Left Main Renal Artery Research Articles

Pseudoaneurysm and renal arteriovenous fistula after nephrectomy: two cases treated by transcatheter coil embolization

Pseudoaneurysms and arteriovenous fistulas of renal arteries are rare clinical lesions. Invasive renal procedures may lead to pseudoaneurysm or arteriovenous fistulas (AVFs). We report two pseudoaneurysms and arteriovenous fistula cases that were treated by transcatheter embolization with metallic coils. The first case is left main renal artery pseudoaneurysm after nephrectomy in a patient with a solid renal tumor. The second case is right main renal artery AVF with giant pseudoaneurysm after both gunshot injury and nephrectomy. On the basis of color Doppler sonography and computed tomography (CT) findings, cases were diagnosed as pseudoaneurysm after nefrectomy. Contrast-enhanced CT scans showed a hyperdense area within the hematoma consistent with pseudoaneurysm. Endovascular treatment with coil embolization succeeds to total occlusion in renal artery pseudoaneurysm. Delayed hemorrhage related to postnephrectomy may be life-threatening conditions because of diagnostic difficulties. AVF and pseudoaneurysm can be treated safely and successfully by transcatheter arterial embolization.

MDCT Angiography of the Renal Arteries in Patients with Atherosclerotic Renal Artery Stenosis: Implications for Renal Artery Stenting with Distal Protection

Use of distal protection in renal artery stenting entails overcoming challenges unique to renal artery anatomy. We used 3D image reconstruction to review high-spatial-resolution MDCT angiographic data to better characterize the anatomy of stenotic renal arteries. A total of 218 abdominal MDCT angiograms from a single tertiary care referral center were reviewed. The subjects were 108 patients who had 127 arteries with more than 50% ostial atherosclerotic renal artery stenosis. Vessel analysis software was used to measure renal artery length, cross-sectional area, and maximum diameter. Differences between mean values for women and men and for left and right renal arteries were measured with a two-tailed Student's t test. Significant differences for men and women were found in average maximum cross-sectional area distal to the point of stenosis (0.3 +/- 0.19 vs 0.23 +/- 0.09 cm2, p = 0.006) and the corresponding maximum diameter (6.9 +/- 1.7 vs 6.1 +/- 1.1 cm2, p = 0.003). Average lengths of the main renal artery did not differ significantly for men and women. Differences for the left and right main renal arteries were found in minimum area (i.e., area of maximum stenosis, 0.08 +/- 0.04 vs 0.06 +/- 0.03 cm2, p = 0.03), area proximal to the bifurcation (0.26 +/- 0.11 cm2 vs 0.23 +/- 0.07 cm2, p = 0.02), and length (38.5 +/- 12.6 vs 48.7 +/- 16.2 mm, p = 0.0002). Significant anatomic differences exist between the left and right renal arteries, between the renal arteries in men and those in women, and from one person to the next. Many of these differences are relevant to the design and use of distal protection devices in stenting of the renal arteries.

Bipolar supernumerary renal artery

The variations of renal arteries are considered critical issues that surgeons should have thorough envision and appreciation of the condition. Variations of these vessels may influences urological, renal transplantation and laparoscopic surgeries. We present a case of bilateral accessory renal artery with a striking pre-hilar branching pattern encountered upon digital subtraction angiography (DSA) for imaging of the renal arteries of a healthy 30-year-old man, renal transplant donor. The right kidney received two renal arteries from the aorta including a main hilar and one lower polar. However, the left accessory artery while originated from the aorta, simultaneously, supplied both upper and lower renal poles following its pre-hilar division that replaced upper/apical and lower segmental arteries of the single main renal artery, respectively. The left main renal artery divided into two anterior and posterior segmental arteries. Whether this should be categorized either as an accessory hilar artery or a unique variant of renal arterial supply, the so-called bipolar supernumerary renal artery, is a matter of debate. We discuss possible embryologic origin and clinical aspects of accessory renal artery.

