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General Surgery
Peritoneum, Omenta, and Internal Hernias
Built from Skandalakis' Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery
What’s inside
13 sections · 198 slides
Overview
- Peritoneum: largest serous membrane, ~22,000 cm2, parietal and visceral layers. Embryology explains every adult ligament, fossa and fusion plane the surgeon meets. Peritoneal reflections partition the abdomen into named spaces where pus collects. The omenta: greater (dorsal mesogastrium) and lesser (ventral mesentery derivative). Internal hernias arise at fossae and mesenteric defects; <1% of intestinal obstruction. Operative themes: paracentesis, exploration, adhesions, peritonitis, omentoplasty.
Historical landmarks
- Anatomic and Surgical History of the Peritoneum and Omenta
- Anatomic and Surgical History of the Peritoneum and Omenta (continued)
- Anatomic and Surgical History of the Peritoneum and Omenta (continued)
- Anatomic and Surgical History of the Peritoneum and Omenta (continued)
- Anatomic and Surgical History of the Peritoneum and Omenta (continued)
- Anatomic and Surgical History of the Peritoneum and Omenta (continued)
Embryogenesis
- Gut tube begins closed, fixed by dorsal and ventral mesenteries. Around the third week mesoderm splits into lateral plate, intermediate, paraxial. Lateral plate divides into somatic and splanchnic layers enclosing the coelom. Right and left intraembryonic coeloms unite into a single cavity. That cavity subdivides into pleural, pericardial and peritoneal cavities. The processus (tunica) vaginalis is the same coelom carried into the scrotum.
- Derivatives of the differentiating coelom
- Organ relations to the ventral and dorsal mesenteries
- Older view: an independent recess or cleft starts the lesser sac. Liebermann-Meffert and White: omentum develops independently, close to the spleen. On that view the organs do not rotate at all. Krutsiak and Voitiv: lesser sac forms in three sections. Vestibulum bursae omentalis, bursa omentalis proper, cavity omentum majus. The text states plainly that omental development remains controversial.
- Greater omentum arises from dorsal mesentery as a double-layered evagination. Its origin lies between the left gastric artery and the common hepatic artery. At the fifth week the dorsal mesentery elongates downward after the bursa forms. That elongation forms the inferior recess of the omental bursa. The result is a four-layered structure, the greater omentum or fat apron. By definition it attaches to the greater curvature, the original dorsal surface.
- Sequence of greater omental formation
- Formation of the greater omentum, four stages
- The greater omental sac is closely related to the transverse mesocolon. Adult transverse mesocolon fuses embryonic mesocolon with dorsal mesogastrium. Where two bursal layers meet two mesocolic layers there are initially four layers. Only the two outer layers, above and below, survive in the adult mesocolon. The right portion, from the gastric antrum, often fuses to the pancreatic head. Free the omentum from the pancreas from left to right.
- The peritoneal cavity has two principal spaces. Greater sac is the general peritoneal cavity. Omental bursa is the lesser sac behind the stomach. They communicate only through the epiploic foramen of Winslow. In the male the peritoneal cavity is a truly closed sac. In the female the uterine tube ostia open it to the exterior.
Congenital anomalies
- Anomalies here are rare and reported only sporadically. Absence of the omentum and its ligaments is rarely described. Kiuchi et al. reported hypoplasia of the greater omentum with asplenia syndrome. That case showed dysplasia of length, breadth and thickness. The omentum may fail to form the gastrocolic ligament, partly or totally. It may fail to attach to the greater curvature, or attach where it should not.
- Most congenital omental defects are asymptomatic. Obstruction follows if a small bowel loop passes through the omentum. Skandalakis saw symptomatic defects in the greater omentum. Defects found in the lesser omentum were asymptomatic. Bifid omentum may occur, though no supporting references were found. Congenital adhesions to the abdominal wall or other organs are rare.
- Benign solid omental tumours occur in children; congenital origin is hard to support. True cysts are lined with epithelium or endothelium. Pseudocysts, or false cysts, have no such lining. Spurney and McCormack reported a rare immature omental teratoma. Boehner studied a solid ovarian teratoma metastatic to the omentum. Skandalakis reported idiopathic segmental infarction of the right lower omental border.
- Root of the mesentery runs from L1 or L2 to the right sacroiliac joint. It is normally fused to the retroperitoneal space. Failure to fuse, or a hole, allows small bowel herniation. Nonfusion deformity produces a hernia of Waldeyer. It may combine with nonfusion of the colonic mesentery. Such internal hernias may be symptomatic or silent.
- Jejunal atresia with agenesis of the dorsal mesentery has several names. It is called apple peel syndrome, Christmas tree deformity or maypole atresia. Internal hernia follows if the transverse mesocolon fails to attach normally. Normal attachment is to the second part of the duodenum and anterior pancreas. It also attaches to the lower pole of the left kidney. The intersigmoid fossa or any sigmoid mesocolic site may herniate.
- Sites of omental and mesenteric cysts
- Moynihan described nine paraduodenal fossae as fusion folds from physiologic adhesions. The text accepts five as clinically important and constant enough to study. Each carries the name of its original investigator. The fossae appear to be congenital. They may form in the 10th week as ascending and descending mesocolon fuse. Fusion is to the parietal peritoneum of the posterior abdominal wall.
