Pleura and Peritoneum 2016; 1(4): 193–201 Opinion Paper Wiebke Solass, Florian Struller, Philipp Horvath, Alfred Königsrainer, Bence Sipos and Frank-Jürgen Weinreich* Morphology of the peritoneal cavity and pathophysiological consequences DOI 10.1515/pap-2016-0023 pathophysiological implications: it impacts on the pro- Received November 17, 2016; accepted November 29, 2016; pagation of intraabdominal infections, determines the previously published online January 10, 2017 spreading of peritoneal metastasis and can cause Abstract: The peritoneal cavity (cavum peritonei) is bowel volvulus. Internal hernias can arise at the junc- incompletely divided into spaces and recessus (or fos- tion between intraperitoneal and extraperitoneal bowel sae), which are playing an important role in health and segments, in particular into the left paraduodenal reces- disease. Peritoneal subspaces are determined by the sus. Knowledge of peritoneal morphology is a precondi- parietal attachments of the abdominal organs, the liga- tion for developing locoregional therapeutic strategies ments and mesenteries. These include the splenorenal, in peritoneal disease and for effective peritoneal the falciform, the triangular, the gastrosplenic, the phre- dialysis. nicocolic and the gastrocolic ligaments; the greater Keywords: anatomy, morphology, pathophysiology, omentum and the lesser omentum (formed by the gas- peritoneum trohepatic and hepatoduodenal ligaments); the small bowel mesenterium and the mesocolon. These ligaments and mesenteries divide the peritoneal cavity into several Introduction distinct anatomic and functional regions. The suprame- socolic compartment is divided into a bilateral subphre- The peritoneal cavity (cavum peritonei) is the portion of nic space and a subhepatic space continuing into the the abdominal cavity delineated by the peritoneum. lesser sac (bursa omentalis). The inframesolic compart- Beyond this cavity is placed the subperitoneal (or retro- ment is divided into a left and right region by the peritoneal) space. The peritoneal cavity is delineated by mesentery. The right paracolic gutter communicates the parietal peritoneum and the visceral peritoneum and with the pelvis and with the right suphrenic space. The is a closed anatomic space. An open anatomic commu- left paracolic gutter is separated from the left subphre- nication with the external environment is only present in nic space by the phrenocolic ligament. The peritoneal women through the genital canal (continuum of the space is virtual, is completely occupied by the intraab- tubes, uterus and vagina) [1]. This communication is dominal organs and can only be visualized by radiolo- indeed a precondition for the transport and the feconda- gical means in the presence of air (organ perforation), tion of ovula. In the presence of sexually transmitted liquid (ascites, pus, bile, gastrointestinal fluids) or diseases, pathogens might migrate along this path into tumor invasion. Peritoneal morphology has numerous the peritoneal space and cause a tubo-ovarial abscess or peritonitis [2]. *Corresponding author: Frank-Jürgen Weinreich, Department of General and Transplant Surgery, Experimental Surgery, University ofTübingen,Hoppe-SeylerStr.3,72076Tübingen,Germany, Visualization of the peritoneal space E-mail: [email protected] Wiebke Solass, Institute of Pathology, University of Tübingen, Under physiological conditions, the peritoneal space is Tübingen, Germany completely occupied by the intraabdominal organs. Thus, Florian Struller, Philipp Horvath, Alfred Königsrainer, Department the peritoneal space is virtual and cannot be visualized of General and Transplant Surgery, Experimental Surgery, by radiological means. This space only becomes apparent University of Tübingen, Tübingen, Germany Bence Sipos, Institute of Pathology, University of Tübingen, under pathological conditions, in the presence of gas, Tübingen, Germany liquid or tumor. 194 Solass et al.: Morphology of the peritoneal cavity Pneumoperitoneum ligaments, mesenteries, and omenta and the natural flow of peritoneal fluid determine the route of spread of intra- The presence of free air within the peritoneal space peritoneal fluid and disease processes within the abdom- (“pneumoperitoneum”) is always abnormal and is usually inal cavity [7]. Starting from the organ of origin, the flow of caused by perforation of a hollow organ. Expansion of the pathological liquids within the peritoneal cavity is a gas within the peritoneal cavity, e.g. following a perfora- directed by the body position, the anatomy of the liga- tion of a gastric ulcer, is independent from gravity. ments and mesenteries and intraabdominal pressure gra- Radiological features of hollow organ perforation include dients (Figure 1B). As