Dopplerfluxometria das artérias renais: valores normais das velocidades sistólica e diastólica e do índice resistivo nas artérias renais principais

Dopplerfluxometry of renal arteries has been used to estimate renal perfusion in humans. The aim of this study was to use Dopplerfluxometry technique to calculate the resistive index of main renal arteries in dogs, measuring their systolic and diastolic blood flow velocities. Twenty (10 males, 10 females), adult mongrel dogs, were used in this study. The dogs were submitted to Doppler sonographic evaluation of left and right main renal arteries. The systolic and diastolic blood flow velocities, expressed (in centimeters per second) as mean and standard deviation were 79.96± 8.82 and 28.86± 5.11 in the right main renal artery and 80.22± 6.99 and 29.62± 4.14 in the left main renal artery. The value of resistive index expressed as mean ± standard deviation was 0.64± 0.04 for the right main renal artery and 0.63± 0.028 in the left main renal artery.

Quantitative estimation of renal blood flow by power Doppler ultrasonography in renovascular hypertensive dogs

We estimated the value of power Doppler (PD) imaging analysis for the quantitative assessment of renal cortical blood flow (RCBF) in chronic two-kidney, one-clip (2K-1C) hypertensive dogs. To evaluate the correlation between RCBF and PD signals, RCBF and the mean pixel intensity (MPI) of PD signals were simultaneously obtained at same region in renal cortex under progressive constriction of left main renal artery in five mongrel dogs. RCBF was measured by electrolytic hydrogen gas clearance method, and PD images were transferred to computer and analyzed by the image-analysis software Openlab. To assess the value of quantitative PD imaging analysis on RCBF in renovascular hypertension, in six mongrel dogs with chronic 2K-1C hypertension, PD images in both of clipped kidneys (CK) and non-clipped kidneys (NK) were obtained and analyzed before and 60 minutes after the intravenous infusion of captopril or sodium nitroprusside at 10-minute intervals. There was a linear correlation between RCBF and MPI (r= 0.878, P < 0.0001). MPI in both CK and NK significantly increased after the infusion of captopril, while no significant change was observed in both CK and NK after the infusion of sodium nitroprusside, despite similar reduction of mean arterial blood pressure. Our data suggest that the acute inhibition of angiotensin-converting enzyme increased RCBF in both CK and NK of chronic 2K-1C dogs. The quantitative analysis of PD flow signals in kidney is noninvasive and a useful method to evaluate regional changes of renal tissue blood flow in various renal diseases.

Main arterial supply of a kidney from the opposite renal artery: an unusual case

Variations in renal anatomy and blood supply are not uncommon, but a supplementary renal artery arising from the opposite renal artery is rare. In such cases the kidneys are usually malrotated and anomalous in position and form. The case of a 65-year-old man with the left main renal artery arising from the opposite renal artery and without such anomalies of the kidneys is presented.

Renovascular hypertension complicated with VATER association

We report herein a case of a girl with renovascular hypertension associated with VATER association. Her plasma renin activity and aldosterone were high. The ultrasonic echogram and renogram revealed a right hypoplastic kidney without function and a normal-sized left kidney with normal function. Renal angiography revealed a small diameter right main renal artery and a normal left main renal artery with segmental stenosis of left branching renal arteries in the middle segment. Selective renal vein sampling indicated that renin secretion was primarily from the left kidney. This is the first report of renovascular hypertension complicated with VATER association.

Iatrogenic Main Renal Artery Injury: Treatment by Endovascular Stent-Graft Placement

We report on a patient who presented with perforation of the left main renal artery as a complication of a percutaneous retroperitoneal drainage procedure. Only a small number of cases of iatrogenic main renal artery perforations have been reported, none of them due to a percutaneous drainage attempt. Endovascular treatment by means of a coronary stent-graft was successful.

