Applied Peritoneal Anatomy - A Pictorial review. Poster No.: C-1925 Congress: ECR 2011 Type: Educational Exhibit Authors: R. Patel, I. Beal, K. Planche; London/UK Keywords: MR, CT, Anatomy, Abdominal wall, Abdomen DOI: 10.1594/ecr2011/C-1925 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 54
Learning objectives To review and simplify the complex anatomy of the peritoneum, its attachments and reflections forming the peritoneal boundaries. To describe normal anatomy using schematic illustrations with corresponding CT and MRI images including CT peritoneograms. Furthermore, to demonstrate how understanding the relevant peritoneal and extraperitoneal anatomy allows the diagnosis of different pathological processes. Background Primary abnormalities of the peritoneum are rare but involvement of the peritoneal cavity secondary to infections, malignancy and trauma are common. Detailed anatomical knowledge of the peritoneum spaces allows more accurate localisation of pathology to enable the radiologist to narrow the differential diagnoses. Peritoneal Anatomy The peritoneum is the largest and most complex serous membrane of the body. It consists of two, transparent layers which are continuous with each other. The parietal peritoneum lines and attaches, in places, to the internal surface of the abdomino-pelvic cavity. The visceral peritoneum invests and covers the external surface of viscera. Page 2 of 54
Fig.: Sagittal CT peritoneogram with diagram References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Terminology Strictly speaking there are no organs within the peritoneal cavity itself which normally only contains peritoneal fluid. Instead intraperitoneal organs invaginate and are almost completely covered by the visceral layer. Extra- or retroperitoneal organs also lie outside the peritoneal cavity, either exterior or posterior to the parietal peritoneum. These organs are usually only partially covered by peritoneum. Various terms are used to describe parts of the peritoneum that connect organs with other organs or to the abdominal wall. A mesentery suspends the small and large bowel from the posterior peritoneal cavity by way of a double layer of peritoneum. It acts as a conduit Page 3 of 54
for neurovascular and lymphatic structures between the organ and posterior abdominal wall. A ligament is also formed by two layers of the peritoneum, it supports a structure within the peritoneal cavity and is named according to the the structures it connects. An omentum refers to a double-layered extension of ligaments of the peritoneum joining the stomach and proximal duodenum to other adjacent structures, the greater and lesser omentum extending from the greater and lesser curvatures of the stomach respectively. Fig.: Sagittal view from CT peritoneogram showing the greater and lesser omenta. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Peritoneal spaces and ligaments The boundaries of the peritoneal spaces are formed by the mesenteries and ligaments. A basic knowledge of peritoneal embryological development is required to understand the formation of the communicating peritoneal spaces. Page 4 of 54
In the developing foetus, the peritoneal cavity is divided into right and left peritoneal cavities by the ventral and dorsal mesenteries of the primitive gut. Many of the ligaments and mesenteries are formed from remnants of the ventral and dorsal mesenteries. Fig.: Schematic diagram demonstrating the formation of the peritoneal spaces. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Above the transverse mesocolon, the ventral mesentery contains the liver bud and the dorsal mesentery contains the splenic bud. As development continues, these organs migrate anticlockwise taking the attached mesenteries with them. This migration divides the right peritoneal cavity into the perihepatic space and the lesser sac. The left peritoneal space forms the left subphrenic space. Page 5 of 54
Fig.: Diagram demonstrating peritoneal spaces References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 6 of 54
