The Peritoneal Cavity

Part I: Abdominal Sonography

Abdomen and Superficial Structures

Objectives

Identify the potential spaces of the peritoneum and the organs and/or ligaments that divide them on diagram.Identify

Identify the potential spaces of the peritoneum on sonogram.Identify

State the organs located in the peritoneum.State

Explain the role greater omentum and mesentery play in limiting the extent of pathology.Explain

Recognize the sonographic appearance of benign and malignant changes seen in the peritoneum. Recognize

Analyze sonographic images of the peritoneum for pathology.Analyze

THE PERITONEUM

The Peritoneum is the serous membrane lining the walls of the abdominal cavity. It covers the abdominal viscera.

• The peritoneum that covers the abdominal organs is known as the visceral peritoneum.

The peritoneum that lines the abdominal cavity is known as the parietal peritoneum

Layers

• The outer layer: parietal peritoneum

• The inner layer: visceral peritoneum

Parietal peritoneum

is attached to the abdominal wall.

Visceral peritoneum

is wrapped around the internal organs that are located inside the abdominal cavity.

The peritoneum both supports the abdominal organs and serves as a conduit for their blood and lymph vessels and nerves.

Peritoneal cavity

• The peritoneal cavity is a potential space between the parietal and visceral peritoneum.

• Contains peritoneal fluid having (water, electrolytes, leukocytes and antibodies)

Peritoneal cavity

The fluid functions are:

It acts as a lubricant, enabling free movement of the abdominal viscera.

The antibodies fight infection.

Peritoneal cavity

Ordinarily, the peritoneal cavity is only of capillary thinness; however, it is referred to as a potential space because excess fluid can accumulate in the peritoneal cavity resulting in the clinical condition of ascites.

• The peritoneal cavity forms a completely closed sac in the male; in the female there is a communication with the retroperitoneal cavity through the uterine tubes, uterus, and vagina.

Subdivisions of the Peritoneal Cavity

The peritoneal cavity can be divided into the greater and lesser peritoneal sacs.

Subdivisions of the Peritoneal Cavity

The greater sac comprises the majority of the peritoneal cavity.

Greater sac

The Greater Sac

Divided into two compartments by the mesentery of the transverse colon .

• The supracolic compartment

• The infracolic compartment

The Greater Sac

The supracolic compartment lies above the transverse mesocolon and contains the stomach , liver and spleen.

The Greater Sac

The infracolic compartment lies below the transverse mesocolon and contains the small intestine, ascending and descending colon.

The infracolic compartment is further divided into left and right infracolic spaces by the mesentery of the small intestine.

The Greater Sac

The supracolic and infracolic compartments are connected by the paracolic gutters

Subdivisions of the Peritoneal Cavity

The lesser sac (also known as the omental bursa) is smaller and lies posterior to the stomach and lesser omentum.

Lesser Sac (Omental Bursa)

The omental bursa allows the stomach to move freely against the structures posterior and inferior to it.

Lesser Sac (Omental Bursa)

Lesser Sac (Omental Bursa)

The omental bursa is connected with the greater sac through an opening in the omental bursa, the epiploic foramen.

Lesser Sac (Omental Bursa)

The epiploic foramen is situated posterior to the free edge of the lesser omentum (the hepatoduoden al ligament).

Omental Foramen(epiploic foramen)

OMENTUM

The omentum is made up of two layers of fatty tissues and both supports and covers the organs and intestines found in this area of the body.

OMENTUM

There are two parts of the omentum:

• the greater omentum

• the lesser omentum.

OMENTUM

The omentum is responsible for storing fat deposits and connecting the intestines and stomach to the liver respectively.

OMENTUM

Hangs in front of the stomach and intestine

It is an apron-like flap of tissue which hangs from the underside of the stomach and aids circulation in the abdomen

The greater omentum is given off from the greater curvature of the stomach, forms a large sheet that lies over the intestines.

Contains blood vessels, nerves, and other structures between these layers.

