Pulmonary Hypoplasia: Lung Weight and Radial Alveolar Count As Criteria of Diagnosis
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Arch Dis Child: first published as 10.1136/adc.54.8.614 on 1 August 1979. Downloaded from Archives of Disease in Childhood, 1979, 54, 614-618 Pulmonary hypoplasia: lung weight and radial alveolar count as criteria of diagnosis S. S. ASKENAZI AND M. PERLMAN Hadassah Hospital, Jerusalem SUmmARY A working definition of pulmonary hypoplasia (PH) was established by retrospective assessment of lung growth both in recognised and hypothetical PH-associated conditions. Lung weight: body weight ratios (LW:BW) were calculated, and morphometry was determined by the radial alveolar count (RAC) (Emery and Mithal, 1960). Both parameters were reduced compared with those of normal controls in diaphragmatic hernia, anencephalus, anuric renal anomalies, chondrodystrophies, and osteogenesis inperfecta. Comparison of LW:BW ratio and RAC indicated that the RAC was the more reliable criterion of PH, LW:BW ratio of .0-012 (67% of mean nor- mal ratio) and/or RAC of < 4.1 (75 % of mean normal count) are suggested as diagnostic criteria of PH. Evidence ofPH was incidentally discovered in a number ofclinically unsuspected cases and retro- spectively clarified the clinical and radiological findings. Routine assessment of lung growth should be an essential part of the neonatal necropsy. Pulmonary hypoplasia (PH) is a poorly defined establish. There has been only one study of both copyright. condition considered to be almost invariably LW:BW ratio and morphometry in a substantial secondary to other anomalies and is usually diag- number of pathological cases (Reale and Esterly, nosed in association with them; primary or isolated 1973). PH has not been reported (Reale and Esterly, 1973). These diagnostic criteria of lung growth were PH is lethal within hours of birth in many instances studied in an attempt to establish a working defini- of diaphragmatic hernia (Potter, 1961; Kitagawa et tion of PH. Lungs of patients dying perinatally with al., 1971; Reale and Esterly, 1973), anencephalus PH-associated conditions were examined. In addi- http://adc.bmj.com/ (Potter, 1961; Naeye and Blanc, 1971; Reale and tion to these anomalies, neonates with other condi- Esterly, 1973), anuric renal anomalies with oligo- tions in whom there were theoretical grounds to hydramnios (Potter, 1972; Reale and Esterly, 1973; anticipate PH were examined. Perlman and Levin, 1974; Thomas and Smith, 1974), and skeletal anomalies restricting thoracic volume Materials and methods (Finegold et al., 1971). There is however a spectrum Material was obtained from the pathology depart- of severity of PH, often proportional to the severity ments of the Hadassah University Hospital, on September 23, 2021 by guest. Protected of the underlying condition, and sublethal forms exist Jerusalem; Kaplan Hospital, Rehovot; and the (Kohler and Babbitt, 1970; Chatrath et al., 1971; Soroka Medical Centre, Beer-Sheva. About 200 Perlman et al., 1975). liveborn and stillborn subjects were selected accord- Because histological findings lack specificity ing to recognised PH associations (diaphragmatic (Potter, 1961; Reale and Esterly, 1973), diagnosis hernia, anencephalus, anuric renal anomalies, depends on detection of low lung weight in relation chronic to body weight (low LW:BW ratio), or of low amniotic fluid leakage, and chondrodystro- alveolar counts determined by morphometric phies) and, in unprecedented cases, where PH was methods (Reale and Esterly, 1973). Severe PH is easy anticipated on theoretical grounds (osteogenesis to diagnose at necropsy from the low LW:BW ratio imperfecta, hydrops fetalis). In addition, PH was but identified incidentally in some patients who died alone, lesser or borderline PH is more difficult to during the study period because of a low LW:BW Neonatal Unit, Department of Paediatrics, Hadassah Hospital, ratio at necropsy (central nervous system anomalies, Jerusalem gross ascites due to long-standing meconium S. S. ASKENAZI, intern peritonitis). No patient with PH lived for more than M. PERLMAN, senior lecturer 72 hours. 614 Arch Dis Child: first published as 10.1136/adc.54.8.614 on 1 August 1979. Downloaded from Pulmonary hypoplasia: lung weight and radial alveolar count as criteria ofdiagnosis 615 'Normal' control liveborn and stillborn infants 7 (0 Normal a were selected randomly, but subjects with birth- Anencephalus n weights outside the 10th to 90th centile for gestational * Diaphragmatic o a 6v I 0 hernia age were excluded. Patients with clinically diagnosed I and pathological confirmed lung disease--such as . hyaline membrane disease and meconium pneumoni- :: a tis-or with congenital anomalies including heart 5. defects other than those with PH associations were U + m also excluded. In all control infants death resulted 4. 