Equine Abdomen Anatomy PDF

Anatomy of the Equine Gastrointestinal Tract Cristian Dezdrobitu, DVM, MSc, PhD Review Topics: Wall of the abdominal cavity (skin, fascia, muscles) - tunica flava abdominis (large animal only) Inguinal rings, inguinal canal, vaginal ring Abdominal cavity versus peritoneal cavity...

Anatomy of the Equine Gastrointestinal Tract Cristian Dezdrobitu, DVM, MSc, PhD Review Topics: Wall of the abdominal cavity (skin, fascia, muscles) - tunica flava abdominis (large animal only) Inguinal rings, inguinal canal, vaginal ring Abdominal cavity versus peritoneal cavity Parts of the peritoneum: - parietal peritoneum, connecting peritoneum (= “meso-”, e.g., mesojejunum etc.), visceral peritoneum, parietal and visceral vaginal tunic (male), vaginal process (female), vaginal ring ( & ) 1 External abdominal oblique m. 5 Internal abdominal oblique m. 7 Transversus abdominis m. 8 Rectus abdominis m. 2 Aponeurosis of mm.  Left Lateral Equine Abdomen Caudal Cranial Acetabulum Tunica flava abdominis (found in horses and cattle): Associated with EAO. Consists largely of elastic tissue. Yellowish in color (“flava” = “yellow” in latin) Thickest ventrally, where fibers of the Tunica flava abdominis merge with the aponeurosis of the external abdominal oblique m. on its way to the linea alba. Like a built-in “Girdle” Careful suturing of this area (must appose surgical margins accurately) http://vetmed.iastate.edu/dguide/?chapter=3 Left side equine abdomen (EAO (1) reflected ventrally from cut margin).  Cranial Caudal   DOG: There are similarities with connecting mesenteries between dog and horse, but they are not all “equal” in nature. Intestinal strangulation is relatively rare in carnivores compared to equine. Whereas gastric volvulus is more common in large breed / deep chested dogs than in horses.  Equine Gastrointestinal (GI): Regions and Orientation Esophagus – lower esophageal (cardiac) sphincter is extremely strong in the horse; no regurgitation Stomach – Simple stomach with non-glandular mucosa (fundus) and glandular mucosa; The Margo plicatus divides the two – Fundus is large and often called the “blind sac” (saccus cecus) in the horse TVA  Fundus: blind sac Margo plicatus Veterinary anatomy of domestic mammals-Textbook and colour atlas, H.E KONIG and H. G. LIEBICH Gastric ulcers and “Bot Fly” larvae Normal (when present) are often found near the margo plicatus Ulcerations  Equine Gastrointestinal (GI): Regions of and Orientation Small intestine – Duodenum: cranial flexure, descending (2), caudal flexure, ascending (3) and duodenocolic fold (mesentery) – Jejunum (4): suspended by root of mesentery – Ileum(5): ileocecal fold, ileocecal orifice and ileal papilla Cranial   We can identify the ileum in the canine by the antimesenteric ileal artery, but this artery is absent in the horse. Instead, we can use the length of the ileocecal fold to determine where jejunum ends and ileum begins.  Equine Gastrointestinal (GI): Regions of and Orientation Large intestine – Possesses taeniae coli (bands) and haustra (pouches), which are variable in number from one region to another – Cecum (6): base, body, apex and cecocolic fold (6’) (mesentery) CANINE EQUINE The ascending colon of the canine looks drastically 1 Stomach, 2 Small Intestine, 3 Cecum, 4 Ascending different in its simplicity (“large”) colon, 5 descending (“small”) colon Equine is called a “Hind Gut fermenter” Taeniae (“bands”) are formed by longitudinal muscle and elastic fibers. Sacculations or haustra result from the shortening of the Taenia. DDF VDF LDC RDC RVC LVC PF CECUM  Cranial Equine DORSAL View (as seen from above) Left Right A: Ileum B: Cecum C: R V C Transverse section line for next slide image Ventral diaphragmatic flexure D: L V C E: Pelvic flexure F: L D C Dorsal diaphragmatic flexure G: R D C H: Transverse Colon I: Descending colon  Equine Large Intestine: Bands The equine large intestine possesses taeniae coli, or bands, which are NOT present in the small intestine. 