Recovery of Renal Function after 3 Months of Dialysis in a Patient with Atherosclerotic Renovascular Disease Following Aortoiliac Bypass and Left Renal Artery Reimplantation

A 67-year-old Caucasian man was admitted in September 2001 because of dyspnœa and oliguria. He had a history of smoking, hypertension, and hyperlipemia. On admission, the blood pressure was 160/110 mmHg, there were inspiratory crackles at both lung fields, peripheral œdema, and a bilateral murmur in the periumbilical region. Laboratory investigations showed a normocytic anemia (Hb 8.6 g/dl, MCV 92 fl), with a serum creatinine of 397 mmol/l. The chest X-ray showed cardiomegaly, parahilar pulmonary œdema and a left pleural effusion. An echocardiogram showed severe impairment of systolic function. Abdominal ultrasonography showed a small right kidney (polo-polar length: 5.8 cm; left kidney: 8.6 cm) and an aortic aneurysm (length 6.2 cm, transverse diameter 4.8 cm) involving both common iliac arteries. The right common iliac artery had maximum longitudinal and transversal diameters of 4 and 4.7 cm, respectively. Doppler ultrasonography revealed significantly reduced blood flow to the left kidney (with resistance index of 0.53) and absence of flow to the right kidney. MR angiography (Fig. 1(a)) showed a significant stenosis of the left renal artery (Fig. 1(b)). The clinical course was characterised by progressive renal failure and difficulty in maintaining cardiac output despite the use of diuretics, nitrates and dopaminergic drugs. Angiography was performed to explore the possibility of percutaneous angioplasty (PTA). It showed complete occlusion of the left main renal artery, and a sub-occlusive stenosis of a left accessory renal artery (probably corresponding to the patent vessel on MR). PTA was unsuccessful. Hemodialysis was started, with rapid improvement of cardiopulmonary function. The serum creatinine stabilised around 700 mmol/l, with minimal urine output. In December 2001, an echocardiogram showed improvement of systolic function. Neither angina nor ischemic ECG changes were recorded during dypiridamole echo-stress. Because of the improvement in cardiac function, and the characteristics of the aortoiliac aneurysm, surgical correction by aortoiliac bypass was planned, including reimplantation of the left renal artery. The procedure was successfully performed in January 2002. Immediately after surgery, the patient recovered a good urine output. On day one, dialysis was performed because of hyperkalemia. Over the next few days the serum creatinine progressively fell to 486 mmol/l. MR angiography showed adequate flow in the reimplanted artery (Fig. 2). Fourteen months later, the serum creatinine was 500 mmol/l, and the patient no longer required hemodialysis. Eur J Vasc Endovasc Surg 28, 562–564 (2004) doi: 10.1016/j.ejvs.2004.05.006, available online at http://www.sciencedirect.com on

Exclusion of accessory renal arteries during endovascular repair of abdominal aortic aneurysms

Objective: Adequate proximal neck length is important for proper endovascular treatment of abdominal aortic aneurysms (AAAs). Placement of endografts in AAAs with relatively short proximal necks may require covering the origin of accessory renal arteries. Exclusion of these arteries carries the theoretical concern of regional renal ischemia associated with loss of parenchyma or worsening hypertension. We reviewed our experience with accessory renal exclusions during endovascular AAA repair to determine the frequency and severity of complications. Methods: Complete records were available for review on 311 of 325 consecutive patients treated with endovascular grafts for AAAs from February 6, 1996, to March 15, 2001. The presence of accessory renal arteries was ascertained from preoperative/intraoperative aortography or from computed tomographic scanning. Sizes of the accessories were measured by using the main renal arteries as a reference. Considerations for excluding the accessory renal arteries were based on the likelihood of successful proximal attachment to healthy aorta, an accessory vessel whose size does not exceed the diameter of the main renal artery, and the absence of renal disease. Results: The mean follow-up was 11.5 months. Fifty-two accessory renal arteries were documented in 37 patients (12%), ranging from 1 to ≥3 per patient. Of these, 26 accessory renal arteries were covered in 24 patients. Patients ranged in age from 57 to 85 years (mean, 74.1 years), with 20 men and 4 women. The Ancure device was used in 23 patients and the Excluder device in one. Of the accessories excluded, 22 originated above the aneurysm and 4 originated directly from the aneurysm itself. There were no perioperative mortalities. One patient died 5 months after surgery from an unrelated condition. There was one type I (distal) endoleak and no type II endoleaks. Five patients (21%) had segmental renal infarction associated with the side of accessory renal artery exclusion. Only one patient with segmental infarction had significant postoperative hypertension that resulted in changes in blood pressure medication. The blood pressure reverted to normal 3 months later. One patient with a stenotic left main renal artery required exclusion of the accessory renal artery for successful proximal attachment. Serum creatinine levels remained unchanged throughout follow-up in all but one patient, in whom progressive postoperative renal failure developed despite normal renal flow scan, presumably from intraoperative manipulation and contrast nephropathy. Conclusion: Exclusion of accessory renal arteries to facilitate endovascular AAA repair appears to be well tolerated. Long-term sequelae seem infrequent and mild. (J Vasc Surg 2001;34:878-84.)

