Repetitive brief ischemia: intermittent reperfusion during ischemia ameliorates the extent of injury in the perfused kidney

In Situ Treatment of Branch Renal Artery Aneurysms With Pantaloon Vein Graft

Introduction:

The optimal method of operative management of complex renal artery aneurysms (RAAs) involving distal branches (BRAAs) remains unclear. When more than 1 artery is involved within the BRAA, endovascular techniques are not advisable and an ex vivo approach is often preferred. In this study, we introduce an alternative surgical in situ technique to treat BRAAs.

Methods and Surgical Technique:

Five aneurysms involving the main or second-order bifurcation of the renal artery (RA) were treated in 4 patients at our institute between November 2012 and January 2017. The treatment of the BRAAs was based on resection of the aneurysm wall and reconstruction with autologous Pantaloon vein graft (PVG): a “Y-shaped” bypass created on-bench with autogenous great saphenous vein. Sequential clamping/reperfusion of the kidney allows to reduce renal function impairment.

Results:

No perioperative mortality or morbidity was observed, including none nephrectomy. In all the cases, aneurysms were treated with an in situ technique as previously planned. All the grafts were patent at the follow-up time (mean 64.1 ± 11.7 months). Renal function was preserved in all the cases. Vascularization of the renal parenchyma was satisfactory both on arterial echo Doppler and contrast-medium ultrasound in all the cases. Average cross-clamping times of the main RA and of a single branch RA were 15.8 ± 1.7 and 17.7 ± 4.6 minutes, respectively. Mean total operating time was 266.3 ± 18.9 minutes.

Conclusion:

The PVG with sequential clamping applied in the surgical treatment of BRAAs permits to reduce the ischemic effects to the renal parenchyma. To our knowledge, these are the first cases described in which BRAAs are treated with a PVG and our experience suggests that it is a feasible technique, with good long-term results and without severe adverse events recorded.

Hyperuricemia increases the risk of acute kidney injury: a systematic review and meta-analysis

Background

Mounting evidence indicated that the elevated serum uric acid level was associated with an increased risk of acute kidney injury (AKI). Our goal was to systematically evaluate the correlation of serum uric acid (SUA) level and incidence of AKI by longitudinal cohort studies.

Methods

We searched electronic databases and the reference lists of relevant articles. 18 cohort studies with 75,200 patients were analyzed in this random-effect meta-analysis. Hyperuricemia was defined as SUA levels greater than 360-420 μmol/L (6–7 mg/dl), which was various according to different studies. Data including serum uric acid, serum creatinine, and incidence of AKI and hospital mortality were summarized using random-effects meta-analysis.

Results

The hyperuricemia group significantly exerted a higher risk of AKI compared to the controls (odds ratio OR 2.24, 95% CI 1.76-2.86, p < 0.01). Furthermore, there is less difference of the pooled rate of AKI after cardiac surgery between hyperuricemia and control group (34.3% vs 29.7%, OR 1.24, 95% CI 0.96-1.60, p = 0.10), while the rates after PCI were much higher in hyperuricemia group than that in control group (16.0% vs 5.3%, OR 3.24, 95% CI 1.93-5.45, p < 0.01). In addition, there were significant differences in baseline renal function at admission between hyperuricemia and control groups in most of the included studies. The relationship between hyperuricemia and hospital mortality was not significant. The pooled pre-operative SUA levels were higher in AKI group than that in the non-AKI group.

Conclusions

Elevated SUA level showed an increased risk for AKI in patients and measurements of SUA may help identify risks for AKI in these patients.

Are allopurinol dose and duration of use nephroprotective in the elderly? A Medicare claims study of allopurinol use and incident renal failure

OBJECTIVE

To assess the effect of allopurinol dose/duration on the risk of renal failure in the elderly with allopurinol use.

METHODS

We used the 5% random Medicare claims data from 2006 to 2012. Multivariable-adjusted Cox regression analyses assessed the association of allopurinol dose/duration with subsequent risk of developing incident renal failure or end-stage renal disease (ESRD) (no prior diagnosis in last 183 days) in allopurinol users, controlling for age, sex, race and Charlson-Romano comorbidity index. HRs with 95% CIs were calculated. Sensitivity analyses considered a longer baseline period (365 days), controlled for gout or used more specific codes.

RESULTS

Among the 30 022 allopurinol treatment episodes, 8314 incident renal failure episodes occurred. Compared with 1-199 mg/day, allopurinol dose of 200-299 mg/day (HR 0.81; 95% CI 0.75 to 0.87) and ≥300 mg/day, 0.71 (0.67 to 0.76), had significantly lower hazard of renal failure in multivariable-adjustment model, confirmed in multiple sensitivity analyses. Longer allopurinol use duration was significantly associated with lower hazards in sensitivity analyses (365-day look-back; reference, <0.5 year): 0.5-1 year, 1.00 (0.88, 1.15); >1-2 years, 0.85 (0.73 to 0.99); and >2 years, 0.81 (0.67 to 0.98). Allopurinol ≥300 mg/day was also associated with significantly lower risk of acute renal failure and ESRD with HR of 0.89 (0.83 to 0.94) and 0.57 (0.46 to 0.71), respectively.

