Pathophysiology of acute renal failure

The combination of vitamin D3 and erythropoietin alleviates acute kidney injury induced by ischemia-reperfusion via inhibiting inflammation and apoptosis

OBJECTIVES

Acute renal ischemia may cause acute renal dysfunction due to lack of blood supply; the manifestations are renal tubular cell apoptosis, infiltration of macrophages, and microvascular destruction. Many studies have shown that erythropoietin (EPO) and vitamin D3 (VD3) can be used to prevent or treat renal ischemia-reperfusion (I/R) injury, and VD3 may interact with EPO. In the present study, the effects of the combination of VD3 and EPO in I/R acute kidney injury were studied.

MATERIALS AND METHODS

Rats were divided into 5 groups: sham-operated (SHAM), AKI without treatment (AKI-control), AKI treatment with VD3(AKI+VD3), AKI treatment with EPO(AKI+EPO), AKI treatment with VD3 and EPO(AKI+VD3+EPO). The effects of the combination of VD3 and EPO on AKI were assessed by histologic, inflammation, and apoptosis studies.

RESULTS

The degree of damage in renal tissue was significantly reduced in VD3, EPO, and combined groups. Combination therapy with VD3 and EPO markedly improved Creatinine clearance rate (CCr). The combined treatment group showed the lowest F4/80+ and CD68+ expressions. The expression of Bcl-2 in the combined treatment group was higher than those in VD3 group and the EPO group, while Bax's expression goes in the opposite direction.

CONCLUSION

This provides further evidence that VD3 and EPO have beneficial effects in I/R injury via anti-inflammatory and anti-apoptosis pathways. The synergistic protective effect of VD3 and EPO is of profound significance in the development of new strategies for the prevention and treatment of acute kidney injury (AKI).

Comparative Renal Toxicopathology of Antisense Oligonucleotides

This review summarizes the current understanding of nephrotoxicity related to the administration of therapeutic oligonucleotides, particularly those with 2'-methoxy-ethyl (2'-MOE) modifications. To best understand the effects of antisense oligonucleotides (ASOs) on the kidney, the reader should have a general understanding of renal microanatomy, physiology, and general mechanisms related to toxicity, so a short review is presented. Preclinical-clinical correlates are also discussed. Collectively, the data for PS ODN and 2'-MOE-modified ASOs have shown the laboratory animal species utilized in toxicology studies generally overpredict renal effects of these agents. As such, 2'-MOE ASOs do not appear to pose as much of a risk to patients as the preclinical data would suggest. This observation has been confirmed so far in clinical investigations.

The pathophysiology of acute renal failure after chlorprothixene overdosage

Renal failure after an overdose of chlorprothixene has been attributed to a direct nephrotoxic effect of the drug. We report a carefully investigated case. No evidence of specific nephrotoxicity was revealed and we suggest that the renal failure is due to ischaemia during a transitory syncope, a well known side-effect of chlorprothixene.

Treatment of acute renal failure

Acute renal failure is a life threatening illness whose mortality has remained high since the introduction of hemodialysis 25 years ago, despite advances in supportive care. Acute renal failure is an extremely morbid and costly disorder with a significant proportion of patients progressing to end-stage renal disease requiring dialysis. To the nephrologist, acute renal failure remains an extremely frustrating disease, because the pathophysiology is not well understood and the limited therapeutic options force the nephrologist to sit on the sidelines and wait for renal function to return. For example, dialysis remains the only FDA-approved treatment for acute renal failure, but dialysis may also cause renal injury that prolongs renal failure. The purpose of this perspective is to understand the results of the recent, largely negative, clinical trials in view of recent advances in the epidemiology of ARF. This review will also discuss diagnostic tools, strategies for improved design of clinical trials, and other therapeutic interventions that will be needed to properly treat acute renal failure in the 21st century.

