214 lines
19 KiB
Markdown
214 lines
19 KiB
Markdown
---
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title: "Peritoneal Spaces and Structures"
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docid: "9c50ad6a-e96b-44a1-93d1-a4e7de5212c2"
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authors:
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- key: "07469ec4-05aa-4d65-a788-08b4d64048af"
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value: "Jade Wong-You-Cheong, MBChB, MRCP, FRCR, FSRU, FSAR"
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breadcrumbs:
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-
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name: "Ultrasound"
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slug: "ultrasound"
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treeNodeId: "e7cdfeb1-bb55-4cca-9854-46cadee515d2"
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name: "Anatomy"
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slug: "anatomy"
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treeNodeId: "d4765014-54f9-4477-8c9c-4b2ae0b82f24"
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name: "Abdomen"
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slug: "abdomen"
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treeNodeId: "1e981810-ddca-4af9-82b9-38d5fdecad76"
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-
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name: "Peritoneal Spaces and Structures"
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slug: "peritoneal-spaces-and-structures"
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treeNodeId: null
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category: "Ultrasound"
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documentVersionId: "8c87a1a2-008f-4d2b-a0a8-57d919e883c3"
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imageCount: 19
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lastUpdated: "06/01/21"
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pageDescription: "Peritoneal Spaces and Structures"
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pageKeywords: "Ultrasound, Anatomy, Abdomen, Peritoneal Spaces and Structures"
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pageTitle: "Peritoneal Spaces and Structures | STATdx"
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enhancedTitle: "Peritoneal Spaces and Structures"
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type: "ANATOMY"
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references: true
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breadcrumbs:
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- "Ultrasound"
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- "Anatomy"
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- "Abdomen"
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- "Peritoneal Spaces and Structures"
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---
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# TERMINOLOGY
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- ## Definitions
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- Peritoneal cavity: Potential space in abdomen between visceral and parietal peritoneum, usually containing only small amount of peritoneal fluid (for lubrication)
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- Abdominal cavity: Not synonymous with peritoneal cavity
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- Limited by abdominal wall muscles, diaphragm, and (arbitrarily) by pelvic brim
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- Peritoneum divides peritoneal cavity from subperitoneal space, which contains all abdominal viscera, ligaments, and mesenteries
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# GROSS ANATOMY
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- ## Divisions
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- Greater sac of peritoneal cavity
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- 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; posteriorly by pancreas, left adrenal, and kidney; on left by splenorenal and gastrosplenic ligaments; on right by epiploic foramen and lesser omentum
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- ## Compartments Divided by Transverse Mesocolon
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- 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: Includes right subphrenic space, right subhepatic space, and lesser sac
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- Left supramesocolic space: Includes left perihepatic spaces (anterior and posterior) and left subphrenic (anterior perigastric and posterior perisplenic)
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- 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
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- ## Peritoneum
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- 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
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- ## Mesentery
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- Double layer of peritoneum that encloses organ and connects it to abdominal wall
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- 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
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- Most mobile parts of intestine have mesentery, while ascending and descending colon are considered retroperitoneal (peritoneum covers only anterior surface)
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- Root of mesentery is its attachment to posterior abdominal wall
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- Root of small bowel mesentery is ~ 15 cm in diameter and passes from left side of L2 vertebra downward and to right; contains superior mesenteric vessels, nerves, and lymphatics
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- Transverse mesocolon crosses almost horizontally in front of pancreas, duodenum, and right kidney
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- ## Omentum
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- Multilayered fold of peritoneum that extends from stomach to adjacent organs
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- 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
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- 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, containing variable amounts of fat and abundant lymph nodes
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- Mobile, filling gaps between viscera, acting as barrier to generalized spread of intraperitoneal infection or tumor
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- ## Ligaments
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- All double-layered folds of peritoneum, other than mesentery and omentum, are peritoneal ligaments
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- Connect 1 viscus to another (e.g., splenorenal ligament) or viscus to abdominal wall (e.g., falciform ligament)
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- Contain blood vessels or remnants of fetal vessels
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- ## Folds
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- 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)
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- ## Peritoneal Recesses
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- Dependent pouches formed by peritoneal reflections
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- Many have eponyms [e.g., Morison pouch for posterior subhepatic (hepatorenal) recess; pouch of Douglas for rectouterine recess]
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# ANATOMY IMAGING ISSUES
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- ## Imaging Recommendations
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- Transducer: Typically 2-5 MHz for abdominal survey and deep recesses, up to 9 MHz for thinner patients
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- High-frequency linear transducer 8-15 MHz may be used to evaluate anterior abdominal wall and parietal peritoneum
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- Patient examined supine with additional decubitus positions to determine if fluid collection is free or loculated
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- Peritoneal cavity and its various mesenteries and recesses are usually not apparent on imaging studies unless distended or outlined by intraperitoneal fluid or air
