Decreased Cerebral Perfusion in Carotid Artery Stenosis, Carotid
Renal artery stenosis and peripheral vascular disease: implications for ACE inhibitor therapy
1
321 However, assessment of turbidity plus a dipstick test was effective in supporting the protocol suggested by Flanagan et al.’ 1 Departments of Internal Medicine and Bacteriology, Hôpital Louis Mourier, University of Paris VII, 92700 Colombes, France JACQUES POUCHOT ISABELLE LAUNAY PIERRE CAHEN YVES BOUSSOUGANT PHILIPPE VINCENEUX 1. Flanagan PG, Rooney PG, Davies EA, Stout RW. Evaluation of four screening tests for bacteriuria in elderly people. Lancet 1989, i. 1117-19. SiR,—Dr Rawal and colleagues report that, in a group of 396 patients, the 288 whose urine was crystal clear, with or without acidification, did not have urinary infections and imply that this finding means that observation of crystal-clear urine renders culture unnecessary. Unfortunately, they do not present enough information about their patients to justify the general clinical application of their method. We need to know the proportion of patients with clear urine in whom a urinary-tract infection might be regarded as a likely cause of a clinical problem. The use of specimens from accident departments may have led to the inclusion of a large number of afebrile, symptomless individuals in whom the absence of a urinary-tract infection would be unremarkable. From a bayesian perspective, if the prior probability of a urinary tract infection in the 288 individuals was low to begin with, any finding that correlates with lack of infection would not be surprising. If, on the other hand, many of these patients with clear urine were febrile or had other signs or symptoms that might ordinarily lead to a decision to do a urine culture, then the prior probability of a urinary-tract infection would be much higher and the failure to detect any infections would tend to support the clinical utility of the method. School of Public Health, University of California, Berkeley, California 94720, USA ERNEST B. HOOK SIR,-We were fascinated to see that doctors at Guy’s Hospital have revived the charming practice of uroscopy. While this has an excellent historical pedigree1 we wonder if the benefits in the 20th century are as great as Dr Rawal and colleagues suppose. Rawal et al claim that a urine test costs ;[4--5. We use an accurate and reproducible method but even after the most careful accounting to include all possible costs we can come to a figure nowhere near this. The average cost per specimen in this laboratory is ;[1.30. We have for several years been using the WELCAN workload measurement system.2 This has proved to be a reliable tool that allows us to measure staff time accurately. Our urine culture method3 is partly automated and considerable use is made of medical laboratory assistants. Under these circumstances the savings to be made by uroscopy in clinics will be much less impressive. In addition, account should be taken of "hidden" clinic time (initial examination and, possibly, addition of acid will take up a certain amount of nursing time). Rawal et al assume that in busy clinics uroscopy will always be done carefully. Lastly, we see no mention of symptoms in their account. Our experience suggests that the best approach is to culture samples by a well-standardised technique in a department with good protocols rigorously applied. The contribution of the clinic lies in history taking and examination so that only patients with suggestive histories or signs are sampled in the first place. Department of Pathology, Cheltenham General Hospital, Cheltenham GL53 7AN, UK S. G. EDMONDSON P. SHREAD 1 Asscher AW. The challenge of urinary tract infections. London. Academic Press, 1980: 86-87. 2. WELCAN: workload measurement system for pathology. Cardiff: Welsh Office, 1988. 3 Edmondson SG, Ennght LJ. Semi-automated method for quantitative urine culture. J Clin Pathol 1984; 37: 831-33 Renal artery stenosis and peripheral vascular disease: implications for ACE inhibitor therapy SIR,-Angiotensin converting enzyme (ACE) inhibitors have greatly improved our management of hypertension in people of all ages1 and have revolutionised the management of cardiac failure.2 However, major risks to renal function remain when these agents are used in the presence of renal artery stenosis. When unilateral stenosis is present, glomerular filtration rate (GFR) can be reduced on that side though overall GFR remains normal, but when stenosis is bilateral there is a risk of acute renal failure. These agents are commonly used in elderly patients, many of whom already have widespread vascular disease, but it is neither feasible nor cost- effective to investigate all such patients for the presence of single or bilateral renal artery stenosis before starting these agents. To estimate the frequency of renal artery stenosis in patients with peripheral vascular disease we have done mainstream digital subtraction aortography in 228 male and 146 female patients (aged 50-85) referred for angiographic assessment of lower-limb peripheral vascular disease. Renal artery stenosis was judged mild if the stenosis was between 25 and 50% and severe if 50% or more. Details of hypertensiori or other concurrent medical disorders in these patients were unavailable. Overall, 17% had mild and 14% had severe renal artery stenosis (table). 