modern proteomic approaches makes gradual improvement.

Urine proteomics--prospects for future diagnostics

This brief overview of the potential diagnostic, prognostic and pathophysiological value of studies into the urine proteome describes hypothesis-driven investigations of individual proteins and proteome-wide search for urinary biomarkers of various diseases and their progression. It is intended to illustrate the recent progress in the area of urine proteomics and proselytize for the promise of this centuries-old technique of uroscopy, yet to reveal its secrets, using modem approaches.

Biomarkers of acute renal injury and renal failure

Acute renal failure (ARF) is a frequent problem in the intensive care unit and is associated with a high mortality. Early recognition could help clinical management, but current indices lack sufficient predictive value for ARF. Therefore, there might be a need for biomarkers in detecting renal tubular injury and/or dysfunction at an early stage before a decline in glomerular filtration rate is noted by an increased serum creatinine. A MEDLINE/PubMed search was performed, including all articles about biomarkers for ARF. All publication types, human and animal studies, or subsets were searched in English language. An extraction of relevant articles was made for the purpose of this narrative review. These biomarkers include tubular enzymes (alpha- and pi-glutathione S-transferase, N-acetyl-glucosaminidase, alkaline phosphatase, gamma-glutamyl transpeptidase, Ala-(Leu-Gly)-aminopeptidase, and fructose-1,6-biphosphatase), low-molecular weight urinary proteins (alpha1- and beta2-microglobulin, retinol-binding protein, adenosine deaminase-binding protein, and cystatin C), Na+/H+ exchanger, neutrophil gelatinase-associated lipocalin, cysteine-rich protein 61, kidney injury molecule 1, urinary interleukins/adhesion molecules, and markers of glomerular filtration such as proatrial natriuretic peptide (1-98) and cystatin C. These biomarkers, detected in urine or serum shortly after tubular injury, have been suggested to contribute to prediction of ARF and need for renal replacement therapy. However, excretion of these biomarkers may also increase after reversible and mild dysfunction and may not necessarily be associated with persistent or irreversible damage. Large prospective studies in human are needed to demonstrate an improved outcome of biomarker-driven management of the patient at risk for ARF.

Gamma-glutamyltransferase is a reliable marker for tubular effects of contrast media

The aim of this study was to evaluate the usefulness of the measurement of urinary excretion of the brush-border enzyme gamma glutamyl-transferase (GGT), in comparison with that of alanine aminopeptidase (AAP), as a marker for tubular toxicity due to contrast media (CM). Urinary activities of AAP and GGT were measured prior to the administration of CM and 1, 3 and 5 days after in forty-nine adult renal patients undergoing a radiological examination with intravascular administration of CM. The behavior of GGT was similar to that of AAP. In fact, urinary activities of both AAP and GGT increased greatly after CM. This effect was maximal on the 1st day and statistically significant for both enzymes. Furthermore, on the 1st day a relevant increase of enzyme activity (at least +50% over the basal value) was observed in the same number of patients (67%) for AAP and GGT. The concordance between GGT and AAP variations was high and statistically significant. Finally, different variables (osmolarity, dose of CM, and baseline renal function of the patients) had a similar effect on urinary excretion of AAP and GGT. The repeatability of duplicated determinations of GGT resulted better than that of AAP. In conclusion, the good concordance of the results of GGT with those of AAP justifies the use of GGT as a marker for tubular effects due to CM. Furthermore, the measurement of GGT has a better repeatability than that of AAP.

Tubular toxicity is the main renal effect of contrast media

The aim of this study is to evaluate the effects of contrast media on both tubular and glomerular function. Different parameters of tubular and glomerular function were determined before and at 1, 3, and 5 days after the intravascular administration of contrast media in 100 adult renal patients (plasma creatinine 0.6-10.8 mg/dL, mean: 1.3). Urinary activities of five tubular enzymes (alanine aminopeptidase, gamma-glutamyltransferase, alkaline phosphatase, lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase) increased significantly on the first day after the administration of contrast media, indicating a tubular damage. Glomerular filtration rate and the conventional tests of glomerular function (plasma creatinine, creatinine clearance, and urinary proteins) presented only slight variations after the administration of contrast media. In conclusion, contrast media principally affected the renal tubule (as demonstrated by enzymuria), while their effects on glomerular function were very mild.

