Contrast-induced nephropathy: the wheel has turned 360 degrees.

Contrast-induced nephropathy (CIN) has been a hot topic during the last 5 years due its association with increased morbidity and mortality. CIN is an important complication, particularly in patients with advanced chronic kidney disease (CKD) associated with diabetes mellitus. Methods to diminish the incidence of CIN have been highly contentious. They include choice of contrast, pharmacologic manipulation, and volume expansion. The pathophysiology of this complication remains uncertain, but reduction in renal blood flow and direct toxicity of tubular cells has been implicated. More than 900 publications under the heading CIN have been published during the last 5 years. Fewer than 5% of these publications are randomized prospective controlled studies. In spite of the large number of reports on CIN, very little has been changed. The use of the smallest possible dose of low- or iso-osmolar contrast media, volume expansion, stopping nephrotoxic drugs, and avoiding repeat contrast injections within 48 hours remain the most effective approach to reduce the risk of CIN.

Prevention of contrast media nephrotoxicity--the story so far.

Contrast media nephrotoxicity (CMN) in patients with pre-existing renal impairment remains a clinically significant problem. The first step to reduce the chance of CMN is to identify patients at risk through the use of screening questionnaires and renal function measurement. Patients at risk requiring injection of contrast medium (CM) because of important clinical indications should receive a small dose of either non-ionic iso-osmolar dimeric or non-ionic low osmolar monomeric CM and hydration. Intravenous infusion (1 ml/kg body weight/h) of 0.9% saline starting 4 h before CM injection and continuing for at least 12 h afterwards is effective in reducing the incidence of CMN. Prophylactic haemodialysis does not lower the risk of this complication. The value of pharmacological manipulation with renal vasodilators (calcium channel blockers, dopamine, atrial natriuretic peptide, fenoldopam (selective dopamine-1 receptor agonist), prostaglandin E(1), non-selective adenosine receptors antagonist (theophylline), non-selective endothelin receptor antagonist or the antioxidant acetylcysteine has not been fully proven. However, haemofiltration for several hours before and after contrast medium injection offers good protection against CMN in patients with advanced renal disease.

Multislice helical CT: the value of multiplanar image reconstruction in assessment of the bronchi and small airways disease.

We examined 23 consecutive patients (11 males and 12 females with mean age of 56 years) with possible airway diseases to assess the impact of multiplanar image reconstruction (MPR) on the degree of confidence and accuracy in diagnosing bronchial abnormalities and emphysema. The thorax was scanned contiguously at 1 mm slice thickness using Siemens Volume Zoom Multislice CT scanner. Images were reconstructed at 1 mm slice thickness (lung windows L-600HU W-1600HU utilizing high spatial frequency algorithm) in the axial (10 mm apart), sagittal (4 images per lung) and coronal (6 images) plane. Paddle wheel image reconstructions were also performed in the assessment of bronchiectasis. Axial images were assessed with and without the help of MPR by three chest radiologists at two separate occasions (at least 4 weeks apart). The presence of bronchiectasis, emphysema and bronchiolitis in each lobe was documented on a confidence scale of 0 to 3. The overall mean confidence for each observer with and without MPR was compared. Consensus diagnosis was used as the gold standard for the assessment of the diagnostic accuracy of each observer. A confidence score of 2 or more for any lobe was considered diagnostic of the particular airway disease. The diagnostic accuracy for each observer with and without MPR was compared. Consensus reporting diagnosed bronchiectasis in 7 patients (30.4%), bronchiolitis in 5 patients (21.7%) and emphysema in 12 patients (52%). MPR did not increase the confidence of assessing the different abnormalities for all observers but improvement in diagnosing bronchiectasis was noted in two observers. The improvement did not reach statistical significance. However, agreement between observers in the diagnosis of bronchiectasis and emphysema was improved when the MPR images were used in conjunction with standard axial imaging (Kappa statistic improved from 0.29 to 0.54 for bronchiectasis and from 0.7 to 0.81 for emphysema). Agreement on the diagnosis of bronchiolitis was not improved by MPR for all observers. Our results suggest that MPR seems to improve the confidence in diagnosing bronchiectasis and emphysema.

Effects of adenosine receptor antagonists on the responses to contrast media in the isolated rat kidney.

