Chapter 11 Flashcards
How long is the small bowel?
What is its major function?
8 m
Absorb nutrients
What are the three sections, and how long is each section?
Duodenum- 40 cm
Jejunum- 200 cm
Ileum- 300 cm
How are the jejunum and ileum covered and anchored?
Covered by visceral peritoneum and tethered to posterior anterior wall by a mesentery
Duodenal bulb
Superior to the pancreatic head and anterior to the gastroduodenal artery and common bile duct
Position and blood supply of the duodenal bulb
Intraperitoneal position
Blood supply from the supraduodenal branch of the hepatic artery and the gastroduodenal artery
The duodenal bulb is the site of _____ of duodenal ulceration
90%
Position of the second part of the duodenum
Borders the head of the pancreas
Retroperitoneal
Position of the third part of the duodenum
Retroperitoneal, coursing between the SMA and the aorta
From where do the second and third portions of the duodenum receive their blood supply?
From the anteriosuperior and posterosuperior pancreaticoduodenal branches of the gastroduodenal artery and anterioinferior and posteroinferior pancreaticoduodenal branches of the superior mesenteric artery
Where does the fourth portion of the duodenum receive its blood supply?
First jejunal branch of the superior mesenteric artery
What is an anatomic landmark for the transition between the duodenum and the jejunum?
The ligament of Treitz
How is the small bowel differentiated?
By the valvulae conniventes, circular folds of mucosa and submucosa that markedly increase absorptive surface area
What is the difference between the jejunum and ileum?
The messenteric vessels of the jejunum form only one or two arterial arcades and send out long vasa recta
The ileum contains multiple arterial arcades that give off short vasa recta
From where do the ileum and jejunum derive their blood supply?
From the superior mesenteric artery and venous drainage via the superior mesenteric vein
What are the four layers of the bowel wall from inside to outside?
Mucosa
Submucosa
Muscularis
Serosa
How can the mucosa be further divided?
Muscularis
Lamina propria
Epithelium
Muscularis
A thin layer of the muscle separating the mucosa from the submucosa
Lamina propria
A continuous layer of connective tissue between the muscularis and epithelium, serves as a supportive base for the villi and a protective barrier against microorganisms
What is one type of cells residing in the lamina propria?
Cells of the immune system, including Peyer’s patches (aggregates of lymphoid tissue containing immune cells)
Epithelium
Villi and crypts of Lieberkuln
Functions as digestion, absorption, cell renewal, and secretion of hormones
What is the purpose of the submucosa?
Support and strength layer
Contains blood vessels, lymphatics and nerves
What is the muscularis (general layer)?
An inner circular and an outer longitudinal layer
What is sandwiched between the muscularis layers?
Ganglion cells that constitute the myenteric (Auerbach) plexus
What is the serosa composed of?
Flattened mesothelial cells
How is pain mediated?
Through visceral afferent fibers of the sympathetic nervous system
Sympathetic innervation
3 sympathetic ganglia are located around the base of the superior mesenteric artery and control blood vessel tone and to a lesser extent gut secretory function and motility
Parasympathetic innervation
Parasympathetic nerve fibers are derived form the vagus nerve and primarily regulate gut secretory function and motility
What is one of the most common pathologic processes affecting the small bowel?
Obstruction
What are the most common causes of obstruction?
Adhesion (result of >60%)
Hernias
Tumors
What appear to be associated with a higher incidence of adhesive obstruction?
Lower abdominal and pelvic operations (appendectomy and adnexal procedures)
Labs for obstruction
Hypokalemic Hypochloremic Metabolic alkalosis Metabolic acidosis Hematocrit may be falsely elevated d/t volume depletion and anemia may indicate underlying malignancy
External hernias
Include those found in the inguinal canal, femoral canal, and in previous incisions
Internal hernias
Include those related to the inadequate closure of mesenteric defects created by prior operations, congenital mesenteric defects, and obturator foramen hernias
Imaging for obstruction
Upright chest, supine and upright abdominal X-ray
Imaging findings for obstruction
Dilated loops of bowel and air fluid levels, often with a step-like appearance
What may provide a therapeutic effect in some cases of SBO?
Oral contrast
Gastrogradin (diatrizoic acid) is a hyperosmolar gastrointestinal water-soluble agent, which has been shown to speed the resolution of partial SBO and has also been shown to reduce hospital length of stay
Strangulation
Thickening of the bowel wall, pneumatosis instestinalis, ascites or mesenteric hematoma
Tx of SBO
Partial SBO- initially nonoperative
-Defined as no or minimal sx in 3-5 days
-Parenteral nutrition should be started
-Pts who initially resolve a partial SBO but then recur need surgical exploration
Pts with a complete SBO are at a high risk of strangulation
Surgical tx of SBO
Lysis of adhesions, resection of nonviable or diseased bowel with anastamosis or intestinal bypass
One should palpate the root of the small bowel mesentery for a pulse in the SMA to be certain vascular compromise is not d/t occlusion of the SMA
How can bowel viability be further confirmed?
