What is a Pleuroperitoneal Cavity? A Guide to Fetal Development

September 24, 2025 •

3 min read

During embryonic development, the intraembryonic coelom undergoes a remarkable transformation, partitioning into the major body cavities. The pleuroperitoneal cavity is a critical, transient stage in this process, connecting the developing chest and abdominal spaces before the diaphragm is fully formed. Understanding this cavity is key to grasping the origins of the final anatomical structure.

Quick Summary

The pleuroperitoneal cavity is the temporary embryonic space that connects the primitive chest (pleural) and abdominal (peritoneal) cavities, a stage that exists until the pleuroperitoneal membranes grow to form the complete diaphragm. Its proper closure is a fundamental step in fetal development, ensuring the thoracic and abdominal organs are correctly separated.

Key Points

Embryonic Stage: The pleuroperitoneal cavity is a temporary space that connects the primitive chest and abdominal cavities in the developing fetus.
Diaphragm Formation: Its closure is crucial for the diaphragm's development, with the pleuroperitoneal membranes fusing to partition the thoracic and abdominal spaces.
Associated Condition: Failure of this closure leads to congenital diaphragmatic hernia (CDH), allowing abdominal organs to enter the chest and compress the lungs.
Surgical Application: Pleuroperitoneal shunts are medical devices used to drain fluid from the pleural cavity into the peritoneal cavity for certain conditions like malignant effusions.
Left-Side Dominance: Congenital diaphragmatic hernias occur more frequently on the left side due to the later fusion of the left pleuroperitoneal membrane compared to the right.
Adult Communications: In some adults, conditions like peritoneal dialysis can cause a recurrence of pleuroperitoneal communication, leading to fluid migration.

Embryonic Development of the Pleuroperitoneal Cavity

At the start of the fourth week of embryonic development, the intraembryonic coelom is a single, horseshoe-shaped cavity. As the embryo folds, this cavity is gradually compartmentalized into the pericardial, pleural, and peritoneal cavities. The primitive pleuroperitoneal cavity refers to the paired canals that connect the cranial pericardial region with the caudal peritoneal region. The separation of these spaces begins with the growth of specific structures.

The Role of Pleuroperitoneal Membranes

The separation of the pleuroperitoneal cavity is primarily achieved by the pleuroperitoneal membranes. These membranes originate from the lateral body walls and extend towards the midline of the embryo. They eventually fuse with the septum transversum and the dorsal mesentery of the esophagus, which seals the connection between the thoracic and abdominal cavities. This fusion generally occurs around the sixth week of gestation, with the right side typically closing before the left.

The Septum Transversum

The septum transversum also plays a significant role in this process. It is a mass of mesoderm that moves from the neck region down to the developing thoracic cavity, forming the central tendon of the diaphragm and serving as an attachment point for the pleuroperitoneal membranes.

The Clinical Significance of the Pleuroperitoneal Cavity

Proper closure of the pleuroperitoneal cavity is essential for normal anatomy. Failure of this process can result in congenital diaphragmatic hernia (CDH), a condition where a defect in the diaphragm allows abdominal organs to enter the chest cavity. Understanding this transient embryonic structure provides valuable insight into both developmental anatomy and related clinical conditions.

Congenital Diaphragmatic Hernia (CDH)

CDH is a serious birth defect affecting approximately 1 in 2,000 to 5,000 births. It is caused by the incomplete fusion of the pleuroperitoneal membranes. The most common type is the posterolateral Bochdalek hernia, frequently occurring on the left side. The left side's later closure and the protective presence of the liver on the right are thought to contribute to this asymmetry. When abdominal organs protrude into the chest, they can impede lung development, leading to pulmonary hypoplasia and pulmonary hypertension, which are major factors in infant mortality.

