The earliest point at which a CPAM can be detected is by prenatal ultrasound. The classic description is of an echogenic lung mass that gradually disappears over subsequent ultrasounds. The disappearance is due to the malformation becoming filled with fluid over the course of the gestation, allowing the ultrasound waves to penetrate it more easily and rendering it invisible on sonographic imaging. When a CPAM is rapidly growing, either solid or with a dominant cyst, they have a higher incidence of developing venous outflow obstruction, cardiac failure and ultimately "hydrops fetalis". If "hydrops" is not present, the fetus has a 95% chance of survival. When hydrops is present, risk of fetal demise is much greater without "in utero" surgery to correct the pathophysiology. The greatest period of growth is during the end of the second trimester, between 20–26 weeks.

A measure of mass volume divided by head circumference, termed cystic adenomatoid malformation volume ratio (CVR) has been developed to predict the risk of "hydrops". The lung mass volume is determined using the formula (length × width × anteroposterior diameter ÷ 2), divided by head circumference. With a CVR greater than 1.6 being considered high risk. Fetuses with a CVR less than 1.6 and without a dominant cyst have less than a 3% risk of hydrops. After delivery, if the patient is symptomatic, resection is mandated. If the infant is asymptomatic, the need for resection is a subject of debate, though it is usually recommended. Development of recurrent infections, rhabdomyosarcoma, adenocarcinomas "in situ" within the lung malformation have been reported.

CPAMs are often identified during routine prenatal ultrasonography. Identifying characteristics on the sonogram include: an echogenic (bright) mass appearing in the chest of the fetus, displacement of the heart from its normal position, a flat or everted (pushed downward) diaphragm, or the absence of visible lung tissue.

CPAMs are classified into three different types based largely on their gross appearance. Type I has a large (>2 cm) multiloculated cysts. Type II has smaller uniform cysts. Type III is not grossly cystic, referred to as the "adenomatoid" type. Microscopically, the lesions are not true cysts, but communicate with the surrounding parenchyma. Some lesions have an abnormal connection to a blood vessel from an aorta and are referred to as "hybrid lesions."

Medical diagnosis of pulmonary hypoplasia in utero may use imaging, usually ultrasound or MRI. The extent of hypoplasia is a very important prognostic factor. 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. In a study of 23 fetuses, subtle differences seen on MRIs of the lungs were informative. In a study of 29 fetuses with suspected pulmonary hypoplasia, the group that responded to maternal oxygenation had a more favorable outcome.

Pulmonary hypoplasia is diagnosed also clinically.

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.

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. Subsequent to this report, use of a vesicoamniotic shunting procedure (VASP) has been attempted, with limited success.

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.

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. 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.

After delivery, most affected babies will require supplemental oxygen. Some severely affected babies may be saved with extracorporeal membrane oxygenation (ECMO). Not all specialty hospitals have ECMO, and ECMO is considered the therapy of last resort for pulmonary insufficiency. An alternative to ECMO is high-frequency oscillatory ventilation.

Diagnosis is made through a combination of patient history, neurological examination, and medical imaging. Magnetic resonance imaging (MRI) is considered the best imaging modality for Chiari malformation since it visualizes neural tissue such as the cerebellar tonsils and spinal cord as well as bone and other soft tissues. CT and CT myelography are other options and were used prior to the advent of MRI, but they characterize syringomyelia and other neural abnormalities less well.

By convention the cerebellar tonsil position is measured relative to the basion-opisthion line, using sagittal T1 MRI images or sagittal CT images. The selected cutoff distance for abnormal tonsil position is somewhat arbitrary since not everyone will be symptomatic at a certain amount of tonsil displacement, and the probability of symptoms and syrinx increases with greater displacement, however greater than 5 mm is the most frequently cited cutoff number, though some consider 3–5 mm to be "borderline," and symptoms and syrinx may occur above that. One study showed little difference in cerebellar tonsil position between standard recumbent MRI and upright MRI for patients without a history of whiplash injury. Neuroradiological investigation is used to first rule out any intracranial condition that could be responsible for tonsillar herniation. Neuroradiological diagnostics evaluate the severity of crowding of the neural structures within the posterior cranial fossa and their impact on the foramen magnum. Chiari 1.5 is a term used when both brainstem and tonsillar herniation through the foramen magnum are present.