Contrast media can induce both a decrease in renal blood flow and a reduction in glomerular filtration rate (GFR) when administered to both experimental animals and humans. In the present study we have examined the role of adenosine in mediating these effects using the isolated perfused rat kidney. Kidneys were perfused with a 6. 7%-(w/v)-albumin-based perfusate supplemented with glucose and amino acids (n=6 per group). They were exposed to diatrizoate [20 mg of iodine (mgI)/ml; osmolality 1650 mOsm/kg of water] or iotrolan (20 mgI/ml; osmolality 320 mOsm/kg of water) in the presence or absence of theophylline (10.8 microg/ml), or to diatrizoate in the presence or absence of a specific adenosine A(1) receptor antagonist (KW-3902; 2 microg/ml) or a specific A(2) receptor antagonist (KF17837; 6 microg/ml). Diatrizoate (n=6) produced a fall in GFR from 0.65+/-0.04 to 0.42+/-0.03 ml.min(-1).g(-1) (P<0.05); renal perfusate flow (RPF) also declined, from 36.5+/-3.8 to 22.0+/-3.2 ml. min(-1).g(-1) (P<0.05). Iotrolan (n=6) produced a fall in GFR from 0. 64+/-0.02 to 0.48+/-0.04 ml.min(-1).g(-1) (P<0.05) and in RPF from 33.3+/-3.8 to 24.0+/-3.0 ml.min(-1).g(-1) (P<0.05). Theophylline (10.8 microg/ml) prevented the fall in GFR caused by either diatrizoate (baseline, 0.63+/-0.05 ml.min(-1).g(-1); diatrizoate+theophylline, 0. 60+/-0.04 ml.min(-1).g(-1)) or iotrolan (baseline, 0.64+/-0.04 ml. min(-1).g(-1); iotrolan+theophylline, 0.67+/-0.05 ml.min(-1).g(-1)), but did not affect the decreases in RPF caused by either agent. KW-3902 (2 microg/ml) also prevented the fall in GFR produced by diatrizoate (baseline, 0.66+/-0.05 ml.min(-1).g(-1); diatrizoate+KW-3902, 0.61+/-0.05 ml.min(-1).g(-1)), while the fall in RPF remained unaffected. KF17837 (6 microg/ml) had no effect on the decreases in either GFR or RPF induced by diatrizoate (n=6 per group). The results suggest a role for adenosine acting at the A(1) receptor in mediating the decrease in GFR induced by contrast media. This effect is independent of a change in renal vascular resistance, and possibly secondary to mesangial cell contraction causing a decrease in the ultrafiltration coefficient.

Congenital bronchial atresia--presentation of three cases and a pictorial review.

Congenital bronchial atresia (CBA) is a rare anomaly that results from a congenital focal obliteration of a proximal segmental or subsegmental bronchus with the normal development of distal structures. The short atretic segment leads to accumulation of mucus within the distal bronchi to form a bronchocoele and underventilation of the affected part of the lung. The clinical and radiographic features of three cases of CBA are reported and the literature is reviewed. Radiologically, CBA is characterized by the presence of a branching opacity, the bronchocoele, radiating from the hilum surrounded by an area of hyperlucency. These features can be recognized on the chest radiograph but are more clearly defined by computed tomography. Fibreoptic bronchoscopy (FOB) is often required to exclude acquired proximal bronchial obstruction by tumour, foreign body or inflammatory stricture. In CBA a blind-ending bronchus may be revealed, although FOB is often normal. Bronchographic examination is generally abnormal but the appearances may be confusing and is rarely performed. Pathologically, CBA is characterized by a blind-ending bronchus associated with dilated distal bronchi containing impacted mucus. The surrounding lung parenchyma is hyperinflated due to collateral air drift. CBA can be identified accurately by imaging techniques which may make surgery unnecessary in asymptomatic cases.

Contrast media-induced nephrotoxicity--questions and answers.

The intravascular administration of contrast media (CM) can produce acute haemodynamic changes in the kidney characterized by an increase in renal vascular resistance and a decrease in the glomerular filtration rate (GFR). These changes may lead to clinically significant reduction in renal function in patients with pre-existing risk factors such as diabetic nephropathy, congestive heart failure and dehydration. The pathophysiology of the renal haemodynamic effects of CM involves activation of the tubuloglomerular feedback (TGF) mechanism and the modulation of the intrarenal production of vasoactive mediators such as prostaglandins, nitric oxide, endothelin and adenosine. The TGF response is osmolality-dependent and accounts for about 50% of the acute functional effects of high osmolar CM on the kidney. Reduction in the synthesis of the endogenous vasodilators nitric oxide and prostaglandins increases the nephrotoxicity of CM. Endothelin and adenosine play a crucial role in mediating the acute functional effects of CM. Antagonists of these mediators attenuate the reduction in renal function induced by contrast agents. Vacuolization of the cells of the proximal tubules and necrosis of those of the medullary ascending limbs of loops of Henle are the main structural effects of CM in the kidney. The reduction in renal function induced by CM could be minimized by the use of low osmolar CM and adequate hydration. The prophylactic administration of calcium channel blockers and adenosine antagonists such as theophylline may also offer some protective effect.