LAPAROSCOPIC REPAIR OF RENAL ARTERY ANEURYSM

We describe technical considerations of the laparoscopic repair of a renal artery aneurysm. A 57-year-old woman presented with a 3 cm. aneurysm of the distal left main renal artery at its bifurcation. Using a purely laparoscopic 4-port transperitoneal technique the aneurysm was completely mobilized from its location behind the renal vein. Its 3 feeding vessels were controlled individually with bulldog clamps. The aneurysm sac was bivalved and precisely trimmed to conform with the diameter of the main renal artery. Vascular reconstruction was performed with running freehand laparoscopic suturing and intracorporeal knot tying using 4-zero polypropylene suture. Warm ischemia time was 31 minutes, total operative time was 4.2 hours, blood loss was 100 cc and hospital stay was 2 days. Postoperatively renal scan showed improved perfusion and renal arteriography confirmed adequate repair of the aneurysm. Laparoscopic repair of the renal artery aneurysm is feasible. To our knowledge we present the initial clinical report of laparoscopic renovascular surgery in the literature.

Hipertensão arterial experimental e prenhez em ratas: repercussões no peso da placenta e no índice placentário

Objetivo: estudar as repercussões da hipertensão sobre o peso da placenta e índice placentário. Métodos: foram utilizadas 82 ratas virgens da linhagem Wistar em idade de reprodução. Após a indução da hipertensão arterial experimental (Modelo Goldblatt I -- 1 rim-1 clipe) as ratas foram sorteadas para compor os 4 grandes grupos experimentais (controle, manipulação, nefrectomia e hipertensão). A seguir, as ratas foram distribuídas por sorteio em 8 subgrupos, sendo quatro prenhes (P) e quatro não-prenhes. Após acasalamento, dos quatro grupos prenhes obtivemos com o nascimento dos recém-nascidos (RN) os seguintes grupos: RN-C, RN-M, RN-N e RN-H, respectivamente, controle, manipulação, nefrectomizado e hipertenso. Resultados: quanto ao peso da placenta, o do grupo RN-C (<IMG SRC="http:/img/fbpe/rbgo/v23n2/06151s1.gif"> = 0,58 ± 0,12) foi estatisticamente maior que o de todos os demais grupos. Por outro lado, verifica-se que o peso das placentas provenientes do grupo RN-M (<IMG SRC="http:/img/fbpe/rbgo/v23n2/06151s1.gif"> = 0,51 ± 0,05) foi maior que o dos grupos RN-N (<IMG SRC="http:/img/fbpe/rbgo/v23n2/06151s1.gif"> = 0,45 ± 0,07) e RN-H (<IMG SRC="http:/img/fbpe/rbgo/v23n2/06151s1.gif"> = 0,42 ± 0,04), os quais não diferiram entre si. Os índices placentários dos grupos P-C (Md = 0,1085) e P-M (Md = 0,1110) não diferiram entre si, mas foram menores que os dos grupos P-N (Md = 0,1175) e P-H (Md = 0,1211), os quais também não diferiram entre si. Conclusões: a hipertensão e a nefrectomia unilateral determinaram redução do peso das placentas e aumento do índice placentário, evidenciando repercussões no desenvolvimento placentário e fetal.

