Endoscopic Ultrasound

TRAINING COURSE
Year
: 2019  |  Volume : 8  |  Issue : 3  |  Page : 161--171

Imaging of infracolic and pelvic compartment by linear EUS


Malay Sharma1, Amol Patil1, Avinash Kumar1, Amit Pathak1, Piyush Somani1, Srijaya S Sreesh2, Chittapuram Srinivasan Rameshbabu3,  
1 Department of Gastroenterology, Jaswant Rai Speciality Hospital, Meerut, Uttar Pradesh, India
2 Department of Gastroenterology, Government Medical College, Thiruvananthapuram, Kerala, India
3 Department of Anatomy, Muzaffarnagar Medical College, Muzaffarnagar, Uttar Pradesh, India

Correspondence Address:
Dr. Malay Sharma
Jaswant Rai Speciality Hospital, Meerut - 250 001, Uttar Pradesh
India

Abstract

The peritoneal cavity is subdivided into supracolic and infracolic compartments by transverse mesocolon, which attaches the colon to the posterior abdominal wall. Infracolic compartment is subdivided into right and left compartment by small bowel mesentery. Left infracolic space freely communicates with pelvic compartment. The infracolic compartment contains the coils of small bowel which is separated from paracolic gutter on either side by ascending and descending colon. Pelvic compartment mainly contains bladder, rectum and genital organ (prostate, seminal vesicle in male and uterus in female). The evaluation of different compartments of peritoneum is gaining importance in multimodality imaging. It has become essential that clinicians and endosonographers thoroughly understand the peritoneal spaces and the ligaments and mesenteries that form their boundaries in order to localize disease to a particular peritoneal/subperitoneal space and formulate a differential diagnosis on the basis of that location. In this article we describe the applied EUS anatomy of peritoneal ligaments, infracolic and pelvic compartments of peritoneum and there technique of imaging from stomach, duodenum, sigmoid colon and rectum. Imaging from stomach images the infracolic compartment through transverse mesocolon, imaging from duodenum images the infracolic compartment through the mesentery and imaging from rectum and sigmoid images the infracolic and pelvic compartments through the sigmoid mesocolon and pelvic peritoneum.



How to cite this article:
Sharma M, Patil A, Kumar A, Pathak A, Somani P, Sreesh SS, Rameshbabu CS. Imaging of infracolic and pelvic compartment by linear EUS.Endosc Ultrasound 2019;8:161-171


How to cite this URL:
Sharma M, Patil A, Kumar A, Pathak A, Somani P, Sreesh SS, Rameshbabu CS. Imaging of infracolic and pelvic compartment by linear EUS. Endosc Ultrasound [serial online] 2019 [cited 2019 Jul 15 ];8:161-171
Available from: http://www.eusjournal.com/text.asp?2019/8/3/161/258797


Full Text



 Introduction



The peritoneal cavity is subdivided into supracolic and infracolic compartments by transverse mesocolon, which attaches the colon to the posterior abdominal wall.[1] The supracolic compartment contains the liver, spleen, stomach, and lesser omentum.[2],[3],[4] The infracolic compartment contains the coils of small bowel surrounded by the ascending, transverse, and descending colon [Figure 1] and [Figure 2].[3],[4] The evaluation of different compartments of the peritoneum is gaining importance in multimodality imaging.[5],[6],[7],[8],[9] The applied EUS anatomy of the peritoneal ligaments has been described.[10] In this review, we describe the applied EUS anatomy of infracolic and pelvic compartments of the peritoneum. Some of the images have been taken in patients of ascites to aid description of different compartments. Few images of radial EUS and computer tomography scan have been included, and the transverse mesocolon, mesentery (of the small bowel), and pelvic peritoneum are discussed.{Figure 1}{Figure 2}

The transverse mesocolon

The base of the transverse mesocolon lies horizontally across the duodenum and pancreas. To the right of the pancreas, this attachment line crosses the vertical segment of the duodenum and terminates at the hepatic flexure, whereas on the left, it terminates at the splenic flexure [Figure 2]. The upper limit of the infracolic compartment is the transverse colon, and the lower limit is in communication with the pelvis [Figure 1].