- The major paraduodenal fossae
- The paraduodenal fossae: anatomic boundaries
- The paraduodenal fossae: anatomic boundaries (continued)
- The paraduodenal fossae: incidence and significance
- Several intraperitoneal fossae and apertures allow protrusion of contents. Internal hernias account for less than 1% of intestinal obstructions. Of those, paraduodenal hernias account for more than half. Congenital hernial sacs open at the sites of the fossae. No evidence shows a congenital fossa becomes a hernial sac later in life. A fossa marks where a congenital hernia might have formed but did not.
- Left hernia: a loop enters unfused descending mesocolon in the 10th week. As the mesocolon fuses, a hernial sac is produced around the loop. The same process under the ascending mesocolon gives a right paraduodenal hernia. Laslie et al. proposed the sac is not mesocolon at all. They argued it is the lining of the extraembryonic coelom returning with the loops. Where that avascular sac does not fuse, the condition is called internal omphalocele.
Surgical anatomy of the peritoneum
- Largest serous membrane in the body, surface area about 22,000 cm2. Parietal layer lines abdominal and pelvic cavities and the diaphragmatic surface. Visceral layer covers the viscera and includes the mesenteries. Parietal layer is loosely connected to the wall by the tela subserosa, an adipose layer. Visceral peritoneum is usually tightly attached to the organ it covers. Peritoneum has a fibrous tunica subserosa and a mesothelial tunica serosa.
- Normally a potential space with only a thin lubricating film of fluid. That film allows frictionless movement of the gastrointestinal tract. In disease, litres of fluid may occupy the cavity. Peritoneum does not line the whole abdominopelvic cavity. Organs lying against the posterior wall lift it away, creating the retroperitoneal space. The parietal peritoneum can withstand great stretching as fluid accumulates.
- An organ covered only in part by peritoneum is retroperitoneal. An organ covered everywhere except where vessels enter is intraperitoneal. Secondary retroperitonealisation follows fusion, as for duodenum and pancreas. Ascending and descending colon are likewise secondarily retroperitoneal. The fusion plane left behind is avascular and can be reopened surgically. Knowing which organ is which predicts where a leak will collect.
- Parts of the Peritoneum
- Parts of the Peritoneum (continued)
- Vertical disposition of the peritoneum
- Roughly triangular bilaminar fold from anterior wall and diaphragm to the liver. Inclined to the right in a nearly coronal plane as it ascends from the umbilicus. Two layers separated by loose connective tissue. At the diaphragm-liver junction the two layers separate. Right layer becomes the anterior lamina of the coronary ligament. Left layer becomes the anterior layer of the left triangular ligament.
- Free crescentic inferior margin carries a firm cordlike thickening. That cord is the ligamentum teres hepatis, the round ligament of the liver. It is the remnant of the left umbilical vein. The right umbilical vein disappeared early in embryonic life. It runs from the umbilicus to end at the umbilical segment of the left portal vein. Paraumbilical veins of Sappey run in the same ligament from liver to umbilical skin.
- Runs from the left portal vein to the inferior vena cava below the diaphragm. It is the vestige of the embryonic continuation of the left umbilical vein. In intrauterine life it is the ductus venosus. Maternal blood passed from the left umbilical vein to the liver. Some was shunted into the liver by the portal system, the rest to the IVC. Falciform, round and venosum together split the left lobe into medial and lateral segments.
- Visceral peritoneum passes over the inferior margin of the liver to its visceral surface. On the right it leaves the liver to cover the right adrenal and upper right kidney. That reflection is the hepatorenal ligament. It continues left as the posterior or inferior layer of the coronary ligament. Below, peritoneum invests the first part of the duodenum and the hepatic flexure. It covers the part of the IVC forming the posterior border of the foramen of Winslow.
- Peritoneal reflections of the diaphragm and the bare area
- At the right liver margin the coronary reflection forms the right triangular ligament. That ligament secures the right lobe to the diaphragm. It forms the apex of the large posterosuperior bare area. At the bare area the liver has no peritoneal covering. Base of the triangular bare area lies to the left, at the groove for the IVC. At the left margin the reflection forms the left triangular ligament.
- Left margin of the two-layered lesser omentum connects to the oesophagus. Right free margin forms the anterior border of the epiploic foramen of Winslow. That free border ensheathes the hepatic arteries and extrahepatic biliary vessels. It also contains the portal vein, lymph nodes and vessels, and the hepatic nerve plexus. Behind it lies the epiploic foramen. That foramen is the sole passageway between greater cavity and lesser sac.
- Laminae separate at the lesser curvature, investing the left gastric vessels and nerves. This part of the lesser omentum is the hepatogastric ligament. Beyond the stomach and first part of duodenum, gastric peritoneal layers leave the greater curvature. They continue as the anterior layer of the greater omentum. That layer descends across the transverse colon to the lower end of the apron. The posterior layer ascends, fuses with transverse mesocolon, reaches head and body of pancreas.
- Peritoneum is carried away from the midline by the superior mesenteric vessels. That reflection is the radix or root of the mesentery of the small intestine. Continuing about jejunum and ileum, it covers the left side of that mesentery. It passes left over the secondarily retroperitoneal descending colon. It is then elevated as the anterior layer of the sigmoid mesocolon. After investing the sigmoid it ascends as the posterior layer to the left iliac fossa.
- Peritoneum covers ventral and lateral aspects of the first part of the rectum. It covers only the ventral surface of the second part. It then forms the floor of the rectovesical pouch in the male. In the female it forms the rectouterine pouch of Douglas. Lateral to the rectum it forms right and left pararectal fossae. The depth of those fossae varies with rectal distension.
