Pulmonary hypoplasia

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Pulmonary hypoplasia
Other namesFamilial primary pulmonary hypoplasia
Autosomal recessive - en.svg
This condition is inherited in an autosomal recessive manner
Specialty Pulmonology

Pulmonary hypoplasia is incomplete development of the lungs, resulting in an abnormally low number or small size of bronchopulmonary segments or alveoli. A congenital malformation, it 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.

Contents

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.

Causes

Causes of pulmonary hypoplasia include a wide variety of congenital malformations and other conditions in which pulmonary hypoplasia is a complication. [1] These include congenital diaphragmatic hernia, congenital cystic adenomatoid malformation, fetal hydronephrosis, caudal regression syndrome, mediastinal tumor, and sacrococcygeal teratoma with a large component inside the fetus. [3] [4] [5] [6] Large masses of the neck (such as cervical teratoma) also can cause pulmonary hypoplasia, presumably by interfering with the fetus's ability to fill its lungs. In the presence of pulmonary hypoplasia, the EXIT procedure to rescue a baby with a neck mass is not likely to succeed. [7]

Fetal hydrops can be a cause, [8] or conversely a complication. [9]

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 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 entering 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]

Pulmonary hypoplasia is associated with dextrocardia of embryonic arrest in that both conditions can result from early errors of development, resulting in Congenital cardiac disorders.

PH is a common direct cause of neonatal death resulting from pregnancy induced hypertension. [11]

Diagnosis

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]

Often, a baby with a high risk of pulmonary hypoplasia will have a planned delivery in a specialty hospital such as (in the United States) a tertiary referral hospital with a level 3 neonatal intensive-care unit. The baby may require immediate advanced resuscitation and therapy. [24]

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]

See also

Related Research Articles

<span class="mw-page-title-main">Teratoma</span> Type of germ cell tumor

A teratoma is a tumor made up of several different types of tissue, such as hair, muscle, teeth, or bone. Teratomata typically form in the tailbone, ovary, or testicle.

<span class="mw-page-title-main">Polyhydramnios</span> Excess of amniotic fluid in the amniotic sac

Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in about 1% of pregnancies. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 24 cm. There are two clinical varieties of polyhydramnios: chronic polyhydramnios where excess amniotic fluid accumulates gradually, and acute polyhydramnios where excess amniotic fluid collects rapidly.

Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index (AFI) measures less than 5 cm or when the single deepest pocket (SDP) of amniotic fluid measures less than 2 cm. Amniotic fluid is necessary to allow for normal fetal movement, lung development, and cushioning from uterine compression. Low amniotic fluid can be attributed to a maternal, fetal, placental or idiopathic cause and can result in poor fetal outcomes including death. The prognosis of the fetus is dependent on the etiology, gestational age at diagnosis, and the severity of the oligohydramnios.

Potter sequence is the atypical physical appearance of a baby due to oligohydramnios experienced when in the uterus. It includes clubbed feet, pulmonary hypoplasia and cranial anomalies related to the oligohydramnios. Oligohydramnios is the decrease in amniotic fluid volume sufficient to cause deformations in morphogenesis of the baby.

<span class="mw-page-title-main">Pediatric surgery</span> Medical subspecialty of surgery performed by pediatrics

Pediatric surgery is a subspecialty of surgery involving the surgery of fetuses, infants, children, adolescents, and young adults.

<span class="mw-page-title-main">Pulmonary sequestration</span> Medical condition

A pulmonary sequestration is a medical condition wherein a piece of tissue that ultimately develops into lung tissue is not attached to the pulmonary arterial blood supply, as is the case in normally developing lung. This sequestered tissue is therefore not connected to the normal bronchial airway architecture, and fails to function in, and contribute to, respiration of the organism.

<span class="mw-page-title-main">Hydrops fetalis</span> Human disease of fetuses

Hydrops fetalis or hydrops foetalis is a condition in the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments. By comparison, hydrops allantois or hydrops amnion is an accumulation of excessive fluid in the allantoic or amniotic space, respectively.

<span class="mw-page-title-main">Congenital diaphragmatic hernia</span> Medical condition

Congenital diaphragmatic hernia (CDH) is a birth defect of the diaphragm. The most common type of CDH is a Bochdalek hernia; other types include Morgagni hernia, diaphragm eventration and central tendon defects of the diaphragm. Malformation of the diaphragm allows the abdominal organs to push into the chest cavity, hindering proper lung formation.

<span class="mw-page-title-main">Pulmonary atresia</span> Medical condition

Pulmonary atresia is a congenital malformation of the pulmonary valve in which the valve orifice fails to develop. The valve is completely closed thereby obstructing the outflow of blood from the heart to the lungs. The pulmonary valve is located on the right side of the heart between the right ventricle and pulmonary artery. In a normal functioning heart, the opening to the pulmonary valve has three flaps that open and close.