Functions of the greater omentum

The functions of the greater omentum are:

• Fat deposition, having varying amounts of adipose tissue.

• Infection and wound isolation; It may also physically limit the spread of intraperitoneal infections.

Greater Omentum

Lesser omentum

Also known as the gastrohepatic omentum or small omentum.

A double layer structure located from the beginning of the duodenum and stomach’s lesser curvature to the liver.

Lesser Omentum

The term mesentery is often used to refer to a double layer of visceral peritoneum

Mesentery

Attaches the small intestine and much of the large intestine to the posterior abdominal wall.

Mesentery vs omentum

Mesentery is the support tissue that the intestine is rooted into, and the omentum is a fatty blanket that hangs down in front of all of the intestines.

Retroperitoneal Organs and Vascular Structures

• Retroperitoneal organs and vascular structures remain posterior to the cavity and are covered anteriorly with peritoneum:

• Urinary system

• Aorta

• Inferior vena cava

• Colon

• Pancreas

• Uterus

• Bladder.

Potential spaces of the peritoneum

• Left anterior subphrenic space

• Right subphrenic space

• Left posterior suprahepatic space

• Hepatorenal space also known Morrison pouch or space

• Omental bursa

• Right and left paracolic gutters

• Vesicorectal space

• Rectouterine space also known as posterior cul de sac or pouch of Douglas or rectovaginal pouch

• Uterovesicle space also known uterovesicle pouch or anterior cul de sac

• Space of Retzius also called prevesicle or retropubis space

Subphrenic spaces

The subphrenic spaces are recesses in the greater sac of the abdominal cavity between the anterior diaphragmatic surface of the liver and diaphragm.

Subphrenic spaces

They are separated into left and right subphrenic spaces by the falciform ligament of the liver.

Subphrenic abscesses

Subphrenic abscesses generally occur as a result of accumulation of pus in the left or right suphrenic spaces as consequence of peritonitis.

They are more common in the right side due to increased frequency of appendicitis and rupture of duodenal ulcer.

Hepatorenal Space

Also referred to as Morrison Pouch

This peritoneal potential space is created by the peritoneum, reflecting from the liver over the right kidney and right posterior peritoneal wall. When the patient is in a supine position this space is most gravity-dependent potential space of the abdominal cavity, collecting fluid from the supracolic area and the lesser sac.

Right and Left Paracolic Gutters

Potential spaces found along the lateral ascending and descending colon that conducts fluid between the supracolic compartment of the abdomen and infracolic compartment of the inferior abdomen and pelvis. Important determining the extension of disease.

Vesicouterine pouch

Known as Anterior cul-de-sac.

Located anterior to fundus between uterus and bladder

49

Rectouterine pouch

Known as Posterior cul-de-sac or Pouch of Douglas.

Located posterior to uterine body and cervix, between uterus and rectum.

50

Rectouterine pouch

When the female is in a supine position this space is the most gravity dependent.

Retropubic space

Also known as Space of Retzius or prevesicle space.

Located between bladder and symphysis pubis

52

Vesicorectal space

Potential space in males

Potential space created by the peritoneal reflection over the rectum and posterior bladder wall

Pathologies of the peritoneal cavity

• Ascites

• Peritoneal abscess

• Hemoperitoneum

• Hematoma

• Pseudomyxoma peritonei

• Fluid collections (seroma, Lymphocele, biloma and urinoma)

• Peritoneal masses

Ascites refers to an

accumulation of excess

fluid in the peritoneal

cavity.

It can occur in

conjunction with

infection and

peritonitis, however it is

more commonly caused

by portal

hypertension secondary

to cirrhosis of the liver.

Other causes

include:

• malignancies of

the GI tract

• malnutrition

• heart failure

• mechanical

injuries which

result in internal

bleeding.

Patients

present with :

• distended

abdomen

• discomfort

• nausea

• dyspnea.

Ascites

Ascites the ***excessive accumulation of serous fluid in the peritoneal cavity.