- Lateral boundaries of the pararectal fossae continue forward as the sacrogenital folds. Those folds overlie dense connective tissue, the ureter, and nerves and vessels. Peritoneum of the rectovesical pouch ascends over the superior seminal vesicles. It does not come into contact with the prostate gland. It sweeps up over the base and superior surface of the bladder to the anterior wall. Lateral to the bladder it floors the right and left paravesical fossae.
- Peritoneum over the fibrous urachus forms the median umbilical fold. The urachus is the remnant of the embryonic allantois, apex of bladder to umbilicus. Peritoneum over the obliterated umbilical arteries forms the medial umbilical folds. Peritoneum over the inferior epigastric vessels forms the lateral umbilical folds. Those lateral folds pass toward the rectus muscles, not truly to the umbilicus. The text therefore considers them probably named inappropriately.
- Bladder and anterior abdominal wall from behind
- Supravesical fossae lie between the median and the medial umbilical folds. Their depth depends on the fullness of the bladder. The medial inguinal fossa lies lateral to the medial umbilical ligament. The lateral inguinal fossa lies just lateral to the lateral umbilical ligament. The lateral inguinal fossa contains the deep or internal inguinal ring. A shallow femoral fossa overlies the abdominal surface of the femoral ring.
- Rectouterine pouch of Douglas ascends over posterior fornix and vaginal apex to the cervix. Uterosacral folds are prominent in the pararectal fossae and rectouterine pouch. They contain peritoneum, connective tissue, smooth muscle and pelvic nerve plexus elements. Peritoneum reflects from the uterus at the isthmus toward the bladder. Between uterus and bladder lies the shallow vesicouterine pouch. Anterior arrangement then resembles that in the male.
- Peritoneum continues laterally from the uterine fundus and body. Two layers ensheathe the uterine tubes as the broad ligament. Peritoneum adjacent to the tube is the mesosalpinx. Peritoneum suspending ovary and its proper ligament is the mesovarium. Laterally over the ovarian vessels it becomes the infundibulopelvic ligament. The ovary itself is not covered by peritoneum.
- Transverse section at the level of the spleen
- Abdominal parietal peritoneum is supplied by branches of the abdominal wall arteries. Pelvic parietal peritoneum is supplied from the vessels of the pelvic wall. Visceral peritoneum takes branches of the coeliac trunk. It also takes branches of the superior and inferior mesenteric arteries. Pelvic visceral peritoneum is supplied by pelvic visceral vessels. Supply therefore follows the somatic or visceral identity of the layer.
- Parietal peritoneal lymphatics join those of the body wall and drain to parietal nodes. Visceral peritoneal lymphatics join those of the related organ. Allen and Weatherford described removal of 10-20 micron particles from the cavity. That occurs through openings of the basement membrane via peritoneal lymphatics. Those specialised lymphatics were found only on the abdominal surface of the diaphragm. Von Recklinghausen first described these modified lymphatics in 1863.
- Parietal peritoneum contains somatic afferent nerves. It carries many sensory fibres for pain. The anterior portion is especially sensitive. It is therefore comparable in sensitivity to the parietal pleura. Irritation gives sharply localised pain. A perforated viscus may produce anterior abdominal wall rigidity.
- Visceral peritoneum has no somatic afferent nerves. It is relatively insensitive to pain. Sensations are poorly perceived and not clearly localised. The principal stimuli are tension or stretching of the tissue, and ischaemia. An intraperitoneal collection may give traction or tension sensations, not localised pain. Sensory fibres for pain run in thoracic and lumbar splanchnic nerves.
Peritoneal fossae and recesses
- Pockets of peritoneum on the posterior abdominal wall near the duodenojejunal junction. They lie particularly to the left of that junction. They are enigmatic embryologically, anatomically and clinically. They are inconstant: any, all or none may be present in one person. Boundaries are complex; size, length, depth and direction all enter the naming. A paraduodenal fossa may be intimately related to the inferior mesenteric vein.
- It is an open, normal aperture, not a defect. It is the sole passageway between greater peritoneal cavity and lesser sac. Its anterior boundary is the free right margin of the lesser omentum. That margin is the hepatoduodenal ligament carrying the portal triad. Its posterior boundary includes the inferior vena cava. The cystic duct lies in the free edge of the lesser omentum.
- Superior and inferior ileocecal folds form the ileocecal fossae. A third, the retrocecal or subcecal fossa, may occasionally appear. Its boundaries are inconstant, depending on depth and medial-lateral expansion. It lies between the right colic gutter and the posterior surface of the cecum. It does not exist in the presence of a mobile cecum. Skandalakis has seen herniation of the terminal ileum behind the cecum.
- Superior and inferior ileocecal folds forming the fossae
- Bowel loop trapped by the right mesocolon
- It lies in the pelvic mesocolon, which occupies the space from pelvic wall to S3. The pelvic mesocolon has the shape of the Greek letter lambda. Attachment of the mesosigmoid usually starts in the left iliac fossa. It runs downward and to the right on a diagonal. Attachment may instead be sinuous, or shaped like a C, an S or an inverted U. Length and breadth of this mesentery may vary by race and diet.
- Sigmoid mesocolon dimensions and the left ureter
- They lie between the median umbilical ligament and the medial umbilical ligament. The median ligament is the obliterated or non-obliterated urachus. The medial ligaments are the obliterated umbilical arteries. The fossa partly overlies the modern boundaries of the triangle of Hesselbach. Its floor is formed by endopelvic fascia, transversalis fascia and preperitoneal tissue. With an empty bladder the proximal part of the floor is transversalis fascia.
