SPLEEN, OMENTAL BURSAE AND INTESTINES kenn.pptx

SURGICAL ANATOMY OF OMENTAL BURSA , INTESTINE AND SPLEEN

1. SPLEEN, OMENTAL BURSA AND INTESTINES PRESENTER: DR HESBON M. KENNETH UNIVERSITY OF NAIROBI DR ILYAS QASSIM

2. OBJECTIVES/OUTLINE Development and Anomalies Anatomy review blood supply lymphatic drainage Surgical anatomy Anatomical considerations in surgery

3. SPLEEN Galen called it ‘Organ of mystery’ Hippocrates ‘source of black bile’ Largest lymphoid organ Function Remove worn-out RBCs Manufacture RBCs in fetal life and lymphocytes Immunity body immunoglobulin Store RBCs and release circulation when required

4. Position and dimensions Located in upper left quadrant of abdomen. Lies under the diaphragm The Harris’s dictum of odd numbers. 1, 3, 5, 7, 9, 11 1 inch in thickness 3 inches in breadth, 5 inches in length, weighs 7 oz, (150gm) lies deep to 9, 10, and 11 ribs along midaxillary line. Weight decreases with age. Surface anatomy: long axis corresponds with the surface of the 10th rib, upper board (9th rib), and lower board (11th rib).

5. Posterior view and Shapes

6. External features 3 Borders superior, inferior and intermediate. 2 Surfaces Diaphragmatic and visceral. 2 Ends Anterior and posterior. 2 Angles Anterobasal and posterobasal. Clinical angle- anterobasal 1 hilum, at an angle between the stomach and left kidney Anterior border is notched

7. Peritoneal relations Lies in the left margin of lesser sac below the diaphgram Visceral peritoneum invest in all surfaces Peritoneal reflection form Gastrosplenic ligament Splenorenal ligament Phrenico-colic Phrenicosplenic Ligament

8. Visceral relations Concave visceral surface oriented towards other abdominal organs Renal impression Gastric impression Colic impression Splenic hilum – pancreatic tail impression

9. Visceral relationship

10. Arterial Supply Tortuous Splenic artery arising from the coeliac trunk. Through the lionerenal ligament, gives branches at the hilum of the spleen. Divides into superior and inferior with an avascular plane in between. The two do not anastomose and hence relevant in resection.

11. Splenic artery variation

12. Circulation concept Closed circulation Continuity of epithelium from arterioles to sinusoid, without leaving the vascular system into venous system Open circulation Blood empties into cords of billroth in red pulp, through sinusoidal spaces and re-enters the vasculature through sinusoida walls

13. Venous Drainage

14. Lymphatics are confined at the capsule, trabeculae and visceral peritoneum. These drain along the splenic vessels into the pancreaticolieal lymph nodes. Nerve supply S ympathetics from coeliac plexus.

15. Spleen

16. Development of the spleen Begins developing at the 5 th week. Condensation of mesenchymal cells located between the layers of the dorsal mesogastrium. Capsulin , NKx2-5, Hox 11 and Bapx1 regulate its development. Fetal spleen is lobulated, but the lobules disappear before birth. The adult notches are remnants of the grooves that separated the lobules. The mesenchymal cells differentiate to form the capsule, CT and parenchyma,

17. Development of the spleen

18. Development of the spleen Rotation of the stomach in a 90 degree clockwise direction causes fusion of the mesogastrium with peritoneum over the left kidney. As a result Splenorenal ligament acquires a dorsal attachment. Splenic artery follows a tortuous course posterior to the omentum and anterior to the left kidney.

19. Derivatives of mesogastrium

20. Accessory Spleens Remnants of splenunculi that do not fuse with the primary gland. Occur in about 20% of the population, rarely larger than 2cm Fully functional Commom site ar e Hilum of spleen 50% Splenic vesse Tail of pancreas Ligament of spleen Mesocolon Greater omentum Considered in splenectomy.

