Peritoneal cavity: Potential space in abdomen between visceral and parietal peritoneum, usually containing only small amount of peritoneal fluid (for lubrication)

Abdominal cavity: Not synonymous with peritoneal cavity

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  Contains all of abdominal viscera (intra- and retroperitoneal)

  
  
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  Limited by abdominal wall muscles, diaphragm, and (arbitrarily) pelvic brim

Greater sac of peritoneal cavity

Lesser sac (omental bursa)

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  Communicates with greater sac via epiploic foramen (of Winslow)

  
  
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  Bounded anteriorly by caudate lobe, stomach, and greater omentum

  
  
  
  
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    Posteriorly by pancreas, left adrenal, and kidney

    
    
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    On left by splenorenal and gastrosplenic ligaments

    
    
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    On right by epiploic foramen and lesser omentum

  
  

Supramesocolic space

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  Divided into right and left supramesocolic spaces, which are separated by falciform ligament

  
  
  
  
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    Right supramesocolic space: Composed of right subphrenic space, right subhepatic space, and lesser sac

    
    
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    Left supramesocolic space: Divided into left perihepatic spaces (anterior and posterior) and left subphrenic (anterior perigastric and posterior perisplenic)

  
  

Inframesocolic compartment

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  Divided into right inframesocolic space, left inframesocolic space, paracolic gutters, and pelvic cavity

  
  
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  Pelvic cavity is most dependent part of peritoneal cavity in erect and supine positions

Thin serous membrane consisting of single layer of squamous epithelium (mesothelium)

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  Parietal peritoneum lines abdominal wall

  
  
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  Visceral peritoneum (serosa) lines abdominal organs

Double layer of peritoneum that encloses organ and connects it to abdominal wall

Covered on both sides by mesothelium and has core of loose connective tissue containing fat, lymph nodes, blood vessels, and nerves passing to and from viscera

Most mobile parts of intestine have mesentery, while ascending and descending colon are considered retroperitoneal (covered only by peritoneum on anterior surface)

Root of mesentery is its attachment to posterior abdominal wall

Root of small bowel mesentery is ~ 15 cm and passes from left side of L2 vertebra downward and to right

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  Contains superior mesenteric vessels, nerves, and lymphatics

Transverse mesocolon crosses almost horizontally in front of pancreas, duodenum, and right kidney

Multilayered fold of peritoneum that extends from stomach to adjacent organs

Lesser omentum joins lesser curve of stomach and proximal duodenum to liver

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  Hepatogastric and hepatoduodenal ligament components contain common bile duct, hepatic and gastric vessels, and portal vein

Greater omentum

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  4-layered fold of peritoneum hanging from greater curve of stomach like apron, covering transverse colon and much of small intestine

  
  
  
  
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    Contains variable amounts of fat and abundant lymph nodes

    
    
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    Mobile and can fill gaps between viscera

    
    
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    Acts as barrier to generalized spread of intraperitoneal infection or tumor

  
  

All double-layered folds of peritoneum, other than mesentery and omentum, are peritoneal ligaments

Connect 1 viscus to another (e.g., splenorenal ligament) or viscus to abdominal wall (e.g., falciform ligament)

Contain blood vessels or remnants of fetal vessels

Reflections of peritoneum with defined borders, often lifting peritoneum off abdominal wall (e.g., median umbilical fold covers urachus and extends from dome of urinary bladder to umbilicus)

Dependent pouches formed by peritoneal reflections

Many have eponyms [e.g., Morison pouch for posterior subhepatic (hepatorenal) recess; pouch of Douglas for rectouterine recess]

Transducer: Typically 2-5 MHz for abdominal survey and deep recesses, up to 9 MHz for thinner patients

High-frequency linear transducer 8-15 MHz may be used to evaluate anterior abdominal wall and parietal peritoneum

Patient examined supine with additional decubitus positions to determine if fluid collection is free or loculated

Peritoneal cavity and its various mesenteries and recesses are usually not apparent on imaging studies unless distended or outlined by intraperitoneal fluid or air