- Overlap of the supravesical fossa with the Hesselbach triangle
- Adhesions, bands and folds may exist in a virgin peritoneal cavity. A virgin cavity is one without previous surgery or inflammatory process. In most cases their presence is quite benign. At times they cause partial or complete intestinal obstruction. Their embryogenesis is enigmatic and their dimensions are not constant. Peritoneal folds are not adhesions: they convey vessels, lymphatics and nerves.
- Inconstant peritoneal folds of the gallbladder
Compartments and perihepatic spaces
- An imaginary cross-sectional plane through the transverse mesocolon divides the cavity. Above it is the supracolic compartment, below it the infracolic compartment. Within the supracolic compartment the liver defines right and left suprahepatic spaces. It also defines right and left infrahepatic spaces. The infracolic compartment is divided by the small bowel mesentery. That gives right supramesenteric, left inframesenteric and pelvic compartments.
- Arbitrary compartments of the abdominal cavity
- Two paracolic gutters lie lateral and medial to the ascending and descending colon. The right lateral gutter communicates freely with the right posterior subphrenic space. Pelvic fluid can therefore reach the diaphragm along it. Upper abdominal fluid can likewise drain into the pelvis. The phrenicocolic ligament blocks the left gutter from the perisplenic and left subphrenic areas. There is no right phrenicocolic ligament.
- The ventral mesentery disappears except for that of the foregut. Its persisting segment runs from umbilicus to abdominal oesophagus. The liver divides it into falciform ligament in front, lesser omentum behind. Falciform, coronary and hepatogastric ligaments are ventral mesogastrium derivatives. Greater omentum and gastrophrenic ligament come from the dorsal mesogastrium. The supracolic compartment is technically the most difficult surgical area.
- Mesenteries of the stomach
- Primitive embryonic and adult peritoneal relations
- Lesser omentum divides into hepatogastric and hepatoduodenal ligaments. Hepatogastric ligament runs from porta hepatis to lesser curvature and abdominal oesophagus. Its two leaves rejoin on the left as the gastrosplenic ligament. The posterior leaf does not reach the gastro-oesophageal junction. That leaves a small bare area on the posterior gastric wall on the left crus. It relates to the left adrenal gland and the left gastric artery and vein.
- It contains the left gastric artery and vein. It carries the hepatic division of the anterior vagal trunk. It may occasionally contain the right gastric vessels and both vagal trunks. In about one-fourth of subjects it contains an aberrant left hepatic artery. That vessel arises from the left gastric artery. It is at risk in highly selective vagotomy and in gastric devascularisation.
- It extends between liver and first part of the duodenum. It practically forms the right border of the hepatogastric ligament. It contains the common bile duct, hepatic artery and portal vein. About one in five patients has an aberrant right hepatic artery, usually from the SMA. That vessel invariably lies behind the portal vein as it passes to the liver. It is therefore not usually in danger during bile duct or ligament resection.
- The primitive dorsal mesentery persists, unlike the ventral. In the supracolic compartment it forms the greater omentum. It originally ran from the dorsal border of the stomach to the dorsal body wall midline. That relation is altered by counterclockwise rotation of the stomach through 90 degrees. The developing spleen alters it further. For practical purposes the embryonic dorsal mesogastrium is the adult greater omentum.
- Gastrophrenic ligament runs from proximal greater curvature and cardia to the diaphragm. Its upper part is avascular. Its lower part contains some short gastric vessels and lymph nodes. The middle portion is interrupted by the spleen. That gives a posterior splenorenal and an anterior gastrosplenic ligament. Together these two form the splenic pedicle.
- Long and short splenic pedicles
- Development of the omentum and the lesser sac
- Changing relations of duodenum and pancreas
- At its earliest appearance the mesogastrium includes duodenum and pancreas. By the fourth month duodenum and pancreas have become retroperitoneal. The future omentum has formed a sac extending in front of the transverse colon. Fusion of the dependent walls obliterates most of the lower recess. Only the superior cavity behind the stomach and in front of the colon remains. The name gastrocolic ligament applies only after the posterior layer fuses with the colon.
- Parts of the liver and diaphragm touch directly, barren of peritoneum: the bare area. Its margins are the falciform, coronary and triangular ligaments. Elsewhere the two serous surfaces lie apposed with a potential space between. That potential space may fill with fluid or a suprahepatic abscess. The falciform ligament divides it into right and left suprahepatic spaces. These spaces matter as much to the radiologist as to the surgeon.
- It lies between diaphragm and the anterosuperior surface of the liver. That surface includes the right lobe and the medial segment of the left lobe. Its medial boundary is the falciform ligament. Posteriorly it is bounded by the right anterior coronary and right triangular ligaments. Inferiorly the boundary is the liver itself. It opens into the general peritoneal cavity anteriorly and inferiorly.
- Right suprahepatic and subhepatic spaces in parasagittal section
- It lies between diaphragm and the superior surface of the lateral segment of the left lobe. It also relates to the fundus of the stomach. Medially it is bounded by the falciform ligament. Posteriorly by the left coronary and triangular ligaments. Anteriorly and laterally it communicates with the infrahepatic space and general cavity. On the left the anterior and posterior leaves of the coronary ligament lie in apposition.