a rule, secondary to gravity, the presence of free gas or fluid within the supra- and/or intraperitoneal fluid flows predominantly into the decline inframesocolic compartments, segmental bowel wall thick- regions of the abdomen. In the upright position, most fluid ening, bowel wall discontinuity, stranding of the mesen- accumulates in the pelvis, whereas in the supine position teric fat and abscess formation [3]. Historically, induction most fluid is found in the right and left paracolic gutter of a pneumoperitoneum with 500 to 1,000 mL air 24 h and in the pelvis [8]. before plain abdominal X-ray was used until the 1960s as an aid to visualize indirectly the abdominal organs [4]. Tumor invasion Liquid Malignant tumor (peritoneal metastasis, peritoneal carci- nomatosis, malignant peritoneal mesothelioma, primary Under physiological conditions, a volume of about 1 L of adenocarcinoma of the peritoneum) or tumors of inter- peritoneal fluid is produced within 24 h [5]. This peritoneal mediate malignity (pseudomyxoma peritonei) can also fluid is reabsorbed by the subperitoneal lymphatic chan- invade the peritoneal spaces and make them visible by nels. Only a capillary film of serous fluid (approximately radiological means (CT-scan, MRI, etc.). Exfoliated tumor 50–100 mL) separates the parietal and visceral layers of cells are transported throughout the peritoneum by phy- peritoneum from one another and lubricates the peritoneal siological peritoneal fluid and disseminate within the surfaces [6]. This volume increases considerably under abdominal cavity. Extensive seeding of the peritoneal pathological conditions such as portal hypertension, cavity by tumor cells is often associated with ascites, portal venous thrombosis, malignant ascites, peritonitis, particularly in advanced, high-grade serous ovarian car- etc.. The peritoneal reflections that form the peritoneal cinomas [5]. Figure 1: The peritoneal cavity is divided into several anatomic compartments by the ligaments and mesenteries. (A) Peritoneal spaces, organs in place. The supramesocolic compartment is divided into a bilateral subphrenic space and a subhepatic space continuing into the lesser sac. The inframesolic compartment is divided into a left and right region by the mesentery. (B) The movement of fluids within the peritoneal cavity is determined by the peritoneal compartments. Note the large volume and the anatomic boundaries of the lesser sac. Yellow: parietal areas covered with peritoneum. Brown: bare parietal areas. BA: bare area of the right diaphragm. Adapted from Ref. (8). Solass et al.: Morphology of the peritoneal cavity 195 Divisions and compartments of the Right subphrenic space (Figure 1A, pink) peritoneal cavity The right subphrenic space is located underneath the right diaphragm. It does not communicate with the left The peritoneal cavity (cavum peritonei) is incompletely subphrenic space since the falciform ligament attaches divided into spaces and fossae (or recesses), which are ventrally to the anterior abdominal wall and divides the playing an important role in the circulation of the intra- supramesocolic compartment. The right subhepatic space peritoneal fluid and the spreading, respectively limitation continues caudally lateral to the liver to the right para- of infections. The anatomy of the peritoneal spaces is colic gutter, located between the ascending colon and the determined by the parietal attachments of the organs. lateral abdominal wall. Peritoneal ligaments are double layers or folds of perito- neum that support a structure within the peritoneal cav- ity; omentum and mesentery are specifically named Subhepatic space (Figure 1A, yellow) peritoneal ligaments. Most abdominal ligaments arise from the ventral or dorsal mesentery [7]. They include The right subhepatic space continues medially through the triangular ligament, the falciform ligament, the sple- the foramen of Winslow (epiploic foramen) to the lesser norenal ligament, the gastrosplenic ligament, the phreni- sac (bursa omentalis). The organs surrounding the lesser cocolic ligament, the gastrocolic ligament, the greater sac are the spleen on the left, the stomach and duode- omentum, the lesser omentum (formed by the gastrohe- num anterior and right, the transverse colon anterior, patic ligament and hepatoduodenal ligament), and the and the pancreas on its posterior aspect (Figures 1B transverse mesocolon [9]. and 2). The transverse colon and mesocolon are the major The lesser sac is a potentially large cavity with var- landmarks dividing the peritoneal cavity into suprameso- ious recesses into the subphrenic area cranially and into colic and inframesocolic compartments. On the anterior the greater omentum caudally (Figure 3). The left gastric aspect of the