Modern Medical Relevance: The Pleuroperitoneal Shunt

A pleuroperitoneal shunt is a device surgically implanted to drain excess fluid from the pleural cavity into the peritoneal cavity. A shunt consists of a catheter and a one-way valve, with one end placed in the pleural space and the other tunneled into the peritoneal cavity. A subcutaneous pump is often included to help move the fluid. Though less common now due to alternative treatments, pleuroperitoneal shunts remain a useful option for managing certain types of recurrent pleural effusions, such as malignant pleural effusions, refractory chylothorax, and trapped lung.

Comparing Embryonic Cavities

To understand the pleuroperitoneal cavity fully, it is helpful to compare it to the definitive cavities it helps create. Here is a comparison:


Feature	Pleuroperitoneal Cavity	Pleural Cavity	Peritoneal Cavity
Embryonic Status	Transient, temporary	Definitive, permanent	Definitive, permanent
Function	Connects developing thoracic and abdominal spaces	Houses lungs; facilitates respiration	Houses abdominal organs; provides lubrication
Fate	Obliterated by the developing diaphragm	Formed by division of the coelom	Formed by division of the coelom
Associated Pathology	Congenital Diaphragmatic Hernia (CDH)	Pneumothorax, pleural effusion	Ascites, peritonitis
Lining	Lined by mesothelium	Lined by pleura (visceral and parietal)	Lined by peritoneum (visceral and parietal)

Pleuroperitoneal Communication (PPC) in Adults

Even in adulthood, conditions can lead to pleuroperitoneal communication (PPC), where fluid can pass between the pleural and peritoneal cavities despite an apparently intact diaphragm. This can occur in individuals undergoing peritoneal dialysis due to pressure differences. Inflammatory conditions or liver disease can also contribute to this communication. Identifying PPC is important for appropriate clinical management. For more authoritative information on this topic, consult the {Link: NIH https://pmc.ncbi.nlm.nih.gov/articles/PMC10469182/}.

Conclusion: The Journey from Cavity to Closure

The pleuroperitoneal cavity represents a critical, temporary stage in embryonic development, acting as a link between the future thoracic and abdominal spaces. Its successful closure through the formation of the diaphragm is vital for the proper separation and function of organ systems. Failure in this process is a leading cause of congenital diaphragmatic hernia. Understanding this transient embryonic structure provides valuable insight into both developmental anatomy and related clinical conditions.

Frequently Asked Questions

The pleuroperitoneal cavity is a transitional space that primarily acts as a connection between the developing chest (pleural) and abdominal (peritoneal) cavities. Its primary function is to facilitate the subsequent separation of these two major body spaces by providing the site where the diaphragm will form.

Closure is achieved by the growth and fusion of the pleuroperitoneal membranes. These membranes grow from the lateral body walls and merge with other structures, such as the septum transversum, to create a complete diaphragm, thereby separating the chest and abdominal cavities.

If the cavity fails to close, it can result in a congenital diaphragmatic hernia (CDH). This condition allows abdominal organs to push into the chest, potentially causing severe lung underdevelopment (pulmonary hypoplasia).

No. The pleuroperitoneal cavity is a temporary, embryonic precursor. The pleural and peritoneal cavities are the definitive, separate spaces that exist after the diaphragm has completely formed and partitioned the chest from the abdomen.

The left side is more commonly affected because the left pleuroperitoneal canal typically closes later than the right side during embryonic development. This prolonged opening provides a greater opportunity for a developmental defect to occur.

Yes. While rare, a pathological communication can sometimes occur in adults, known as pleuroperitoneal communication (PPC). This can be seen in patients on peritoneal dialysis or with certain diseases, allowing fluid to pass between the cavities.

A pleuroperitoneal shunt is a medical device used to deliberately create a connection between the pleural and peritoneal cavities to drain excess fluid from the chest. It is used for refractory pleural effusions when other treatments are not effective.

The pleuroperitoneal membranes contribute a significant portion of the diaphragm, primarily the central tendon and surrounding muscular tissue, as they fuse with the septum transversum and esophageal mesentery.