- Left suprahepatic and subhepatic spaces in parasagittal section
- Each suprahepatic space may be divided into anterior and posterior portions. The distinction is unimportant in the absence of disease. On the right, an abscess may form anteriorly, just beneath the sternum. Or it may form at the reflection of the anterior leaf of the coronary ligament. The single anatomical space is then divided by pseudomembranes into two. Large left-sided collections may extend into the subhepatic space.
- Abscess in the anterior right suprahepatic space
- Abscess in the posterior right suprahepatic space
- Abscess in the anterior left suprahepatic space
- Abscess in the posterior left suprahepatic space
- Localisation, extension and size determine the approach. Surgeon and radiologist must jointly assess anatomy altered by membranes and pressure. The anterior approach beneath the costal margin has no anatomic complications. A posterior approach must be at the level of the spinous process of the first lumbar vertebra. That level avoids entering the pleura. Do not open the bed of the twelfth rib.
- Nowak et al. advocated a dorsolateral approach to the left subphrenic area. The same route reaches the omental bursa and the tail of the pancreas. It is useful for drainage of a left-sided pancreatic abscess in acute pancreatitis. It may be used by surgeon or by radiologist. The approach does not violate the peritoneal cavity. It provides dependent drainage in the recumbent patient.
- Also called the subhepatic space, hepatorenal space or pouch of Morison. Bounded superiorly and anteriorly by right lobe, medial segment of left lobe and gallbladder. Superiorly and posteriorly by the posterior coronary and right triangular ligaments. Inferiorly it opens into the general peritoneal cavity. It is partly bounded below by the hepatic flexure and transverse mesocolon. Medially it is bounded by the hepatoduodenal ligament.
- Abscess relations in the right infrahepatic and subhepatic spaces
- Quadrangular space of Mitchell is bounded above by the quadrate lobe. Below by the transverse colon, on the left by the falciform ligament, on the right by the gallbladder. The left infrahepatic space divides into a small antegastric space and the lesser sac. The anterior space lies between left lobe above and stomach below and behind. Boundaries are left lobe and anterior abdominal wall in front, stomach and lesser omentum behind. Inferiorly it is bounded by the middle third of the transverse colon.
- Abscess relations in the left infrahepatic space
- Two potential extraperitoneal spaces can harbour abscesses. On the right, the bare area of the liver. It is outlined by the falciform, coronary and triangular ligaments. On the left, a poorly defined space bounded by distal pancreas and descending colon. Also by the upper pole of the left kidney and the left adrenal gland. And by Gerota perirenal fascia and fat.
- Spread of fluid in the cavity follows a defined set of factors. Infection and metastatic seeding both follow transcoelomic patterns. Meyers found the pouch of Douglas most frequently seeded, at 50%. It is the most dependent part of the peritoneum. Mesentery of the small intestine was seeded in 40%, sigmoid mesocolon in 20%. The right paracolic gutter was seeded in 20% of cases.
- Mesenteric attachments and chief sites of peritoneal seeding
- Defined by bowel distension, oedema and intraperitoneal fluid collection such as exudate or blood. Packs left intentionally for tamponade, or accidentally, may also produce it. Raised abdominal pressure reduces pulmonary compliance by diaphragmatic compression. Renal dysfunction, hepatic and intestinal ischaemia and shock follow. It is defined by raised intra-abdominal pressure with raised airway pressures. Hypoxia, hypercarbia and oliguria or anuria complete the picture.
- Consequences of intra-abdominal hypertension
- Damage control is a staged approach replacing repair of all injuries at one operation. Phase one: immediate laparotomy for haemorrhage and contamination control, rapid closure. Phase two: continued resuscitation in intensive care. That corrects acidosis, coagulopathy and hypothermia. Phase three: definitive repair of all injuries after resuscitation. Ertel et al. recommended continuous urinary bladder pressure measurement in at-risk patients.
The omenta and the omental bursa
- Rutherford Morison developed the concept of the omentum as abdominal policeman. Its role shows both protection and brutality. Protection appears in inflammatory processes. Brutality appears in omental involvement in cancer, such as ovarian. There are two omenta, the greater and the lesser. The greater omentum is the embryologic home of spleen, pancreas and splenic vessels.
- Anson et al. studied 125 cadavers. The omentum could not be visualised in 19% of cases. It was a mere fringe in 2%. It extended 14.0-19.5 cm below the xiphisternal joint in 8%. It extended 20-36 cm below the xiphisternal articulation in the remaining 71%. In infancy it is small and poorly developed; adult width also varies widely.
- Liebermann-Meffert and White describe attachment to duodenum and ascending colon. Also attachment from the pyloric area only, to the stomach, and to the spleen. They also discuss the possibility of no attachment to those organs. It is unusual to find the greater omentum floating free. Attachments must usually be lysed for full mobilisation. Through a transverse or subcostal incision they are difficult to visualise and divide.
- The omentum is a transparent network with an excellent blood supply. Supply comes from the right and left gastroepiploic arteries. They anastomose to form the arc of Barkow through right and left epiploic branches. The arc of Barkow lies in the posterior omental layer. It is reinforced by anterior epiploic arches from both gastroepiploic arteries. Posterior epiploic branches from the pancreatic vessels also reinforce it.
- Arterial supply of the greater omentum
- Griffith advised ligating the anterior epiploic branches. Alternatively ligate the right gastroepiploic distal to the right epiploic origin. That preserves the arc of Barkow and fosters omental viability. The alternative is ligating the gastric branches to the greater curvature. The book's authors consider that alternative better and safer. Reason: most surgeons know gastroepiploic anatomy better than epiploic anatomy.