The diagnosis of a Chiari II malformation can be made prenatally through ultrasound.

Lymphatic malformations may be detected in the human fetus by ultrasound if they are of sufficient size. Detection of a cystic malformation may prompt further investigation, such as amniocentesis, in order to evaluate for genetic abnormalities in the fetus. Lymphatic malformations may be discovered postnatally or in older children/adults, and most commonly present as a mass or as an incidental finding during medical imaging.

Verification of the diagnosis may require more testing, as there are multiple cystic masses that arise in children. Imaging, such as ultrasound or MRI, may provide more information as to the size and extent of the lesion.

ACD commonly is diagnosed postmortem, by a pathologist.

Sometimes ACD is diagnosed clinically. This is common when there is a family history of ACD, but rare otherwise. A clinical differential diagnosis of ACD excludes fetal atelectasis.

ACD is not detectable by prenatal imaging. However, some babies with ACD have associated congenital malformations that are detectable by imaging. The identification of genes involved in ACD offers the potential for prenatal testing and genetic counseling.

In the late 19th century, Austrian pathologist Hans Chiari described seemingly related anomalies of the hindbrain, the so-called Chiari malformations I, II and III. Later, other investigators added a fourth (Chiari IV) malformation. The scale of severity is rated I – IV, with IV being the most severe. Types III and IV are very rare.

Other conditions sometimes associated with Chiari malformation include hydrocephalus, syringomyelia, spinal curvature, tethered spinal cord syndrome, and connective tissue disorders such as Ehlers-Danlos syndrome and Marfan syndrome.

Chiari malformation is the most frequently used term for this set of conditions. The use of the term Arnold–Chiari malformation has fallen somewhat out of favor over time, although it is used to refer to the type II malformation. Current sources use "Chiari malformation" to describe four specific types of the condition, reserving the term "Arnold-Chiari" for type II only. Some sources still use "Arnold-Chiari" for all four types.

Chiari malformation or Arnold–Chiari malformation should not be confused with Budd-Chiari syndrome, a hepatic condition also named for Hans Chiari.

In Pseudo-Chiari Malformation, Leaking of CSF may cause displacement of the cerebellar tonsils and similar symptoms sufficient to be mistaken for a Chiari I malformation.

Bronchopulmonary sequestration (BPS) is a rare congenital malformation of the lower respiratory tract.

It consists of a nonfunctioning mass of normal lung tissue that lacks normal communication with the tracheobronchial tree, and that receives its arterial blood supply from the systemic circulation.

BPS is estimated to comprise 0.15 to 6.4 percent of all congenital pulmonary malformations, making it an extremely rare disorder.

Sequestrations are classified anatomically.

Intralobar sequestration (ILS) in which the lesion is located within a normal lobe and lacks its own visceral pleura.

Extralobar sequestration (ELS) in which the mass is located outside the normal lung and has its own visceral pleura

The blood supply of 75% of pulmonary sequestrations is derived from the thoracic or abdominal aorta.

The remaining 25% of sequestrations receive their blood flow from the subclavian, intercostal, pulmonary, pericardiophrenic, innominate, internal mammary, celiac, splenic, or renal arteries.

Prenatal Diagnosis:

- Aymé, "et al." (1989) reported prenatal diagnosis of Fryns syndrome by sonography between 24 and 27 weeks.

- Manouvrier-Hanu et al. (1996) described the prenatal diagnosis of Fryns syndrome by ultrasonographic detection of diaphragmatic hernia and cystic hygroma. The diagnosis was confirmed after termination of the pregnancy. The fetus also had 2 erupted incisors; natal teeth had not been mentioned in other cases of Fryns syndrome.

Differential Diagnosis:

- McPherson et al. (1993) noted the phenotypic overlap between Fryns syndrome and the Pallister–Killian syndrome (601803), which is a dysmorphic syndrome with tissue-specific mosaicism of tetrasomy 12p.