The spaces related to transverse mesocolon

The ascending, transverse, and descending colon enclose the central compartment. The right and left paracolic gutters are located lateral to the ascending and descending colon [Figure 3]. The right paracolic gutter is larger than left and both communicate with the pelvis. The right paracolic gutter communicates superiorly with the right intrahepatic space and thus connects the hepatorenal recess and rectovesical/rectouterine pouch of Douglas with each other in male and female, respectively [Figure 4]. The left paracolic gutter is separated from the left supracolic space by the phrenicocolic ligament, which is present near the lower pole of the spleen [Figure 3]. A similar kind of supporting ligament is not found near the hepatic flexure on the right side.{Figure 3}{Figure 4}

Imaging from stomach

Imaging of the infracolic compartment below the level of transverse mesocolonis possible through the posterior, inferior, and lateral wall of the stomach [Figure 5]. When imaging is done through the lateral wall of the stomach, the lower pole of the spleen and the inferior margin of the liver can be identified. In the presence of ascites, the paracolic gutters can be identified below the lower pole of the spleen and the inferior margin of the liver [Figure 6]. The hepatic and splenic flexures of the colon may be localized on the undersurface of the liver and spleen, respectively. In this position, limited evaluation of air-filled transverse colon is possible [Figure 7], [Figure 8], [Figure 9]. When the imaging beam is directed posteroinferiorly through the wall of the stomach, visualization of the small bowel loops of infracolic compartment is possible through the transverse mesocolon below the inferior border of the pancreas [Figure 10]a and [Figure 10]b.{Figure 5}{Figure 6}{Figure 7}{Figure 8}{Figure 9}{Figure 10}

Imaging from duodenum

Imaging of the transverse mesocolon and greater omentum is possible from the second and third parts of the duodenum [Figure 11]. The branches arising from the superior mesenteric artery (SMA), and the tributaries joining the superior mesenteric vein (SMV) can be located from this position. Identification of the mesenteric and antimesenteric borders of the vessels helps in further evaluation. The mesenteric border is identified by the presence of fan-shaped jejunal and ileal vessels. The transverse mesocolon is identified after following the middle colic artery, which is the second branch of the SMA arising from the antimesenteric border [Figure 12], [Figure 13], [Figure 14], [Figure 15].{Figure 11}{Figure 12}{Figure 13}{Figure 14}{Figure 15}

The mesentery

The first 2 cm of the first part of the duodenum is intraperitoneal and lies in the supracolic compartment where it is surrounded by the lesser omentum above and the greater omentum below. The duodenum passes horizontally from the right to the left side of the infracolic compartment in front of the third lumbar vertebra and reaches the duodenojejunal flexure on the left side of the third lumbar vertebra [Figure 16]. The second part of duodenum passes behind the transverse mesocolon. The second part of the duodenum above the transverse mesocolon is related to supracolic compartment and the part below the second part of duodenum is related to infracolic compartment [Figure 16]. The mesentery and the mesenteric vessels are the most important home bases of imaging from the infracolic compartment. The mesentery is attached diagonally across the posterior wall of the infracolic compartment from the left side of L2 to the front of the right sacroiliac joint, extending from the duodenojejunal flexure to the ileocecal junction [Figure 16].{Figure 16}

The spaces related to mesentery

The root of the mesentery acts as the divider of the infracolic compartment into right and left infracolic spaces, and generally, the imaging of SMA is possible at the point of origin from the third part of the duodenum [Figure 17]. The apex of the triangular right infracolic space lies between the root of the mesentery, ascending colon, right two-third of the transverse colon, and transverse mesocolon. The base of the left infracolic space is directed downward and lies between root of the mesentery, descending colon, left one-third of the transverse colon, and transverse mesocolon. In the left iliac fossa, the infracolic compartment is limited inferiorly by the sigmoid colon and its mesentery, the sigmoid mesocolon [Figure 2]. The apex of the triangular right infracolic space lies at the ileocecal junction which separates it from the pelvic peritoneal spaces. It communicates with the left infracolic space toward the left side of attachment of root of the mesentery. The left infracolic space widens below and freely communicates with the pelvic peritoneal spaces through the pelvic inlet [Figure 2].{Figure 17}

