Percutaneous radiofrequency ablation of small renal tumours in patients with a single functioning kidney: long-term results.

OBJECTIVES: To evaluate the long-term results of percutaneous radiofrequency ablation (RFA) of small renal tumours in patients with a single functioning kidney (SFK). METHODS: This is a single-centre prospective study. Patients with an SFK and a tumour smaller than 3.5 cm, treated with RFA over a 7.5-year period, were included. Nineteen consecutive patients (12 male), aged between 33 and 83 years (mean 61.4), were treated for 23 lesions. Primary endpoints were technical success and tumour recurrence rate. Secondary endpoints were the deterioration of renal function and overall survival rate. RESULTS: The mean follow-up was 56.1 months (range 36-102). Primary technical success was 100 %. There were no major peri-procedural complications. In two cases, minor complications occurred. There was no significant difference between the baseline glomerular filtration rate (GFR) and GFR at 3, 12 and 24 months post-procedure. In four lesions (17 %), recurrence was detected and an additional RFA session was performed. None of the patients developed renal failure during their lifetime. Three of the patients died because of other reasons. CONCLUSIONS: Percutaneous RFA of small renal tumours in patients with an SFK offers very satisfactory long-term results regarding preservation of renal function, local tumour control and overall survival. KEY POINTS: • Tumour in a single functioning kidney requires minimally invasive treatment. • Radiofrequency ablation plays an established role in managing small renal tumours. • Long-term results of radiofrequency ablation have shown satisfactory local tumour control. • Long-term results have also shown that renal function may be preserved.

Radiology: does it have a sell-by date?

In a few years we are likely to see 3D images generated instantly, and with comparable resolution to today's 2D views. Inclusion of functional information, possibly at the molecular level, could also assist in clinical decision-making. Some specialist clinicians with intimate knowledge of their field of interest are likely to have a better understanding of the pathology and physiology of an organ system than a general radiologist. So given that the images will be presented in a more familiar format, why should clinicians and surgeons wait for a general radiologist to read them? If radiologists wish to retain their role as the experts in image interpretation, they will not only need a thorough understanding of imaging and radiological anatomy, but also a detailed understanding of pathology and physiology. It is clearly unrealistic to expect most people to gain that knowledge across a range of fields, hence the need for subspecialization. There are already commercial moves to harness the expertise of superspecialist radiologists, using teleradiology, to provide expert opinions in particularly difficult cases. This is just the beginning of a major shift in the pattern of practice in radiology. The radiology community cannot ignore impending technological developments. If radiologists take no interest in the emergence of highly detailed, user-friendly images, then the clinicians and surgeons will organise their own department-based image interpretation. However, radiologists are very good at adapting to technological change and are very likely to rise to these challenges. Far from having a sell-by date, radiology has a bright future.

Epidemiology and prognostic implications of contrast-induced nephropathy.

Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 0.5 mg/dL (44.2 mumol/L), or a 25% increase from the baseline value 48 hours after the procedure, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, responsible for approximately 11% of cases. CIN may be difficult to distinguish from cholesterol embolization, another cause of postprocedure renal impairment. The reported incidence of CIN varies depending on the patient population studied. The impact of postprocedural renal impairment on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention. CIN is associated with increased mortality both in hospital and at 1 year. A higher incidence of in-hospital and late cardiovascular events, as well as longer hospital stays, has been reported in patients developing CIN. In a small proportion of patients, CIN is severe enough to require dialysis, and these patients have a particularly poor prognosis. Many of the risk markers for CIN are also predictive of a worse prognosis.

Pathophysiology of contrast-induced nephropathy.

Contrast-induced nephropathy (CIN) is the third leading cause of acute kidney injury in hospitalized patients and is associated with significant patient morbidity. The pathogenesis of CIN is complex and not fully understood, but iodinated contrast agents induce intense and prolonged vasoconstriction at the corticomedullary junction of the kidney. Moreover, high-osmolar dyes directly impair the autoregulatory capacity of the kidney through a loss of nitric oxide production. These effects, coupled with direct tubular toxicity of contrast media, lead to overt acute tubular necrosis and the syndrome of CIN.

Baseline renal function screening.

Renal impairment at baseline (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m(2)) is the most important risk marker to predict the risk of contrast-induced nephropathy (CIN) in patients receiving iodinated contrast media. Hence, it is important to assess renal function before administration of contrast medium to ensure that appropriate steps are taken to reduce the risk. Serum creatinine alone does not provide a reliable measure of renal function, hence the National Kidney Foundation Kidney Disease Outcome Quality Initiative (K/DOQI) recommends that clinicians should use an eGFR calculated from the serum creatinine as an index of renal function. The CIN Consensus Working Panel agreed that eGFR should be determined before contrast administration, using the abbreviated Modification of Diet in Renal Disease (MDRD) formula, recommended by K/DOQI as the preferred equation for the calculation of eGFR in adults. Where a serum creatinine measurement or eGFR is not available, a simple survey or questionnaire can be used before contrast agent administration to identify patients at higher risk for CIN compared with the general population. In emergency situations, where the benefit of very early imaging outweighs the risk of waiting, the CIN Consensus Working Panel agreed that the procedure can be performed without assessment of renal function.

Risk prediction of contrast-induced nephropathy.