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- Focused assessment with sonography for trauma (FAST) point-of-care ultrasound is widely used in acute abdominal trauma and undifferentiated hypotension and shock; right and left supramesocolic spaces and pelvis are scanned for free fluid/acute hemorrhage
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- ## Imaging Pitfalls
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- Acute intraperitoneal bleeding is typically anechoic and may be confused with ascites
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03c66bee-31f2-43af-906d-f0e7f2bcb141
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## References
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# Selected References
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1. [Pannu HK et al: The subperitoneal space and peritoneal cavity: basic concepts. Abdom Imaging. 40(7):2710-22, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=26006061%5Bpmid%5D)
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1. [Tirkes T et al: Peritoneal and retroperitoneal anatomy and its relevance for cross-sectional imaging. Radiographics. 32(2):437-51, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22411941%5Bpmid%5D)
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## Images
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### Peritoneal Cavity, Divisions, and Compartments
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*Graphic of a sagittal section of the abdomen shows the peritoneal cavity artificially distended with air. Note the margins of the lesser sac, including the caudate lobe of the liver, stomach, and gastrocolic ligament anteriorly and pancreas posteriorly. The mesenteries convey blood vessels, nerves, and lymphatics to the intraperitoneal abdominal viscera. The greater omentum extends down from the stomach, covering much of the colon and small intestine. The layers are generally fused together caudal to the transverse colon. The gastrocolic ligament is part of the greater omentum.*
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*Graphic of a sagittal section of the abdomen shows the peritoneal cavity artificially distended with air. Note the margins of the lesser sac, including the caudate lobe of the liver, stomach, and gastrocolic ligament anteriorly and pancreas posteriorly. The mesenteries convey blood vessels, nerves, and lymphatics to the intraperitoneal abdominal viscera. The greater omentum extends down from the stomach, covering much of the colon and small intestine. The layers are generally fused together caudal to the transverse colon. The gastrocolic ligament is part of the greater omentum.*
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*The borders of the lesser sac (omental bursa) include the lesser omentum, which contains the common bile duct and hepatic and gastric vessels. The left border includes the gastrosplenic ligament (with short gastric vessels) and the splenorenal ligament (with splenic vessels).*
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*The paracolic gutters are formed by reflections of the peritoneum covering the ascending and descending colon and the lateral abdominal wall. Note the innumerable potential peritoneal recesses lying between the bowel loops and their mesenteric leaves.*
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### Peritoneal Divisions and Compartments
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*In this graphic, the liver has been retracted upward. The lesser omentum is comprised of the hepatoduodenal and hepatogastric ligaments. It forms part of the anterior wall of the lesser sac and contains the common bile duct, hepatic and gastric vessels, and the portal vein. The aorta and celiac artery can be seen through the lesser omentum, as they lie just posterior to the lesser sac.*
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*Frontal view of the abdomen, with all of the intraperitoneal organs removed, shows that the root of the transverse mesocolon divides the peritoneal cavity into supramesocolic and inframesocolic spaces that communicate only along the paracolic gutters. The coronary and triangular ligaments suspend the liver from the diaphragm. The superior mesenteric vessels traverse the small bowel mesentery, whose root crosses obliquely from the upper left to the lower right posterior abdominal wall.*
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### Right and Left Supramesocolic Spaces and Inframesocolic space
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*Longitudinal transabdominal grayscale ultrasound shows fluid in the right posterior subhepatic space, also known as the Morison pouch, and hepatorenal fossa. This space is continuous with the right anterior subhepatic space and right paracolic gutter.*
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*Longitudinal grayscale ultrasound of the left upper quadrant shows a small amount of perisplenic fluid extending under the left hemidiaphragm. The left subphrenic space is separated from the right subphrenic space by the falciform ligament.*
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*Longitudinal grayscale ultrasound of the female pelvis shows a large amount of free fluid. The uterus divides the pelvic cavity into the vesicouterine and rectouterine (pouch of Douglas) spaces. In this case, the bladder is empty.*
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### Right and Left Inframesocolic Spaces and Pelvic Cavity
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*Transverse ultrasound of the right lateral mid abdomen shows simple ascites in the paracolic gutter.*
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*On this transverse ultrasound through the left lower quadrant, ascites surrounds small bowel.*
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*Transverse ultrasound of a female pelvis above the level of the bladder shows ascitic fluid encircling the uterus.*
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### Right Supramesocolic Space: Lesser Sac
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*Subxiphoid transverse grayscale ultrasound shows a fluid collection in the lesser sac, which extends to the left behind the stomach and anterior to the pancreas. The lesser sac is part of the right supramesocolic space and communicates with the rest of the peritoneal cavity through the epiploic foramen (of Winslow).*
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*Subxiphoid transverse color Doppler ultrasound of the same patient shows moderate fluid in the lesser sac posterior to the stomach. The splenic vein was dilated in this patient with portal hypertension status post liver transplant.*
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*Axial CECT of the same patient shows fluid in the lesser sac and peritoneal cavity as well as diffuse anasarca.*
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### Additional Images
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*Intercostal oblique grayscale ultrasound (in a patient with cirrhosis) shows the dome of the right lobe of the liver and moderate fluid in the right subphrenic region extending anterior to the liver. The fluid is separated from the right-sided pleural effusion by the right diaphragmatic leaf.*
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*Subcostal oblique transverse ultrasound of the right upper quadrant shows fluid in the right anterior subhepatic space and in the hepatorenal space. The ascites are secondary to hepatic cirrhosis and the gallbladder is physiologically distended.*
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*Subxiphoid transverse grayscale ultrasound shows fluid anterior to the left lobe of the liver that is localized to the left posterior subhepatic space. Incidental calculi are seen within a dilated intrahepatic biliary duct.*
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*Longitudinal ultrasound of the midline suprapubic region in a male patient demonstrates intraperitoneal fluid between bowel loops and extending into the dependent rectovesical pouch. There is a distended urinary bladder.*
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*Transverse transabdominal ultrasound of the central abdomen reveals moderate to large ascites with floating small bowel loops. The left inframesocolic space is larger compared to the right and communicates directly with the pelvic cavity.*
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