Fig.: Schematic illustration of peritoneal spaces and ligaments correlated with axial CT peritoneogram. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Remnants of the dorsal mesentery form the gastrocolic, gastrosplenic, gastrophrenic, gastropancreatic ligaments forming part of the greater omentum. The splenorenal and phrenicocolic ligaments also arise from the dorsal mesentry. The ventral mesenteric remnant give rise to the faciform ligament, (dividing the supramesolic compartment, which contains the stomach, liver and spleen, into left and right), the gastrohepatic and hepatoduodenal ligament, the latter two form part of the lesser omentum. The inframesocolic compartment lies posterior to the greater omentum, below the transverse mesocolon but medial to the ascending and descending colon. It contains the small bowel and ascending and desending colon. It is divided in right and left by the oblique small bowel mesentery. Both the transverse mesocolon and the small bowel mesentery are remnants of the foetal dorsal mesentery, as is the sigmoid mesentery and the mesoappendix. The ventral mesentery regresses below the transverse mesocolon. Page 7 of 54
Fig.: Diagram illustrating the omenta, mesenteries and spaces References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Lateral to the ascending and descending colons are the right and left paracolic gutters. The right paracolic gutter is continous with the right perihepatic space. Conversely on the left, the phrenicocolic ligament prevents direct communication between the left paracolic gutter and the left subphrenic space. Page 8 of 54
Fig.: Coronal CT peritoneogram showing peritoneal spaces References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 9 of 54
Fig.: Coronal and sagittal CT peritoneograms showing peritoneal spaces References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM The urogenital peritoneum reflects over the pelvic organs to form most of the pelvic ligaments and mesenteries. These include the broad and round ligaments of the uterus and the median, medial and lateral umbilical folds creating the midline recto-vesical pouch in a male and the recto-uterine pouch in a female and the paravesical fossae. Page 10 of 54
Fig.: Sagittal and coronal views from CT peritoneogram demonstrating pelvic peritoneal folds and spaces. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Peritoneal Circulation The peritoneal cavity normally contains only a thin film of fluid. This fluid is continually produced, circulated and resorbed. The direction of flow is determined by diagphragmatic movement, bowel peristalsis and limitations imposed by peritoneal attachments and ligaments. The fluid takes the path of least resistance which involves flow up the right paracolic gutter which is wider and more dependant then the left. The majority of the fluid is resorbed via lymphatics in the subphrenic space. Page 11 of 54
Fig.: Coronal CT peritoneogram demonstrating regions of fluid stasis correlated with diagram References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM 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. Images for this section: Page 12 of 54
Fig. 1: Sagittal CT peritoneogram with diagram Page 13 of 54
Fig. 2: Sagittal view from CT peritoneogram showing the greater and lesser omenta. Page 14 of 54
Fig. 3: Schematic diagram demonstrating the formation of the peritoneal spaces. Page 15 of 54
Fig. 4: Diagram demonstrating peritoneal spaces Page 16 of 54
Fig. 5: Schematic illustration of peritoneal spaces and ligaments correlated with axial CT peritoneogram. Page 17 of 54
Fig. 6: Diagram illustrating the omenta, mesenteries and spaces Page 18 of 54
Fig. 7: Coronal CT peritoneogram showing peritoneal spaces Page 19 of 54
Fig. 8: Coronal and sagittal CT peritoneograms showing peritoneal spaces Page 20 of 54
Fig. 9: Sagittal and coronal views from CT peritoneogram demonstrating pelvic peritoneal folds and spaces. Page 21 of 54
Fig. 10: Coronal CT peritoneogram demonstrating regions of fluid stasis correlated with diagram Page 22 of 54
Imaging findings OR Procedure details Schematic diagrams with corresponding CT (including CT peritoneograms) are used to illustrate peritoneal anatomy and different pathological processes affecting various peritoneal spaces. Supramesocolic compartment The subphrenic space is divided into right and left by the falciform ligament. Fig.: Axial views from CT peritoneogram demonstrating peritoneal spaces in the upper abdomen. Correlated with schematic diagram References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM The right subphrenic space communicates freely with the perihepatic and subhepatic spaces, including Morison's pouch, which communicates with the lesser sac via the epiploic foramen (foramen of Winslow). Page 23 of 54
Fig.: Coronal and sagittal view from CT peritoneogram demonstrating upper abdominal peritoneal spaces. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM These supramesocolic spaces are preferential sites for peritoneal fluid stasis and therefore are common sites to detect ascites, abcesses and peritoneal spread of metastases. Page 24 of 54