- Veldman et al. (2002) discussed the differentiation between Fryns syndrome and Pallister–Killian syndrome, noting that differentiation is important to genetic counseling because Fryns syndrome is an autosomal recessive disorder and Pallister–Killian syndrome is usually a sporadic chromosomal aberration. However, discrimination may be difficult due to the phenotypic similarity. In fact, in some infants with 'coarse face,' acral hypoplasia, and internal anomalies, the initial diagnosis of Fryns syndrome had to be changed because mosaicism of isochromosome 12p was detected in fibroblast cultures or kidney tissue. Although congenital diaphragmatic hernia is a common finding in both syndromes, bilateral congenital diaphragmatic hernia had been reported only in patients with Fryns syndrome until the report of the patient with Pallister–Killian syndrome by Veldman et al. (2002).

- Slavotinek (2004) reviewed the phenotypes of 52 reported cases of Fryns syndrome and reevaluated the diagnostic guidelines. She concluded that congenital diaphragmatic hernia and distal limb hypoplasia are strongly suggestive of Fryns syndrome, with other diagnostically relevant findings including pulmonary hypoplasia, craniofacial dysmorphism, polyhydramnios, and orofacial clefting. Slavotinek (2004) stated that other distinctive anomalies not mentioned in previous guidelines include ventricular dilatation or hydrocephalus, agenesis of the corpus callosum, abnormalities of the aorta, dilatation of the ureters, proximal thumbs, and broad clavicles.

Usually the sequestration is removed after birth via surgery. In most cases this surgery is safe and effective; the child will grow up to have normal lung function.

In a few instances, fetuses with sequestrations develop problematic fluid collections in the chest cavity. In these situations a Harrison catheter shunt can be used to drain the chest fluid into the amniotic fluid.

In rare instances where the fetus has a very large lesion, resuscitation after delivery can be dangerous. In these situations a specialized delivery for management of the airway compression can be planned called the EXIT procedure, or a fetal laser ablation procedure can be performed. During this minimally invasive fetal intervention, a small needle is inserted into the sequestration, and a laser fiber is targeted at the abnormal blood vessel going to the sequestration. The goal of the operation is to use laser energy to stop the blood flow to the sequestration, causing it to stop growing. Ideally, after the surgery, the sequestration steals less blood flow from the fetus, and the heart and lungs start growing more normally as the sequestration shrinks in size and the pleural effusion goes away.

The treatment for this is a wedge resection, segmentectomy, or lobectomy via a VATS procedure or thoracotomy.

Pulmonary sequestrations usually get their blood supply from the thoracic aorta.

Baylor College of Medicine in Houston, Texas has conducted ACD research since 2001.

This condition can often be diagnosed before birth and fetal intervention can sometimes help, depending on the severity of the condition.

Infants born with diaphragmatic hernia experience respiratory failure due to both pulmonary hypertension and pulmonary hypoplasia. The first condition is a restriction of blood flow through the lungs thought to be caused by defects in the lung. Pulmonary hypoplasia or decreased lung volume is directly related to the abdominal organs presence in the chest cavity which causes the lungs to be severely undersized, especially on the side of the hernia.

Survival rates for infants with this condition vary, but have generally been increasing through advances in neonatal medicine. Work has been done to correlate survival rates to ultrasound measurements of the lung volume as compared to the baby's head circumference. This figure known as the lung to head ratio (LHR). Still, LHR remains an inconsistent measure of survival. Outcomes of CDH are largely dependent on the severity of the defect and the appropriate timing of treatment.

A small percentage of cases go unrecognized into adulthood.

Congenital diaphragmatic hernia has a mortality rate of 40–62%, with outcomes being more favorable in the absence of other congenital abnormalities. Individual rates vary greatly dependent upon multiple factors: size of hernia, organs involved, additional birth defects, and/or genetic problems, amount of lung growth, age and size at birth, type of treatments, timing of treatments, complications (such as infections) and lack of lung function.

In France, Aymé, "et al." (1989) estimated the prevalence of Fryns syndrome to be 0.7 per 10,000 births based on the diagnosis of 6 cases in a series of 112,276 consecutive births (live births and perinatal deaths).