Perioperative renal dysfunction and cardiovascular anesthesia: concerns and controversies

In patients with renal disease undergoing cardiovascular surgery, perioperative management continues to be a challenge. Traditional answers have turned into new questions with the introduction of new agents and the redesign of old techniques. For ARF prevention, early recognition of pending deleterious compensatory changes is critical. Theoretically, therapeutic intervention designed to prevent ischemic renal failure should be designed to preserve the balance between RBF and oxygen delivery on one hand and oxygen demand on the other. Maintenance of adequate cardiac output distribution to the kidney is determined by the relative ratio of renal artery vascular resistance to systemic vascular resistance. Indeed, it should not be surprising to learn that norepinephrine (despite its vasoconstricting effect) has been reported to have no deleterious renal effects in patients with low systemic vascular resistance. Until recently, strategies for the treatment of ARF have been directed to supportive care with dialysis (to allow tubular regeneration). Various therapeutic maneuvers have been introduced in an attempt to accelerate the recovery of glomerular filtration, including dialysis, nutritional regimens, and new pharmacologic agents. A recent small prospective trial of low-dose dopamine in the prophylaxis of ARF in patients undergoing abdominal aortic aneurysm repair showed no benefit in those patients receiving dopamine. Conversely, the effects of intravenous atrial natriuretic peptide in the treatment of patients with ARF appear to offer benefit in patients with oliguria. Among 121 patients with oliguric renal failure, 63% of those who received a 24-hour infusion of atrial natriuretic peptide required dialysis within 2 weeks compared with 87% who did not. Whether this effect will be borne out in the future remains to be determined. The administration of epidermal growth factor after induction of ischemic ARF in rats has been shown to enhance tubular regeneration and accelerate recovery of kidney function. Human growth factor administration has been shown to increase GFR 130% greater than baseline in patients with chronic renal failure, but no data for clinical ARF have been reported. In addition, there have been significant improvements in dialysis technology in the treatment of ARF. Modern dialysis uses bicarbonate as a buffer as opposed to acetate, which reduces cardiovascular instability, and has more precise regulation of volume removal. Dialysate profiles and temperatures improve hemodynamics and reduce intradialytic hypotension. Techniques of hemodialysis without anticoagulation have reduced bleeding complications. Finally, dialysis membranes activate neutrophils and complement less with the biocompatible membranes used today that reduce recovery time and dialysis treatment. Evidence indicates that activation of complement and neutrophils by older dialysis membranes caused a greater incidence of hypotension, adding to ischemic renal injury. It remains to be determined whether early and frequent dialysis with biocompatible membranes, as well as other therapeutic interventions, will increase the survival of patients with perioperative ARF.

NMR studies of the effect of Mg2+ on post-ischemic recovery of ATP and intracellular sodium in perfused kidney

Ischemia is often implicated as a cause of acute renal failure. We have investigated the effect of various concentrations of extracellular Mg2+ on the post-ischemic recovery of ATP and low intracellular Na+ in the isolated perfused rat kidney using 31P and triple-quantum filtered (TQ) 23Na-NMR spectroscopy. Following a 1 h period of stopped flow ischemia, the kidneys exposed to 0.3 mM Mg2+ throughout the experiment exhibited a significantly (p < 0.05) decreased post-ischemic fractional recovery of ATP (56 +/- 7%) as well as a significantly (p < 0.05) increased accumulation of P(i) (250 +/- 30%) as compared to kidneys exposed to 1.2 mM Mg2+ throughout (88 +/- 5% recovery of [ATP] and 158 +/- 8% accumulation of [P(i)]). Kidneys exposed to 0.3 mM Mg2+ during the pre-ischemic and ischemic periods but to 1.2 mM Mg2+ during reperfusion also showed better recovery of ATP (83 +/- 6%) and lower accumulation of P(i) (143 +/- 8%) compared to kidneys exposed to low Mg2+ (0.3 mM) throughout the experiment. Measurements of the 23Na TQ signal following ischemia-reperfusion revealed that kidneys exposed to 1.2 mM Mg2+ exhibited significantly improved maintenance of low intracellular Na+ as compared to those exposed to 0.3 mM Mg2+ ([Na+]i = 107 +/- 7% in 1.2 mM Mg2+ vs. 152 +/- 3% in 0.3 mM Mg2+). No significant difference was found in the pre-ischemic basal intracellular free Ca2+ level (as measured by 19F-NMR in combination with 5 FBAPTA) between kidneys perfused with 1.2 mM and 0.3 mM Mg2+, and comparable depletion of ATP occurred during ischemia under both experimental conditions. These data indicate that increased extracellular Mg2+ has a protective effect against post-ischemic damage, probably related to its role in resynthesis of ATP during post-ischemic reperfusion. Our results would imply a greater vulnerability of the kidney to ischemic damage in hypomagnesemic clinical conditions such as alcoholism and diabetes.

