Congenital Lung Malformations (CPAM, Sequestration)
- Congenital lung malformations are construction errors from fetal life: a chunk of lung that grew wrong, in the wrong place, or plumbed into the wrong vessels.
- The two headliners are CPAM (a region of cystic, malformed lung) and bronchopulmonary sequestration (normal-ish lung tissue that never connected to the airway and gets its blood from a rogue systemic artery).
- The single most useful question on imaging is: where does this thing get its blood? A feeding artery off the aorta is the giveaway for sequestration.
- Many are spotted on prenatal ultrasound, may shrink before birth, and a surprising number of kids are asymptomatic — so CT after birth is about mapping anatomy, not panicking.
- These lesions overlap, coexist, and love to imitate pneumonia, which is the classic trap.
Imagine the fetal lung as a contractor building millions of tiny rooms (alveoli) and the hallways that connect them (airways), all hooked up to the building's water main (the pulmonary arteries). Congenital lung malformations are what happen when the contractor has a bad day: a wing of rooms gets built as weird cysts, or a whole section gets finished but nobody connects the hallway or runs the right water line to it. The lung is mostly fine. One zip code is just off.
The good news for you: a small handful of patterns explains almost all of it, and they're distinguished by a couple of concrete questions you can actually answer on a scan.
CPAM: the cystic one
Congenital pulmonary airway malformation (CPAM) — older textbooks call it CCAM (congenital cystic adenomatoid malformation), and you'll still hear both — is a region of lung where the airways and air sacs developed into a disorganized mass of cysts. Picture a patch of normal honeycomb where the bees gave up and built a few big lopsided chambers instead.
The thing to internalize is that CPAM connects normally to the airway and gets its blood from the pulmonary artery, like the rest of the lung. That last point matters because it's exactly what separates it from sequestration.
CPAMs come in a spectrum from "one or a few big cysts" to "lots of tiny cysts that look almost solid." Rather than memorize a numbered classification, just describe what you see: how big are the cysts, how many, and how much lung does the lesion occupy.
An air-filled cystic CPAM on a chest radiograph can look identical to a lung full of pneumonia with cavitation or abscesses — or vice versa. A kid with "pneumonia" that keeps recurring in the exact same spot deserves a hard look for an underlying malformation hiding beneath the infection.
Sequestration: the lung that got disconnected
Bronchopulmonary sequestration is a piece of lung tissue that is "sequestered" — walled off from the normal system. It typically does not connect to the airway, and here's the kicker: it draws its blood supply from a systemic artery, usually a branch straight off the aorta, instead of the pulmonary artery. It's a room someone built and then accidentally plumbed into the city water main instead of the building's.
That anomalous systemic feeding vessel is the whole game. If you find an artery coming off the aorta (often the descending thoracic or upper abdominal aorta) to feed an abnormal chunk of lung, you've basically made the diagnosis.
See an abnormal lung lesion? Hunt for its feeding artery. Pulmonary artery supply points toward CPAM; a systemic artery off the aorta points toward sequestration.
Sequestrations come in two flavors based on their wrapping. Intralobar sits inside the normal lung's pleural envelope and shares its visceral pleura with the surrounding lung. Extralobar has its own separate pleural covering — a true outsider — and is more often found in newborns, classically in the left lower zone or even below the diaphragm.
Why CT angiography is the answer
You'll often hear these picked up first on prenatal ultrasound, sometimes alongside or instead of neonatal respiratory distress workups after birth. But ultrasound and plain films can only get you so far.
The definitive test is a contrast-enhanced CT (ideally timed to show the arteries), because it does two things at once: it maps the cysts and lung tissue and it shows you the blood supply. That single feeding-vessel question is why we reach for contrast here rather than guessing from a radiograph.
These categories are not a tidy multiple-choice list. Hybrid lesions — a CPAM that also has a systemic feeding artery — are well recognized, and malformations can coexist. When the features blur, describe the components honestly rather than forcing the lesion into one box.
What actually happens to these kids
Plenty of these lesions are found before birth, and some genuinely shrink or become hard to see as the pregnancy continues — which does not mean they vanished, just that they're quieter on imaging. After birth, many children are asymptomatic. Others present with recurrent infection in the same region, or, less often, respiratory distress from a big lesion crowding the chest.
Management is a real conversation between surgeons and radiologists, and practice varies; some lesions are resected and some asymptomatic ones are watched. Your job on imaging isn't to settle that debate — it's to give the team a clean map: where the lesion is, what it's made of, and, above all, where it gets its blood.
If you remember one sentence from this page, make it this: congenital lung malformations are sorted out by following the plumbing. Find the feeding artery, and the diagnosis usually finds you.