- The veins drain into the portal system. Whether omental blood supply is ever insufficient is unknown. Idiopathic infarction of the greater omentum has been reported by Skandalakis. Liebermann-Meffert and White describe two lymphatic draining pathways. One travels right toward the subpyloric nodes. The other travels left toward the splenic nodes.
- Lymphatic drainage of the greater omentum
- The omental bursa is a potential space behind the stomach. It divides into a vestibule and the bursa proper. The vestibule begins at the epiploic foramen. It is formed by the pancreaticogastric fold, containing the left gastric artery. A finger-breadth below lies the pancreaticoduodenal fold, containing the hepatic artery. The opening of vestibule into bursa proper is called the second epiploic foramen.
- Anteriorly bounded by lesser omentum, stomach and gastrocolic ligament. Posteriorly bounded by the retroperitoneal space. Roof formed by the caudate lobe of the liver. Also by the coronary ligament on the right and the abdominal oesophagus on the left. Floor formed by transverse colon and mesocolon. The peritoneum from spleen to posterior wall over the pancreas is primitive dorsal mesogastrium.
- The omental bursa
- Omental Angiogenesis
Histology, physiology and peritonitis
- Loose connective tissue plus flat mesothelial cells form the histologic pattern. The mesothelial covering resembles vascular endothelium. Both parietal and visceral parts share the same structure. Each is a basement membrane covered by a single layer of mesothelial cells. Loss of these cells produces nonphysiologic adhesions between the two parts. Omenta and mesenteries share the same microscopic network.
- The cavity contains approximately 50 ml of isotonic fluid. That fluid contains approximately 300 mononuclear cells. Composition is water, proteins, electrolytes and diverse cell types. Cells include mast cells, fibroblasts, lymphocytes, macrophages and leucocytes. The fluid lubricates movement of viscera against each other and the wall. Parietal peritoneum is loosely attached to preperitoneal fat; visceral is fixed to subserosa.
- Golden and Shaw showed the fluid volume rises during inflammation. Cell numbers rise to approximately 3000. Neutrophils predominate in that rise. With abnormal collections, absorption is limited in the lower abdomen. Absorption is more active in both subphrenic spaces. That reflects specialised subphrenic peritoneum with stomata and slitlike orifices.
- The peritoneum may clear bacteria within minutes by an unknown mechanism. It may also rapidly transport bacteria into the circulation via the diaphragm. That may produce bacteraemia. Sinanan: abscess formation is the final defence of this membrane. It occurs when cellular, humoral and clearance mechanisms are overwhelmed. Milky spots are dense aggregations of macrophages, lymphocytes and monocytes.
- The peritoneum in gastrointestinal disease
- Causes and origins of peritonitis
- Bacterial counts along the gastrointestinal tract
- Classification According to Etiology
- Classification According to Etiology (continued)
- Classification According to the Spread of Infection
- Recurrent or persistent intraperitoneal infection can occur despite good treatment. It follows adequate treatment of primary or secondary peritonitis. Nathens et al. reported tertiary peritonitis may develop in 74% of patients. Commonest organisms are Enterococcus and Candida. Also Staphylococcus epidermidis and Enterobacter. The same authors regard it as more a reflection than a cause of adverse outcome.
Internal abdominal hernias
- The sac lies behind the superior mesenteric or the ileocolic artery. It sits at the base of the mesentery, the mesentericoparietal fossa of Waldeyer. The mouth of the sac opens to the left. The sac is directed to the right in the retroperitoneal space. It lies behind the right or the transverse mesocolon. Ring: duodenum superiorly, SMA or ileocolic artery anteriorly, vertebrae posteriorly.
- Right paraduodenal hernia
- The mouth usually lies behind the inferior mesenteric vein and the left colic artery. It is situated at the duodenojejunal flexure. The mouth opens to the right. The sac is directed to the left in the retroperitoneal space behind the left mesocolon. A downward incision of the ring avoids injury to the inferior mesenteric vein. Finck et al. used laparoscopy to diagnose and treat a congenital left paraduodenal hernia.
- Left paraduodenal hernia
- Constant sites of paraduodenal herniation
- The ring of a transomental hernia is formed of omentum. A blood vessel usually forms one margin of the defect. Partial or total omentectomy is the procedure of choice. The defect may be congenital or acquired. Greater omental defects are the symptomatic ones. The apron hangs over small bowel, so a loop can fall through it.
- Transomental hernia through a defect in the greater omentum
- Occurs through rents in the mesentery, transverse mesocolon or sigmoid mesocolon. A branch of the superior or inferior mesenteric artery forms one or more edges. Most mesenteric defects lie between the ileocolic trunk and the last ileal branch of the SMA. In the transverse mesocolon most lie between the middle and left colic vessels. Traumatic transmesenteric hernia may present as strangulated ileus. Small operative mesenteric holes should be closed, or else widely opened.
- Transmesenteric hernia through the sigmoid mesocolon
- Intestinal loops are present in about two-thirds of such hernias. Cecum and right colon are present in one-third. The transverse colon is occasionally present. Nagayoshi and Nakashima described a retrogastric colon mimicking this hernia. The neck must not be incised: many nearby structures are subject to injury. The hepatogastric omentum may be incised to decompress the proximal loop.