21. Others congenital anomalies Asplenia Asplenia may be associated with several other congenital anomalies. Asplenia is autosomal recessive, while splenic hypoplasia is autosomal dominant. Polysplenia Polysplenia may be associated with several other congenital anomalies. It is distinct from accessory spleen, in which the normal spleen is present Wandering spleen error in the embryologic development of the spleen's primary supporting ligaments, excessive splenic mobility

22. Splenomegaly Normal spleen is not palpable. Splenomagally results into a palpable spleen below the costal margin, usually double the size by this time. Spenomegally versus kidney Downwards and medially. Splenic notch. No colonic resonance Causes of massive splenomegaly are; Malaria (TMS) Liver cirrhosis Chronic myeloid leukemia Leishmaniasis.

23. Splenic Injury Protected behind ribs 9-11. M ost commonly injured solid abdominal organ trauma. Presents with shock Kehr’s sign - pain in the left shoulder 15mins after limb elevation, clot collected under the diaphragm irritated, phrenic nerve causing referred in pain Balance’s sign- dullness in the left flank which does not shift Causes mortality (up to 14% of cases). Gland preservation when possible.

24. Splenic injury Vascular injuries e.g. active splenic bleeding, pseudo aneurysm and arteriovenous fistula are associated with increased rates of unsuccessful non surgical treatment. Multidetector CT scanning plays a critical role in diagnosing splenic injury in a hyamodynamically stable patient. Major CT findings in splenic injuries encompass lacerations, sub capsular and parenchymal hemorrhage, active hemorrhage and vascular injuries.

25. Splenic injury Active hemorrhage appears as an area of high attenuation on CT due to extravasation of contrast. Sub capsular hematoma appear as elliptical collection between the splenic capsule and the parenchyma. Also present is flattening of the underlying splenic margin.

26. Splenectomy Surgical removal of the spleen by essentially cutting the two pedicles. Indications Medical conditions leading to massive splenomegally and sequestration. Rupture following trauma or iatrogenic injury. Neoplasms Infections Attempts to restore the organ’s immune functions are done through immunization against encapsulated organisms Strep pneumonia, N meningitides and H influenza. .

27. Splenectomy Laparascopic approach Standard laparoscopic approach. Open approach Extended midline Left subcostal incision.

28. Step 1:  Dissection of the inferior aspect of the spleen Step 2:  Dissection of the lateral and retroperitoneal attachments. Step 3:  Transaction of the splenic hilum. Step 4:  Dissection of the short gastric vessels. Step 5:  Removing the spleen.

29. Major complications of splenectomy Injury to surrounding structures. Bleeding- elective vs emergency. Sub phrenic abscess. Thromboembolic complications. Splenosis . Missed accessory spleen. Overwhelming post-splenectomy sepsis. Conversion from laparoscopic to open.

30. OMENTAL BURSA Multiple names Lesser sac Epiploic bursa Bursa epiploica Lesser posterior intraperitoneal compartment Is a diverticulum of peritoneal cavity behind the stomach. It communicates with the greater sac through a slit-like aperture called epiploic foramen (or foramen of Winslow).

31. Boundaries of lesser sac Anterior wall Caudate lobe of the liver Posterior layer of lesser omentum Peritoneum over the posterior aspect of stomach The posterior of the two layers of greater omentum Right border Epiploic foramen Posterior wall Posterior layers of greater omentum , and the peritoneum that covers pancreas, left kidney, left suprarenal gland, commencement of abdominal aorta, coeliac artery and part of diaphragm Left border Splenorenal and gastrosplenic ligament

32. Boundaries and recesses

33. Subdivision of lesser sac Superior recess- upward behind the liver Inferior recess- Between the two layers of the greater omentum . Splenic recess- Between the gastrosplenic and lienorenal ligaments.