2 Bands are longitudinal thickenings of 3 1 the tunica muscularis Bands can be hidden (covered over by connecting peritoneum) or free (not covered by the connecting peritoneum) Cecum: 4 bands Right ventral colon, ventral diaphragmatic flexure (sternal flexure), left ventral colon: 4 bands Pelvic flexure, left dorsal colon: 1 band Dorsal diaphragmatic flexure, right 4 dorsal colon: 3 bands Transverse colon, descending (small) CB – Colic branch of ileocolic a. LCA – Lateral cecal a. colon: 2 bands MCA – Medial cecal a. RCA – Right colic a.  3 4 1 Haustra are much more prominent in the VENTRAL colon  Lateral band of cecum connects to ventrolateral band of the colon Dorsal band of Cecum leads to “cecocolic fold” the “ileocecal fold” (Right Lateral View) Figure 21-15 The interior of the base of the cecum, right lateral view. 1, termination of ileum at the ileocecal orifice; 2, cecocolic orifice; 3, body of cecum; 4, right ventral colon; 6, duodenum.  Equine Colon Carnivore *Ruminants: Ileum enters the large intestine at the ileocecocolic junction *Carnivores have ileocolic orifice and cecocolic orifice * Equine have ileocecal orifice (papilla) (1) and cecocolic orifice (2). - Right ventral Colon (4), Cecum (3) Ruminant Veterinary anatomy of domestic mammals-Textbook and colour atlas, H.E KONIG and H. G. LIEBICH  Equine Gastrointestinal (GI): Regions of and Orientation Large intestine – CONTINUED Right Ventral Colon (RVC) (7) Ventral Diaphragmatic Flexure (8) Left Ventral colon (LVC) (9) Pelvic flexure (10) Left Dorsal Colon (LDC)(11) Dorsal diaphragmatic flexure (12) Right Dorsal Colon (RDC)(13) – Transverse (“Small”) colon (14) – Descending (“Small”) colon (15) – Rectum (16) Try to orient these structures in your 3D imagination as we follow ingesta through the tract. Some common terminology: - The large intestine is comprised of cecum, and ALL of the colon, however clinicians will often subdivide the colon into “Large” and “Small” colon. “large colon” may be used in reference to the ascending colon (both L&R ventral & L&R dorsal segments of colon) “small colon” may be used in reference to the transverse and descending colon  Apple has just left the cecum and is now in the Right Ventral colon Cecum is faintly outlined on these images in order to make the rest of the large colon more visible Right Ventral Colon Ventral Diaphragmatic Flexure AKA “sternal” flexure Left Ventral Colon Left Ventral Colon Pelvic Flexure Left Dorsal Colon Dorsal Diaphragmatic Flexure Right Dorsal Colon  Right Dorsal Colon; Just “oral” to the transverse colon Right Lateral View Cranial  aka (Mesocolon) The Large colon has a massive range of motion! - Between cecum and transverse colon, there is nothing to stop this section of ascending colon from moving. - Sometimes this range of motion allows for pathology: * Displacement * Torsion * Volvulus  Cranial Equine DORSAL View (as seen from above) Large changes in diameter at E and H Left Right A: Ileum B: Cecum C: R V C Ventral diaphragmatic flexure D: L V C E: Pelvic flexure F: L D C Dorsal diaphragmatic flexure G: R D C H: Transverse Colon I: Descending (“Small”) colon Visceral Projections on the Equine Abdominal Wall (Develop your “X-Ray Vision”) Visceral Projections on Left Wall: Liver (3) Stomach (2) Spleen (4) Descending (small) colon (5) Jejunum (6) Left dorsal colon (7) Left ventral colon (8) Viscera located between the left costal arch and tuber coxae: Left dorsal quadrant: jejunum and descending (small) colon Left ventral quadrant: left ventral and left dorsal ascending (large) colon  Left Lateral View  Cranial http://www.vet.cornell.edu/oed/horsedissection/Search.asp?Fun=SBM#  Visceral Projections on Right Wall: Liver (2), Right kidney (3)Descending duodenum (4)Right Dorsal Colon (7) Cecum: (5) Base: in contact with abdominal roof; connected to Right kidney via peritoneum attachment Body(10): extends cranioventrally; in contact with the right flank Apex (11): blind, ventral; terminates near the xiphoid cartilage between: (Develop your “X-Ray Vision”) -Right ventral colon (6) -Left ventral colon (8) Right Viscera located between the right costal 6 arch and tuber coxae: Right dorsal quadrant: base and dorsal part 10 of body of cecum 11 9 Right ventral quadrant: right ventral and right dorsal ascending (large) colon Visceral Projections on Ventral Wall: 8 Left Body (10) and apex (11) of the cecum lie between the ventral parts of the ascending Ventral View colon; Right ventral (6), ventral Cranial diaphragmatic flexure (9), Left ventral (8).  