Contrast nephrotoxicity: predictive value of urinary enzyme markers in a rat model

RATIONALE AND OBJECTIVES

We tested whether urinary enzymes are an accurate and useful marker of renal damage in a rat model of contrast media nephrotoxicity.

METHODS

Thirty rats were pretreated with a combination of salt depletion, indomethacin, and contrast material. Alanine aminopeptidase (AAP), gamma-glutamyltranspeptidase (GGT), and N-acetyl-beta-D-glucosaminidase (NAG) were measured before and 24 hr after injection of contrast material. Enzyme concentrations were correlated with glomerular filtration rate (GFR) and histology.

RESULTS

Decreasing GFR and histopathologic changes were found only in rats treated with all three variables. NAG levels increased from baseline for both diatrizoate meglumine- and ioversol-treated animals (from 83.9 +/- 48.6 to 145.5 +/- 55.4 and from 69.41 +/- 43.6 to 123.1 +/- 50.7, respectively; P < 0.05 from baseline for ioversol) and declined in other groups. GGT and AAP levels did not correlate well with structural and functional changes.

CONCLUSIONS

In this model of contrast nephrotoxicity, NAG concentration appears to correlate with structural and functional changes associated with contrast media nephrotoxicity. However, the large range of baseline values makes this of dubious clinical use. AAP and GGT levels appear less helpful in detecting renal damage.

Glomerulotubular function in patients undergoing moderate surgical stress

Glomerular function and renal tubular function assessed by measurements of creatinine clearance rates (CCR), lithium clearance rates (CLi, and N-acetyl-beta-D-glucosaminidase (NAG) enzymuria were measured immediately prior to and within 24 h of operation (average operative time 150 min) in 16 patients undergoing a moderate surgical stress. Although serum creatinine concentrations and CCR were similar pre- and postsurgery at 105 +/- 21 and 108 +/- 21 mumol/L and 108 +/- 67 and 110 +/- 59 mL/min/100 kg body weight (mean +/- SD), respectively, both CLi and NAG were significantly increased following the surgical insult. CLi was increased from 19.7 +/- 6.1 to 31.7 +/- 16.7 mL/min/100 kg (p less than 0.01) and NAG from 71 +/- 58 to 164 +/- 10 U/mmol urinary creatinine (p less than 0.001). In addition, the absolute distal tubular reabsorption of sodium and water increased from 18.3 +/- 5.9 and 15.8 +/- 9.7 to 30.6 +/- 16.4 and 27.6 +/- 12.2 mL/min/100 kg body weight (both p less than 0.05), respectively. These results indicate early postoperative renal tubular dysfunction following a moderate surgical stress, undetected by conventional screening.

Persistent CT nephrogram: significance in the diagnosis of contrast nephropathy--an update

Contrast nephropathy (CN), a well-known complication of intravascular contrast medium, is associated with dense cortical nephrograms. These may be detected on unenhanced computed tomography (CT). We report the initial findings of a series of patients at risk for CN who received contrast for coronary arteriography or aortic arch angiography. Unenhanced CT scans were performed 22-26 h after contrast, and the mean cortical attenuation measured. These results were correlated with serial blood urea nitrogen (BUN) and serum creatinine measurements. The patients in this study, all of whom had either elevated baseline creatinine values, were over 73 years or both, had a high incidence of cortical contrast retention and contrast nephropathy.

Induction and prevention of radiocontrast-induced nephropathy in dogs with heart failure