34. Communications Greater sac via foramen of Winslow located at T12 level.

35. Development

36. Surgical Anatomy/Relevance Internal hernia loops of intestines may herniate through the foramen of Winslow. Free boarder of the lesser omentum and structures to be protected. Can be pushed at Anterior 2 layers of the greater omentum . Transverse mesocolon. Pancreatic pseudocyst inflammation of pancreas Posterior gastric ulcer perforation into the lesser sac, collection of pass, general peritonitis, spread through foramen of winslow

37. Surgical relevance Internal hernia -Loop of bowel through the foramen, becomes strangulated. -NB: the boundaries of the foramen of winslow cannot be incised. -The bowel can be compressed by a needle to allow its reduction Pringle manoeuvre Compression of hepatic artery between fingers within the foramen. When the cystic artery is torn during cholecystectomy

38. Surgical approaches to lesser sac Opening hepatogastric ligament Through gastrocolic and gastrosplenic ligament (Above approaches for upper GI surgery) e.g Fundoplication Opening transverse mesocolon at the level of the pancreas- in colorectal surgery for mobilization of splenic flexure

39. Intestines Small intestines Part between pylorus and ileocaecal juction spanning over 6m. Divided into Duodenum- proximal, retroperitonel and fixed. Small intestines proper jejunum ileum From the duodenojejunal flexure to the ileocaecal junction. Upper two-fifth: jejunum. Lower three-fifth: ileum. Large intestines Part between ileocaecal junction and anus spanning 1.5m. Has Fixed parts Caecum Ascending colon Descending colon Rectum Anal canal Appendix Transverse colon Sigmoid colon

40. Layers-small intestines Mucosa with its modifications to increase SA Plicae circulares (or valves of Kerckring)- permanent circular folds. Villi- small finger-like projections on the surface of circular folds. Microvilli- the striated border covering the villi. Submucosa containing loose areolar tissue, blood vessels, lymph vessels, and Meissner’s nerve plexus. Muscle Layer with an outer longitudinal and inner circular layers and an intervening Auerbach’s nerve plexus. Serosa mainly comprising of visceral peritoneum.

41. Modifications In the large intestine there are no villi and plicae circulares, only glands (crypts) containing a high proportion of goblet cells. Muscular layer arranged into thicker taeniae coli, appendices epiploicae and haustra. In the upper part of the anal canal , the columnar epithelium gives place to the stratified squamous type. In the appendix the glands are rather shallower and less closely packed than in the rest of the large intestine, and there are numerous lymphoid follicles in the mucosa and submucosa. No appendices epiploicae.

42. Caecum Blind sac at the proximal large intestines below the level of ileal opening. Communicates with the colon, appendix and terminal ileum. Relations Anterior- small intestines, greater omentum and ant abd wall. Posterior Right psoas major,iliacus muscles. Femoral nerve, lateral cutaneous nerve of the thigh Genitofemoral nerve of the right side Right gonadal vessels Retrocaecal recess with appendix

43. Folds and recesses Superior ileocaecal fold/vascular fold: ileum and the ascending colon. raised by the anterior caecal artery. superior ileocaecal Inferior ileocaecal fold/ bloodless fold of Treves anteroinferior ileum to the caecum or appendix. ileocaecal recess which looks. Caecal fold posterior surface and forms the right boundary of the posterior ileocaecal recess.

44. Vermiform Appendix Worm like extension of the caecum 2 cm below the ileocaecal junction. 9cm (2-20cm) long by 5 mm width (Longer and thicker in children). Has a base, body and tip. The base has surgical importance surgeons guide- convergence of the caecal taeniae. surface anatomy for pain locatization in diagnosis. Located at a point 2 cm below the intersection of the transtubercular plane and the right midclavicular line (right lateral plane) NB: not McBurney’s. Stump appendicitis Suspended via its mesentry; the mesoappendix containing the appendicular artery along its free border.

45. Positions

46. Sigmoid mesocolon Triangular ( inverted V )fold that suspends sigmoid from pelvic wall. Apex lies at the division of LT common iliac artery. Intersigmoid recess is located at the apex; lateral and upward extension and the left ureter lying behind this recess. Lt limb of V is attached along the upper half of the left external iliac artery. Rt limb extends downward and medially up to S3 vertebra. Sigmoid volvulus Redundant long sigmoid loop Long narrow sigmoid mesocolon

47. SIGMOID MESOCOLON

48. Development Gastrulation and formation of the three germ layers. Each contributes to formation of bowel endoderm- epithelial layer of the intestinal mucosa and glands of the tract. mesoderm- forms the muscular layer and the lamina propria. Also submucosal connective tissue and blood vessels. ectoderm- Edges i.e. mouth and anal lining. Also creates the enteric nervous system which develops from neural crest cells. By the 4th week, the primitive gut tube, the endodermal layer recruits the splanchnopleuric mesoderm which goes on to become the bowel mesentery, connecting the gut tube posteriorly in the embryo.

49. Just before the sixth week of embryonic life the alimentary canal is a simple tube passing through to the hind end, its whole length supported by a dorsal mesentery attached in the midline in front of the aorta. Three gut arteries leave the aorta and pass ventrally to supply the tube. The most cranial passes in the dorsal mesogastrium to supply the foregut, coeliac trunk. T he next passes through the dorsal mesentery to supply the midgut , the superior mesenteric. T he last passes through the dorsal mesocolon to supply the hindgut , the inferior mesenteric.

50. Herniation Small and large intestines undergo rapid growth during weeks four and five of development. The enlarging intestines quickly outgrow the space available in the abdominal cavity causing the entire midgut to herniate into the umbilical cord forming a loop. Superior limb- ileum and inferior limb- colon. Vitelline duct connects intestines to the yolk sac.

51. Rotation and return of the midgut Intestine rotates ninety degrees counterclockwise around the mesentery causing; the proximal loop migrates from the superior position to the right side. the distal portion of the loop migrates from the inferior position to the left. At week ten, the bowel retracts back into the abdominal cavity where it rotates one hundred and eighty degrees more counterclockwise. The cecum is now in the right upper quadrant of the abdominal cavity. Enlargement of the large intestine pushes the cecum down into its final position in the right lower quadrant.

52. Return Distal midgut swings to the right and mesentry fuses with parietal peritoneum. Hindgut swings to the left and mesentry fuses to with the parietal peritoneum. Line of Toldt- white, vessels anterior to it. plane of dissection in surgical mobilization.

53. Week Key Events 4 Primitive gut tube forms; connected to yolk sac 5 Gut elongation; early organ differentiation 6 Midgut loop forms; herniates into umbilical cord 7–8 90° rotation; villi begin; lumen forms 9–10 Total 270° rotation; intestines return to abdomen 11–12 Cell differentiation; villi/crypts mature; peristalsis begins 13–27 Rapid growth; meconium forms; enzyme production starts 28–40 Maturation; motility; prep for feeding

54. Diagram illustrates the intestinal rotation of embryological development. The red arrow represents the axis of the superior mesenteric artery. Blue circle represents the physiological hernia. a Primitive intestinal loop in the 6th week of fetal life. b Eighth week of fetal life, development of cecal bud (yellow). The first rotation of 90° is counterclockwise (gray arrow). c In the 9th week a second rotation occurs, during the reintegration of the digestive tract in the abdominal cavity, of 90° counterclockwise, toggling the third duodenum behind the superior mesenteric artery. d A third rotation of 90° counterclockwise occurs at the 12th week of fetal life, positioning the cecum in the right iliac fossa. e Complete intestinal rotation

55. Toldt’s plane/fascia Not just a plane but a structure with defined thickness. Between mesocolon and retroperitoneum. Contains loose fibrous tissue and minute vessels present. Surgical dissection within for Colorectal surgery. (Liang et al., 2019) and ( Culligan et al., 2014)