12% had bilateral renal artery stenosis, which was severe in half these. NUMBER (%) OF PATIENTS WITH PERIPHERAL VASCULAR DISEASE AND RENAL ARTERY STENOSIS I I I I Therefore, when ACE inhibitor therapy is used in people with peripheral vascular disease-eg, for the management of cardiac failure or hypertension-it should be remembered that there is at least a 12% chance that bilateral renal artery stenosis is present and thus acute renal failure may develop. In fact, the frequency of bilateral renal artery stenosis is likely to be higher than we estimated since our patients were not selected for the presence of heart failure or hypertension. ACE inhibitors do not always cause acute renal failure, even when used in the presence of bilateral renovascular disease,3 but our findings suggest that careful monitoring of renal function should be mandatory in any patient with peripheral vascular disease who receives ACE inhibitors. St George Hospital, Sydney, NSW 2217, Australia PAUL SALMON MARK A. BROWN 1. Weber MA. Clinical experience with converting-enzyme inhibitors in hypertension. Am J Kidney Dis 1987; 10 (suppl 1): 45-51. 2. Captopril Multicentre Research Group. A placebo-controlled trial of captopril in refractory chronic congestive heart failure. J Am Coll Cardiol 1983; 2: 755-63. 3. Hollenberg NK. The treatment of renovascular hypertension: surgery, angioplasty, and medical therapy with converting-enzyme inhibitors. Am J Kidney Dis 1987; 10 (suppl 1): 52-60. Tumour necrosis factor to treat chronic hepatitis B virus infection SiR,—Tumour necrosis factor alpha (TNF-a), a cytokine with antiviral properties,l.2 is produced by peripheral blood mononucleat cells during the seroconversion to hepatitis B e antibody that accompanies successful interferon ex (IFN-ot) treatment in chronic hepatitis B virus infection.3 In a pilot study we have assessed recombinant human TNF-a (rTNF) in the treatment of patients with chronic hepatitis B virus (HBV) infection who had not responded to IFN-ot. The six male patients (aged 30-51 years; anti-HIV, anti-HDV, and HDAg negative; three heterosexual, three homosexual) had
Transcript of Renal artery stenosis and peripheral vascular disease: implications for ACE inhibitor therapy
321
However, assessment of turbidity plus a dipstick test was effective insupporting the protocol suggested by Flanagan et al.’ 1
Departments of Internal Medicineand Bacteriology,
Hôpital Louis Mourier,University of Paris VII,92700 Colombes, France
JACQUES POUCHOTISABELLE LAUNAYPIERRE CAHEN
YVES BOUSSOUGANTPHILIPPE VINCENEUX
1. Flanagan PG, Rooney PG, Davies EA, Stout RW. Evaluation of four screening testsfor bacteriuria in elderly people. Lancet 1989, i. 1117-19.
SiR,—Dr Rawal and colleagues report that, in a group of 396patients, the 288 whose urine was crystal clear, with or withoutacidification, did not have urinary infections and imply that thisfinding means that observation of crystal-clear urine renders cultureunnecessary. Unfortunately, they do not present enoughinformation about their patients to justify the general clinical
application of their method. We need to know the proportion ofpatients with clear urine in whom a urinary-tract infection might beregarded as a likely cause of a clinical problem. The use of specimensfrom accident departments may have led to the inclusion of a largenumber of afebrile, symptomless individuals in whom the absenceof a urinary-tract infection would be unremarkable. From a
bayesian perspective, if the prior probability of a urinary tractinfection in the 288 individuals was low to begin with, any findingthat correlates with lack of infection would not be surprising. If, onthe other hand, many of these patients with clear urine were febrileor had other signs or symptoms that might ordinarily lead to adecision to do a urine culture, then the prior probability of aurinary-tract infection would be much higher and the failure todetect any infections would tend to support the clinical utility of themethod.