Right Lateral View Cranial  NO GALL BLADDER Topography of Equine Intestine: Ventral View Can you identify labels 2 – 6? 1. Sternum – Xiphoid process 2. Body of the cecum 3. Apex of the cecum 4. Right ventral colon 5. Ventral diaphragmatic flexure 6. Left ventral colon 7. Dorsal sternal flexure  Gall bladder absent in Equidae! Veterinary anatomy of domestic mammals-Textbook and colour atlas, H.E KONIG and H. G. LIEBICH Things can get quite messy in there! How do we distinguish?  USE the taeniae (bands) Left View If “yes”, then must be large intestine – How many taeniae? If “no”, then must be small Caudal intestine Mesenteric folds Cranial “ligaments” Duodenocolic fold: to identify ascending duodenum and descending colon Right View Ileocecal fold: to identify ileum and cecum Cecocolic fold: to identify cecum and right ventral colon Intercolic fold (mesocolon) attach dorsal and ventral large colon Caudal Cranial Is this jejunum? Why or why not? What is this?  Cecocolic fold. Right lateral view of abdomen Connects lateral band of cecum to ventro-lateral band of right ventral colon Cranial CANINE EQUINE  Review: Canine Intestinal Blood Supply The cranial mesenteric artery: Cecum – Cecal a. of ileocolic a. Ascending colon – Colic br. of ileocolic a. – Right colic a. Transverse colon – Middle colic a. and right colic artery Descending colon – Left colic a. Anastomosis between Left Colic br. of caudal mesenteric a. and Middle colic artery Rectum (cranial part of) – Cranial rectal a. of caudal mesenteric a. Ventral large colon = Colic branch of ileocolic a. (oral) Dorsal large colon = Right colic a. (aboral) “A Guided Tour of Veterinary Anatomy”. Twenty-Ten Edition James Smallwood, 2010  Not required, but may be useful https://www.youtube.com/watch?v=fdz78HU_fkM Ruminant Gastrointestinal System Cristian Dezdrobitu, DVM, MSc, PhD  The ruminant stomach consists of 4 chambers: The first 3 are collectively known as the forestomach (rumen, reticulum, omasum) and one “”true stomach” (abomasum) The abomasum is the equivalent of the simple stomach in monogastric species View from the Right  Caudal Cranial  Bovine stomach Fig. 28.7 (A) left side. (B) Bovine stomach, right side. 1, Reticulum; 2, omasum; 3, abomasum; 4, rumen. Adapted from: Dyce et. Textbook of Veterinary Anatomy, 5th Edition. W.B. Saunders Company, 2018, 669. Left side of the abdominal cavity is dominated by the rumen Rumen is not in direct contact with the right abdominal wall  Trade off for Fermentation: SIZE The ruminant stomach is laterally compressed, filling the left side of the abdomen Extends from the diaphragm to the pelvic inlet Extends over the median plane into the right half of the abdominal cavity 1, Esophagus; 2, outline of spleen; 3, reticulum; 4, dorsal sac of rumen; 5, ventral sac of rumen, covered by superficial wall of greater omentum; 6, fundus of abomasum, covered by superficial wall of greater omentum; 8, body of abomasum; 14, descending duodenum; 15, pyloric part of abomasum; 18, position of caudoventral border of liver. Figure 28-4 Topography of the abdominal viscera. A, Relationship of abdominal viscera to the left abdominal wall. B. Position of the parts of the stomach seen from the right. Adapted from: Dyce et. Textbook of Veterinary Anatomy, 5th Edition. W.B. Saunders Company, 2018, 668.  