Abdominal aortic aneurysm and a horseshoe kidney

A 60-year-old man presented with a 5-cm abdominal aortic aneurysm and a horseshoe kidney. On 3-month followup CT scan (A), the aneurysm had expanded to 5.5 cm. Operative repair with preoperative angiography was recommended. Flush aortagram (B) demonstrated a solitary right renal artery (B1), two left renal arteries (B2, B3), and an artery to the isthmus arising from a nonaneurysmal left common iliac artery (B4). Selective views of the right (C), left main (D), left accessory (E), and accessory isthmus (F) renal arteries were obtained. Operative repair was performed through a midline laparotomy with reflection of the left and sigmoid colon to the patient’s right, allowing full mobilization of the leftsided renal parenchyma and isthmus. Aneurysmorrhaphy was performed with aortobiiliac reconstruction. To minimize risk of injury to nerves crossing over the left common iliac artery with subsequent retrograde ejaculation, the artery to the isthmus was ligated close to the kidney, rather than reimplanted. Postoperatively, the patient’s creatinine and sexual function remained unchanged.

Hipertensão Arterial Experimental e Prenhez em Ratas: Repercussões sobre o Peso, Comprimento e Órgãos dos Recém-nascidos

Purpose: to study the repercussion of arterial hypertension regarding body weight gain and body length, as well as liver and brain weight of offspring. Methods: a total of 82 animals in reproductive age were used. They were randomly assigned to 4 different groups (control, handled, nephrectomized and hypertensive). Renal hypertension was produced by a controlled constriction of the main left renal artery and contralateral nephrectomy, according to the technique described by Goldblatt (Goldblatt I: one kidney - one clip hypertension). Afterwards, they were distributed among nonpregnant and pregnant groups. The following newborn groups resulted from the pregnant groups: RN-C (control-newborn group of pregnant rats without surgical treatment), RN-M (manipulation-newborn group of the pregnant rats with surgical manipulation), RN-N (nephrectomized-newborn group of pregnant rats with nephrectomy) and Rn-H (hypertensive-newborn group of pregnant rats with hypertension). Results: the RN-N and RN-H groups showed body weight gain ( = 3,64 ± 0,50; = 3,37 ± 0,44), body length ( = 3,89 ± 0,36; = 3,68 ± 0,32) and brain weight ( = 0,16 ± 0,01; = 0,16 ± 0,05), respectively, smaller than the control group ( = 5,40 ± 0,51; = 4,95 ± 0,23 and = 0,22 ± 0,04, respectively). In addition, the RN-H group showed the lowest liver weight ( = 0,22 ± 0,03) compared with the other three groups. Conclusion: after statistical analysis, the results obtained showed that the arterial hypertension determined a reduction in body weight, body length, and liver and brain weight of the offspring.

Feasibility of Gadodiamide Compared with Dilute Iodinated Contrast Material for Imaging of the Abdominal Aorta and Renal Arteries