- Structures surrounding the foramen of Winslow
- Herniation into the lesser sac through the foramen
- Classification of these hernias is genuinely confused in the literature. All start in the supravesical fossa, but their subsequent course varies. Keynes, Adler and others used prevesical, paravesical and retrovesical. Burton used prevesical, supravesical and paravesical, excluding retrovesical. The text classifies by course in front of, beside, or behind the bladder. Invaginating and posterior supravesical hernias are extremely rare.
- Courses of the internal supravesical hernia
- Supravesical hernias
- Landmarks of the spaces around the bladder
- Anterior compared with posterior internal supravesical hernia
- Invaginating anterior internal supravesical hernia
- Pathways of posterior internal supravesical hernia in men
- Pathways of posterior internal supravesical hernia in women
- Estrada described six fossae related to the cecum; the text describes three. Superior ileocecal fossa: key boundary is the ileocolic or ileocecal fold. That fold contains the anterior branch of the ileocolic artery; the sac runs under the right mesocolon. Inferior ileocecal fossa has a prominent ileoappendicular fold. That fold occasionally contains the ileoappendicular artery; the sac may lie under the cecum. Paracolic fossa lies at the right gutter from nonfusion of the ascending colon.
- The broad ligament is the triangular mesentery of uterus, tubes and ovaries. It extends from each lateral uterine side to the lateral pelvic wall. Upper free part relates to tubes as mesosalpinx and ovaries as mesovarium. The lower fixed part attaches to levator ani through the cardinal ligament. It has thin vascular areas, or defects, through which a viscus may pass. The cause of this rare hernia is unknown, as with other mesenteric defects.
- Repair of a hernia through the broad ligament
- Falciform ligament runs from umbilicus to the superior surface of the left lobe. It separates the lateral and medial segments of the left lobe. Its free edge contains the cordlike round ligament, the left umbilical vein remnant. That remnant is often patent for much of its length. A defect in the mesentery of the falciform ligament may produce a herniation. Reduction is by proximal and distal ligation, then incision of falciform and round ligaments.
- Repair of a hernia through the falciform ligament
- These are iatrogenic hernias occurring after operation. They follow gastrojejunostomy, retrocolic or antecolic. After a retrocolic gastrojejunostomy a ring is formed at the mesocolic defect. That ring should not be incised; reduce by enterostomy, then close the ring. After an antecolic gastrojejunostomy the ring forms where the afferent loop meets the stomach. No incision should be made; close the ring after reducing the herniated loop.
- Repair after retrocolic gastrojejunostomy
- Repair after antecolic gastrojejunostomy
Surgery of the peritoneum and omenta
- The site may be determined after a sonogram or a CAT scan. Usual sites are the four quadrants, either flank, or the midline below the umbilicus. It must be performed under absolutely sterile conditions to avoid peritonitis. Some surgeons give antibiotics for that purpose. The needle can puncture the intestine. That is not usually dangerous, because the needle hole seals itself.
- Sites of abdominal paracentesis
- The results of paracentesis require careful evaluation. A negative tap gives no information. Unclotted blood signals intraperitoneal bleeding. Clotting blood suggests aspiration from a blood vessel in the abdomen or wall. That is not uncommon in obese patients. Ultrasonography-guided paracentesis is now the procedure of choice.
- Fluid from intraperitoneal spread of intra-abdominal cancer is malignant ascites. The term applies when neoplastic cells are identified. Treatment is extensive surgical debulking, that is cytoreductive surgery. That is followed by local or systemic chemotherapy, hyperthermia or phototherapy. Ross et al. advocated sonographically guided paracentesis for short-term relief. Jennings et al. recommended paracentesis through the umbilical ring in ectopic pregnancy.
- The needle is inserted at the posterior fornix into the cul-de-sac. That is the rectovaginal pouch of Douglas. It should not be performed after vaginal or abdominal hysterectomy. Nor after low anterior rectosigmoid resection. It should not be attempted if the intestines are distended. Other contraindications are the same as for abdominal paracentesis.
- Exploration defines the limits of known disease and finds unsuspected disease. Not every patient with an abdominal complaint can or should be fully explored. The incision may be too small, as for appendicitis. There may be extensive adhesions, or the patient may be too ill. Peritoneal pus or fluid collections contraindicate further exploration until drained. Common sense dictates when to explore and when not to.
- Bassett described regional, systemic and circular sequences. First inspect the abdomen for obvious pathology needing immediate treatment. Also for pathology contraindicating further exploration. Then pull the transverse colon downward and examine from right to left. Include right kidney and adrenal, foramen of Winslow, common bile duct, gallbladder, right lobe. Then duodenum, pancreas, left lobe, pylorus, lesser curvature, fundus, spleen, left adrenal.
- Pull the transverse colon upward and examine the infracolic region right to left. Cecum and appendix, right colon and hepatic flexure, right retroperitoneum and lower renal pole. Third and fourth parts of duodenum and superior mesenteric artery, small intestine and mesentery. Tail of pancreas, left kidney, aorta and left retroperitoneum, left colon, splenic flexure, sigmoid. Then the pelvis: sigmoid, rectum and uterosacral ligaments, uterus, tubes and ovaries. Also pelvic wall, inguinal and femoral regions, and iliac vessels.
- Multiple organ dysfunction syndrome questions the value of relaparotomy for persisting sepsis. Koperna and Schulz: aggressive surgical treatment has reached its limit in some patients. Those are patients whose source could not be controlled at the initial operation. To improve survival, the decision to reoperate on demand must be made within 48 hours. It must at least be made before MODS emerges. Bassett's goal: gentleness, accuracy, thoroughness and speed.