Topography of Structures R 3 Dorsal view 1 4 2 L 1, Reticulum, 2 Rumen, 3 Omasum, 4 Abomasum L 4 2 Ventral view 1 3 R  The orientation and size of the abdominal viscera varies with age and with pregnancy. In the newborn calf (A): Right Side Left Side Large abomasum - important for milk digestion rather than fermentation. In the 5-year-old cow (B): The rumen is large and occupies the entire left side of the abdomen. The liver is pushed cranially In a 6-year-old heavily pregnant cow (C): The uterus displaces the rumen dorsally and the abomasum cranially. Ventral Views Figure 28-20 Ventral views of the abdominal viscera of a newborn calf (A), a 5-year-old cow (B), and a 6-year-old heavily pregnant cow (C) based on reconstructions of transverse sections of animals frozen in the standing position. Dyce et. Textbook of Veterinary Anatomy, 4th Edition. W.B. Saunders Company, 2010, 689.  The Rumen is divided into various compartments by GROOVES on the serosal surface of the rumen that correlate with internal PILLARS on the luminal surface Cranial (a) and caudal (b) grooves Dorsal ruminal sac Longitudinal grooves, left and right d (c, c’) e Accessory grooves, left and right (d, c b b d’) l a f Coronary grooves, dorsal (e, e’) and k Ventral ruminal sac g h ventral (f, f’) Atrium ruminis (g) l i j Left Side Caudodorsal blind sac (h) Interior of right ruminal wall Ventral ruminal sac with ruminal recess (i) and caudoventral blind sac e’ d’ k c’ (j) Insula ruminis (k, right side only) f’ Ruminoreticular groove (l) Right Side Right view: Grooves (green arrows) Vs. Pillars (red arrows) DSR- dorsal sac of the rumen VSR – ventral sac of the rumen R – reticulum O – omasum Ab –abomasum DD – duodenum E -esophagus Concave groove outside / Convex Pillar inside  Right Dorsal Left Dorsal 16 Caudal 13 Caudal 16 3 19 9 2 11 7 15 2 15 18 4 1 1 17 6 6 20 5 20 8 14 13 12 10 12 14 Left ventral Right ventral Left 1 ventral: – Note this Reticulum left side is upside 2 – Cranial pillar down! 12 – Ventral sac 3 – Reticular groove 13 – Dorsal sac 4 – Right Accessory pillar 14 – Caudal ventral blind sac 5 – Right Longitudinal pillar 15 – Caudal dorsal blind sac 6 – Caudal pillar 16 – Atrium Ruminis 7 – Right dorsal coronary pillar 17 – Insula Ruminis 8 – Right ventral coronary pillar 18 – Left longitudinal pillar 9 – Left accessory pillar 19 – LACK of insula ruminis (left) 10 – Left ventral coronary pillar 20 – Ruminal recess 11 – Left dorsal coronary pillar Left Dorsal The internal aspect of the rumen is covered with papilla that will vary in size according to diet, and location in the rumen. Note the variation of the papilla within the different compartments The Rumen contents will vary from gas of the rumen. dorsally to dense liquid ventrally Fig 28.17 Stratification of ingesta in the ruminoreticulum, left lateral view. 1, Gas bubble; 2, coarse forage (“floating mat”); 3, more finely ground material with higher specific gravity than 2; 4, liquid zone; 5, atrium ruminis; 6, reticulum; 7, esophagus. al, Dyce et. Textbook of Veterinary Anatomy, 5th edition, page 675  RETICULUM: immediately caudal to the diaphragm. Traumatic reticulitis or “hardware disease” (Metal will fall here) - - - Ruminoreticular opening Locate: Reticular groove (4) - left (cranial) lip 1, Heart; 2, diaphragm; 3, atrium ruminis; 4, reticular - right (caudal) lip groove; 5, reticulum; 6, ruminoreticular fold; 7, abomasum; 8, ventral sac of rumen  The paralumbar fossa is an important regional landmark in cattle. The paralumbar fossa is an important surgical region Borders of the Paralumbar Fossa: Base: lumbar transverse processes Cranioventral border: last rib Caudoventral border: ridge formed by the part of the internal abdominal oblique muscle that extends from the tuber coxae to the ventral end of the last rib of the ox. The paralumbar fossa is shallower on the left side because of internal pressure from gas in the dorsal sac of the rumen. In starved cattle the fossa is deep. The blood supply to the paralumbar fossa comes from the dorsal costoabdominal artery (located caudal to the last rib), the lumbar arteries, and the cranial branch of the deep circumflex iliac. The internal aspect of the omasum is occupied by mucosal folds or laminae of varying length.  