Fig.: Hydatid cysts in the subhepatic, right paracolic gutter and pelvis on sagittal and coronal MR. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 25 of 54
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Fig.: Coronal CT demonstrating hydatid disease in intraperitoneal regions of peritoneal fluid stasis. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM The lesser sac communicates with the other peritoneal spaces via the epiploic foramen. By way of the greater and lesser omentum (and the ligaments that constitute them) and the transverse mesocolon, which all form the lesser sac boundaries, pathological involvement can also be seen in the anterior pararenal space, mesenteric root and and along the transverse colon. For example, gastric neoplasms can spread to involve the the superior border of the transverse colon, and vice versa. Similar patterns of spread can also be seen with pancreatic pathology with preferential involvement of the inferior border of the colon Page 27 of 54
Fig.: Axial CT demonstrating peripancreatic collections involving the lesser sac, left anterior pararenal space, mesenteric root and transverse mesocolon. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Inframesocolic compartment The supramesocolic compartments communicates with the inframesocolic compartments by way of the right paracolic gutter. Free communication between the left paracolic gutter and left subphrenic space is prevented by the phrenicocolic ligament. Page 28 of 54
Fig.: Coronal CT peritoneogram demonstrating peritoneal spaces. Note, free communication between the subphrenic and paracolic spaces is prevented on the left by the phrenicocolic ligament. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 29 of 54
Fig.: Coronal CT demonstrating malignant ascites within all the intraperitoneal spaces. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Perforation The location of free gas within the peritoneal spaces shows the likely site of perforation. If there is a perforated duodenal ulcer, free gas will travel along the hepatoduodenal ligament to collect in the ligamentum teres fissure. This may be the only manifestation of pneumoperitoneum. Page 30 of 54
Fig.: Coronal and axial CT in a patient with a perforated duodenal ulcer demonstrating the location of free gas. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 31 of 54
Fig.: Coronal CT demonstrating the distribution of free gas following a perforated duodenal ulcer. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM If there is perforation of the colon, most commonly from sigmoid diverticulitis, free gas will initially pass along the sigmoid mesentery to collect in the peritoneal spaces, primarily inferiorly. Page 32 of 54
Fig.: Axial CT in patient with perforated diverticulits showing extensive free gas spreading along mesenteric planes References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 33 of 54
Fig.: Axial and coronal CT in patient with perforated diverticulits showing extensive free gas spreading along mesenteric planes References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Pelvis The broad ligament is a peritoneal reflection forming the mesentery for the ovaries, fallopian tubes and posterior myometrium. It also drapes over the ureters and round ligament of the uterus. These ligaments and mesenteries act as a pathway for local spread between structures. Page 34 of 54
Fig.: Axial and coronal CT peritoneogram demonstrating pelvic peritoneal reflections and spaces. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM The recto-uterine (females) and rectovesical (males) are the most dependent regions within the pelvis resulting in fluid stasis and therefore, these are common sites for abscesses, fluid collections and metastases. Page 35 of 54
Fig.: Top right: Sagittal schematic diagram of pelvic peritoneal spaces Bottom left and right: sagittal CT peritoneogram and MR demonstrating the recto-vesical space and recto-uterine space, respectively. Top right: sagittal MR demonstrating hydatid disease within this dependent pelvic space. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Extraperitoneal spaces The small bowel mesentery divides the inframesocolic compartment into right and left. Fluid collections between the leaves of the mesentery, and therefore extraperitoneal, are often triangular shaped. Fluid from bowel injuries, as opposed to solid organs injury, may initially bleed between mesenteric folds. Fluid/blood is not seen in the paracolic gutters or pelvis. Conversely, solid organ injury will initially bleed around the injured organ. Fluid/blood then extends down the paracolic gutters and into the pelvis. Only once these readily accesible spaces are filled will fluid/blood extend between the mesenteric leaves. Page 36 of 54