0 from either perinatal asphyxia or traumatic intra- * On a 0 * U cranial haemorrhage within 3 days of birth. 8 :* U 3- c. a The following information was obtained from the 0 0o 0 0 necropsy record: sex, gestational age, body weight, C aan c a lung weight, age at death, anatomic diagnoses, and C cause of death. LW:BW ratios were computed. 2 iIi~~~~~~~~~~~~~~~ Normal S Morphometry was performed by one ofus (S.A.A.) Biliary A at microscopical magnification of x 40, using a X agenesis 0 modification of the method of Emery and Mithal 6- * 40 Polycystic O kidneys (1960), without knowledge of the anatomical 0 diagnoses or cause of death. Before beginning the 0. 0 5- *41 0 study, experience ofinterobserver error was obtained .00 with the help of Professor E. Rosenmann: the error 0 was < ± 10%. A line was dropped from the centre ( a of each respiratory bronchiole (bronchioles only 4.- partially lined with epithelium) to the nearest 2j_TAAA connective tissue septum at right-angles to the 3- copyright. epithelium. The number of alveolar septi (as distinct 8AIn, AI from the number of alveoli counted by Emery and Mithal) cut by this line were counted. At least 10 2 counts were made for each patient, mainly from 2-3 7. 0 Normal 0 histological sections. Hydrops fetalis 0 Mean values of LW:BW ratios and of RACs and Chondrodystrophies 0 6- ** * Osteogenesis A SDs of the mean were calculated for each diagnostic 0 o e@ impertecta http://adc.bmj.com/ group. The significance ofthe difference of the means Q 0 of each of the pathological groups compared with 5- 0i ~~0 the control group was determined by Student's t 0 test. Subgroups of infants <36 weeks' gestation a 4- and >35 weeks' gestation were treated statistically 0 in the same manner and compared. AAoAEIj 0 A on September 23, 2021 by guest. Protected Results 3- 0 200 cases for 111 Of about screened study, had 2 adequate perinatal data and histological preparations 0 0-05 010 015 0-20 0 25 suitable for morphometry. LW:BW ratios were not Figure Comparison of lung weight:body weight ratio and available in 12 cases. Mean gestational age and mean radial alveolar count for each aetiological category as birthweight were similar in each group. The data for indicated. Values for individual patients are plotted LW:BW ratio and RAC for infants of gestational according to absolute values of LWW:BW ratio (abscissa, ages <36 weeks were compared with data for >36 bottom), and mean RAC (ordinate, left). Additional weeks and there was no significant difference, so horizontal and vertical lines, respectively, represent the the total data were analysed. values for the lower limits ofnormalfor RAC and With the exception of LW:BW ratios in anen- LW:BW ratio. cephalics, LW:BW ratios and RAC were much reduced in each pathological group (Table). The indicate the lower limits of normal for each of the results are illustrated graphically by plotting LW:BW two parameters. The number of measurements ratios against RAC (Figure). Lines were drawn to below the normal range (mean -2 SDs) for each Arch Dis Child: first published as 10.1136/adc.54.8.614 on 1 August 1979. Downloaded from 616 Askenazi and Perlman Table Lung weight; body weight ratios andradial alveolar counts in different aetiological categories Group Category Mean Mean Lung weight :body weight ratio Radial alveolar count gestational birthweight age (kg) No. of Mean SD Range No. of Mean SD Range (weeks) cases cases Normal 38 2-8 17 0-018 0-003 0-012-0025 17 5-3 0-6 4-1-6-3 2 Diaphragmatic hernia 38 2-7 17 0-009 0-006 0-003-0020 23 3-1 0.5 2-04-1 3 Anencephalus 38 2-2 20 0-016 0-006 0-005-0.025 22 3-1 0-4 2-5-3 *7 4 Renal anomalies 36 2-4 23 0.01 0-004 0-005-0016 27 3 *2 0-8 2.1-5-6 5 Chondrodystrophies 36 2.5 4 0.01 0.004 0-006-0-015 4 3.5 0-2 3.4-3.8 6 Osteogenesis imperfecta 36 1-9 4 0.007 0-001 0-005-0008 4 3.2 0.4 2-6-3-5 7 Amniotic fluid leakage 35 1-7 2 - - 0.012-0.016 2 - - 2-0-2.4 8 Hydrops fetalis 34 2-1 8 0.013 0-007 0.001-0.021 8 4.4 1.0 3.1-5-6 9 Hydrocephalus 38 3-2 2 0-008 - 0.005-0011 1 - - 4.0 10 Meconium peritonitis 37 2-8 1 - - 0-012 1 - - 3.8 P value for the differences of the means of each of the groups 2-6 and of group 1 was at least <0*01 for LW:BWratio and <0.005 for RAC. group was greater for LW:BW ratio than for RAC. anomalies (Potter, 1961), the pathogenesis of PH The number of cases with values for both LW:BW in anencephalus has never been satisfactorily ratio and RAC within the normal range is also given.