Abomasum is the glandular stomach in ruminants and is the closest “equivalent” to the simple stomach found in monogastric species. 1. Omasoabomasal opening 2. Abomasal Folds (Spiral folds) 2 3. Fundus 4. Body 5. Pyloric Part 6. Torus pyloricus 7. Pylorus Longitudinal section of the abomasum. Figure 28-22 Dyce et. al. Textbook of Veterinary Anatomy, 4th Edition. W.B. Saunders Company, 2010, 690.  The edges of the reticular groove can contract (close) to form a tube (tunnel)-like Gastric groove which can take ingesta from the esophagus directly to the abomasum. WHY?? a) Don’t need to ferment milk (calf) Gastric groove consists of 3 b) Thirsty adult  water can bypass parts: 1. Reticular groove – located rumen during dehydrated status, between the Cranial and Caudal lips. going directly to the abomasum for faster absorption. Closure of the reticular groove to form a tube-like gastric groove is stimulated by ADH. Sequence of flow if wall of reticular groove is CLOSED (forming a “tunnel”): - cardia, reticular groove, reticulo- omasal orifice, omasal groove, omasoabomasal orifice, abomasum. Gastric groove is essentially a tunnel or “Shunt” from Esophagus to Abomasum  Gastric groove: cross section, schematic Walls of the groove are relaxed “Closed”: Walls of groove close to form a tube or tunnel to direct fluid and “open” = not functional past the fore stomachs directing it to the abomasum “tunnel” for fluid (Creating a “direct route” from esophagus to the abomasum) From: Budras and Habel, Bovine Anatomy, 2nd Ed, 2011 1. Reticular groove (previous slide) 2. Omasal groove 3. Abomasal groove (not clear) 1+2+3= Gastric groove The Greater Omentum Attachments: Left longitudinal groove of the rumen (superficial leaf) L R Right longitudinal groove of the rumen (deep leaf) CAUDAL TO CRANIAL VIEW 1, Dorsal sac of rumen; 2, ventral sac of rumen; 3, superficial wall of greater omentum; 4, deep wall of greater omentum; 5, omental bursa; 6, descending duodenum; 7, intestinal mass; 8, right kidney; 9, aorta; 10, caudal vena cava; 11, supraomental recess; 12, retroperitoneal attachment of rumen  The Greater Omentum Attachments: Left longitudinal groove of the rumen (superficial leaf) Right longitudinal groove of the rumen (deep leaf) Superficial (3) and deep (4) leaves of the greater omentum border the omental 1, Dorsal sac of rumen; 2, ventral sac of rumen; 3, superficial wall of greater bursa (5). omentum; 4, deep wall of greater omentum; 5, omental bursa; 6, descending duodenum; 7, intestinal mass; 8, right kidney; 9, aorta; 10, caudal vena cava; 11, supraomental recess; 12, retroperitoneal attachment of rumen Rumen left side https://www.youtube.com/watch?v=PSQke-Gt6N0 Caudal aspect of the rumen Both walls of the omentum meet in the caudal groove Caudal groove https://www.youtube.com/watch?v=PSQke-Gt6N0 Omental bursa - contains the ventral sac of the rumen!!!! Dorsal sac of the rumen Ventral sac of the rumen Caudal groove https://www.youtube.com/watch?v=PSQke-Gt6N0 Supraomental recess is the space dorsal to the bursa and to the right of the rumen The superficial and deep leaves of the greater omentum surround the intestines. Superficial leaf of greater omentum Deep leaf of greater omentum Descending duodenum with mesoduodenum (6) Omental bursa (5) The intestinal mass (7) is located in the Supraomental recess (11) Figure 28-13 Schematic transverse section of the abdominal cavity to show the disposition of the greater omentum. 1, Dorsal sac of rumen; 2, ventral sac of rumen; 3, superficial wall of greater omentum; 4, deep wall of greater omentum; 5, omental bursa; 6, descending duodenum; 7, intestinal mass; 8, right kidney; 9, aorta; 10, caudal vena cava; 11, supraomental recess; 12, retroperitoneal attachment of rumen. https://www.youtube.com/watch?v=PSQke-Gt6N0 Dyce et. Al. Textbook of Veterinary Anatomy, 4th Edition. W.B. Saunders Company, 2010, 685.  