Chapter 14 Peritoneal Cavity /Abdominal Wall

Chapter 14: Peritoneal Cavity and Abdominal Wall

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Peritoneal Cavity Overview

  • Definition: The peritoneal cavity is a space within the abdomen that contains various structures and organs.
  • Components:
    • Multiple peritoneal ligaments and folds connecting viscera to each other and to the abdominopelvic walls.
    • Contains:
      • Lesser omentum
      • Greater omentum
      • Mesenteries
      • Ligaments
      • Fluid spaces: lesser sac, perihepatic, and subphrenic spaces.

Anatomy of the Peritoneal Cavity

  • Peritoneum:
    • A smooth membrane encompassing the abdominal cavity and organs:
      • Parietal peritoneum: Lines the abdominal cavity walls.
      • Visceral peritoneum: Covers the abdominal organs (viscera) to varying extents
      • Refer to Figure 17-1 in the textbook for visuals.

Characteristics of the Peritoneal Cavity

  • Men: The peritoneum forms a closed cavity.
  • Women: The peritoneum communicates outside via:
    • Uterine tubes
    • Uterus
    • Vagina
    • Note: The structure of these organs tends to prevent airflow into the cavity.

Suspension of Organs

  • Small intestine is connected to the posterior abdominal wall by the mesentery.
  • Transverse colon is suspended by the transverse mesocolon.
  • Sigmoid colon is suspended by the sigmoid mesocolon.

General and Lesser Sac

  • The general peritoneal cavity is known as the greater sac.
  • The lesser sac, or omental bursa, is a recess located posterior to the stomach.
  • Communication occurs through a small opening called the epiploic foramen.

Abnormal Fluid Accumulation

  • Fluid location and movement in the abdomen depend on peritoneal attachments.
  • In the supine position, fluid accumulates in the pelvic area and lateral flanks.
  • Pathological Collections: Pelvis and lateral flanks should be examined for abnormal fluid collections.

Compartmentalization of the Peritoneum

  • Lesser Omentum:
    • Composed of a double layer of peritoneum from the liver to the lesser curvature of the stomach.
    • Functions as a sling for the stomach.
  • Greater Omentum:
    • An apronlike fold from the greater curvature of the stomach, lying over the intestine.
    • Adheres to diseased organs and walls off infections, guarding adjacent regions.
    • Perfused with vessels from the gastroepiploic branches.

Distinguishing Fluid Types

  • Intraperitoneal Fluid: Must differentiate from other fluid types.
    • Pleural Fluid: Collections may appear apposed to the bare area of the liver unless loculated.
    • Subcapsular Fluid: Seen in the liver or spleen, maintaining organ contours.
    • Retroperitoneal Fluid: Mass is retroperitoneal if it displaces renal structures.

Abdominal Fluid Collections

  • Ascites:
    • The buildup of serous fluid in the peritoneal cavity.
    • Influenced by peritoneal pressure, area of origin, and presence of adhesions.
    • Identifiable characteristics depend on fluid distribution and patient position.

Pathological Conditions

Ascites
  • Characteristics:
    • Variable depending on volume, location, and rate of accumulation.
    • Look for: Internal echoes, loculation, unusual distribution, and interface thickening.
Abscess Formation
  • Bacterial Entry Points:
    1. Portal system
    2. Ascending cholangitis from the common bile duct (most common cause)
    3. Hepatic artery secondary to bacteremia
    4. Direct infection extension
    5. Trauma to the abdominal wall.
  • Abscesses: Present as cavities from necrotic tissue or purulent material.

Types of Abscesses

  • Gas-containing Abscesses:
    • Show varying echo patterns; may have acoustic shadowing.
    • Appears densely echogenic.
Peritonitis
  • Can be generalized or localized.
  • Must record the number and sizes of multiloculated abscesses for drainage planning.
Lymphoceles and Extraperitoneal Hematomas
  • Lymphoceles: Fluid collections post-surgery; can be differentiated from loculated ascites.
  • Extraperitoneal hematomas: Result from trauma or surgeries, require careful monitoring and evaluation.

Pathologies of the Mesentery and Omentum

  • Lesions may exhibit solid or cystic appearances with considerable malignancy potential.

Sonographic Assessments

  • Areas to assess for abscesses include:
    • Subdiaphragmatic area
    • Hepatic recess
    • Pouch of Douglas
    • Area anterior to the bladder.

Tumors and Malignancies

  • Lymphoma: Characterized by a thick, hypoechoic band; sonographically may show lobulated appearances.
  • Mesotheliomas: Often due to asbestos exposure; may present as large masses with irregular configurations.

Conclusion

  • The study of the peritoneal cavity and abdominal wall involves understanding complex anatomical relationships and various pathologies that can arise in this region.
  • Sonographic evaluations are critical for accurate diagnosis and management of abdominal conditions.