56. Fusion fascia of Fredet The plane between the ascending mesocolon and the visceral duodenal-pancreatic peritoneum. Medial extent is vascular SMV/ trunk of Henle Not extensively studied and applied. Relevance Minimally invasive D3-lymphadenectomy (D3-L). Complete mesocolic excision (CME)

57. Blood supply

58. SMA

59. Anastomosis; Small intestines 12-15 jejunal and ileal branches arise from the convex aspect of the SMA and traverse the two layers of the mesentry. Branch and anastomose to for arterial arcades . These arcades form even more branches up to the fifth tier. The arcardes are more complex in the ileum. Straight arteries i.e. vasa recta emerge to supply the small intestines. more and longer in jejunum

60. Anastomosis; colon Marginal Artery of Drummond A circumferential anastomotic arterial channel extending from the ileocaecal junction to the rectosigmoid junction. 3 cm to inner margin of the colon. Arises from anastomoses of the SMA and IMA branches. Critical point of the colon Poor development of the anastomosing branches Left branch of middle colic and ascending branch of Left colic. Replaced by arc of riolan from middle colic. Griffins point . Sigmoidal branches of inferior mesenteric and superior rectal arteries; critical point of Sudeck .

61. SMA variations Multiple variations in origin and branching system. Unusual origin of right hepatic artery Celiomesenteric trunk (2%) Branching system Pattern I- independent origin of the three main branches Pattern II- common trunks of origin: Pattern IIa, common trunk between RCA and MCA Pattern IIb, common trunk between RCA and ICA. Pattern IIc, common trunk for the three main branches. Pattern III Absence of RCA Pattern IV Presence of accessory arteries

62. IMA variant anatomy Origin is less variant but branching system has several variations. Branching with a colo-sigmoid trunk Branching with recto-sigmoid trunk Common trifurcation.

63. Venous flow SMV Begins as small veins of the ileocaecal region. Follows SMA branches remaining to its right. Drains to the portal vein. IMV Continuation of superior rectal vein. Remains lateral to the artery. Anterior to the left renal vein and joins splenic vein.

64. Gastrocolic Trunk of Henle Vascular structure formed by the superior right colic vein joining the right gastroepiploic vein and the anterior superior pancreaticoduodenal vein. Has multiple variations. Surgical landmark in colorectal surgery.

65. Nerve supply Via the Enteric nerve plexus comprising of The myenteric plexus (of Auerbach) situated between the two muscle layers of the gut. Submucous plexus (of Meissner) is in the submucosa. Has both Postganglionic sympathetic (inhibitory) Preganglionic parasympathetic (excitatory) fibres Stimulate the peristalsis and are inhibitory to the sphincters.

66. Lymphatic flow Small intestine Circular fashion- Circular tuberculous ulcers may heal with constrictions Follow SMA branches and drain to the superior mesenteric nodes. Can be mural, intermediate or aortic Lymph nodes of the large intestine have been divided into four groups Epicolic (under the serosa of the wall of the intestine) Paracolic (on the marginal artery) Intermediate (along the large arteries [superior and inferior mesenteric arteries]) Principal (at the root of the superior and inferior mesenteric arteries).

67. Lymphatic spread of Ca colon

68. Carcinoma Staging based on LN involvement. Wide resection of the colon should include the entire segment supplied by a major artery. This will also remove most, but not all, the lymphatic drainage of the segment . I leocecal artery always arises from the superior mesenteric artery and lymph node metastases of cecum cancer a re limited to nodes along the ileocolic artery, cecum cancer can be cured by ileocecal resection . The lymphatic vessels of the distal 2 cm of the anal canal drain to the inguinal nodes .