Glomerular and tubular factors in urine flow rates of acute renal failure patients

Distinguishing between oliguric and nonoliguric acute renal failure (ARF) has clinical relevance. However, there is a paucity of data regarding the pathophysiologic basis for variations in urine flow rates in ARF. This study was designed to determine whether differences in residual levels of glomerular filtration rate (GFR) or differences in tubular reabsorption of filtered solutes and H2O accounted for the variations in urine flow rates among ARF patients. Twenty-five patients with ARF of 3 to 6 days duration having ischemic and nephrotoxic etiologies, increasing serum creatinines of more than 0.7 mg/dL/d, urine sodium concentrations and fractional excretions of sodium (FENa) of more than 20 mEq/L and more than 1%, respectively, 12 hours after stopping diuretics and urine sediments consistent with acute tubular necrosis were studied. Urine and serum collections were made over an 8-hour period to determine creatinine clearance (Ccr), filtered osmolar load, urine to serum creatinine ratio (U/Scr), urine to serum creatinine osmolality (U/Sosm), and FENa. These were compared with urine flow rates. Creatinine clearance was validated as an estimate of GFR in ARF with simultaneous inulin clearances x 12 measurements (r = 0.935, P < 0.001). Residual Ccr was strongly correlated with urine flow rate (r = 0.857, P < 0.001), as was filtered osmolar load (r = 0.810, P < 0.001). However, the latter relationship was totally dependent on Ccr. There was no correlation between U/Scr, U/Sosm, or FENa and urine flow rates. It is concluded that the residual level of GFR is the primary determinant of variations in urine flow rate in patients with ARF.

Endothelium-derived relaxing factor/nitric oxide modulates angiotensin II action in the isolated microperfused rabbit afferent but not efferent arteriole

It has been reported that sensitivity to angiotensin II (Ang II) is higher in efferent (Ef) than afferent (Af) arterioles (Arts). We tested the hypothesis that this is due to arteriolar differences in the interaction between Ang II and endothelium-derived relaxing factor/nitric oxide (EDNO). Rabbit Af-Arts with glomerulus intact were microperfused in vitro at a constant pressure. Ef-Arts were perfused from the distal end of either the Af-Art (orthograde perfusion) or the Ef-Art (retrograde perfusion) to eliminate influences of the Af-Art or glomerulus, respectively. Ang II did not alter Af-Art luminal diameter until the concentration reached 10(-9) M, which decreased the diameter by 11 +/- 2.6% (n = 11; P < 0.002). In contrast, Ef-Arts became significantly constricted at concentrations as low as 10(-11) M with either perfusion. Surprisingly, the decrease in Ef-Art diameter at 10(-10), 10(-9), and 10(-8) M was significantly greater with retrograde perfusion (44 +/- 6.9%, 70 +/- 5.6%, and 74 +/- 4.1%, respectively; n = 5) than with orthograde perfusion (16 +/- 4.2%, 25 +/- 2.9%, and 35 +/- 3.5%; n = 9). ENDO synthesis inhibition with 10(-4) M nitro-L-arginine methyl ester (L-NAME) decreased the diameter to a greater extent in Af-Arts (22 +/- 3.0%; n = 11) compared to Ef-Arts with either orthograde (9.5 +/- 2.3%; n = 8) or retrograde perfusion (1.2 +/- 2.1%; n = 6). With L-NAME pretreatment, Af-Art constriction induced by 10(-10) M (14 +/- 4.0%, n = 9) and 10(-9) M Ang II (38 +/- 3.9%) was significantly greater compared to nontreated Af-Arts. In contrast, L-NAME pretreatment had no effect on Ang II-induced constriction in Ef-Arts with either perfusion. In conclusion, this study demonstrates higher sensitivity of Ef-Arts to Ang II, particularly with retrograde perfusion. Our results suggest that EDNO significantly modulates the vasoconstrictor action of Ang II in Af-Arts II but not Ef-Arts, contributing to the differential sensitivity to Ang II.