In order to make appropriate decisions about clinical management, it is important for physicians to be able to stratify patients according to their risk for contrast-induced nephropathy (CIN). The most important risk marker for nephropathy after exposure to iodinated contrast media is preexisting renal impairment. The risk of CIN is elevated and becomes clinically important in patients with chronic kidney disease characterized by an estimated glomerular filtration rate <60 mL/min per 1.73 m(2). In patients with renal impairment, diabetes mellitus amplifies the risk of CIN and complicates postprocedure management. Other markers associated with an increased risk of CIN include cardiovascular disease, periprocedural hemodynamic instability, use of nephrotoxic drugs, and anemia. The effect of risk factors is additive, and the presence of multiple risk factors in the same patient can create a very high risk for CIN and acute renal failure requiring dialysis. Risk models incorporating baseline and periprocedural characteristics have been developed using data from large databases of percutaneous coronary intervention patients. These schemes are potentially valuable, but at present the most practical approach to risk prediction is based on a simple model incorporating renal function and diabetes mellitus.

High-risk situations and procedures.

With the wider use of imaging and interventional techniques that require the use of iodinated contrast media in seriously ill patients, many clinical situations occur where patients may be at increased risk for contrast-induced nephropathy (CIN). There is little guidance for clinicians in these areas. The aim of this review is to assess the available literature. Acute renal failure is a common complication following coronary artery bypass surgery, and exposure to contrast medium may increase the risk for this condition, although there is insufficient evidence to make a definitive statement. Evidence is also limited for patients with liver disease: in those undergoing transarterial chemoembolization, cirrhosis may be a risk factor for renal failure. There is some evidence that periprocedural hypotension may be a risk factor for CIN after percutaneous coronary intervention, but no published information was identified on the significance of shock or hypotension in other groups of patients. The published evidence on the risk of CIN in renal transplant recipients is inconsistent. In emergency situations, the course of action is usually dictated by clinical circumstances; the renal status of a patient is likely to be unknown and it is important to ensure adequate volume expansion, especially after the procedure. In all clinical situations that are potentially associated with a high risk for CIN, the decision to administer contrast medium is a matter for clinical judgment, based on the clinical status of the patient and the expected benefits of the investigation or procedure.

Contrast medium use.

Various properties of iodinated contrast media (osmolality, ionic versus nonionic, and viscosity) may contribute to contrast-induced nephropathy (CIN). Therefore, the choice of contrast medium affects the risk for CIN. There is good evidence that low-osmolar contrast media are less nephrotoxic than high-osmolar contrast media in patients at increased risk for CIN who receive intra-arterial iodinated contrast. Current evidence suggests that nonionic isosmolar contrast presents the lowest risk for CIN in patients with chronic kidney disease (CKD), particularly in those patients with diabetes mellitus. Intra-arterial administration of contrast media may be associated with a greater risk for CIN above that observed with intravenous administration. The use of gadolinium or CO(2) as alternative contrast media to avoid the risk of nephrotoxicity cannot be substantiated by clinical trials and therefore cannot be recommended. Most studies show that, within a class, higher volumes (>100 mL) of iodinated contrast medium are associated with a higher risk for CIN. However, in patients at high risk, such as those with CKD and diabetes, even small volumes of contrast medium can have adverse effects on renal function.

Strategies to reduce the risk of contrast-induced nephropathy.

In view of the clinical importance of contrast-induced nephropathy (CIN), numerous potential risk-reduction strategies have been evaluated. Adequate intravenous volume expansion with isotonic crystalloid (1.0-1.5 mL/kg per hr) for 3-12 hours before the procedure and continued for 6-24 hours afterward can lessen the probability of CIN in patients at risk. There are insufficient data on oral fluids (as opposed to intravenous volume expansion) as a CIN-prevention strategy. No adjunctive medical or mechanical treatment has been proved to be efficacious in reducing risk for CIN. Prophylactic hemodialysis and hemofiltration have not been validated as effective strategies. The CIN Consensus Working Panel considered that, of the pharmacologic agents that have been evaluated, theophylline, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), ascorbic acid, and prostaglandin E(1) deserve further evaluation. N-acetylcysteine is not consistently effective in reducing the risk for CIN. Fenoldopam, dopamine, calcium channel blockers, atrial natriuretic peptide, and l-arginine have not been shown to be effective. Use of furosemide, mannitol, or an endothelin receptor antagonist is potentially detrimental. Nephrotoxic drugs should be withdrawn before contrast administration in patients at risk for CIN.

Contrast-Induced Nephropathy (CIN) Consensus Working Panel: executive summary.

With the advances made in radiology and cardiology, greater numbers of patients are expected to undergo exposure to iodinated contrast media in the years to come. Contrast-induced nephropathy (CIN) accounts for a significant number of cases of hospital-acquired renal failure, with adverse effects on prognosis and healthcare costs. The CIN Consensus Working Panel is an international multidisciplinary group convened to address the challenges of CIN. The group reviewed 865 published papers, chosen for potential relevance from a comprehensive literature search that identified over 4000 references. The results were used to compile reviews covering the epidemiology and pathogenesis of CIN, baseline renal function measurement, risk assessment, identification of high-risk patients, contrast medium use, and preventive strategies. In this executive summary, consensus statements and an algorithm for the risk stratification and management of CIN are presented.