Imaging from stomach

Imaging of the infracolic compartment is possible from the stomach through the gastrocolic ligament, which is identified on the greater curvature of the stomach. Gastrophrenic, gastrosplenic, and gastrocolic ligaments are attached to the greater curvature. During imaging from the stomach, when the diaphragm is seen, it shows the gastrophrenic ligament; when the spleen is seen, it shows the gastrosplenic ligament; and on continued rotation, when the lower border of the spleen is seen, it starts showing the gastrocolic ligament. The presence of parallel mesenteric vessels (SMA and SMV) which cross the uncinate process together and enter the mesentery is seen as the main home base [Figure 18] and [Figure 19]a. SMV can be followed down from the portal venous confluence [Figure 12]. A clockwise rotation from this position can trace the left infracolic compartment. The structures of the left infracolic compartment visualized during clockwise rotation are aorta and left kidney in front of the psoas major [Figure 19]b, [Figure 19]c, [Figure 19]d. On counterclockwise rotation, the inferior vena cava (IVC) and right kidney can be seen [Figure 20] and [Figure 21].{Figure 18}{Figure 19}{Figure 20}{Figure 21}

Imaging from duodenum

The numerous coils of the jejunum fill the upper part of the infracolic compartment, whereas the coils of the ileum fill the lower part of the infracolic compartment and pelvis [Figure 22]. The mesentery contains the blood vessels, lymphatics, and lymph nodes embedded in fat [Figure 23] and [Figure 24]. The root of the mesentery has right and left laminas. A clockwise rotation with the root of the mesentery and mesenteric vessels as a neutral home base will show the right peritoneal lamina and the right infracolic compartment and counterclockwise rotation will show the left peritoneal lamina and left infracolic compartment. The upper part of the right peritoneal lamina covers the pancreas and duodenum, and the lower part of the right peritoneal lamina covers the right ureter, the lower pole of the right kidney, and muscles of the posterior abdominal wall. Since the mesentery lies obliquely, the right lamina also covers the upper part of the IVC and aorta [Figure 2]. The left peritoneal lamina is continuous with the parietal peritoneum of an extensive quadrangular area that leads down into the pelvis. In this area, of the left infracolic compartment, retroperitoneal structures include the lower pole of the left kidney, the left ureter, the lower part of the IVC and the aorta, and both the left and right common iliac vessels [Figure 25]. The division into the right and left infracolic compartments help in factual understanding of the anatomical details.{Figure 22}{Figure 23}{Figure 24}{Figure 25}

The pelvic peritoneum and sigmoid mesocolon

The imaging of peritoneal cavity can be done from the middle and upper parts of the rectum and sigmoid colon. The peritoneal reflections near the rectum are different in males and females due to the presence of organs of reproduction. In males, the peritoneum covers the upper two-third of the anterior and upper one-third of the lateral surfaces of the rectum. The peritoneum sweeps forward from the rectum to the bladder and in this process dips slightly downward to the level of upper end of the seminal vesicles where it lies about 7.5 cm from the anal orifice [Figure 26]. In females, the peritoneum covers the upper two-third of the anterior and upper one-third of the lateral surfaces of the rectum, sweeps forward from the rectum, covers the posterior fornix of the vagina, and then passes onto the back of the cervix and body of the uterus, forming the rectouterine fold. This fold dips downward to form the rectouterine pouch (of Douglas), the bottom of which is about 5.5 cm from the anal orifice. It invests completely the posterior and anterior surfaces of the uterus before reflecting onto the superior surface of the bladder forming the uterovesical pouch [Figure 27]. Anteriorly, the peritoneum ascends from the superior surface of the bladder toward the umbilicus in both sexes where it is folded up into the median, medial, and lateral umbilical folds. Laterally, the peritoneum of the rectum (and the bladder) continues with the parietal peritoneum of the pelvic wall. The sigmoid colon lies in front of the sacrum. The sigmoid mesocolon is an inverted V-shaped mesentery that attaches the sigmoid colon to the posterior pelvic wall along the line of an inverted V [Figure 2]. The left limb of the V is in the left iliac fossa and the right limb descends into the pelvis. The apex of the right limb is located in front of the left ureter and division of the left common iliac artery [Figure 2] and [Figure 28]. Imaging of the iliac vessels is a key point of rectosigmoid imaging, and it is usually possible to see the bifurcation of the aorta and the union of iliac vessels to form the IVC from the sigmoid colon [Figure 29], [Figure 30], [Figure 31], [Figure 32], [Figure 33]. Laterally, the peritoneum of the rectum/sigmoid colon comes within 1 to 2 cm distance of the iliac vessels which run close to the ischial spine and are easily seen with the application of color Doppler against the bony shadow of the ischium. In the presence of ascites, the ischial spine creates an indentation on the rectovesical/rectouterine pouch and gives an hourglass appearance in the presence of ascites.{Figure 26}{Figure 27}{Figure 28}{Figure 29}{Figure 30}{Figure 31}{Figure 32}{Figure 33}