Causes of ascites:

• ***Cirrhosis (most Common)

• Congestive heart failure

• Cancer

• Tuberculosis

• Peritonitis

Ascites

Gallbladder thickening is usually seen with ascites

Ascites

The mechanism that produces ascites are complex and incompletely understood.

Two mechanism that produce ascites are:

• ***Low serum osmotic pressure (protein loss).

• ***High portal venous pressure.

Ascites

Ascites is commonly found

• Inferior aspect of the Right lobe of the liver

• Morrison pouch

• Pelvic cul de sac

• Paracolic gutter

Ascites

• Ascites can be treated successfully with ***Transjugular intrahepatic portal systemic shunt which lower portal pressure. This shunt is place using jugular access and it is place between the RHV and the RPV)

Ascites

• Benign ascites is indicated by freely floating bowel .

• With malignant ascites , the bowel loop is tethered to the posterior abdominal wall surrounded by complex or loculated fluid collection.

Causes of ascites

include:

• An abdominal

injury

• An abdominal

infection

(peritonitis)

• Scarring of the

liver tissue

(cirrhosis)

• Liver failure

• Cancer

Ascites

Loculated Ascites

Exudative Ascites

Paracentesis

is a procedure to

remove fluid that has

collected in the

abdomen (peritoneal

fluid).

The fluid buildup is

called ascites.

Paracentesis can relieve

abdominal pressure and

pain, improve kidney and

intestinal function and

help patients overcome

difficulty breathing. It may

also be performed to

check for liver cancer or

other types of cancer.

For the procedure, the

patient’s belly is cleaned

and a local anesthetic is

administered to numb the

area. A long, thin needle

is then carefully inserted

into the belly. The excess

fluid is extracted through

the hollow needle. In

some cases, doctors use

ultrasound to show

where the fluid is in the

belly.

• Localized fluid collections in the abdominal wall may due by:

• Seroma

• Abscesses

• Hematomas

Fluid Collections

Seroma

A seroma is an

accumulation of fluid in a

tissue or organ that can

occur after surgery, or

sometimes after an injury

such as blunt trauma.

The fluid, called serum,

leaks out of nearby

damaged blood and

lymphatic vessels. Cells

are typically present in the

fluid, which is normally

clear.

Seroma

Seromas can occur after a number

of different types of surgeries,

especially those that are extensive

or involve significant tissue

disruption. These include hernia

repairs, significant plastic surgeries

such as breast augmentation or

reconstruction, abdominoplasties

(tummy tucks), and surgeries

performed for breast cancer.

Seroma formation may be

associated with an increased risk of

infection and breakdown of the

surgical site.

Seroma: abdominal wall seroma after

splenectomy

Abscess

An abdominal abscess is a pocket of infected fluid and pus located inside the belly (abdominal cavity). This type of

abscess can be located near or inside the liver, pancreas, kidneys or other organs. There can be one or more abscesses.

Round image with hypoechoic contents (A) with thick and irregular

walls

Abscess

There can be one or more abscesses.

The most reliable finding in patients with abscess are:

•**Fever

•**Increased white blood cell count

Round image with hypoechoic contents (A) with thick and irregular

walls

• An abscess may form

in an area of the body

from different causes:

inflammatory bowel

disease (Crohn’s

disease)

• trauma

• surgery

• intestinal perforation.

The main symptoms

of an abscess are pain

and fever.

Abscess

Typically an abscess is a complex mass(solid and cystic) . Debris, septation and gas can be seen within the abscess .

• Gas within the abscess typically produce reverberation ***(come-tail) artifact.

• Can show acoustic enhancement depending of the cystic component.

Round image with hypoechoic contents (A) with thick and irregular

walls

ABSCESS

Peritoneal Abscess

Culdocentesis involves the

extraction of fluid from

the rectouterine pouch (pouch of

Douglas) through a needle inserted

through the posterior fornix of the

vagina.