One way to determine if a baby does in fact have a Bochdalek hernia, would be to have a pediatrician perform a physical on the infant. A chest x-ray can also be done to examine the abnormalities of not only the lungs but also the diaphragm and the intestine. In addition to these, a doctor can also take a blood test, drawing arterial blood to check and determine how well the baby is breathing and his or her ability to breathe. A chromosomal test (done by testing the blood) can also be performed to determine whether or not the problem was genetic. The doctors can also take an ultrasound of the heart (echocardiogram) to evaluate the health of the heart.

In regards to the diagnosis of pulmonary atresia the body requires oxygenated blood for survival. pulmonary atresia is not threatening to a developing fetus however, because the mother's placenta provides the needed oxygen since the baby's lungs are not yet functional. Once the baby is born its lungs must now provide the oxygen needed for survival, but with pulmonary atresia there is no opening on the pulmonary valve for blood to get to the lungs and become oxygenated. Due to this, the newborn baby is blue in color and pulmonary atresia can usually be diagnosed within hours or minutes after birth.

The diagnosis of pulmonary atresia can be done via the following exams/methods: an echocardiogram, chest x-ray, EKG and an exam to measure the amount of in the body.

A baby with a prenatally diagnosed cystic hygroma should be delivered in a major medical center equipped to deal with neonatal complications, such as a neonatal intensive care unit. An obstetrician usually decides the method of delivery. If the cystic hygroma is large, a cesarean section may be performed. After birth, infants with a persistent cystic hygroma must be monitored for airway obstruction. A thin needle may be used to reduce the volume of the cystic hygroma to prevent facial deformities and airway obstruction. Close observation of the baby by a neonatologist after birth is recommended. If resolution of the cystic hygroma does not occur before birth, a pediatric surgeon should be consulted.

Cystic hygromas that develop in the third trimester, after thirty weeks gestation, or in the postnatal period are usually not associated with chromosome abnormalities. There is a chance of recurrence after surgical removal of the cystic hygroma. The chance of recurrence depends on the extent of the cystic hygroma and whether its wall was able to be completely removed.

Treatments for removal of cystic hygroma are surgery or sclerosing agents which include:

- Bleomycin

- Doxycycline

- Ethanol (pure)

- Picibanil (OK-432)

- Sodium tetradecyl sulfate

Because it is rare and has a wide spectrum of clinical, histological, and imaging features, diagnosing lymphangiomatosis can be challenging. Plain x-rays reveal the presence of lytic lesions in bones, pathological fractures, interstitial infiltrates in the lungs, and chylous effusions that may be present even when there are no outward symptoms.

The most common locations of lymphangiomatosis are the lungs and bones and one important diagnostic clue is the coexistence of lytic bone lesions and chylous effusion. An isolated presentation usually carries a better prognosis than does multi-organ involvement; the combination of pleural and peritoneal involvement with chylous effusions and lytic bone lesions carries the least favorable prognosis.

When lung involvement is suspected, high resolution computed tomography (HRCT) scans may reveal a diffuse liquid-like infiltration in the mediastinal and hilar soft tissue, resulting from diffuse proliferation of lymphatic channels and accumulation of lymphatic fluid; diffuse peribronchovascular and interlobular septal thickening; ground-glass opacities; and pleural effusion. Pulmonary function testing reveals either restrictive pattern or a mixed obstructive/restrictive pattern. While x-rays, HRCT scan, MRI, ultrasound, lymphangiography, bone scan, and bronchoscopy all can have a role in identifying lymphangiomatosis, biopsy remains the definitive diagnostic tool.

Microscopic examination of biopsy specimens reveals an increase in both the size and number of thin walled lymphatic channels along with lymphatic spaces that are interconnecting and dilated, lined by a single attenuated layer of endothelial cells involving the dermis, subcutis, and possibly underlying fascia and skeletal muscle. Additionally, Tazelaar, et al., described a pattern of histological features of lung specimens from nine patients in whom no extrathoracic lesions were identified, which they termed "diffuse pulmonary lymphangiomatosis" (DPL).

Recognition of the disease requires a high index of suspicion and an extensive workup. Because of its serious morbidity, lymphangiomatosis must always be considered in the differential diagnosis of lytic bone lesions accompanied by chylous effusions, in cases of primary chylopericardium, and as part of the differential diagnosis in pediatric patients presenting with signs of interstitial lung disease.

Congenital lobar emphysema (CLE), also known as congenital lobar overinflation and infantile lobar emphysema, is a neonatal condition associated with enlarged air spaces in the lungs of newborn children. It is diagnosed around the time of birth or in the first 6 months of life, occurring more often in boys than girls. CLE affects the upper lung lobes more than the lower lobes, and the left lung more often than the right lung. Although CLE may be caused by abnormal development of airways (bronchi, for example) or compression of airways by nearby tissues, no cause is identified in half of cases.

No treatment is needed for correcting lung hernias. Some surgeons offer cosmetic surgery to remove the protruding mass.

Bochdalek hernia can be a life-threatening condition. Approximately 85.3% of newborns born with a Bochdalek hernia are immediately high risk. Infants born with a Bochdalek hernia have a "high mortality rate due to respiratory insufficiency". Between 25–60% of infants with a Bochdalek hernia die. The lungs, diaphragm, and digestive system are all forming at the same time, so when a Bochdalek hernia permits the abdominal organs to invade the chest cavity rather than remain under the diaphragm in the correct position, it puts the infant in critical condition. These "foreign bodies" in the chest cavity compress the lungs, impairing their proper development and causing pulmonary hypoplasia. Since the lungs of infants suffering from a Bochdalek hernia have fewer alveoli than normal lungs, Bochdalek hernias are life-threatening conditions due to respiratory distress. Also, if the invasion of the intestine or stomach punctures the lung, then the lungs cannot fill completely with air. The baby will not be healthy or stable with this condition because he or she cannot take in enough air and oxygen to keep the body operating properly. Like the lungs, the intestines may also have trouble developing correctly. If the intestines are trapped within the lungs, then the lungs and intestines may not be receiving the amount of blood they need to stay healthy and function properly.

Respiratory diseases may be investigated by performing one or more of the following tests

- Biopsy of the lung or pleura

- Blood test

- Bronchoscopy

- Chest x-ray

- Computed tomography scan, including high-resolution computed tomography

- Culture of microorganisms from secretions such as sputum

- Ultrasound scanning can be useful to detect fluid such as pleural effusion

- Pulmonary function test

- Ventilation—perfusion scan

AVMs are diagnosed primarily by the following methods:

- Computerized tomography (CT) scan is a noninvasive X-ray to view the anatomical structures within the brain to detect blood in or around the brain. A newer technology called CT angiography involves the injection of contrast into the blood stream to view the arteries of the brain. This type of test provides the best pictures of blood vessels through angiography and soft tissues through CT.

- Magnetic resonance imaging (MRI) scan is a noninvasive test, which uses a magnetic field and radio-frequency waves to give a detailed view of the soft tissues of the brain.

- Magnetic resonance angiography (MRA) – scans created using magnetic resonance imaging to specifically image the blood vessels and structures of the brain. A magnetic resonance angiogram can be an invasive procedure, involving the introduction of contrast dyes (e.g., gadolinium MR contrast agents) into the vasculature of a patient using a catheter inserted into an artery and passed through the blood vessels to the brain. Once the catheter is in place, the contrast dye is injected into the bloodstream and the MR images are taken. Additionally or alternatively, flow-dependent or other contrast-free magnetic resonance imaging techniques can be used to determine the location and other properties of the vasculature.

AVMs can occur in various parts of the body:

- brain (cerebral AV malformation)

- spleen

- lung

- kidney

- spinal cord

- liver

- intercostal space

- iris

- spermatic cord

- extremities – arm, shoulder, etc.

AVMs may occur in isolation or as a part of another disease (for example, Von Hippel-Lindau disease or hereditary hemorrhagic telangiectasia).

AVMs have been shown to be associated with aortic stenosis.

Bleeding from an AVM can be relatively mild or devastating. It can cause severe and less often fatal strokes. If a cerebral AVM is detected before a stroke occurs, usually the arteries feeding blood into the nidus can be closed off to avert the danger. However, interventional therapy may also be relatively risky.

The diagnosis is made by transthoracic or transesophageal echocardiography, angiography, and more recently by CT angiography or MR Angiography.