- Laparoscopy is now used as a diagnostic procedure for peritoneal exploration. Muensterer et al.: biopsy of peritoneal nodules establishes a histologic diagnosis. They warned that port sites must be excised to prevent dissemination of malignancy. Estrada Saiz et al. found it useful in diagnosing primary peritoneal mesothelioma causing ascites. Ditmars and Bongard concluded it is valuable for triage of penetrating trauma. Maffei Faccioli et al. used laparoscopy and peritoneal wash in staging pancreatic carcinoma.
- All adhesions, congenital, postoperative or post-irradiation, should be treated with care. Transparent adhesions should be incised carefully to protect the serosa. Thick adhesions should be cut between two clamps with both parts ligated. Morgenstern et al. advised lysis of radiation adhesions only when absolutely necessary. Minute openings into the intestine can lead to perforation or fistulae. Performing a bypass or a resection is a wise decision in that setting.
- The omentum may protect sutured intestinal anastomotic lines. It may occasionally close perforations of the gastrointestinal tract. It is used to wrap anastomoses and cover perforated duodenal ulcers. It fills large cavities after evacuation of hepatic or splenic cysts. Kuroyama et al. advised early single-stage omental transposition for sternomediastinitis. Ovnat et al. used omentopexy for recurring lymphoceles after renal transplantation.
- Goti et al. presented laparoscopic treatment of idiopathic segmental infarction. Segmental infarction may be caused by torsion of the omentum. A case of omental torsion has been reported in pregnancy. Al-Husaini et al. advised a high index of suspicion for primary omental torsion. That applies when a small right lower abdominal incision reveals a normal appendix. Especially in the presence of free intraperitoneal serosanguinous fluid.
- The peritoneum heals very rapidly, restoring large defects within hours or days. Differentiated stem cells in subperitoneal tissue may be responsible. Transperitoneal migration and ingrowth of mesothelial cells may also contribute. Adhesions are formed by a delay in peritoneal healing. Mazier et al. found no difference between primary pelvic peritoneal closure and no closure. Spernol et al. and Nagele et al. strongly advocated leaving the pelvic peritoneum open.
Anatomic complications
- Anatomic complications of peritoneal procedures: vascular and nerve injury
- Anatomic complications of peritoneal procedures: organ injury and inadequacy
- Peritonitis is the single unifying complication of intraperitoneal procedures. Inflammation may be sterile from leakage of bile, pancreatic juice or blood. It may be septic from contamination by aerobic or anaerobic bacteria. It is a possible sequel to any intra-abdominal procedure, clean or contaminated. Perforation peritonitis is the most common form of acute intra-abdominal infection. Peritonitis is also a major complication of peritoneal dialysis.
- The text declines to enter the irrigation and drainage controversy. Cruse and Foord studied over 23,000 surgical wounds in Calgary. Two studies indicate drainage is unnecessary in uncomplicated cholecystectomy. Hunt compared no irrigation, intraoperative irrigation, and intraoperative plus postoperative. He found no significant mortality difference among the three groups of 44 patients. Mortality doubles, or more than doubles, with increasing age.
- the Prevention of Peritonitis
- Bleeding may follow injury to superior or inferior epigastric vessels. Or to intra-abdominal vessels of omentum, mesentery or pelvic region. The result is a haematoma within the cavity or the abdominal wall. Slight discomfort may follow injury to branches of the 9th to 12th spinal nerves. Puncture of intestine, gallbladder or bladder is always possible. Empty the bladder to minimise the chance of puncturing it.
- Injury to the liver during paracentesis resembles that from liver biopsy. Bleeding from the spleen and splenic rupture are both possible. An ovarian cyst may be injured. Bleeding or even carcinomatosis may follow rupture of a malignant cyst. Roberts and Athey reported six occurrences of air in the myometrium after culdocentesis. Dicker et al. reported 14 severe abdominal complications in 3,656 oocyte retrievals.
- Failure to find or recognise pathology is itself an inadequate procedure. Cutting folds and bands mistakenly thought bloodless can cause haemorrhage. Traction on the spleen occasionally leads to rupture. The lower pole is often joined to the gastrocolic ligament by an accessory ligament. Morgenstern called that band the criminal fold; traction on it tears the spleen. Van Garderen et al. reported necrosis and infarction of pedicled omental flaps.
Consolidation
- Ventral mesentery exists only above the umbilicus; everything else is dorsal. The foramen of Winslow is the only communication between greater and lesser sacs. The right paracolic gutter reaches the diaphragm; the left is dammed by the phrenicocolic ligament. There is no right phrenicocolic ligament. Parietal peritoneum is somatic and localises pain; visceral responds only to stretch and ischaemia. The pouch of Douglas is the most dependent recess and the commonest seeding site.
- Never incise the neck of a hernia at the foramen of Winslow. Incise a paraduodenal ring downward: IMV on the left, SMA or ileocolic on the right. Close mesenteric defects, or open them widely; never leave them partly closed. Approach perihepatic collections at the L1 spinous level; never transpleural. Enter the lesser sac through the avascular fusion plane, freeing omentum left to right. Identify the left ureter before dividing anything at the base of the sigmoid mesocolon.
- Sources cited in the text
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- Sources cited in the text (continued)
- Skandalakis' Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery
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