School of Public Health,University of California,Berkeley, California 94720, USA ERNEST B. HOOK
SIR,-We were fascinated to see that doctors at Guy’s Hospital haverevived the charming practice of uroscopy. While this has anexcellent historical pedigree1 we wonder if the benefits in the 20thcentury are as great as Dr Rawal and colleagues suppose.Rawal et al claim that a urine test costs ;[4--5. We use an accurate
and reproducible method but even after the most careful accountingto include all possible costs we can come to a figure nowhere nearthis. The average cost per specimen in this laboratory is ;[1.30. Wehave for several years been using the WELCAN workloadmeasurement system.2 This has proved to be a reliable tool thatallows us to measure staff time accurately. Our urine culturemethod3 is partly automated and considerable use is made ofmedical laboratory assistants.Under these circumstances the savings to be made by uroscopy in
clinics will be much less impressive. In addition, account should betaken of "hidden" clinic time (initial examination and, possibly,addition of acid will take up a certain amount of nursing time).Rawal et al assume that in busy clinics uroscopy will always be donecarefully. Lastly, we see no mention of symptoms in their account.Our experience suggests that the best approach is to culture
samples by a well-standardised technique in a department withgood protocols rigorously applied. The contribution of the clinic liesin history taking and examination so that only patients withsuggestive histories or signs are sampled in the first place.
Department of Pathology,Cheltenham General Hospital,Cheltenham GL53 7AN, UK
S. G. EDMONDSONP. SHREAD
1 Asscher AW. The challenge of urinary tract infections. London. Academic Press,1980: 86-87.
2. WELCAN: workload measurement system for pathology. Cardiff: Welsh Office,1988.
3 Edmondson SG, Ennght LJ. Semi-automated method for quantitative urine culture.J Clin Pathol 1984; 37: 831-33
Renal artery stenosis and peripheral vasculardisease: implications for ACE inhibitor
therapySIR,-Angiotensin converting enzyme (ACE) inhibitors have
greatly improved our management of hypertension in people of allages1 and have revolutionised the management of cardiac failure.2However, major risks to renal function remain when these agentsare used in the presence of renal artery stenosis. When unilateralstenosis is present, glomerular filtration rate (GFR) can be reducedon that side though overall GFR remains normal, but when stenosisis bilateral there is a risk of acute renal failure. These agents are
commonly used in elderly patients, many of whom already havewidespread vascular disease, but it is neither feasible nor cost-effective to investigate all such patients for the presence of single orbilateral renal artery stenosis before starting these agents.To estimate the frequency of renal artery stenosis in patients with
peripheral vascular disease we have done mainstream digitalsubtraction aortography in 228 male and 146 female patients (aged50-85) referred for angiographic assessment of lower-limb
peripheral vascular disease. Renal artery stenosis was judged mild ifthe stenosis was between 25 and 50% and severe if 50% or more.
Details of hypertensiori or other concurrent medical disorders inthese patients were unavailable. Overall, 17% had mild and 14%had severe renal artery stenosis (table). 12% had bilateral renalartery stenosis, which was severe in half these.
NUMBER (%) OF PATIENTS WITH PERIPHERAL VASCULARDISEASE AND RENAL ARTERY STENOSIS
I I I I
Therefore, when ACE inhibitor therapy is used in people withperipheral vascular disease-eg, for the management of cardiacfailure or hypertension-it should be remembered that there is atleast a 12% chance that bilateral renal artery stenosis is present andthus acute renal failure may develop. In fact, the frequency ofbilateral renal artery stenosis is likely to be higher than we estimatedsince our patients were not selected for the presence of heart failureor hypertension. ACE inhibitors do not always cause acute renalfailure, even when used in the presence of bilateral renovasculardisease,3 but our findings suggest that careful monitoring of renalfunction should be mandatory in any patient with peripheralvascular disease who receives ACE inhibitors.
St George Hospital,Sydney, NSW 2217, Australia
PAUL SALMONMARK A. BROWN
1. Weber MA. Clinical experience with converting-enzyme inhibitors in hypertension.Am J Kidney Dis 1987; 10 (suppl 1): 45-51.
2. Captopril Multicentre Research Group. A placebo-controlled trial of captopril inrefractory chronic congestive heart failure. J Am Coll Cardiol 1983; 2: 755-63.
3. Hollenberg NK. The treatment of renovascular hypertension: surgery, angioplasty,and medical therapy with converting-enzyme inhibitors. Am J Kidney Dis 1987; 10(suppl 1): 52-60.
Tumour necrosis factor to treat chronichepatitis B virus infection
SiR,—Tumour necrosis factor alpha (TNF-a), a cytokine withantiviral properties,l.2 is produced by peripheral blood mononucleatcells during the seroconversion to hepatitis B e antibody thataccompanies successful interferon ex (IFN-ot) treatment in chronichepatitis B virus infection.3 In a pilot study we have assessedrecombinant human TNF-a (rTNF) in the treatment of patientswith chronic hepatitis B virus (HBV) infection who had notresponded to IFN-ot.The six male patients (aged 30-51 years; anti-HIV, anti-HDV,
and HDAg negative; three heterosexual, three homosexual) had
