Anatomy
Abdomen
A 26 year old woman is brought to ED following a road traffic accident. Focussed assessment for sonography in trauma (FAST) on the supine patient demonstrates free intraperitoneal fluid. Which of the following spaces is most likely to be affected:
Answer:
In a supine patient, fluid accumulation will occur most often in the hepatorenal pouch (of Morrison), which is the lowest space in the peritoneal cavity in the supine position, located behind the liver and anterior to the right kidney. The vesicouterine (between the bladder and the uterus) and rectouterine (between the uterus and the rectum) spaces are also potential spaces for fluid accumulation, however fluid accumulation occurs in the erect position.Peritoneal Compartments
Anatomy / Abdomen / Topography of Abdominal Cavity
Last Updated: 10th June 2020
The peritoneal cavity is divided into the greater sac and the omental bursa (lesser sac).
Table: Anatomical Overview of the Abdominal Cavity
| Structure | Key anatomy |
|---|---|
| Peritoneal cavity | Divided into greater and lesser sacs |
| Greater sac | Divided into supracolic and infracolic compartments by transverse mesocolon, compartments connected by paracolic gutters |
| Supracolic compartment | Contains stomach, liver and spleen, lies under cover of costal limits of thoracic cage |
| Infracolic compartment | Divided into left and right parts by oblique attachment of mesentery, contains small intestine and ascending/descending colon, continuous with pelvic cavity |
| Lesser sac (omental bursa | Lies posterior to stomach and liver and anterior to pancreas, continuous with greater sac through epiploic foramen |
| Greater omentum | Descends from greater curvature of stomach and first part of duodenum, drapes inferiorly over transverse colon, jejunum and ileum, folds back up and ascends to adhere to transverse colon/mesocolon before arriving at posterior abdominal wall |
| Lesser omentum | Extends from lesser curvature of stomach and first part of duodenum to inferior surface of liver |
| Mesentery | Connects jejunum and ileus to posterior abdominal wall, attaches superiorly to duodenojejunal junction and passes oblique downwards and to the right to end at ileocecal junction |
| Transverse mesocolon | Connects transverse colon to posterior abdominal wall, leaves posterior abdominal wall across anterior surface of head and body of pancreas and passes outwards to surround transverse colon |
| Sigmoid mesocolon | Connects sigmoid colon to abdominal wall, V-shaped fold with apex near division of left common iliac artery, left limb descending along medial border of left psoas major muscle and right limb descending into pelvis to end at vertebral level S3 |
Greater Sac
The greater sac accounts for most of the space in the peritoneal cavity, beginning superiorly at the diaphragm and continuing inferiorly in the pelvic cavity. It is further divided into two compartments by the transverse mesocolon:
- The supracolic compartment lies above the transverse mesocolon and contains the stomach, liver and spleen. It lies largely under cover of the costal limits of the thoracic cage.
- The infracolic compartment lies below the transverse mesocolon, is divided into left and right parts by the oblique attachment of the mesentery and contains the small intestine and the ascending and descending colon. The left infracolic compartment is continuous with the pelvic cavity.
The supracolic and infracolic compartments are connected by the paracolic gutters which lie between the posterolateral abdominal wall and the lateral aspect of the ascending or descending colon.
The supracolic space can be arbitrarily divided into right and left supracolic spaces and subspaces.
The left supracolic space has two subspaces:
- Left subphrenic space
- Left perihepatic space
The right supracolic space has three subspaces:
- Right subphrenic space
- Right subhepatic space
- This is further divided into anterior and posterior spaces.
- The posterior right subhepatic space (Morrison's pouch) separates the liver from the right kidney. Fluid (e.g. ascites or haemoperitoneum) accumulates here as it is the lowest dependant spaces of the peritoneal cavity from a wide range of causes. It is also a preferential site for metastases and abscesses.
- Lesser sac
Lesser Sac
The omental bursa (lesser sac) is a smaller subdivision of the peritoneal cavity posterior to the stomach and liver and anterior to the pancreas, and is continuous with the greater sac through the epiploic foramen.
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/02/Peritoneum-1.png)
Peritoneal Cavity. (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
