M01.06.001 Abdominal Cavity

The peritoneal cavity is a potential space located between the parietal and visceral peritoneum. It normally contains a thin film of peritoneal fluid composed of water, electrolytes, leukocytes, and antibodies. This fluid functions as a lubricant, allowing smooth movement of abdominal organs while also providing immune protection. However, excessive fluid accumulation can result in ascites, a condition with significant clinical implications.

This article explores the anatomy, subdivisions, structure, and clinical significance of the peritoneal cavity.

Subdivisions of the Peritoneal Cavity

The peritoneal cavity is divided into two main compartments:

1. Greater Sac
   • The larger portion of the peritoneal cavity.
   • Subdivided by the transverse mesocolon into:
     • Supracolic compartment: Contains the stomach, liver, and spleen.
     • Infracolic compartment: Contains the small intestine and parts of the colon, further divided into left and right infracolic spaces.
   • Connected to the infracolic compartment via paracolic gutters, allowing fluid movement.
2. Lesser Sac (Omental Bursa)
   • Lies posterior to the stomach and lesser omentum.
   • Allows free movement of the stomach.
   • Connected to the greater sac via the epiploic foramen (of Winslow), located posterior to the hepatoduodenal ligament.

Table 1: Comparison of the Greater and Lesser Sacs

Structure of the Peritoneal Cavity in the Pelvis

The pelvic portion of the peritoneal cavity differs in males and females due to reproductive anatomy.

Males:

• The rectovesical pouch (double folding of the peritoneum) lies between the rectum and bladder.
• The peritoneal cavity is completely closed in males.

Females:

• Contains two peritoneal pouches:
  • Rectouterine pouch (Pouch of Douglas) – Between rectum and posterior uterus.
  • Vesicouterine pouch – Between uterus and bladder.
• The peritoneal cavity is not completely closed due to the uterine tubes opening into it.
• Clinical implication: Potential infection pathway from the female reproductive tract (peritonitis).

Clinical Relevance

Subphrenic Abscesses

• Subphrenic spaces are located between the diaphragm and the liver.
• Pus can accumulate here, commonly on the right side due to:
  • Appendicitis
  • Perforated duodenal ulcers
  • Infection tracking through the right paracolic gutter

Sampling of Peritoneal Fluid

Culdocentesis

• Procedure to extract fluid from the rectouterine pouch.
• Performed via a needle inserted through the posterior vaginal fornix.
• Used to diagnose infection or drain an abscess.

Paracentesis

• Drains ascitic fluid from the peritoneal cavity.
• Performed by inserting a needle through the anterolateral abdominal wall.
• Used for:
  • Diagnosing ascites causes
  • Checking for peritoneal metastasis (e.g., liver cancer)

Disorders of the Peritoneal Cavity

Ascites

• Accumulation of excess fluid within the peritoneal cavity.
• Causes:
  • Portal hypertension (due to liver cirrhosis)
  • GI malignancies
  • Heart failure
  • Injury-related internal bleeding
• Symptoms:
  • Abdominal distension
  • Nausea
  • Breathing difficulties due to lung compression

Peritonitis

• Inflammation and infection of the peritoneum.
• Causes:
  • Surgical contamination
  • Ruptured appendix
  • Gastric ulcers perforating the stomach wall
• Symptoms:
  • Severe abdominal pain
  • Tenderness and guarding (muscle contraction to protect internal organs)
  • Fever, nausea, vomiting, and constipation

Diagram

Figure: Sagittal View of the Peritoneal Cavity
(Illustration showing the subdivisions and connections within the peritoneal cavity, including the greater and lesser sacs, and pelvic structures.)

Points to Remember

The peritoneal cavity is a potential space containing peritoneal fluid for lubrication and immunity.
It is divided into the greater and lesser sacs (omental bursa).
The greater sac contains the supracolic and infracolic compartments.
The lesser sac allows stomach mobility and connects to the greater sac via the epiploic foramen.
Infections can spread via paracolic gutters leading to subphrenic abscesses.
In males, the rectovesical pouch is the most inferior portion; in females, it is the rectouterine pouch.
Paracentesis and culdocentesis are used for peritoneal fluid sampling.
Ascites and peritonitis are clinically significant peritoneal disorders.

This structured approach, with headings, tables, diagrams, and key points, makes the topic more digestible for medical students.