The haemodynamic effects of iodinated water soluble radiographic contrast media: a review.

All classes of iodinated water-soluble radiographic contrast media (RCM) are vasoactive with the iso-osmolar dimers inducing the least changes in the vascular tone. The mechanisms responsible for RCM-induced changes in the vascular tone are not fully understood and could be multifactorial. A direct effect on the vascular smooth muscle cells causing alterations in the ion exchanges across the cell membrane is thought to be an important factor in RCM-induced vasodilatation. The release of the endogenous vasoactive mediators adenosine and endothelin may also play a crucial role in the haemodynamic effects of RCM particularly in the kidney. In addition, the effects of RCM on blood rheology can cause a reduction in the blood flow in the microcirculation. The purpose of this review is to discuss the pathophysiology of the haemodynamic effects of RCM and to offer some insight into the biology of the endothelium and vascular smooth muscle cells as well as the pharmacology of the important vasoactive mediators endothelin and adenosine.

Spontaneous spinal extradural hematoma during pregnancy.

BACKGROUND: Spontaneous spinal hematomas are rare in pregnancy, and only two cases have previously been described. This report reviews other similar cases and discusses the aetiology and management of this condition in relation to pregnancy. CASE: A 26-year-old primigravida presented at 35 weeks of gestation with a history of sudden onset of back pain and weakness with loss of sensation of her legs. On examination there was tenderness over the seventh thoracic vertebra with loss of sensation below the level of the T7 dermatome and reduced power in both lower limbs. Magnetic resonance imaging demonstrated an anterior extradural lesion in the mid-thoracic region of the spinal cord. An elective cesarean section was performed followed by a costotransversectomy and removal of an extradural hematoma. The patient's neurological function subsequently improved. CONCLUSION: Acute spontaneous spinal extradural hematoma occurring during pregnancy can be associated with successful outcome following prompt diagnosis and surgical treatment.

Up-regulation of renal and vascular nitric oxide synthase in iron-deficiency anemia.

Anemia is frequently associated with increased cardiac output and reduced vascular resistance. The latter has been attributed to reduced inactivation of nitric oxide (NO) by hemoglobin. We hypothesized that in addition to reducing NO inactivation, anemia may up-regulate NO production. To test this hypothesis, male Sprague-Dawley rats with chronic iron-deficiency anemia (produced by multiple phlebotomies and an iron-free diet) were studied. The results were compared with those obtained in a group of normal control animals. The anemic group showed marked increases in urinary excretion, plasma concentration, and renal and aorta tissue contents of NO metabolites (total nitrates and nitrites, NOx). This was accompanied by a significant rise in urinary excretion of cGMP, the second messenger for NO. In addition, NO synthase (NOS) activity and endothelial constitutive (ecNOS) and inducible NOS (iNOS) proteins of the thoracic aorta were markedly increased in the anemic group. Likewise, renal tissue ecNOS and iNOS proteins were greatly increased in the anemic animals. NOS activity and protein values were inversely related to hematocrit and directly related to plasma, tissue and urinary NOx. The constellation of these findings points to an increased NOS expression and NO production as opposed to the mere reduction of NO inactivation in iron-deficiency anemia. Further studies are planned to determine the mechanism of NOS up-regulation in iron-deficiency anemia.

Does peppermint oil relieve spasm during barium enema?

The effectiveness of topical peppermint oil added to barium sulphate suspension in relieving colonic muscle spasm during double contrast barium enema examination was assessed in a double blind study. 141 patients were randomized either to a control group (71 patients) examined with standard barium suspension or to the treatment group which received peppermint oil mixed with the barium preparation. No residual spasm was evident in a significant proportion of patients in the treated group (60%) compared with the control group (35%) (p < 0.001). The patients' acceptability of the procedure was good and there were no adverse effects on the overall quality of the examination. In conclusion, the addition of peppermint oil to the barium suspension seems to reduce the incidence of colonic spasm during the examination. The technique is simple, safe, cheap and it may lessen the need for intravenous administration of spasmolytic agents.