Right side of the Bovine abdomen https://www.youtube.com/watch?v=PSQke-Gt6N0 Covers the omasum Right side of the Bovine abdomen https://www.youtube.com/watch?v=PSQke-Gt6N0  Blood Supply of the Ruminant Stomach Rumen From Celiac (just like dog stomach) RIGHT DORSAL CORONARY ARTERY – Main supply of rumen is via the right ruminal a. - a branch of the splenic a Courses in the right accessory groove, through the caudal groove Gives off right and left, dorsal and ventral coronaryRIGHT VENTRAL CORONARY ARTERY aa. From: BUDRAS et al., 2003 The left ruminal a. passes through the cranial groove from right to left and extends into the left accessory groove  Blood Supply of the Ruminant Stomach Omasum From right ruminal artery: LEFT DORSAL CORONARY ARTERY – Main supply is via the left gastric a. (8), a branch of the celiac a. LEFT VENTRAL CORONARY ARTERY Reticulum – Reticular a. (6) of the left ruminal a. (5) From left ruminal artery Abomasum – Greater curvature Left and right gastroepiploic aa. (9, 12) – Lesser curvature BUDRAS et al., 2003 Left and right gastric aa. (8, 11)  Innervation of the Ruminant Stomach The major innervation of the rumen, omasum, abomasum, and reticulum is via the dorsal and ventral vagal trunk “a, j”.  The Ruminant Small Intestine Duodenum (B) Cranial part (1) Cranial flexure (2) Descending part (3) – duodenal papillae – for bile and pancreatic secretion Caudal flexure (4) Ascending part (5) – Duodenocolic fold (21) Duodenojejunal flexure (6) Mesoduodenum (From: Nickel et al., 1967) Jejunum (C) Surrounds spiral loop of ascending colon Jejunal lymph nodes – Note location in ox vs. goat in relation to the jejunum and the last centrifugal loop of the ascending colon Mesojejunum Ileum (D) Ileocecal fold (18) Ileocecocolic junction (7) Ileal papilla (From: Nickel et al., 1967) Jejunum (C) Surrounds spiral loop of ascending colon Jejunal lymph nodes – Note location in ox vs. goat in relation to the jejunum and the last centrifugal loop of the ascending colon Mesojejunum Ileum (D) Ileocecal fold (18) Ileocecocolic junction (7) Ileal papilla (From: Nickel et al., 1967)  Jejunal Lymph nodes Found in the mesentery between the jejunum and spiral colon in the OX. Found in the mesentery between first centripetal and last centrifugal gyri of spiral colon in the goat / sheep. OX GOAT  Jejunal Lymph nodes Veterinary anatomy of domestic mammals-Textbook and colour atlas, H.E KONIG and H. G. LIEBICH  Equine Carnivore *Ruminants: Ileum enters the large intestine where the cecum and colon meet. Called the “Ileocecocolic junction”. *Carnivores have ileocolic orifice and cecocolic orifice * Equine have ileocecal orifice (1) and cecocolic orifice (2). Colon (4), Ruminant Cecum (3) DOG COW  The Ruminant Large Intestine Cecum (E) Ascending Colon (F) Proximal loop (11) Spiral colon – Centripetal gyri (12) – Central flexure (13) – Centrifugal gyri (14) Distal loop (15) Transverse Colon (G) Descending Colon (H) Rectum (J) (From: Nickel et al., 1967 )  Review: Canine Intestinal Blood Supply The cranial mesenteric artery: Cecum – Cecal a. of ileocolic a. Ascending colon – Colic br. of ileocolic a. – Right colic a. Transverse colon – Middle colic a. and right colic artery Descending colon – Left colic a. Anastomosis between Left Colic br. of caudal mesenteric a. and Middle colic artery Rectum (cranial part of) – Cranial rectal a. of caudal mesenteric a.  Cecum l – Cecal a. (g) of ileocolic a. (d) n m c Ascending colon: – Colic br. (d’) of ileocolic a. (d) c – Proximal part of ascending colon (proximal loop and centripetal gyri) d g d’ e – Right colic a. (e) – Distal part of ascending colon (centrifugal gyri and distal loop) Transverse colon – Middle colic a. (c) Descending colon – Left colic (from caudal mesenteric artery (m) Rectum Cranial rectal a. (n) of caudal mesenteric a. (l)  Topography (surface anatomy) LEFT RIGHT Right: Liver, omasum covered by lesser Left: omentum (30), pyloric part of Reticulum, spleen, rumen, greater abomasum, descending duodenum, omentum (superficial leaf attached superficial and deep leaves of the to left longitudinal groove) greater omentum with colon and small intestine in supraomental recess  Lobed kidney Bovine DOG and SMALL 1. Branches of ureter RUMINANTS 2. Calix (calices) 3. Apex of medullary pyramid 4. Cortex 5. Interlobular artery COW  Large Animal GI Cristian Dezdrobitu, DVM, MSc, PhD  COLIC ”Equine abdominal pain” / “Equine Acute Abdomen” DDx list is enormous! – don’t memorize Displacement - (Ex: nephrosplenic entrapment) Volvulus / Torsion Strangulation Gas Distension Spasm / hyper motility Impaction Ulceration Enteritis Intussusception Herniation Peritonitis Extra – GI (liver, kidney, reproductive pain) Sand accumulation Enterolith Parasitic Ileus Toxicity KNOW THE POSITION OF ORGANS Physical Exam: GI Auscultation Sm Intestine Base of Cecum + + Sm Colon + + Dorsal and Dorsal and Ventral Large Ventral Large + = normal Colon Colon - = decreased ++ = hypermotile +/- = inconsistent  Rectal palpation Structures “Palpable” may vary between slightly between DVM’s Left: Dorsal; Sm Colon, Sm Intestine? Nephrosplenic space? Ventral: Pelvic Flexure Caudal right oblique view Right: Dorsal; Base of Cecum Ventral; Body of Cecum Caudal left oblique view Rectal Palpation: - Normal Small Intestine is not perceivably palpable - Abnormal Distended loops of SI feel like stacks of “clown balloons” Abnormal a, Spleen b, Jejunum c, Left ventral colon  Diagnostic tools: Abdominal Ultrasound Abdominocentesis Free abdominal fluid (peritoneal fluid) “Ascites” Distended loops of Sm Intestine Abdominocentesis Near ventral midline at the most gravity dependent portion of the abdomen Thickened Intestinal Wall  Give medical management every possible chance of success! Surgical exploration for “acute abdomen” (colic) is a decision of necessity, not convenience You are not responsible for diagnostic or therapeutic modalities… YET!  1st: Find dorsal band of cecum  ileocecal fold Exploration begins with correct orientation Its called exploratory surgery for a reason. We should have an expectation of what pathology we are about to find…. However, we often don’t know exact pathology until we see it. You may even find more than one disease process concurrently. - So, observe and palpate everything you possibly can! - If you miss a pathology… it should be because it was impossible to observe or palpate.  BE SYSTEMATIC: After finding the ileocolic fold “Run the GI Orally” (palpate the tract from ileum to stomach: jejunum will be visible, duodenum / stomach will not) From Stomach to Ileum: Sm Intestine= 50 – 70 ft Now, get back to the ileocecal fold and “Run” the GI Aborally From ileum to descending colon: Cecum: 25 L Lg Colon: 50 – 75 L Aboral descending colon and rectum will not be visible (palpate what you can)  Displacements and volvulus / torsions happen where the tract is more freely movable Base of cecum and adjacent right ventral / right dorsal colon have very little “range of motion” due to connecting mesenteries to the abdominal wall. The rest of the cecum and ascending (“large colon”) can become displaced more easily.  Colon Torsion Small Intestinal Volvulus Intussusception Check the epiploic foramen (not visible, but it is palpable) Epiploic Foramen HORSE Entrapment Borders of the epiploic foramen: Portal v., Vena Cava, Hepatic a., Liver DOG Sometimes an enterotomy is necesessary Enterotomy: “surgically open the intestinal tract” Therapy 1) To remove abnormal contents (sand, impaction, endotoxins, foreign body) 2) To decompress  ease the correction of displacement 3) Ensure gut is empty and “resting” when patient awakes from surgery Colon Impaction - Diameter narrows:  At the pelvic flexure  From Right Dorsal Colon to Transverse colon Enterolith Right Note luminal lateral diameter changes view Right dorsal colon To Transverse colon Pelvic Flexure Left lateral view  Nephrosplenic Entrapment Important to identify the nephrosplenic ligament and space in the lab  Normal spleen kidney Normal Nephrosplenic entrapment If a section of bowel will not survive, it must be removed: Necrotic from ischemia or obstruction Neoplasia Infection Rupture  Inguinal Rings Cryptorchidism Herniation Superficial Ring: opening through the aponeurosis of EAO Deep Ring: Lateral margin of Rectus