The spaces related to pelvic peritoneum and sigmoid mesocolon

The pelvic spaces are in free communication with the paracolic gutter and infracolic compartments. In women, the space between the rectum and uterus is defined as the rectouterine space (the pouch of Douglas) and the space between the uterus and bladder is called as the uterovesical pouch [Figure 34], [Figure 35], [Figure 36]. In male, the rectovesical space is present between the bladder and rectum [Figure 37].{Figure 34}{Figure 35}{Figure 36}{Figure 37}

Imaging of spaces related to pelvic peritoneum and sigmoid mesocolon

The imaging of the pelvic spaces is possible through the anterior and lateral wall of the rectum and from the sigmoid colon by identifying the home base stations. The presence of the prostate helps in defining the upper boundary of the lower one-third of the anterior wall of the rectum and the upper limit of the seminal vesicle locates the lower limit of the rectovesical space in males [Figure 37]. In females, the anterior wall of the upper rectum shows the uterus and distended bladder [Figure 34], [Figure 35], [Figure 36]. The lateral wall shows the division of the iliac vessels and the ureter. The lower limb of the sigmoid mesentery is identified due to its close proximity with the ileal vessels and the ureter. It is easy to identify the large caliber retroperitoneal vessels through the sigmoid mesentery from the upper rectum and rectosigmoid junction. During imaging from the upper rectum and sigmoid, the left infracolic compartment, the retroperitoneal structures (lower part of the IVC and the aorta and both left and right common iliac vessels), and the bowel loops can be seen [Figure 25].

 Discussion



The imaging of the infracolic compartment and pelvis is possible by EUS from the stomach, duodenum, and rectum. Imaging from stomach images the infracolic compartment through the transverse mesocolon, imaging from the duodenum images the infracolic compartment through the mesentery, and imaging from the rectum and sigmoid images the infracolic and pelvic compartments through the sigmoid mesocolon and pelvic peritoneum. It has become essential that clinicians and endosonographers thoroughly understand the peritoneal spaces and the ligaments and mesenteries that form their boundaries to localize disease to a particular peritoneal/subperitoneal space and formulate a differential diagnosis on the basis of that location. In this article, we have described the normal EUS anatomy of the infracolic compartment of the peritoneum. This information may be useful to understand the spread of disease processes and in sampling of fluids, lymph nodes, or deposits in different compartments of the peritoneum.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Healy JC, Reznek RH. The peritoneum, mesenteries and omenta: Normal anatomy and pathological processes. Eur Radiol 1998;8:886-900.
2Le O. Patterns of peritoneal spread of tumor in the abdomen and pelvis. World J Radiol 2013;5:106-12.
3Yoo E, Kim JH, Kim MJ, et al. Greater and lesser omenta: Normal anatomy and pathologic processes. Radiographics 2007;27:707-20.
4Vikram R, Balachandran A, Bhosale PR, et al. Pancreas: Peritoneal reflections, ligamentous connections, and pathways of disease spread. Radiographics 2009;29:e34.
5Coffin A, Boulay-Coletta I, Sebbag-Sfez D, et al. Radioanatomy of the retroperitoneal space. Diagn Interv Imaging 2015;96:171-86.
6Mirilas P, Skandalakis JE. Surgical anatomy of the retroperitoneal spaces part II: The architecture of the retroperitoneal space. Am Surg 2010;76:33-42.
7Lee SL, Ku YM, Rha SE. Comprehensive reviews of the interfascial plane of the retroperitoneum: Normal anatomy and pathologic entities. Emerg Radiol 2010;17:3-11.
8Tirkes T, Sandrasegaran K, Patel AA, et al. Peritoneal and retroperitoneal anatomy and its relevance for cross-sectional imaging. Radiographics 2012;32:437-51.
9Jeon YS, Lee JW, Cho SG. Is it from the mesentery or the omentum? MDCT features of various pathologic conditions in intraperitoneal fat planes. Surg Radiol Anat 2009;31:3-11.
10Sharma M, Rai P, Rameshbabu CS, et al. Imaging of peritoneal ligaments by endoscopic ultrasound (with videos). Endosc Ultrasound 2015;4:15-27.