Pulsed and continuous Doppler evaluation of renal dysfunction after kidney transplantation

Seventy-eight recipients, average age 36 years, of cadaver kidneys were studied to evaluate the usefulness of Doppler ultrasonography for diagnosis of common complications in renal transplant patients. The patients were divided in five groups: Control (normal renal function), acute rejection (AR), acute tubular necrosis (ATN), obstructive uropathy (OU) and pathological vasculature (PV); renal artery stenosis (RAS) and renal artery thrombosis (RAT). Pulsed Doppler ultrasonography (PDUS) was an effective method to diagnose RAS and RAT, but did not sufficiently differentiate between AR and ATN. Despite this, PDUS may be useful for follow-up of renal transplant patients as specific changes in the PDUS curves or differences in successively recorded patterns indicate abnormality, which may initiate more specific diagnostic methods.

The spasm of resistance vessel concept of ischemic heart disease and other ischemic diseases

This communication will discuss the spasm of resistance vessel concept of ischemic heart disease and other ischemic diseases, and will focus on ischemic heart disease. The hypothesis is regarded as a separate model or paradigm, and is based on the principle that spasm of resistance vessels directly induces symptoms in these conditions. Resistance vessels help maintain vascular homeostasis through autoregulatory mechanisms, and spasm of resistance vessels is considered to represent 'inappropriate' activation of these mechanisms by disease states, which are equated with risk factors. For ischemic heart disease, the most important risk factor is stenotic coronary artery disease, and the concept asserts that severe ischemia secondary to coronary artery disease causes sufficient tissue injury to incite injury-spasm of resistance vessels. While it is universally accepted that occlusions of epicardial arteries by stenotic coronary artery disease, spasm, and thromboses directly induce clinical symptoms, the hypothesis suggests that these occlusions have other roles. The concept accepts all current treatments of ischemic heart disease, but as this disorder is viewed differently, a significantly different direction of research is proposed for improving its treatment and prevention.

Expression of two "immediate early" genes, Egr-1 and c-fos, in response to renal ischemia and during compensatory renal hypertrophy in mice

To identify specific genetic regulatory mechanisms associated with renal ischemia, we measured the accumulation of Egr-1 and c-fos mRNAs in the mouse kidney after occlusion of the renal artery and reperfusion. At 1 h after right nephrectomy and arterial occlusion of the contralateral kidney for 10 or 30 min, Egr-1 mRNA levels were three to five times greater in these kidneys as compared with those in control animals that had sustained unilateral nephrectomy alone and were much greater than levels in the normal organ. Whether ischemia was imposed for 10 or for 30 min, renal Egr-1 mRNA contents were equivalent and remained elevated after 24 h of reperfusion subsequent to 30 min of ischemia. Although c-fos mRNA also accumulated in response to ischemia and reperfusion, the pattern differed from that of Egr-1 in that c-fos mRNA content varied with the duration of ischemia and was undetectable 24 h after injury. Contralateral nephrectomy was not necessary to see the marked accumulation of Egr-1 and c-fos mRNAs with unilateral ischemia. Reflow was necessary, however, since only minimal sequence accumulation occurred by the end of the ischemic period. After left uninephrectomy alone, Egr-1 mRNA levels in the remaining kidney were maximal 30 min after surgery, but were not detectable thereafter; c-fos mRNA levels did not change after unilateral nephrectomy. Differential expression of early growth-related genes implicated in transcriptional activation may influence tissue recovery after renal ischemia.

Renal effects of dopamine infusion in conscious horses

An ultrasonic flow probe was implanted around a branch of the left renal artery in five horses. The effects of dopamine were studied in the unsedated horses 10 days after surgery. Three experiments, separated by at least two days, were performed in random order on each horse. In two experiments, dopamine was infused intravenously for 60 mins at either 2.5 and 5.0 micrograms/kg bodyweight (bwt)/min. Saline was infused for 60 mins before and after each infusion, and for 180 mins in the third experiment as a control. Renal blood flow increased during administration of dopamine at both dose rates (P = 0.0001). Urine volume increased (P = 0.055), and osmolality decreased (P < 0.05), with infusion of dopamine at 5.0 micrograms/kg bwt/min. Arterial blood pressure and heart rate were not significantly affected. Fractional excretions of sodium and potassium were not significantly changed with dopamine infusion. The higher dopamine dose rate was accompanied by dysrhythmias in some horses.