To determine the quality of digital abdominal angiograms obtained with use of full-strength, intra-arterial gadodiamide compared with similar volumes of half-strength iodinated contrast material for evaluating the abdominal aorta and renal vessels. Twenty-five consecutive patients underwent digital subtraction arteriography of the abdominal aorta performed with equal volumes (32 mL) of either half-strength (300 mg/mL iodine) iodinated contrast material or full strength gadodiamide (0.11-0.25 mmol/kg) to evaluate the abdominal aorta and renal arteries. The contrast agent used was not known to the image readers. The abdominal aorta, left and right renal main renal artery, and first and second order segmental branches were graded separately as diagnostic or nondiagnostic by four angiographers. Images of the abdominal aorta were diagnostic 100% of the time for iodine and gadodiamide, 76% and 80% diagnostic for iodine and gadodiamide in the left main renal artery, respectively; and 100% and 80% diagnostic for iodine and gadodiamide in the right main renal artery, respectively. The first order segmental branches of the right and left renal arteries were graded diagnostic 72% and 56% of the time, respectively, for dilute iodinated contrast material, and 40% and 28% of the time, respectively, for gadodiamide. The second order segmental branches of the right and left kidney were graded diagnostic 24% of the time for iodinated contrast and 8% and 4% of the time, respectively, for gadodiamide. Full-strength, intra-arterial gadodiamide at doses smaller than 0.3 mmol/kg can produce diagnostic images of the abdominal aorta and main renal arteries. However, images of the intrarenal branches are usually not diagnostic.

Hypertension secondary to progressive vascular neurofibromatosis

A 4 year old girl with neurofibromatosis type 1 (NF1) was referred for hypertension. An aortogram showed narrowing of the left main renal artery. An angiogram three and a half...

CONGENITAL RENAL ARTERY STENOSIS IN A PREMATURE NEONATE. 1328

Arterial hypertension is rare in the neonate where it has high morbidity and mortality. Renovascular disease is the leading cause of neonatal hypertension. We report a case of severe hypertension in a 34 week gestation male neonate due to 90% right renal artery stenosis. The neonate presented at birth with malignant hypertension, hematuria, proteinuria, and normal GFR. Initial course was complicated by salt wasting, retinal arteriolar narrowing and labile blood pressure. Renal biopsy showed normal fetal architecture with ongoing nephrogenesis. Based on the biopsy findings, antihypertensive therapy with Captopril was temporarily discontinued due to its known adverse affect on the renin angiotensin axis and subsequent renal development. Despite no perfusion to the left kidney on radionuclide studies, renal ultrasound and Doppler flow studies were normal on two occasions. Arteriogram revealed long segment stenosis of the left main renal artery. Left nephrectomy resulted in resolution of hypertension and withdrawal of all medical therapy.

Experimental chronic renal ischemia: Morphologic and immunologic studies

Although unilateral clamping of the renal artery to induce chronic ischemia of the kidney tissue has been utilized in several animal species, the resultant morphologic, ultrastructural and immunologic changes have never been well characterized. Moreover, the pathogenesis of these changes, as well as their roles in causing or facilitating the development of chronic tubulointerstitial nephritis have not been known. To examine some of these issues, male Sprague-Dawley rats were subjected to unilateral stenosis of the left main renal artery for 28 days. Stenotic and contralateral kidneys of experimental animals and kidneys from sham-operated controls were subjected to: (1) light microscopic, electron microscopic and immunofluorescent studies; (2) morphometric quantitation of the structural changes; (3) staining for actin, epithelial membrane antigen, keratin, and vimentin by immunoperoxidase technique; (4) staining for complex glycoproteins by a panel of 13 lectins; and (5) phenotyping and quantitation of the interstitial inflammatory infiltrates by monoclonal antibodies, using immunoperoxidase technique. The results reveal that: (1) The ischemic kidney tissue displays marked tubulointerstitial damages including abundant interstitial chronic inflammatory infiltrates, with good preservation of glomerular structure, which is consistent with the standard criteria of chronic tubulointerstitial nephritis. (2) The antigenic profile of the ischemic tubular epithelium displayed marked alterations including a neo-expression of vimentin and keratin, as well as a loss of endogenous avidin binding activity, Ia antigen and several complex surface glycoproteins detectable by lectins. (3) Neither electron dense deposits nor immunoglobulins are detectable in the kidneys from experimental or control animals. (4) Tubulitis, defined as infiltration of tubular epithelium by inflammatory cells, was present in up to 42.2% of tubular cross sections of the ischemic kidneys. (5) The interstitial inflammatory infiltrates were composed of B lymphocytes, T helper lymphocytes, and macrophages whereas the T non-helper lymphocytes were scanty, a phenotypic pattern similar to that of several other experimental rat models of chronic tubulointerstitial nephritis. It is concluded that: (1) In the Sprague-Dawley rats, ischemia alone can cause a constellation of changes fulfilling the accepted features of chronic interstitial nephritis; (2) ischemia alters the antigenic profile of the tubular epithelium and thereby may initiate a cell mediated immune response, accounting for the observed tubulitis and interstitial inflammation; and (3) ischemia may well be the final common pathway for chronic tubulointerstitial nephritis of diverse etiologies.

Renal arterial Resistance Index in pregnant and nonpregnant women: evaluation with color and pulse Doppler ultrasound.

The Resistance Index (RI) was studied in the main renal arteries in normal nonpregnant women and its change during normal pregnancy. One hundred and seventy color and pulse Doppler sonographic examinations were performed on 31 nonpregnant and 54 pregnant women. The range of gestation was 5-39 weeks, and patients divided into three groups; 5-12, 13-25 and 26-39 weeks of pregnancy, respectively. The RI was calculated in both main renal arteries. In nonpregnant women the left main renal artery RI mean = 0.587 +/- 0.021, and the right main renal artery RI mean = 0.584 +/- 0.028. In pregnant women the left main renal artery RI mean was 0.681 +/- 0.029, and the right main renal artery RI mean was 0.697 +/- 0.034. There was a significant difference between the main renal artery RI in pregnant and nonpregnant women (P less than 0.01). There was no significant difference between left and right main renal artery in pregnant and nonpregnant women (P less than 0.01). There was no correlation between gestational age and RI in the right main renal artery but a statistically significant correlation with gestational age in the left main renal artery (P less than 0.05).

A regulatory role for large vessels in organ circulation. Endothelial cells of the main renal artery modulate intrarenal hemodynamics in the rat.

After arterial denudation by external rubbing of the left main renal artery, we assessed renal plasma flow rate (RPF) and glomerular filtration rate (GFR) in left and right kidneys of Munich-Wistar rats before and after intravenous infusion of acetylcholine (ACH), atrial natriuretic peptide (ANP), or nitroprusside (NP). In the right kidney RPF and/or GFR increased in response to both endothelium-derived relaxing factor (EDRF)-dependent (i.e., ACH) and -independent vasodilators (i.e., ANP and NP); on average, RPF rose by 22 +/- 4% (P less than 0.005), 19 +/- 10% (P less than 0.005), and 37 +/- 12% (P greater than 0.05), respectively. By contrast, in the left kidney RPF failed to increase after ACH (falling by 23 +/- 10%, P less than 0.001) and rose only in response to ANP and NP. To further evaluate the main renal artery's contribution to renal vasodilation, ACH and another EDRF-dependent agent, histamine, were infused through a micropipette into either the proximal or distal portions of the endothelium-intact renal artery. Proximal infusion of ACH led to increases in RPF and GFR, on average by 8 +/- 2% (P less than 0.025) and 10 +/- 3% (P less than 0.01), while bypassing the arterial endothelium by distal infusion failed to increase RPF and GFR, which fell by 24 +/- 6% (P less than 0.025) and 22 +/- 6% (P less than 0.005), respectively. Similarly, proximal infusion of histamine increased RPF by 12 +/- 3% (P less than 0.05), while distal infusion was virtually without effects on plasma flow. Micropuncture study during intravenous ACH infusion revealed significantly higher afferent and efferent arteriolar resistances and lower ultrafiltration coefficients in denuded versus nondenuded kidneys. These data indicate that the main renal artery is a major regulator of renal blood flow and vascular resistances. Similar to other endothelium-derived substances, EDRF may be elaborated mainly by large vessels and may act on the downstream microcirculatory systems, which determine organ blood flow and transcapillary fluid transfer.