Abdominis Caudal margin of IAO Caudal margin of EAO (inguinal ligament) Inguinal hernia  Abomasal Displacements LDA: Left ~ 90% RDA: Right ~10% Classic Syndrome: - Early post postpartum - Dairy Cow - Older (4-7 yrs) Why? - Acute, dramatic change in abdominal fill - Rapid Change in diet (Fiber and Concentrates) - Decreased exercise - Other predisposing factors: mastitis, retained placenta, metritis, endotoxemia Result: - Overall decrease in outflow of contents of the stomach  Gas distention and compromising blood flow A, Abomasum B, Rumen C, Omasum D, Supraomental resess  Therapy You are only responsible for associated ANATOMY Medical Management: correct dehydration, electrolyte imbalance and pH imbalance, treat ketosis and give motility stimulants (5% chance of cure) Rolling: Sedate, decompress, roll the cow and monitor (70 – 75% reoccur ) Closed surgical procedure: Use the “Rolling” technique described previously, then “Pexy” the abomasum in the corrected location using a Toggle-pin. Pexy means “Fixation” “Blind” abomasal pexy OR Laparoscopic assisted abomasal-pexy Toggle-pin The paralumbar fossa is an important regional landmark in cattle. The paralumbar fossa is an important surgical region Borders of the Paralumbar Fossa: Base: lumbar transverse processes Cranioventral border: last rib Caudoventral border: ridge formed by the part of the internal abdominal oblique muscle that extends from the tuber coxae to the ventral end of the last rib of the ox. The paralumbar fossa is shallower on the left side because of internal pressure from gas in the dorsal sac of the rumen. In starved cattle the fossa is deep. The blood supply to the paralumbar fossa comes from the dorsal costoabdominal artery (located caudal to the last rib), the lumbar arteries, and the cranial branch of the deep circumflex iliac. Access to the rumen and reticulum is gained via the left paralumbar fossa. 1, Esophagus; 2, outline of spleen; 3, reticulum; 4, dorsal sac of rumen; 5, ventral sac of rumen, covered by superficial wall of greater omentum; 1, Heart; 2, diaphragm; 3, atrium 6, fundus of abomasum, covered by superficial ruminis; 4, reticular groove; 5, wall of greater omentum; 7, reticular groove; 8, reticulum; 6, ruminoreticular fold; body of abomasum; 9, atrium ruminis; 10, 7, abomasum; 8, ventral sac of caudodorsal blind sac; 11, caudoventral blind rumen sac; 12, ventral sac of rumen Access to the rumen and reticulum is gained via the left paralumbar fossa. Fresh ruminal fluid contains bacteria and protozoa, volatile fatty acids (VFAs), microbial proteins, vitamins, minerals and other buffers. The rumen is permanently fistulated in the left paralumbar fossa to allow cows to be donors for transfaunation of rumen contents to other cows (ruminal acidosis, vagal indigestion and peritonitis). Ruminal fistulas are also used to study ruminant physiology.  Access to the rumen and reticulum is gained via the left paralumbar fossa. https://www.researchgate.net/figure/Findings-of-rumenotomy-in- camels-with-partial-intestinal-obstruction-Together-with- https://www.vethelplineindia.co.in/diagnostic-and-prophylactic- hair_fig3_261401756 measures-of-diaphragmatic-hernia-in-buffaloes/ Anesthesia of spinal nerves T13, L1, L2, L3, L4 will provide regional anesthesia for standing paralumbar surgical procedures; A.K.A. “laparotomy” (Incision into the peritoneal cavity). Examples: Cesarean Section T13(18 horse) = Costoabdominal Rumenotomy L1 = Iliohypogastric Displaced abomasum L2/L3 = Ilioinguinal L3/L4 = Lateral cutaneous femoral nerve  Topography for nerves to block for flank and udder surgery (TVA p667 for annotations) Paralumbar block: Anesthesia of the lower flank and abdominal floor requires blockage of the ventral branches only, and these are most conveniently reached where they pass close to the tips of the lumbar transverse processes (paralumbar block). Lumbar epidural injection provides an alternative procedure. The specific innervation of the cutaneous muscle must be kept in mind regardless of the method chosen.