Radiology Essentials 103 : CT Anatomy of Peritoneal Spaces

By Dr Khanak Nandoliya

We are back with a new topic discussion for Radiology Residents with Dr Khanak Nandoliya As our FOAM(Free online access medicine) Intiative. Dr Khanak is a second year resident in DNB Radiology at Dr Rajendra Prasad Government Medical College , Kangra, Himachal Pradesh. He will crisply describe about CT Anatomy of Peritoneal spaces which is a very important topic in radiology. You can discuss the topic in the comment section below this blog and also at Freeassociation.in Forums Here  

Learning Objectives

• To review and simplify anatomy of peritoneal spaces .
• To review peritoneal attachments and relevance with spaces.
• CT anatomy will be reviewed using images from CT images of CT peritoneography done in pateints undergoing peritoneal dialysis. Dialysate solution acts as a contrast in our study.

Understanding  terminology

Peritoneum

• The largest and the most complex serous membrane of body.
• Made of 2 transparent layers which are contiguous with each other.
• Visceral peritoneum: invests and covers lining of viscera.

Parietal peritoneum: lines internal surface of abdominal and peritoneal cavity.

Ligament

Two folds of peritoneum that connect one organ to another or with body wall
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Mesentery:

• Double layer of peritoneum that encloses an organ and connects it to body wall.
• Such organs are called intraperitoneal organs.
• Organs which lie on posterior body wall and are covered by peritoneum only on anterior aspect are called retroperitoneal organs.
• Contains- fat, lymph nodes, vessels and nerves.

Omentum : specialized mesentery

• Doesn’t connect structures to posterior body wall
• Greater omentum: connects stomach to colon. Composed of 3 parts: gastrocolic, gastrosplenic and gastrophrenic ligament.
• Lesser omentum: connects stomach to liver. Composed of 2 parts: gastrohepatic and hepatoduodenal ligament.

Peritoneal spaces

• Peritoneal layers are closely approximated in normal human.
• Peritoneal spaces are potential spaces.
• Peritoneal spaces are evident when they are occupied with fluid or some pathology.
• We will review images of CT peritoneogram to understand anatomy of peritoneal spaces.
• Peritoneal cavity is closed except open Fallopian tubes ends in females.
• Normal fluid content is 50 – 75 ml.

Division of spaces

• Peritoneal spaces are divided by transverse colon and its mesentery :
  • Supracolic spaces
    • Perihepatic space
    • Omental bursa
  • Infracolic space is further divided by the root of mesentery into right and left spaces. Root of mesentery extends from ligament of Treitz to the ileocaecal area.
• Laterally , the pericolonic gutters communicate with the perihepatic spaces and the pelvic region.

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Perihepatic spaces

• Consists of the subphrenic   & the subhepatic spaces.
• The subphrenic space is divided into right & left by the falciform ligament.

Right subphrenic space

• It is continuous with right subhepatic space and right paracolic space.
• Lies adjacent to lateral & superior portion of the liver between the diaphragm and the body wall.
• Posterior margin is formed by coronary ligaments, near bare area of liver.

Left subphrenic space

• Beneath the left diaphragm and surrounds the fundus of stomach anteriorly, the spleen and the space between the liver and the stomach.
• Continuous with the left paracolic space and the left subhepatic space.

Subhepatic spaces

• Right subhepatic space is adjacent to the gall bladder and extends posteriorly to the retroperitoneum over the right kidney.
• Posterior part of the right subhepatic space forms hepatorenal pouch of Morrison.
• Left subhepatic space is immediately below left lobe of liver and continuous with anterior part of left subphrenic space. It is bounded posteriorly by lesser omentum.

Lesser sac (Omental bursa)

• The lesser peritoneal sac is formed due to rotation of the stomach during fetal life, determining a peritoneal pouch separated from the rest of the peritoneal cavity.
• Communication with rest of the peritoneal cavity is through foramen of Winslow.
• Located Behind the stomach and anterior to the pancreas.
• Left margin – gastrosplenic ligament & anterior margin of gastrohepatic ligament
• Right margin – medial surface of coronary ligament
• Cranial margin – caudate lobe of liver
• Caudal margin – mesocolon

Greater omental space

• Greater omentum extends inferiorly from anterior edge of fundus and gastrocolic ligament
• It contains a potential space in the fused membranes that may be split into a true space by infection or bleeding

Paracolic spaces

• Right and left paracolic spaces are contiguous with pelvic region and subphrenic spaces.
• Bounded laterally by peritoneum over abdominal wall and medially by peritoneum over colon.
• Right paracolic space is deeper than the left one due to posterior extension, making it more prone to fluid collections.

Pelvic spaces

• Pelvic spaces are the most dependent portion of body cavity.
• They receive pathways from paracolic spaces.
• Pelvis provides two plateforms for any pathology to settle down and proliferate : sigmoid mesentery and broad ligament.
• Pelvis is divided into anterior and posterior compartments.
• Anterior portion is common in men and women while posterior portion differs.
• Urogenital peritoneum reflects over pelvic organs to form ligaments.

• These include
  • broad and round ligaments of the uterus
  • the median, medial and lateral umbilical folds creating the midline rectovesical pouch
  • in a male and the recto-uterine pouch in a female and the paravesical fossae.

Peritoneal fluid dynamics

• Fluid flow and stasis is dependent on gravity, changes in intra- abdominal pressure and peritoneal reflections.
• Areas of preferential fluid stasis include the Pouch of Douglas, the right lower quadrant at the termination of the small bowel mesentery, superior aspect of the sigmoid mesentery and the right paracolic gutter.
• These are the first sites to be involved in peritoneal spread of infections and metastases.

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