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(Thorax 1992;47:790-796) Major advances have been made in the treatment of pulmonary arteriovenous malformations in the last decade, based on percutaneous transcatheter embolisation with steel coils' or balloons,2' with a greatly reduced need for surgical resection. This, combined with increasing recognition of the high incidence of neurological sequelae from paradoxical embolisation,2A has meant that early intervention is recommended for most patients.56The classical triad of physical signs of pulmonary arteriovenous malformations consists of cyanosis, clubbing, and an overlying bruit and one or more of these is present in about three quarters of patients with pulmonary arteriovenous malformation.7 Arterial oxygen tension was reduced in more than 80% of cases studied by Dines et al.4 All 15 patients in our previous series had a resting arterial oxygen saturation (Sao2) below 95% when it was measured supine, further desaturation occurring in the standing position and with exercise.8The diagnosis of pulmonary arteriovenous malformations and assessment of shunt size are important both in the initial evaluation of patients and in monitoring the effects of treatment. Extra-alveolar shunt is usually measured by the classical 100% oxygen breathing method.9 We have recently described a method using technetium-99m albumin microspheres, 7-25 gum in diameter, to quantify right to left shunt at rest.' As particles greater than 8 ,um in diameter are normally trapped in the pulmonary capillary bed, passage of larger particles into the systemic circulation represents a right to left shunt.Chilvers et al8 commented on the increase in arterial oxygen desaturation that occurs with exercise in patients with pulmonary arteriovenous malformations, despite good exercise capacity in many cases. The mechanism of the progressive hypoxaemia during exercise is not understood. Possible explanations include (1) an increase in the right to left shunt; (2) increased tissue oxygen extraction, leading to the addition of very desaturated mixed venous blood to the systemic arterial blood via the arteriovenous malformation; (3) increasing ventilation-perfusion (V/() mismatch.This paper reports measurement of shunt by 790

Leukocytes labeled with technetium-99m hexamethylpropyleneamine oxime (HMPAO) were used in 100 patients: 32 with suspected inflammatory bowel disease, 17 with fever of unknown origin, 21 with suspected abdominal sepsis, 20 with suspected bone sepsis, seven with bronchiectasis, and three with recent myocardial infarction. The distribution of activity in patients subsequently shown not to have inflammatory bowel disease was similar to that previously described for indium-111-labeled leukocytes. However, in this study, activity was also seen in the kidneys and bladder and occasionally the gallbladder on both early (1-3 hours) and late (24 hours) views, and in the colon in late views. Migration of Tc-99m-labeled granulocytes was seen in inflammatory disease as early as 30 minutes after injection, while normal bowel activity was not seen before 4 hours. The sensitivity of Tc99m-labeled leukocytes in the detection of inflammation was 100%, the specificity was 95%.

The conventional way in which to scale or index a measurement of glomerular filtration rate (GFR) is to express it in relation to body surface area (BSA). However, BSA may not be appropriate for infants and children because, as individuals increase in size, their relative BSA decreases. Several other whole-body variables have been suggested as alternatives, including extracellular fluid volume (vECF). The purpose of the present study was to compare BSA and vECF as variables against which to index GFR, and in particular to look at this comparison in children versus adults. A total of 130 patients (age range 1-80 years; 40 patients <12 years) undergoing clinically indicated routine measurement of GFR using the bolus-injection single-compartment technique were included in the study. GFR was measured as the plasma clearance of [(51)Cr]EDTA as assessed from three peripheral venous blood samples taken between 2 and 4 h after injection of [(51)Cr]EDTA. Volume of distribution (V(d)) was obtained by extrapolation of the clearance curve to zero time. GFR was scaled to a BSA of 1.73 m(2). GFR and GFR/1.73 m(2) were corrected to account for the assumption of a single compartment. The rate constant of the exponential between 2 and 4 h was also corrected to give GFR/litre ECF. GFR and GFR/1.73 m(2) were both divided by GFR/litre ECF, to give vECF and vECF/1.73 m(2) respectively. Weight per unit BSA increases as a linear function of BSA. vECF is always less than V(d), on average by about 30%. vECF increased as an exponential function of BSA and as a linear function of body weight. vECF/70 kg body weight was higher in children (16. 2+/-3 litres) than adults (13.4+/-2.3 litres), but vECF/1.73 m(2) was lower in children (9.7+/-1.7 litres) compared with adults (12. 4+/-2 litres). vECV/1.73 m(2) increased as a function of both age and BSA, but vECF/kg decreased. GFR/12.5 litres vECF was higher than GFR/1.73 m(2) in children, but these values were similar in adults, with the ratio of these two forms of indexed GFR falling significantly with both age and BSA. Although this was not a normal population, but one with a wide range of renal function, GFR/vECF showed a strong inverse association with age, whereas for GFR/BSA the association was weak. In conclusion, these data provide further evidence that vECF is more valid physiologically for indexing GFR than is BSA, especially in children. Nevertheless, a GFR measurement in a child should ideally be expressed as a percentage of normal for that child's age. However, such normal values are not yet available.