<span class="mw-page-title-main">Fetal surgery</span> Growing branch of maternal-fetal medicine

Fetal surgery also known as antenatal surgery, prenatal surgery, is a growing branch of maternal-fetal medicine that covers any of a broad range of surgical techniques that are used to treat congenital abnormalities in fetuses who are still in the pregnant uterus. There are three main types: open fetal surgery, which involves completely opening the uterus to operate on the fetus; minimally invasive fetoscopic surgery, which uses small incisions and is guided by fetoscopy and sonography; and percutaneous fetal therapy, which involves placing a catheter under continuous ultrasound guidance.

<span class="mw-page-title-main">EXIT procedure</span>

The EXIT procedure, or ex utero intrapartum treatment procedure, is a specialized surgical delivery procedure used to deliver babies who have airway compression. Causes of airway compression in newborn babies result from a number of rare congenital disorders, including bronchopulmonary sequestration, congenital cystic adenomatoid malformation, mouth or neck tumor such as teratoma, and lung or pleural tumor such as pleuropulmonary blastoma. Airway compression discovered at birth is a medical emergency. In many cases, however, the airway compression is discovered during prenatal ultrasound exams, permitting time to plan a safe delivery using the EXIT procedure or other means.

Sacrococcygeal teratoma (SCT) is a type of tumor known as a teratoma that develops at the base of the coccyx (tailbone) and is thought to be primarily derived from remnants of the primitive streak. Sacrococcygeal teratomas are benign 75% of the time, malignant 12% of the time, and the remainder are considered "immature teratomas" that share benign and malignant features. Benign sacrococcygeal teratomas are more likely to develop in younger children who are less than 5 months old, and older children are more likely to develop malignant sacrococcygeal teratomas.

<span class="mw-page-title-main">Bochdalek hernia</span> Medical condition

Bochdalek hernia is one of two forms of a congenital diaphragmatic hernia, the other form being Morgagni hernia. A Bochdalek hernia is a congenital abnormality in which an opening exists in the infant's diaphragm, allowing normally intra-abdominal organs to enter into the thoracic cavity. In the majority of people, the affected lung will be deformed, and the resulting lung compression can be life-threatening. Bochdalek hernias occur more commonly on the posterior left side.

The Fetal Treatment Center at the University of California, San Francisco is a multidisciplinary care center dedicated to the diagnosis, treatment, and long-term follow-up of fetal birth defects. It combines the talents of specialists in pediatric surgery, genetics, obstetrics/perinatology, radiology, nursing, and neonatal medicine.

Persistent fetal circulation is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the "normal" pattern. Infants experience a high mean arterial pulmonary artery pressure and a high afterload at the right ventricle. This means that the heart is working against higher pressures, which makes it more difficult for the heart to pump blood.

<span class="mw-page-title-main">Congenital pulmonary airway malformation</span> Medical condition

Congenital pulmonary airway malformation (CPAM), formerly known as congenital cystic adenomatoid malformation (CCAM), is a congenital disorder of the lung similar to bronchopulmonary sequestration. In CPAM, usually an entire lobe of lung is replaced by a non-working cystic piece of abnormal lung tissue. This abnormal tissue will never function as normal lung tissue. The underlying cause for CPAM is unknown. It occurs in approximately 1 in every 30,000 pregnancies.

<span class="mw-page-title-main">Fryns syndrome</span> Medical condition

Fryns syndrome is an autosomal recessive multiple congenital anomaly syndrome that is usually lethal in the neonatal period. Fryns (1987) reviewed the syndrome.

Epignathus is a rare teratoma of the oropharynx. Epignathus is a form of oropharyngeal teratoma that arises from the palate and, in most cases, results in death. The pathology is thought to be due to unorganized and uncontrolled differentiation of somatic cells leading to formation of the teratoma; sometimes it is also referred to as "fetus-in-fetu", which is an extremely rare occurrence of an incomplete but parasitic fetus located in the body of its twin. This tumor is considered benign but life-threatening because of its atypical features and high risk of airway obstruction, which is the cause of death in 80-100% of the cases at the time of delivery.

<span class="mw-page-title-main">Pulmonary agenesis</span> Medical condition

Pulmonary agenesis is an inborn lung underdevelopment that is rare and potentially lethal. The disorder is caused by a complete developmental arrest of the primitive lung during embryonic life, and it is often associated with other developmental defects. Bilateral and unilateral pulmonary agenesis are classified, depending on whether one side of the lung or both sides are affected. Bilateral pulmonary agenesis is lethal, while the mortality rate of unilateral pulmonary agenesis is higher than 50%. Depending on the severity, the symptom ranges from none to various respiratory complaints. It is detectable prenatally, however, its nonspecific clinical features act as the obstacle for diagnosing. The exact cause of pulmonary agenesis is still obscure. However, theories have been raised regarding the vascular, iatrogenic, viral and genetic causes of pulmonary agenesis in an attempt to explain the pathogenesis of the disorder. In most cases of pulmonary agenesis, surgical resection is performed to remove the malformed lobe or the entire defected lung of the patient depending on the severity of the respiratory impairment.

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