Fig.: Coronal CT demonstrating a triangular shaped pocket of fluid between the leaves of the small bowel mesentery. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Page 37 of 54
Fig.: Left: Axial CT demonstrating fluid between leases of mesentery following bowel injury. Right: pattern of free fluid pooling following solid organ injury,in this case traumatic splenic injury. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Retroperitoneal fluid can sometimes be difficult to distinguish from intraperitoneal fluid. Page 38 of 54
Fig.: Axial CT demonstrating intra- and retropeitoneal fluid. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Some fluid collections or heamatomas are easily identified as being retroperitoneal. Page 39 of 54
Fig.: Coronal CT demonstrating retroperitoneal bleed from right kidney following trauma. 25 year old man kicked by a horse. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Extraperitoneal rupture of the bladder shows a typical appearance with fluid seen in the perivesical space giving a classic 'molar tooth' appearance. Page 40 of 54
Fig.: Axial CT image showing extraperitoneal fluid following bladder rupture. References: R. Patel; Radiology, Royal Free Hospital, London, UNITED KINGDOM Images for this section: Page 41 of 54
Fig. 1: Axial views from CT peritoneogram demonstrating peritoneal spaces in the upper abdomen. Correlated with schematic diagram Page 42 of 54
Fig. 2: Coronal and sagittal view from CT peritoneogram demonstrating upper abdominal peritoneal spaces. Page 43 of 54
Fig. 3: Hydatid cysts in the subhepatic, right paracolic gutter and pelvis on sagittal and coronal MR. Page 44 of 54
Fig. 4: Coronal and axial CT in a patient with a perforated duodenal ulcer demonstrating the location of free gas. Page 45 of 54
Fig. 5: Axial and coronal CT in patient with perforated diverticulits showing extensive free gas spreading along mesenteric planes Page 46 of 54
Fig. 6: Axial and coronal CT peritoneogram demonstrating pelvic peritoneal reflections and spaces. Page 47 of 54
Fig. 7: Top right: Sagittal schematic diagram of pelvic peritoneal spaces Bottom left and right: sagittal CT peritoneogram and MR demonstrating the recto-vesical space and rectouterine space, respectively. Top right: sagittal MR demonstrating hydatid disease within this dependent pelvic space. Page 48 of 54
Fig. 8: Coronal CT demonstrating a triangular shaped pocket of fluid between the leaves of the small bowel mesentery. Page 49 of 54
Fig. 9: Left: Axial CT demonstrating fluid between leases of mesentery following bowel injury. Right: pattern of free fluid pooling following solid organ injury,in this case traumatic splenic injury. Page 50 of 54
Fig. 10: Axial CT demonstrating intra- and retropeitoneal fluid. Page 51 of 54
Fig. 11: Axial CT image showing extraperitoneal fluid following bladder rupture. Page 52 of 54
Conclusion A thorough understanding of peritoneal anatomy and physiology can aid radiological interpretation and narrow the differential diagnosis of a wide variety of pathological processes including perforations, trauma, infections and spread of malignancy. Using CT (including CT peritoneograms) and MR we have demonstrated how the peritoneal anatomy determines involvement of the intra- and extraperitoneal spaces following various pathological processes. A thorough understanding of peritoneal anatomy and physiology results in more accurate radiological interpretation. Personal Information Dr. Roopal R. Patel Specialist Registrar in Radiology Royal Free Hospital Radiology Scheme, London Email: roopalrpatel@hotmail.com Dr Isobel Beal Radiology Consultant Royal Free Hospital, London Dr Katie Planche Radiology Consultant Royal Free Hospital, London Email: katie.planche@nhs.net References Page 53 of 54
1. Angela D Levy. Peritoneum and Mesentery - part I Anatomy. Radiology Assistant 2009. 2. Morton A Meyers. Dynamic Radiology of the Abdomen. 3. Yoo et al. Greater and Lesser Omenta: Normal anatomy and pathologic processes. Radiographics 2007;27: 707-720 4. DeMeo et al. Anatomic CT Demonstration of the peritoneal spaces, ligaments and mesenteries: Normal and pathologic processes. Radiographics 1995; 15: 755-770. 5. Elsayes et al. MRI of the peritoneum: Spectrum of abnormalities. AJR 2006; 186: 1368-1379. 6. Moore KL and Dalley AF. Clinically Orientated Anatomy. 1999. Fourth edition: 209-218. Page 54 of 54