Relative density of urine: methods and clinical significance

The physical properties and chemical composition of urine are highly variable and are determined in large measure by the quantity and the type of food consumed. The specific gravity is the ratio of the density to that of water, and it is dependent on the number and weight of solute particles and on the temperature of the sample. The weight of solute particles is constituted mainly of urea (73%), chloride (5.4%), sodium (5.1%), potassium (2.4%), phosphate (2.0%), uric acid (1.7%), and sulfate (1.3%). Nevertheless, urine osmolality depends only on the number of solute particles. The renal production of maximally concentrated urine and formation of dilute urine may be reduced to two basic elements: (1) generation and maintenance of a renal medullary solute concentration hypertonic to plasma and (2) a mechanism for osmotic equilibration between the inner medulla and the collecting duct fluid. The interaction of the renal medullary countercurrent system, circulating levels of antidiuretic hormone, and thirst regulates water metabolism. Renin, aldosterone, prostaglandins, and kinins also play a role. Clinical estimation of the concentrating and diluting capacity can be performed by relatively simple provocative tests. However, urinary specific gravity after taking no fluids for 12 h overnight should be 1.025 or more, so that the second urine in the morning is a useful sample for screening purposes. Many preservation procedures affect specific gravity measurements. The concentration of solids (or water) in urine can be measured by weighing, hydrometer, refractometry, surface tension, osmolality, a reagent strip, or oscillations of a capillary tube. These measurements are interrelated, not identical. Urinary density measurement is useful to assess the disorders of water balance and to discriminate between prerenal azotemia and acute tubular necrosis. The water balance regulates the serum sodium concentration, therefore disorders are revealed by hypo- and hypernatremia. The disturbances are due to renal and nonrenal diseases, mainly liver, cardiovascular, intestinal, endocrine, and iatrogenic. Fluid management is an important topic of intensive care medicine. Moreover, the usefulness of specific gravity measurement of urine lies in interpreting other findings of urinalysis, both chemical and microscopical.

In vitro and in vivo protective effect of atriopeptin III on ischemic acute renal failure

The effect of atriopeptin III (AP-III) on ameliorate ischemic acute renal failure was first examined in the isolated perfused kidney. Isolated rat kidneys were clamped for 1 h and reperfused for 30 min without therapy and then perfused with either 0 (control) or 100 micrograms/dl AP-III. In this system AP-III significantly improved renal plasma flow (39.6 +/- 2.4 vs. 32.2 +/- 2.1 ml/min per g; P less than 0.05) inulin clearance (182.6 +/- 49.2 vs. 24.6 +/- 6.2 microliters/min per g; P less than 0.05), urine flow (52.9 +/- 12.1 vs. 7.1 +/- 0.8 microliters/min per g, P less than 0.01), and net tubular sodium reabsorption (21.2 +/- 6.6 vs. 2.9 +/- 0.9 mumol/min per g, P less than 0.05) as compared with control. A second series of in vivo studies experiments were performed using 1 h of bilateral renal artery clamping followed by an intravenous infusion of either saline alone (control) or AP-III (0.20 microgram/kg per min) for 60 min. The results demonstrated that inulin clearance (244.4 +/- 25.1 vs. 15.8 +/- 8.2 microliters/min per 100 g; P less than 0.01), urine flow (23.1 +/- 5.9 vs. 1.1 +/- 0.5 microliters/min per 100 g; P less than 0.01), and net tubular sodium reabsorption (38.9 +/- 4.7 vs. 4.3 +/- 1.6 mumol/min per 100 g; P less than 0.01) were significantly higher in AP-III-treated rats than controls during the hour of AP-III infusion. In 1 h posttreatment study this significant protective effect of AP-III was documented to persist. In more chronic studies animals treated acutely with AP-III had lower serum creatinine concentration at 24 h (1.8 +/- 0.3 vs. 3.3 +/- 0.4 mg/dl; P less than 0.01) and 48 (1.0 +/- 0.2 vs. 2.4 +/- 4.0 mg/dl; P less than 0.01) after the 60 min of ischemia than controls. Renal adenosine triphosphate regeneration as assessed by P-31 nuclear magnetic resonance during reflow was also significantly improved in AP-III-treated animals at 1 h (3.03 +/- 0.30 vs. 1.45 +/- 0.40 mumol/g dry wt; P less than 0.05) and 2 h (3.98 +/- 0.46 vs. 1.80 +/- 0.05 mumol/g dry wt; P less than 0.01) or reflow as compared with control rats. Thus, AP-III significantly ameliorates ischemic acute renal failure both in vitro and in vivo in the rat.

Acute renal failure in six horses resulting from haemodynamic causes

Six horses had been admitted to the hospital because of illness other than renal failure; diarrhoea, myositis, abdominal pain and/or suspected bacterial sepsis. Hypotension and disseminated intravascular coagulopathy were frequent findings in the horses. Abnormally high serum creatinine concentration and urine specific gravity of less than 1.022 were found in the horses with acute renal failure. Hyponatraemia and hypochloraemia were the most common abnormal electrolyte findings. Pronounced hyperkalaemia was not found. Variable degrees of tubular necrosis were seen in three of the four horses that had kidney sections submitted for microscopic examination. Renal cortical necrosis occurred in one horse. Intravenous fluid and electrolyte replacement was the most important therapy in those cases that were non-oliguric. Furosemide, mannitol and dopamine were used in horses with oliguria. The prognosis was generally good if the predisposing cause could be corrected and the acute renal failure was not oliguric.

Cardiogenic and hypovolemic shock

The symptoms, signs, and pathophysiology of two major forms of shock are discussed. Newer modalities of pharmacologic and supportive therapy for stabilization and reversal of these states are presented, including the use of the intra-aortic balloon pump and early surgical therapy for cardiogenic shock.

Evaluation of renal function and acute renal failure in the neonate

The diagnosis of renal dysfunction in the neonate can be a challenging problem for the practicing pediatrician. Although there are real differences in renal function between term and preterm infants, overall function is quite adequate in both groups when fluid intake and environmental conditions are carefully controlled. When confronted with an infant with a pathologic decrease in urine output, the clinician must provide adequate fluid resuscitation for the infant with prerenal oliguria without inducing fluid overload in the infant with established, intrinsic renal failure. In addition, the infant with obstruction to urine flow must be distinguished. This requires careful assessment of physical findings and a few key laboratory determinations. Once the diagnosis of renal failure is made, frequent clinical monitoring with anticipation of potential complications is critical. Long-term management of renal failure in infancy and intervention for suspected urinary tract malformation in the fetus have emerged as difficult medical and ethical problems as our technology has advanced.

The end of the crystalloid era? A new approach to peri-operative fluid administration

The metabolic response to surgery causes sodium and water retention. It does not seem logical to pour crystalloid solutions into patients in the peri-operative period, particularly when these solutions can cause deterioration in lung function. Plasma volume must be maintained to prevent a decreased blood flow to vital organs such as the kidneys. Blood or colloid solutions, not crystalloid solutions, should be used for this purpose, since the latter are distributed throughout the whole extracellular space and are less effective in maintaining plasma volume. Water given as 5% dextrose should be given in minimal quantities to maintain intracellular hydration. Patients undergoing minor to moderate surgery when they are likely to be drinking within 24 hours do not usually require any intravenous infusion. Moreover, to administer intravenous fluids to these patients may cause harm. No fluid regimens should be inflexible and the patient's size, age and fluid losses should be taken into account.

Acute renal failure--an integrative discussion of morphologic and functional findings

The ultrastructural alterations at the nephron established in animal experiments, were also confirmed, by means of an electron-microscopic examination, in eight cases of human acute renal failure (ARF). Special consideration was given in this study to single cell alterations, particularly in proximal tubular cells, with emphasis being placed on alterations due to single cell damage in the region of the renal fluid compartments. The ultrastructural alterations of the tubular cells in ARF, suggest serious impairment of the cellular capacity for electrolyte transport and metabolic processes. The shunt paths between the tubular fluid compartment and the functional interstitium, arising from necrosis of the tubular cells or dissolution of the gap or tight junctions, were discussed in terms of their significance for the directional, active transport processes of the tubular cells for sodium chloride and the passive water flow. The morphologic findings were reviewed in light of recent findings on cellular membrane processes and electrolyte transport. A reinterpretation of the morphologic and functional findings in ARF is suggested. This takes into consideration single cell function and the integrity of the renal fluid compartments.

Nephrotoxicity from angiographic contrast material. A prospective study

Three hundred and seventy-eight hospitalized patients undergoing nonrenal angiography were evaluated for subsequent changes in renal function. Acute renal failure was defined as a rise in the serum creatinine level of 1.0 mg/dl or more. Several factors that appeared to play no significant role in causing acute renal failure included: the volume of contrast material injected, the anatomic site of injection and the presence of a prior history of cardiovascular disease or diabetes mellitus. The single risk factor identified was the presence of preexistent azotemia (blood urea nitrogen of 30 mg/dl and serum creatinine of 1.5 mg/dl). Whereas nonazotemic patients had a 2 percent incidence of definite acute renal failure, patients with chronic azotemia (mean blood urea nitrogen/creatinine = 47/2.3 mg/dl) had a 33 percent incidence. Three patients required short-term dialysis, and two required potassium-exchange resin therapy. No patient required permanent dialysis, and no patient died of acute renal failure. The persistence of a positive nephrogram 24 hours after angiography was a sensitive detector of a rise in the serum creatinine level although more expensive than the creatinine determination. While urine sediment analysis confirmed the diagnosis in many cases, it was relatively insensitive. Monitoring of urine volume proved to be of little value. We recommend a screening serum creatinine determination 24 to 48 hours after infusion of angiographic contrast material in azotemic patients.

Glomerular and tubular function in non-oliguric acute renal failure

Glomerular and tubular function were evaluated in 30 non-oliguric patients with increasing azotemia following open heart surgery. Fractional clearances (theta) of test solutes relative to that of inulin were determined. In 16 patients, theta dextran (radius 22 to 30 A) exceeded unity, a finding attributed to inulin backleak through necrotic tubules. These patients were classified as having acute renal failure; 14 subsequently required dialysis. In the remaining patients (N = 14), theta dextran was normal. These patients were considered to have prerenal failure; all recovered spontaneously. clearance of inulin (Cin) was lower in acute renal failure than in prerenal failure (12 +/- 2 versus 18 +/- 2 ml/min/1.73 m2; p less than 0.025). The apparent difference in glomerular filtration rate when Cin is used as an index was abolished, however, when Cin in acute renal failure was corrected for tubule backleak of inulin. In acute renal failure, fractional clearance of p-aminohippurate (theta PAH) was 7.1 +/- 1.0, and fractional excretion of potassium (FEk) was 160 +/- 18 percent. These findings strongly suggest that secretory ability in both proximal and terminal tubule augments, respectively, is preserved in acute renal failure. Compared with prerenal failure, the urine-to-plasma inulin ratio was lower (U/Pin = 10 +/- 1 versus 25 +/- 4; p less than 0.005) and FENa was higher (FENa = 5.1 +/- 1.5 versus 0.5 +/- 1.0 percent; p less than 0.01) in acute renal failure.

Evaluation of methods for producing renal dysfunction in rats

The following methods for producing renal dysfunction in rats were compared: single-step 5/6th nephrectomy, two-step 5/6th nephrectomy, bilateral ureteral ligation, and uranyl nitrate injection. Control groups consisted of single- and two-step sham-operated animals and animals that received an injection of normal saline solution. The methods were evaluated on the basis of the following criteria, which were assessed daily for 6 days: survival, body weight, hematocrit, serum creatinine concentration, serum urea nitrogen concentration, serum glutamic pyruvic transaminase activity, serum albumin concentration, and serum protein binding of salicylate (determined every other day). Animals with bilateral ureteral ligation survived only 2 days, single-step 5/6th nephrectomy caused a high incidence of fatalities. Some of the methods were associated with the development of hypoalbuminemia, but no significant elevation of transaminase activity occurred. Serum protein binding of salicylate was reduced in rats with renal dysfunction. A strong positive correlation between the creatinine and urea nitrogen concentrations in the serum of animals with renal dysfunction (r = 0.91, p less than 0.001) and a negative correlation between the serum albumin concentration and salicylate free fraction (r = -0.71, p less than 0.001) were found. Uranyl nitrate injection has the advantages of technical simplicity, a high survival rate (no deaths in this study), and relatively consistent and sustained diminution of renal function (as reflected by serum creatinine and urea nitrogen concentrations).

Pathophysiology of hemodynamically mediated acute renal failure in man

A tubular injury characterized by intraluminal obstruction and transtubular backleak of glomerular filtrate occurs in experimental acute renal failure (ARF) in animals. To determine whether these alterations also occur in human ARF, we studied 44 patients developing nonoliguric ARF following cardiac surgery. The delay in appearance of i.v. administered inulin in urine (Tu) was used as a measure of tubular fluid flow rate. Tu was not longer in 13 ARF patients than it was in control subjects (7.2 vs 9.0 min), suggesting that at least a subpopulation of tubules was widely patent. The fractional urinary dextran clearance profile (thetaD; radii, 20 to 40 A) was then determined in 20 patients with sustained ARF in whom inulin clearance averaged 11 +/- 1 ml/min/1.73 m2. A mass conservation model, which assumes that thetaD in Bowman's space in ARF is the same as that measured in controls, when applied to the experimental observations revealed that, on the average, 42% of filtered inulin was lost by transtubular backleak. A similar fractional inulin backleak (38%) persisted in 11 additional patients in whom ARF had begun to recover and in whom inulin clearance averaged 26 +/- 3 ml/min/1.73 m2. These findings suggest that in hemodynamically-mediated and nonoliguric ARF, (1) tubular obstruction is not homogeneous, and (2) backleak of glomerular filtrate contributes to but does not fully account for depression of inulin clearance.

Excretion of casts and uromucoid in urine after prolonged heavy exercise

Excretion of uromucoid, albumin and casts in urine were determined in twenty well-trained men, ten aged 20-30 years, and ten aged 50-60 years, before, during and after a 70 km cross country ski race. During the race there was only a slight increase in uromucoid excretion, but a marked increase in the excretion of casts and albumin. The older subjects had a tendency to lower urine output during the race compared to the younger group. Reduction of urine output below ca. 25 ml/h was accompanied by a conspicuous increase in urine cast and albumin concentrations, with only a slight increase in uromucoid concentration, and even a reduction in uromucoid excretion. No significant relationship was found between cast excretion and uromucoid concentration. Thus the gross cylindruria observed during longstanding exercise must be ascribed to other urinary factors facilitating the formation of casts.

The effect of chlorpromazine pretreatment on the vascular function of kidneys damaged by warm ischaemia and cold storage in Collins' solution

Vascular resistance was determined in 40 rabbit kidneys after graded warm ischaemia up to 60 minutes and preservation in Collins' solution for 24 and 48 hours. Half of the animals were treated with chlorpromazine 3.5 mg/kg before induction of the ischaemia. Vascular function was determined during short-term perfusion with TIS-U-SOL at 4 degrees C. The experiments showed that warm ischaemia of 30 and 60 minutes duration gave an increase in vascular resistance. The increase was, however, smaller in kidneys pretreated with chlorpromazine. Preservation in Collins' solution for 24 and 48 hours did not change this correlation. Determination of the weights and thereby formation of oedema showed that all kidneys preserved had a small increase in weight. No difference was found between pretreated kidneys and untreated kidneys. It is concluded that pretreatment with chlorpromazine is capable of diminishing vascular contraction during the warm ischaemic period and that preservation in Collins' solution for up to 48 hours does not alter this beneficial effect.

The patterns of peripheral plasma renin concentration in the early post-renal-transplant period

Serial determinations of peripheral plasma renin concentration (PRC) were performed in 11 kidney transplant recipients during the early post-transplant period. In 5 recipients with late onset of graft function, PRC values were increased during the anuric phase and, subsequently, PRC values declined in every during restoration of graft function. In 4 recipients with an acute renal allograft reaction, PRC values were increased at the onset of the allograft reaction in 3 with hypertension whereas PRC values were normal in one normotensive recipient. Subsequently, PRC normalized in the hypertensives coincident with increasing body weights. In 2 recipients with an uncomplicated course and with a normal graft function immediately after transplantation and throughout the study period, PRC values were constantly normal. The results indicate that acute anuria in the early phase after kidney transplantation is associated with an increased release of renin. The results also suggest that an increased activity of the renin-angiotensin system may be counterbalanced by sodium and fluid retention in hypertension following an acute renal allograft reaction.