69. Colectomy Right Hemicolectomy –Terminal Ileum prox part of T.colon ; ligate ileacolic and rt col art near SMA Transverse colectomy- Rt and lft colic flexures, remove transverse mesocolon, g. omentum; ligate middle colic art Left Hemicolectomy- Lft end of T colon, part of sigmoid colon. Ligate lft colic and upper sigmoid vessels Sigmoid colectomy- Lower d.colon to rectum, ligate lft colic and sigmoid vessles

70. Mesocolic Excision

71. Complete Mesocol ic Excision (CME) Inspired by total mesorectal excision (TME) benefits and improved rectal ca outcomes. Same principles that requires En bloc removal of sufficient colon length with intact mesocolon. Extended lymphadenectomy. High ligation of vessels. Increased risks due to surgical dissection involved. (Koh and Tan, 2019)

72. Complete Mesocol ic Excision (CME) Hohenberger’s description of CME involves three key components, namely . Sharp dissection in the embryologically plane to remove an intact envelope of mesentery together with the corresponding lymphatic drainage(Holy Plane) Central Vascular Ligation ( CVL ) to remove apical lymph nodes and; Resection of a sufficient length of bowel. The main benefit of CME lies in the increased number of lymph node yield. (Koh and Tan, 2019)

73. Superior Mesenteric Artery Syndrome Caused by trapping of the 3 rd part of the duodenum between SMA and aorta. SMA normally leaves the aorta at an angle of 50 -60 degrees. The distance between the two vessels is 10-20mm. In SMAS, the degrees is about 20. Acute loss of mesenteric fat is the main cause of SMA dropping posteriorly.

74. Symptoms Intermittent partial UGIT obstruction. Epigastric bloating with cramps. Pain relieved by vomiting. Anorexia with pain leads to further wt loss.

75. Investigations Barium meal Large stomach with dilated bulb and 2 nd part of the duodenum. Knee chest positioning may cause the passage of barium to be suddenly unimpeded. CT abdomen. Angiography. Xray /endoscopy are often negative. High index of suspicion. Rx-division of the ligament of treitz with mobilization of duodenum -Bypass duodenojejunostomy.

76. Developmental anomalies: Meckel Diverticulum Most common congenital GI anomaly Remnant of omphalomesenteric /vitellointestinal duct that connects the yolksac with the primitive midgut. Normally obliterated in the 7th week of development but the failure results in diverticulum. Differential diagnosis for abdominal pain e.g. acute appendicitis with no gross inflammation noted on lap.

77. Omphalocele: T he intestines normally herniate outside the abdominal cavity and then return back inside. If they don't return by the 11th week of pregnancy, an omphalocele can develop.  Gastroschisis: The condition arises early development, when the abdominal wall fails to close properly. Umblical hernia. Malrotation. Aganglionic megacolon, Hirschsprung's (HIRSH- sproongz ) disease . Intestinal atresia/stenosis. Duplication.

78. Subhepatic appendix Subhepatic appendix Failure of the descent of the caecal bud resulting in a right hypochodrial location of the appendix. May mimic cholecystitis.

79. REFERENCES Wilson DJ, Bordoni B. Embryology, Bowel. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK545247 Culligan K, Walsh S, Dunne C, Walsh M, Ryan S, Quondamatteo F, Dockery P, Coffey JC. The mesocolon: a histological and electron microscopic characterization of the mesenteric attachment of the colon prior to and after surgical mobilization. Ann Surg. 2014 Dec;260(6):1048-56. doi: 10.1097/SLA.0000000000000323. Koh FH, Tan KK. Complete mesocolic excision for colon cancer: is it worth it? J Gastrointest Oncol. 2019 Dec;10(6):1215-1221. doi: 10.21037/jgo.2019.05.01. PMID: 31949942; PMCID: PMC6954997. Liang JT, Huang J, Chen TC, Hung JS. The Toldt fascia: A historic review and surgical implications in complete mesocolic excision for colon cancer. Asian J Surg. 2019 Jan;42(1):1-5. doi: 10.1016/j.asjsur.2018.11.006. Epub 2018 Dec 3. PMID: 30522847. Snell’s Clinical Anatomy by regions Vishram Abdomen and lower limb.