Pulmonary hypoplasia is an incomplete development of the lungs, resulting in an abnormally low number or small size of bronchopulmonary segments or alveoli. A congenital malformation, most often occurs secondary to other fetal abnormalities that interfere with normal development of the lungs. Primary (idiopathic) pulmonary hypoplasia is rare and usually not associated with other maternal or fetal abnormalities.
Incidence of pulmonary hypoplasia ranges from 9–11 per 10,000 live births and 14 per 10,000 births.[1] Pulmonary hypoplasia is a relatively common cause of neonatal death.[2] It also is a common finding in stillbirths, although not regarded as a cause of these.
Pulmonary hypoplasia is associated with oligohydramnios through multiple mechanisms. Both conditions can result from blockage of the urinary bladder. Blockage prevents the bladder from emptying, and the bladder becomes very large and full. The large volume of the full bladder interferes with the normal development of other organs, including the lungs. Pressure within the bladder becomes abnormally high, causing abnormal function in the kidneys; hence, abnormally high pressure in the vascular system enters the kidneys. This high pressure also interferes with normal development of other organs. An experiment in rabbits showed that PH also can be caused directly by oligohydramnios.[10]
Medical diagnosis of pulmonary hypoplasia in utero may use imaging, usually ultrasound or MRI.[12][13] The extent of hypoplasia is a very important prognostic factor.[14] One study of 147 fetuses (49 normal, 98 with abnormalities) found that a simple measurement, the ratio of chest length to trunk (torso) length, was a useful predictor of postnatal respiratory distress.[15] In a study of 23 fetuses, subtle differences seen on MRIs of the lungs were informative.[16] In a study of 29 fetuses with suspected pulmonary hypoplasia, the group that responded to maternal oxygenation had a more favorable outcome.[17]
Pulmonary hypoplasia is diagnosed also clinically.
Management
Management has three components: interventions before delivery, timing and place of delivery, and therapy after delivery.
In some cases, fetal therapy is available for the underlying condition; this may help to limit the severity of pulmonary hypoplasia. In exceptional cases, fetal therapy may include fetal surgery.[18][19]
A 1992 case report of a baby with a sacrococcygeal teratoma (SCT) reported that the SCT had obstructed the outlet of the urinary bladder causing the bladder to rupture in utero and fill the baby's abdomen with urine (a form of ascites). The outcome was good. The baby had normal kidneys and lungs, leading the authors to conclude that obstruction occurred late in the pregnancy and to suggest that the rupture may have protected the baby from the usual complications of such an obstruction.[20] Subsequent to this report, use of a vesicoamniotic shunting procedure (VASP) has been attempted, with limited success.[21][22][23]
Early delivery may be required in order to rescue the fetus from an underlying condition that is causing pulmonary hypoplasia. However, pulmonary hypoplasia increases the risks associated with preterm birth, because once delivered the baby requires adequate lung capacity to sustain life. The decision whether to deliver early includes a careful assessment of the extent to which delaying delivery may increase or decrease the pulmonary hypoplasia. It is a choice between expectant management and active management. An example is congenital cystic adenomatoid malformation with hydrops; impending heart failure may require a preterm delivery.[25] Severe oligohydramnios of early onset and long duration, as can occur with early preterm rupture of membranes, can cause increasingly severe PH; if delivery is postponed by many weeks, PH can become so severe that it results in neonatal death.[26]
After delivery, most affected babies will require supplemental oxygen. Some severely affected babies may be saved with extracorporeal membrane oxygenation (ECMO).[27] Not all specialty hospitals have ECMO, and ECMO is considered the therapy of last resort for pulmonary insufficiency.[28] An alternative to ECMO is high-frequency oscillatory ventilation.[29]
History
In 1908, Maude Abbott documented pulmonary hypoplasia occurring with certain defects of the heart.[30] In 1915, Abbott and J. C. Meakins showed that pulmonary hypoplasia was part of the differential diagnosis of dextrocardia.[31] In 1920, decades before the advent of prenatal imaging, the presence of pulmonary hypoplasia was taken as evidence that diaphragmatic hernias in babies were congenital, not acquired.[32]
^ abCadichon, Sandra B. (2007), "Chapter 22: Pulmonary hypoplasia", in Kumar, Praveen; Burton, Barbara K. (eds.), Congenital malformations: evidence-based evaluation and management
^Walton JM, Rubin SZ, Soucy P, Benzie R, Ash K, Nimrod C (September 1993). "Fetal tumors associated with hydrops: the role of the pediatric surgeon". Journal of Pediatric Surgery. 28 (9): 1151–1163. doi:10.1016/0022-3468(93)90152-b. PMID8308682.
^Seo T, Ando H, Watanabe Y, Harada T, Ito F, Kaneko K, Mimura S (November 1999). "Acute respiratory failure associated with intrathoracic masses in neonates". Journal of Pediatric Surgery. 34 (11): 1633–1637. doi:10.1016/s0022-3468(99)90632-2. PMID10591558.
^Goto M, Makino Y, Tamura R, Ikeda S, Kawarabayashi T (2000). "Sacrococcygeal teratoma with hydrops fetalis and bilateral hydronephrosis". Journal of Perinatal Medicine. 28 (5): 414–418. doi:10.1515/JPM.2000.054. PMID11125934. S2CID23998257.