Radiocontrast-induced nephropathy (RCIN) is a clinically important cause of acute renal failure with no effective treatment. Recognizing the high incidence of RCIN in humans with severe congestive heart failure (CHF), this study was designed to test the hypotheses that dogs with experimental CHF are at increased risk for RCIN and that pharmacologic renal levels of atrial natriuretic factor (ANF) can prevent RCIN in this model. In chronic experiments, three groups of five conscious dogs received intravenous radiocontrast (7 ml/kg). One group consisted of normal controls, while the two other groups had experimental CHF induced by eight days of ventricular pacing at 250 beats per minute. One of the CHF groups received an infusion of ANF (30 ng/kg/min) into the suprarenal aorta for one hour before, during and after the infusion of radiocontrast to achieve pharmacologic renal plasma levels. Renal function remained stable in the normal controls in contrast to the consistent decreases in daily creatinine clearance during the five days following radiocontrast in experimental CHF. In addition, ANF prevented radiocontrast-induced reductions in creatinine clearance in dogs with experimental CHF. Additional studies performed in two groups of anesthetized dogs with experimental CHF demonstrated that, in this model of RCIN, the reduction in renal function appears biphasic, and the action of ANF may be to increase glomerular filtration rate prior to radiocontrast, thus allowing a maintenance of renal function during and after radiocontrast.

Renal failure following radiologic procedures

Radiologic procedures that employ intravascular contrast material with or without angiography may lead to renal failure. In procedures that use intravenous contrast alone, the mechanism of renal injury is not precisely known, but direct toxicity to renal tubular cells is likely to be a major factor. Ionic and nonionic contrast agents are both capable of causing this adverse reaction. Renal failure occurring during angiography may also be secondary to the effects of radiocontrast, but the additional possibility that micro cholesterol emboli have been dislodged from atheroma located on the intima of large vessels must be considered. The acute or subacute development of renal failure in the presence of skin changes (livido reticularis), hypertension, multiple organ failure or dysfunction, and a fatal outcome favors the later diagnosis.

Contrast-associated nephropathy

Contrast nephropathy can be defined as an acute impairment of renal function that follows exposure to radiocontrast materials and for which alternative explanations for renal impairment have been eliminated. Based on reported studies, the incidence of contrast associated nephropathy (CAN) varies from 0 to 22%. This wide variation can be traced to differences in study design and the criteria used to designate significant renal impairment. Irrespective of the exact incidence, 2 defined risk factors have been identified: preexisting renal disease and diabetes mellitus. Whereas preexisting renal insufficiency is the single most influential risk factor for CAN, when diabetes coexists the incidence approaches 100%. The clinical presentation of CAN is distinct, having a temporal relation between the performance of the contrast study in the high-risk patient and the onset of an increase in serum creatinine levels within the next 24 hours. Serum creatinine values greater than 50% of baseline or rising 1 mg/dl or more is diagnostic. The peak serum creatinine level occurs within 3 to 5 days of the contrast study and oliguria is associated in approximately 30% of the cases. Monitoring serum creatinine is the most useful clinical procedure in high-risk patients after angiography. At least 5 potential pathophysiologic mechanisms of CAN have been proposed: interference with renal perfusion, altered glomerular perm-selectivity, direct tubular injury, intraluminal obstruction, and immunologic mechanisms. Support for each mechanism, either singularly or in combination, can be found in published reports; however, none has achieved universal acceptance. The single most important clinical axiom regarding the prevention and management of CAN is, "Always use the least invasive diagnostic procedure available."(ABSTRACT TRUNCATED AT 250 WORDS)

Renal, volume, and hormonal changes during therapeutic administration of recombinant interleukin-2 in man

Changes in blood pressure, renal function, and fluid balance were studied in 12 patients receiving intravenous recombinant interleukin-2 (IL-2) (100,000 units/kg every eight hours) over five days for treatment of metastatic melanoma and renal and colorectal cancers. The IL-2 regimen produced progressive hypotension, azotemia, and sodium avidity (fractional excretion of sodium = 0.20 +/- 0.07 percent) despite massive fluid administration (mean: 18.4 liter per five days) and weight gain (mean: 4.0 kg). Plasma renin activity rose. Hypoalbuminemia developed rapidly (3.6 +/- 0.1 g/dl to 2.2 +/- 0.1 g/dl, p less than 0.01) with widespread edema formation despite normal central venous pressures. Hematocrit did not change during the IL-2 period, consistent with a "capillary-leak." Hemodynamic and renal functional changes reversed after the IL-2 regimen was discontinued, but hypoalbuminemia and elevated urinary n-acetyl-glucosaminidase levels persisted after six days. These studies demonstrate widespread hemodynamic and vascular effects of IL-2 administration that limit its safe use and suggest a possible role for the lymphokine in mediating cardiovascular instability under other circumstances, such as endotoxic shock.