It can be used to extract fluid from

the peritoneal cavity or to drain

a pelvic abscess in the rectouterine

pouch.

A Percutaneous

Abscess Drainage is

a procedure

performed by a

doctor to remove or

drain a contained

collection of infected

fluid (abscess) from

an area of the body

such as the chest,

abdomen, or pelvis.

During the procedure, a

doctor places a thin

needle into the fluid

collection using x-ray

guidance such as

Computed Tomography

(CT) scanning. Usually, a

drainage tube is left in

place to drain the abscess

fluid. On occasion, the

fluid collection may need

to be drained in the

operating room.

Hemoperitoneum

Hemoperitoneum is the presence of blood within the peritoneal cavity.

Hemoperitoneum

Etiology

• penetrating or non-penetrating abdominal trauma (often with associated organ injury)

• ruptured ectopic pregnancy

• Ovarian cyst rupture

• Aneurysm or pseudo aneurysm rupture

• neoplasm rupture

• acute hemorrhagic pancreatitis

• iatrogenic

• spontaneous bleeding, especially patients with coagulopathy or on anticoagulant therapy (uncommon )

• Uterine rupture

Ultrasound non-specific appearance of

intra-peritoneal free fluid may

be hypo-, iso- or hyper-echoic

commonly will demonstrated

fluid-fluid levels with mixed

internal echogenicity

Hemoperitoneum – Female Pelvis

Hematomas

Collection of ***blood which is usually confined to an organ, tissue or space.

A ***decrease of hematocrit level indicated the presence of hematoma

Hematocrit is the ***volume of the red blood cells found in 100 ml of blood. Blood spillage outside the circulatory system will result in ***decreased hematocrit levels.

HEMATOMA

Hematomas

The ultrasound appearance of hematomas is ****variable and depends on the age of the collection.

Pseudomyxoma Peritonei

This pathology is caused by ****metastasis or rupture of a mucinous cystadenocarcinoma of the ovary or mucinous tumor of the appendix. This is also referred as ****malignant ascites.

The peritoneal cavity is filled with ***mucinous material and gelatinous ascites.

Pseudomyxoma Peritonei

Biloma

Bilomas are extrahepatic collections of extravasated bile.

They are caused by:

• abdominal trauma

• gallbladder disease

• biliary surgery

Bilomas are predominantly cystic masses located in the right upper quadrant.

Biloma

Urinoma

• Is a ***collection of urine which is located outside of the kidney or bladder.

• Urinomas are most common caused by renal trauma, renal surgery or from an obstructing lesion.

• Most common associated with ***renal transplantation and posterior urethral valve obstruction

• Sonographically appears ***similar to a lymphocele.

Lymphocele

Lymphocele is caused by ****leakage of lymph from a renal allograft or by surgical disruption of the lymphatic channels.

Is not common see internal echoes in lymphocele

Lymphocele is complications of:

• Renal transplantation

• Gynecologic surgery

• Vascular surgery

• Urogenical surgery

Peritoneal Masses

• Mesenteric cyst

• Mesenteric adenopathy

• Peritoneal mesothelioma

• Peritoneal implants and omental caking

•

Mesenteric Cyst *The majority originate from the small bowel mesentery. *It is benign *Peritoneal serous secretion present.

Mesenteric Lymphadenopathy

Peritoneal Mesothelioma *Relative rare primary malignant tumor of the peritoneum . *Associated to asbestos exposure

Peritoneal Implants *They are associated with peritoneal metastases

Omental Caking *Thickening of the greater omentum due to malignant infiltration. *Indicative of peritoneal metastases also known as peritoneal carcinomatosis. *Associated to primary cancers of ovary, stomach or colon.

Peritoneal masses

Endometriosis

Lymphadenopathy

Undescendent testis

Lipoma of the of the Spermatic Cord and Inguinal Canal inguinal canal

LIPOMA OF THE INGUINAL CANAL

References • Kawamura, D. M., & Lunsford, B. M. (2012). Diagnostic medical sonography. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins.