92. Small intestine Flashcards
length of small bowel
5X length of trunk 1-1.5 m cats2-5 m dogs
what and where is the root of the mesentery
attaches to L2contains –cranial mesenteric artery–intestinal lymphatics–large mesenteric plexus of nerves
mucosal layer of small intestine
contains microvili which increase surface area 8 fold in dogs and 15 fold in catstwo cell types:1. columnar epithelial—absorptive function2. goblet cells–mucus secretingepithelium is produced in the intestinal crypts, replacement occurs every 2-6 days (shed at apex), start out as secretory and as the migrate up ddx into absorptive cells that aid in digestion
common bile duct and major duodenal papilla in dogs vs cats
DOGSmajor duodenal papilla: CBD and adjacent pancreatic duct (duct of Wirsung) minor duodenal papilla: accessory pancreatic duct –major contributor (duct of Santorini)80% cats have a single pancreatic duct that FUSES with CBD and empties into major duodenal papilla
muscular layers of SI and motility
inner circular (thick); outter longitudinal (thin)2 movements (PSNS control–vagus):1. segmental (mixes): random, stimulated by stretch, slows transit2. peristaltic (moves aborally): cyclic q 1.5-2 hours
T/Freduced peristalsis leads to ileus, reduced segmental contractions leads to diarrhea
TRUE
what is the functional unit of small intestine
VILLI and associated crypts
ilium and jejunal absorptive capacity for water
jejunum 50%ilium 75%
mechanisms for sodium absorption in the small intestine
Na/Cl passive diffusionN/K/ATPaseNa/glucose (SGLUT1) or other electrolyte co-transporter
branches of cranial mesenteric artery that feed the SI
- jejunal arteries2. caudal pancreaticoduodenal3. ileocolic artery (cecal and antimesenteric arteries)4. right colic5. middle colic
where do digestive enzymes come from
- pancreas2. brush border of SI3. bile from GB for fat digestion
portion of SI in which the majority of chemical digestion takes place
duodenum
role of cholecystokinin (CCK) and secretin in digestion
produced in the small intestine in response to the presence of nutrientsCCK–stimulates gallbladder contraction for digestion of fatSecretin– causes release in bicarb from pancreas to help neutralize acid from stomach
breakdown/digestion of proteins/peptides
breakdown into amino acidsenzymes: trypsin, chymotrypsin (secreted by pancreas), carboxypeptidase (brush border)
breakdown/digestion of CHO
breakdown into simple sugarsenzymes: pancreatic amylase, brush border enzymes, sucrase, lactase, maltase
breakdown/digestion of lipids
breakdown into fatty acids and glycerolenzymes: pancreatic lipase, bile saltsnot water soluble: micelle formation using bile salts and bile acids is necessary (have both hydrophobic and hydrophilic domainsbile acids also increase the surface area of the oil-water interfaces which aids access by pancreatic lipaseinside enterocyte—form chylomicrons and taken into lymphatics thru lacteal
acid base disturbances with small intestinal obstruction
metabolic acidosis if loss of intestinal alkaline fluidsUNLESSproximal duodenal obstructions & vomiting leading to loss of HCl and hypochloremic hypokalemic metabolic alkalosis
objective vs subjective measures of bowel viability
subjective: color, pulse, peristalsis, thickness (may not always correlate to histologic results)objective: fluorescin (gold/green under UV light) 10-15 mg/kg IV. Nonviable areas are non fluorescent >3 mmsurface oximetry: compare with peripheral pulse ox but only measures a small surface
T/Ftrue apposition and approximation of intestinal closures is infrequent
TRUEwant single layer appositional (NOT INVERTING or 2 layer) to avoid avascular cuff and narrowing lumen or second obstructionsimple interrupted eversion is seen 66%simple cotinuous eversion, inversion or misalignment 38%
goal for knot tying force
1.5 N
types of reinforcement for small bowel
- omentum (vascular and lymphatic supply–angiogenic, immunogenic, adhesive properties)2. serosa (jejunal–most common, gallbladder)3. biomaterial (SIS, fascia, goretex)
methods to deal with disparity in luminal sizes
- spatulate smaller side on the anti mesenteric border2. sutures on larger side can be spaced out more than sutures on the smaller side3. cut smaller side at a steeper angle4. partially close the larger diameter side5. Use a GIA functional end to end anastomosis bc luminal disparity is not an issue
staple techniques for bowel R& A closure
- end to end EEA and TA2. side to side (functional end to end) with GIA and TA or additional row of GIA3. skin staples
side to side (functional end to end) with GIA and TA 55Ullman et al Vet Surgery 1991 results
24 animals3/24 complications at TA staple line (two leak, one abscess)recommend omentopexy or SP
advantages of stapling enteric R&A
–decreased surgery time–decreased tissue manipulation–permits anastomoses of 2 portions of bowel with large differences in lumen diameter(CAUTION ILEOCECAL AREA–make sure adequate stoma size)
skin staples for enteric R&A compared to traditional hand sewn simple interruptedCoolman et al Vet Sx 2000
- equivalent bursting strength2. equivalent luminal diameter3. equivalent quality of healing***SIGNIFICANTLY LESS TIME WITH SKIN STAPLES
check for leakage post enteric biopsy while intraop according to Saile et al Vet Sx 2010
GOAL: achieve 20 and 34cm water (15-25mmHg) intraluminal pressure :10 cm healthy jejunum • 16.3–19.0mL (17ml), Digital occlusion • 12.1–14.8mL (13mL), Doyen occlusion (greater correlation)normal peristaltic P 2-4 mm Hg
morbidity associated with enteroplication and outcome
tx intussusception (complete plication, engage submucosa)higher complications with enteroplication (3/20–16%) vs the rate of recurrence with surgical treatment of intussusception alone (1/17—6%)complications seens 1+ mo post op: volvulus, obstruction, strangulation, peritonitis, perforation, abscessationNOT of added benefit in all patients
post op complications following small intestinal surgery
–septic peritonitis: 7-16% occur 2-5 days–adhesions: prevented by active fibrinolytic system–short bowel syndrome: malab, malnutrition–ileus- occur within 24 hrs, consider NG tube, prokinetic
T/Falthough open abdominal drainage can be more labor intensive and costly, it does not appear to have a significant higher morbidity and mortality rate
TRUEmay loose a lot of protein though
peritoneal membrane and omental absorbing fluid rate
3-5% of the animals body weight per hour
mortality associated with dehiscence of an enteric surgical site
50% in generalreports as high as 85% (Ralphs 2003)
prevention of adhesions is through an equilibrium of fibrinolytic and normal fibrin deposition pathways. what disturbs this equilibrium and leads to adhesion formation?
ischemiahemorrhageFBinfectionminimize by atraumatic tissue handling, moistening tissues, asepsis
short bowel syndrome in clinical dogs
some cases have been seen with 50% resection, others tolerate 85% resection without SBSproximal resections seem better tolerated in lab dogssigns: steatorrhea, diarrhea, weight losscauses: decrease surface area of mucosal villi, hypersecretions, bacterial overgrowth, decreased intestinal transit time.
TX short bowel syndrome
supportive: IV fluids, electrolytes, nutrients, highly digestible small frequent meals (fiber 10-15%)+/- tx bacterial overgrowth (Ab)+/- tx diarrhea (loperamide)+/- fat voluble vitaminsnutrition causes adaptive changes in enterocytes: larger # bigger size, increase bowel diameter, increase villus height and crypt depth
causes of ileus
overactivity of sympathetic nervous system which is activated with laparotomy, manipulation of intestine, long operative time, and extensive resectionNG tube–trickle feed, aspirateprokinetic–metoclopramide CRI or intermittent SQ
radiographic sign of bowel dilation
COMPARE TO NARROWEST PART OF THE BODY of L5intestinal diameter: L5 ratio»2.0 VERY likely obstructed«1.6 not likely obstructed
most common intestinal tumors in dogs
–adenocarcinoma (reasonable px depends on mets)–lymphoma (poor px)–leiomyoma (good prognosis)–leimyosarcoma (good prognosis)with surgical resection
how many cats reportedly present with linear FB anchored under tongue
50%if detach after acute presentation 47% will pass through GI tract in 1-3 days (conservative therapy)
how many dogs have peritonitis at the time of surgery for GI linear FB
40%usually anchored at pylorus
dimensions of regular stainless steel skin staples
4.8 x 3.4 mm
parts of an intussusception
= the invagination of one portion of the GI tract (intussusceptum) into the lumen of an adjoining segment (intussuscipien)underlying cause (changes in motility): parasitism, enteritis, viruses, linear FB, cecal inversion, previous ab surgery (older animals think NEOPLASIA), post parturient queens
rectal prolapse vs intussusception
rectal prolapse: probe would not passintussusception: easy passage of a probe btwn prolapsed segment and rectum
recurrence rates of intussusception
6-27%3 days to 3 weeks post opusually recurs proximal to initial site
accuracy blunt probing of a wound over the abdominal for detecting intraabdominal injury
60% SN for detecting peritoneal injury
congenital malformations of the small bowel
- diverticula–buldging pouchlike herniations in the wall of intestine that maintains communication with intestinal lumen2. duplication–lined by mucosa and contain muscle but located in or adjacent to the wall of the intestinal tract–do NOT communicate with the lumen
