Arch Dis Child: first published as 10.1136/adc.56.8.606 on 1 August 1981. Downloaded from Archives of Disease in Childhood, 1981, 56, 606-615 Fetal lung hypoplasia: biochemical and structural variations and their possible significance J S WIGGLESWORTH, R DESAI, AND P GUERRINI Department ofPaediatrics and Neonatal Medicine, Institute of Child Health, Hammersmith Hospital, London SUMMARY Quantitative biochemical criteria for lung growth and maturation were compared with the histological appearances in hypoplastic lungs from 20 fetuses and newborn infants. Cases associated with oligohydramnios showed a characteristic series of changes with narrow airways, retardation of epithelial and interstitial growth, delay in development of blood-air barriers, and low concentrations of phospholipid phosphorus, lecithin phosphorus, total palmitate, and lecithin palmitate. The growth and maturation arrest appeared to affect the peripheral part of the acinus. Examples of other types oflung hypoplasia showed different features. Hypoplastic lungs from infants with normal or increased amniotic fluid were of mature structure with phospholipid concentrations similar to those of infants with normally developed lungs at term. The hypoplastic left lung in 2 cases of congenital diaphragmatic hernia had an immature structure with low phospholipid con- centrations, whereas the right lung was structurally and biochemically more mature. It is suggested that fetal lung growth may be impaired by any influence which reduces thoracic volume but that maturation arrest is due specifically to loss ofthe ability to retain lung liquid. copyright. It is now recognised that hypoplasia of the fetal arrest." Other studies on infants with renal agenesis lungs is the immediate cause of neonatal death in a or dysplasia have found the lungs to be structurally number of malformation syndromes. These include mature with normal surface properties,"1 14 or not to all conditions with failure offetal urine production or differ from those associated with other malforma- or The left and of infants with obstruction of urine output,1 aplasia eventration tions.'5 right lungs http://adc.bmj.com/ of the diaphragm,2 thoracic abnormalities-such as unilateral congenital diaphragmatic hernia have been congenital thoracic dystrophy and thanatophoric found not to differ,15 to differ structurally,2 or to dwarfism3-and abnormalities of the central nervous differ both structurally and biochemically.16 It has system-including anencephaly, iniencephaly, and been claimed that all the differences between the Meckel-Gruber syndrome.4 5 In addition, pulmonary hypoplastic lungs in different malformation hypoplasia may be seen in conditions arising after syndromes are due to variation in the time at which the embryonic period including prolonged rupture of lung growth became retarded."5 the membranes,6 7 or severe hydramnios,8 and as a There is clearly a need to determine whether the on September 25, 2021 by guest. Protected primary condition in otherwise normal infants.9 different structural patterns of lung hypoplasia can Many of the structural and functional features of indeed be explained on the basis of variation in hypoplastic fetal lungs remain poorly defined despite timing of the growth arrest, or whether they reflect an increasing interest in the condition. Morpho- differences in the mechanism which interferes with metric studies suggest that an important component lung growth in different circumstances. Resolution in several forms ofpulmonary hypoplasia is reduction of this problem may well provide new information in the number of generations of bronchial on the mechanisms controlling normal lung branching.10'2 There is less agreement about other development. aspects of lung structure and development. It has We have attempted to answer this question by been claimed that hypoplastic lungs occurring in comparing quantitative biochemical criteria for conditions with reduced intrathoracic space show lung growth and maturation with the histo- decrease in lung parenchyma and have closely logical appearances in a series of hypoplastic packed normal bronchi, whereas those associated lungs associated with a variety of malformation with renal agenesis may show generalised maturation syndromes. 606 Arch Dis Child: first published as 10.1136/adc.56.8.606 on 1 August 1981. Downloaded from Fetal lung hypoplasia: biochemical and structural variations and their possible significance 607 Materials and methods but in the other 4 there was both a normal fetal urinary tract and intact amniotic sac. The external Lungs were examined from 18 fetuses or newborn features of Potter's syndrome were recognised in all infants with uniform bilateral lung hypoplasia ofthe infants with renal agenesis or severe renal cystic defined as described previously17 (lung/body weight dysplasia associated with failure of urine production ratio of .0 015 at <28 weeks' gestation, and (the latter evidenced by thread-like ureters and a lung/body weight ratio .0 012 at 28 weeks' tubular