Fluorescein angiography
Doppler u/s
Fluorescein angiography in SBO
Hemogenous hyperfluorescence with a fine granular or reticular pattern suggests nl bowel, wheras patchy fluorescence or nonfluorescence suggests nonviable bowel
Doppler u/s in SBO
If nonviable bowel is identified during abdominal exploration, it should be resected and a “second-look” laparotomy 24-48 hrs after to reassess bowel viability
What are intraoperative techniques to decrease the formation of adhessions?
Moistening of the mesothelium
Reduction of intra-abdominal foreign materials
Irrigation to remove intra-abdominal blood and clot
Use of sharp scalpel dissection as opposed to cautery
Avoidance of unnecessary bowel manipulation
Agents to decrease adhesion rate
Intercede Gore-Tex Fibrin sheets Polyethylene glycol spray Hyaluronic acid gel Glucose peritoneal installates
Additional causes of SBO
Gallstone ileus
Intussusception
Volvulus
Intestinal pseudo-obstruction
Gallstone ileus
The development of a cholecystoduodenal fistula with distal propagation of a gallstone
How common is a gallstone ileus?
Uncommon, but associated with considerable morbidity and mortality
Who is more likely to get a gallstone ileus?
Elderly
In pts with severe concomitant dz
In pt with gallstones 2-5 cm in diameter
Sx of gallstone ileus
Intestinal obstruction
Pneumobilia
Gallstone
Change of position of a gallstone
Surgical intervention for a gallstone ileus
Laparotomy
Enterotomy
Removal of the stone
Intussusception
Leading edge or intussusception is usually in an intraluminal lesion
CT findings in intussusception
Intraluminal soft tissue “mass” with high attenuation peripherally and low attenuation centrally, known as “target sign”
Volvulus
The twisting of a loop of bowel around the axis of a long narrow mesentery, often associated with malrotation or internal herniation
What procedure should be done if there’s viable bowel in a volvulus?
If viable bowel and malrotation?
Enterolysis
Ladd procedure
Ladd procedure
Counterclockwise reduction of the volvulus, division of Lad bands/adhesions and appendectomy
What are Ladd bands?
Fibrous stalks or peritoneal tissue connecting the cecum to the abdominal wall, which creates the site of duodenal obstruction in malrotation
What is required with a volvulus if the bowel appears nonviable?
A Ladd procedure and bowel resection is required
Presentation of intestinal pseudo-obstruction
Mimics appendicitis
Pt may have a hx of repeated surgical procedures in attempt to detect a mechanical cause of these sx
Most commonly idiopathic but can be familial or associated with scleroderma, hypothyroidism, hypoparathyroidism or celiac dz
Surgical options for intestinal pseudo-obstruction
Enterostomy
Bypass procedure
Bowel resection
What is the most commonly involved site in Crohn’s dz?
The terminal ileum
Who does Crohn’s dz more commonly affect?
Smokers
Ppl who reside in industrial areas
Ashkenazi Jews
What may be found at the time of a Crohn’s surgical exploration?
Bowel perforation
Abscess formation
Enterovisceral fistula
What may be present pathologically with Crohn’s dz?
Areas of thick grayish-white exudate or fibrosis and extension of the mesenteric fat around the circumference of the bowel may be present + fibrosis + ulceration
Cobblestone appearance in Crohn’s
Linear ulceration with surrounding mucosal and submucosal edema
60-70% of Crohn’s pts may have…
Noncaseating granulomas with Langerhans giant cells
Clinical manifestations of Crohn’s dz
Extraintestinal: Arthralgias Uveitis Erythema nodosum Pyoderma gangrenosum Arthritis Hepatitis Pericholangitis
Crohn’s complications requiring surgery
Obstruction Perforation Fistula Abscess Perianal dz
What is the incidence of colonic malignancy in Crohn’s?
6x greater than in the general population
Diagnostic findings in Crohn’s dz
Granular, discrete, aphthous ulcerations surrounded by nl tissue and a cobblestone-like appearance of the mucosa, diffuse narrowing of bowel lumen, and asymmetric involvement of the bowel wall leading to nodular contour
Nutritional considerations in Crohn’s
Protein-calorie malnutrition occurs in 80-90% of pts
What is the MC indication for operation in Crohn’s?
Fistula
EC fistulas in Crohn’s
Treated with resection of affected bowel and debridement of the fistula tract
Enteroenteric fistulas in Crohn’s
May be left alone if asymptomatic; however if large segments are bypassed, significant malabsorption and fluid loss may ensure necessitating surgery.
Surgery for enterovesical and enteroadnexal fistulas in Crohn’s
Involves resection of the affected bowel and fistula tract and closure of the bladder or adnexal defect
Obstruction in Crohn’s
Healthy intervening segments of bowel flanked by diseased segments should only be resected if <5 cm
If a short stricture is the cause of the obstruction, then strictureplasty (Heineke-Mikulicz type) can be performed making a longitudinal incision through the stricture and closing it in a transverse fashion
Contraindications to strictureplasty for Crohn’s
Small bowel perforation
Multiple strictures in a short segment
Concern for malignancy
Prognosis of Crohn’s
The most common site of recurrence is the small bowel, just proximal to the prior site of resection