CONCLUSIONS

Higher allopurinol dose is independently protective against incident renal failure in the elderly allopurinol users. A longer duration of allopurinol use may be associated with lower risk of incident renal failure. Potential mechanisms of these effects need to be examined.

Impact of repeated hilar clamping on renal function during laparoscopic and robot-assisted partial nephrectomy

BACKGROUND AND PURPOSE

Conventional wisdom and small animal studies suggest repeated hilar clamping during partial nephrectomy is deleterious to renal function. We describe the impact of repeated renal hilar clamping during laparoscopic partial nephrectomy (LPN) and robot-assisted partial nephrectomy (RPN) on the overall function of the operated kidney.

PATIENTS AND METHODS

A retrospective analysis of all patients undergoing RPN or LPN with repeated hilar clamping was performed. Patient and tumor characteristics were recorded. All patients had preoperative and postoperative mercaptoacetyltriglycine (MAG)3 renal scans, and the change in function was calculated. Change in glomerular filtration rate (GFR) was calculated with the modified Modification of Diet in Renal Disease equation as well.

RESULTS

Seven patients were studied with an average age of 60 and a body mass index of 32. Tumors averaged 3.6 cm, and there were four and three right- and left-sided tumors, respectively. The reasons for repeated clamping were bleeding in three patients and either gross or microscopic positive margins in four patients, all of whom had repeated resection. The average initial clamp time was 20 minutes, and the average reclamp time was 12 minutes. The average operative time was 185 minutes. and average blood loss was 171 mL. All renal units were functioning postoperatively. The average change in absolute renal function on the operated kidney was -4.9%, and the relative loss of function was -10%, both measured on MAG3 scan. The average GFR before surgery was 61.4 (mL/min/1.73m(2)); after surgery, the average GFR was 57.1 (mL/min/1.73m(2)), for an average loss of -7%. The range of change in GFR was from 0% to -23%.

CONCLUSIONS

Although not optimal, repeated clamping of the renal hilum during partial nephrectomy to control bleeding or to obtain a clear surgical margin is associated with minimal loss of renal function.

Effect of allopurinol on germ cell apoptosis following testicular ischemia-reperfusion injury in a rat

Recent evidence suggests that apoptosis is involved in germ cell loss following testicular ischemia-reperfusion (IR) injury. Allopurinol (Allo) is as a free radical scavenger which prevents tissue damage caused by reperfusion and oxygenation after ischemia; however, its effect on apoptosis in this type of injury has not been studied. To examine the effect of allopurinol on germ cell apoptosis following testicular IR in a rat. Forty rats were divided randomly into 4 experimental groups of 10 rats each: group A (Sham)-Sham operated animals; group B (Sham-Allo)-Sham operated rats treated with allopurinol given PO (by gavage) at a dose of 200 mg/kg, once daily, immediately before and 24 h following operation; group C (IR)-rats underwent 90 min of unilateral testicular ischemia and 48 h of reperfusion; group D (IR-Allo)-rats underwent IR and were treated with allopurinol similar to group B. The ipsilateral and contralateral testes were harvested 48 h following operation. Johnsen's criteria and the number of germinal cell layers were used to categorize spermatogenesis. TUNEL assay was used to determine germ cell apoptosis. Statistical analysis was performed using one-way ANOVA test, with P < 0.05 considered statistically significant. Testicular ischemia in rats led to histological damage in the ipsilateral testis. In the contralateral testis minimal damage was observed. Treatment with allopurinol increased significantly Johnsen's score in both the ischemic (7.3 +/- 0.5 vs 5.6 +/- 0.5, P < 0.05) and contralateral (8.9 +/- 0.1 vs 8.3 +/- 0.2, P < 0.05) testis, compared to IR-animals. Germ cell apoptosis in both the ischemic and the contralateral testis increased significantly after IR. Treatment with allopurinol resulted in a significant decrease in germ cell apoptosis in the ipsilateral testis, expressed as the number of positive tubules per 100 tubules (AI-1, (apoptotic index) threefold decrease, P < 0.005) and the number of apoptotic cells per 100 tubules (AI-2, fivefold decrease, P < 0.005) as well as a significant decrease in germ cell apoptosis in the contralateral testis (AI-1, 3.5-fold decrease, P < 0.05, AI-2- sixfold decrease, P < 0.005) compared to IR animals. In a rat model of testicular IR, treatment with allopurinol decreases germ cell apoptosis in both ischemic and contralateral testes and improves spermatogenesis.