bladder). Similar external appearances were gestation or more). Two additional infants with seen in Cases 2, 3, and 4 with prolonged oligo- left-sided congenital diaphragmatic hernia and hydramnios dating from before 20 weeks' gestation hypoplasia predominantly of the left lung were also but normal renal tract. Of the 4 infants with normal examined. Control material for phospholipid studies renal tract and intact amniotic sac, 2 had exomphalos included lungs from 13 infants who died with and 2 had conditions associated with polyhydramnios hyaline membrane disease (HMD) within the first (intrauterine damage to brain stem nuclei and 36 hours of life at 27-36 weeks' gestation and the cytomegalovirus infection). lungs of 10 infants without HMD who died during Cases 19 and 20 had congenital left diaphragmatic birth or within the first 4 days at 34-41 weeks' hernia with the asymmetrical lung hypoplasia gestation. DNA measurements and histological characteristic of this condition. One of them had material were available from all the lungs of normal suffered amniotic fluid leakage for 5 weeks before and small-for-dates fetuses and infants reported birth at 30 weeks' gestation (lecithin/sphingomyelin in the preceding paper (page 601).17 Initial handling ratio in the leaking amniotic fluid 2 weeks before of the lungs and DNA estimation was as previously delivery was 2-4), and the other was a term infant described. Lung lipids were extracted from the lung who died soon after corrective surgery. homogenates in chloroform/methanol and dried The hypoplastic lungs in all instances had under nitrogen. Acidic and non-acidic phospholipids normal development of lobes and fissures. The 2 were separated by DEAE cellulose acetate colunm cases with prune-belly syndrome showed distortion chromatography using the method of Gluck et al.18 of the rib cage due to pressure from the enlarged copyright. Lecithin was isolated by thin-layer chromatography bladder. This was more pronounced at 35 weeks' as an aliquot of the non-acidic phospholipid fraction gestation than at 20 weeks. The development and on TLC-plastic sheet silica gel 60, No 5748 (Merck). form of the thoracic cage, intercostal muscles, and The running solvent was chloroform :methanol: diaphragm appeared normal in the rest of the water (65:25:4 by volume). Dipalmitoyl lecithin oligohydramnios group. In most of the cases of renal (Sigma) was run as a standard. agenesis or severe renal cystic dysplasia the lungs The concentration of in the lecithin phosphorus were deeply congested with obvious haemorrhage. http://adc.bmj.com/ fraction and in the total phospholipid extract of Several showed pneumothorax and, despite periods each lung was determined by the method ofBartlett.19 of up to 22 hours' mechanical ventilation in life, all The palmitic acid content of the lung lecithin and of appeared totally airless and collapsed at necropsy. the total lung phospholipid was measured by The lungs of the infants with exomphalos appeared gas-liquid chromatography. The fatty acids were oedematous and were associated with severe esterified using 5 % H2SO4 in methanol and extracted lordosis and rib cage distortion in one (Case 14), and in petroleum ether with a boiling point of 60-800C. thoracic narrowing in the other (Case 18). In one of An internal standard of margaric acid (Sigma) was the infants with congenital diaphragmatic hernia on September 25, 2021 by guest. Protected added for quantitation. Separation was achieved in (Case 20) there was good aeration of the moderately 10% (by mass) Silar 10c on Chromosorb W-HP undersized right lung, but the hypoplastic left lung 100-120 mesh (Field Instruments Ltd, Twickenham, was almost entirely airless in both cases. Middlesex) at 1800C using a Pye Unicam Model 104a gas chromatograph. Biochemical findings. The lung DNA content expressed in relation to body weight is shown in Results Table 1. All infants born at 31 weeks' gestation or more had values of less than 100 mg lung DNA per Clinical details and macroscopical findings. Details of kg body weight. The DNA values for the left and right the cases are summarised in Table 1. Cases 1-18 had lungs of Cases 19 and 20 were assessed separately uniform bilateral lung hypoplasia. In 14 this was (Table 2). Both the total DNA and DNA concentra- associated with prolonged oligohydramnios due to tion tended to be lower in the grossly hypoplastic failure of fetal urine production, obstruction to left lung. The lung DNA findings in the cases urinary output, or prolonged rupture of membranes, of bilateral lung hypoplasia are illustrated and Arch Dis Child: first published as 10.1136/adc.56.8.606 on 1 August 1981. Downloaded from 608 Wigglesworth, Desai, and Guerrini Table 1 Details of20 cases with lung hypoplasia Case Sex Gestation Age at death Body weight Lung weight Lung/body DNA Pathological summary (weeks) (hours) (g) (g) ratio (mg/kg) 1 M 20 0 355 5.01 0-014 141 Prune-belly syndrome with total urine outflow obstruction 2 F 25 0 770 9.34 0-012 102 Prolonged rupture of membranes from 14 weeks.