^Merello E, De Marco P, Mascelli S, Raso A, Calevo MG, Torre M, Cama A, Lerone M, Martucciello G, Capra V (March 2006). "HLXB9 homeobox gene and caudal regression syndrome". Birth Defects Research. Part A, Clinical and Molecular Teratology. 76 (3): 205–209. doi:10.1002/bdra.20234. PMID16498628.
^Liechty KW, Hedrick HL, Hubbard AM, Johnson MP, Wilson RD, Ruchelli ED, Howell LJ, Crombleholme TM, Flake AW, Adzick NS (January 2006). "Severe pulmonary hypoplasia associated with giant cervical teratomas". Journal of Pediatric Surgery. 41 (1): 230–233. doi:10.1016/j.jpedsurg.2005.10.081. PMID16410139.
^Kaiser L, Arany A, Veszprémi B, Vizer M (March 2007). "[Hydrops fetalis – a retrospective study]". Orvosi Hetilap (in Hungarian). 148 (10): 457–463. doi:10.1556/OH.2007.27951. PMID17350912.
^Zembala-Nozyńska E, Oslislo A, Zajecki W, Kamiński K, Radzioch J (2005). "[Mediastinal tumor as a cause of fetal hydrops]". Wiadomości Lekarskie (in Polish). 58 (7–8): 462–475. PMID16425805.
^Yoshimura S, Masuzaki H, Miura K, Hayashi H, Gotoh H, Ishimaru T (July 1997). "The effects of oligohydramnios and cervical cord transection on lung growth in experimental pulmonary hypoplasia in rabbits". American Journal of Obstetrics and Gynecology. 177 (1): 72–77. doi:10.1016/s0002-9378(97)70440-x. PMID9240585.
^Zhou X, Du X (July 1997). "[Analysis of the causes of neonatal deaths at term in pregnancy induced hypertension patients]". Zhonghua Fu Chan Ke Za Zhi (in Chinese). 32 (7): 409–411. PMID9639726.
^Kasprian G, Balassy C, Brugger PC, Prayer D (February 2006). "MRI of normal and pathological fetal lung development". European Journal of Radiology. 57 (2): 261–270. doi:10.1016/j.ejrad.2005.11.031. PMID16413987.
^Lally KP, Lally PA, Lasky RE, Tibboel D, Jaksic T, Wilson JM, Frenckner B, Van Meurs KP, Bohn DJ, Davis CF, Hirschl RB (September 2007). "Defect size determines survival in infants with congenital diaphragmatic hernia". Pediatrics. 120 (3): e651–e657. doi:10.1542/peds.2006-3040. PMID17766505. S2CID21529283.
^Ishikawa S, Kamata S, Usui N, Sawai T, Nose K, Okada A (May 2003). "Ultrasonographic prediction of clinical pulmonary hypoplasia: measurement of the chest/trunk-length ratio in fetuses". Pediatric Surgery International. 19 (3): 172–175. doi:10.1007/s00383-002-0912-2. PMID12687395. S2CID12453659.
^Kuwashima S, Nishimura G, Iimura F, Kohno T, Watanabe H, Kohno A, Fujioka M (September 2001). "Low-intensity fetal lungs on MRI may suggest the diagnosis of pulmonary hypoplasia". Pediatric Radiology. 31 (9): 669–672. doi:10.1007/s002470100512. PMID11512012. S2CID24016373.
^Broth RE, Wood DC, Rasanen J, Sabogal JC, Komwilaisak R, Weiner S, Berghella V (October 2002). "Prenatal prediction of lethal pulmonary hypoplasia: the hyperoxygenation test for pulmonary artery reactivity". American Journal of Obstetrics and Gynecology. 187 (4): 940–945. doi:10.1067/mob.2002.127130. PMID12388982.
^Evans MI, Harrison MR, Flake AW, Johnson MP (October 2002). "Fetal therapy". Best Practice & Research. Clinical Obstetrics & Gynaecology. 16 (5): 671–683. doi:10.1053/beog.2002.0331. PMID12475547.
^Muratore CS, Wilson JM (December 2000). "Congenital diaphragmatic hernia: where are we and where do we go from here?". Seminars in Perinatology. 24 (6): 418–428. doi:10.1053/sper.2000.21111. PMID11153903.
^Thibeault DW, Haney B (February 1998). "Lung volume, pulmonary vasculature, and factors affecting survival in congenital diaphragmatic hernia". Pediatrics. 101 (2): 289–295. doi:10.1542/peds.101.2.289. PMID9445506.
^Azarow K, Messineo A, Pearl R, Filler R, Barker G, Bohn D (March 1997). "Congenital diaphragmatic hernia – a tale of two cities: the Toronto experience". Journal of Pediatric Surgery. 32 (3): 395–400. doi:10.1016/s0022-3468(97)90589-3. PMID9094001.
^Abbott, Maude (1908), "Chapter IX: Congenital cardiac disease", in Osler, William (ed.), Modern Medicine: Its Theory and Practice, vol. IV: Diseases of the circulatory system, diseases of the blood, diseases of the spleen, thymus, and lymph-glands, Philadelphia and New York: Lea & Febiger