Effect of elevated serum uric acid on cisplatin-induced acute renal failure

Marked hyperuricemia is known to cause acute renal failure via intrarenal crystal deposition. However, recent studies suggest mild hyperuricemia may have vasoactive and proinflammatory effects independent of crystal formation. We therefore tested the hypothesis that mild hyperuricemia might exacerbate renal injury and dysfunction in a model of cisplatin-induced acute renal failure in the rat. Cisplatin was administered to normouricemic and hyperuricemic rats (the latter generated by administering the urate oxidase inhibitor, oxonic acid). Recombinant urate oxidase (rasburicase) was administered in a third group to assess the effect of lowering uric acid on outcomes. Other control groups include normal rats and hyperuricemic rats without cisplatin-induced injury. Cisplatin induced injury of the pars recta (S3) segment of the proximal tubule in association with a mild monocyte infiltration. Hyperuricemic rats showed significantly greater tubular injury and proliferation with significantly greater macrophage infiltration and increased expression of monocyte chemoattractant protein-1. However, renal function was not different between normouricemic and hyperuricemic rats with cisplatin injury. Treatment with rasburicase reversed the inflammatory changes and lessened tubular injury with an improvement in renal function (relative to the hyperuricemic group). No intrarenal crystals were observed in any groups. These data provide the first experimental evidence that uric acid, at concentrations that do not cause intrarenal crystal formation, may exacerbate renal injury in a model of acute renal failure. The mechanism may relate to a proinflammatory pathway involving chemokine expression with leukocyte infiltration.

Could uric acid have a role in acute renal failure?

Acute renal failure (ARF), induced by either toxins or ischemia, is associated with significant morbidity. The pathogenesis of ARF is complex and is characterized by renal vasoconstriction and oxidative stress in association with tubular and microvascular injury and interstitial inflammation. In many situations, ARF is associated with a rise in serum uric acid as a result of both increased generation and decreased excretion. Although it is widely recognized that markedly elevated levels of uric acid can cause ARF via supersaturation within the tubules with crystallization and intrarenal obstruction ("acute urate nephropathy"), the possibility that uric acid may affect renal outcomes at concentrations that do not lead to tubular obstruction have not been considered. This article reviews both the salutary and the adverse effects of uric acid on biologic processes and presents the hypothesis that hyperuricemia, particularly if chronic and marked, likely represents a true risk factor for ARF. Hyperuricemia also may account for the paradoxic lack of benefit of diuretics in the management of ARF. It is suggested that studies are needed to investigate the role of chronic hyperuricemia on renal outcomes after acute tubular injury.

Allopurinol and enalapril failed to conserve urinary NOx and sodium in ischemic acute renal failure in spontaneously hypertensive rats

BACKGROUND

Ischemia-reperfusion-induced acute renal failure (ARF) is associated with a high mortality in patients with hypertension and with an unfavorable outcome of kidney transplants from marginal donors.

AIM

The influence of allopurinol and enalapril on urinary nitrate/nitrite (UNOx), glomerular filtration rate, plasma and urinary sodium, and hemodynamic parameters was examined in spontaneously hypertensive rats (SHR) with ARF.

METHODS

ARF was induced by right-kidney removal and clamping the left renal artery for 40 min in 50 male 26-week-old SHR weighing 300 +/- 23 g. The rats were randomly allocated to five groups: (1) sham operated; (2) ARF; (3) ARF after pretreatment with 40 mg/kg allopurinol; (4) ARF after pretreatment with 40 mg/kg enalapril, and (5) ARF after pretreatment with 40 mg/kg allopurinol and 40 mg/kg enalapril. Creatinine clearance, UNOx (Griess reaction), cardiac output (dye dilution technique), mean arterial blood pressure, and renal blood flow were measured 24 h after reperfusion. Total vascular resistance and renal vascular resistance were calculated and compared between the groups.

RESULTS

A nonsignificant decrease was found in both daily UNOx excretion and creatinine clearance when pretreated ARF groups and the ARF group without pretreatment were compared (p > 0.05). Significantly lower plasma sodium values (139.5 +/- 4.86 mmol/l) in the allopurinol-pretreated ARF group were found than in the ARF group without pretreatment, in the ARF group pretreated with enalapril, and in the sham SHR group (p = 0.029). The urinary sodium loss was greater in the enalapril-pretreated than in the allopurinol-pretreated ARF group (p = 0.047). Allopurinol and/or enalapril pretreatment decreased total vascular resistance (p = 0.003) in comparison with the sham SHR group.

CONCLUSION

Neither allopurinol nor enalapril nor both were protective against ischemia-reperfusion injury in SHR, nor altered glomerular filtration rate and UNOx in a favorable direction.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.