SR 44 - Small Intestine Flashcards
How long is the duodenum?
12 inches
What marks the end of the duodenum and the start of the jejunum?
Ligament of Treitz
What is the length of the entire small bowel?
~6 meters (20 feet)
What is the blood supply for the small bowel?
Branches of the superior mesenteric artery
What does the small bowel do?
Major site of digestion and absorption
What does the terminal ileum absorb?
B12
Fatty acids
Bile salts
What are the major difference between the jejunum and ileum?
Jejunum - long, large, thick
Ileum - short, small, thin
Vasa recta, plicae circulares, wall
Signs and symptoms of a SBO?
Abdominal discomfort Cramping Nausea Abdominal distention Emesis High-pitched bowel sounds
What lab tests are performed with a SBO?
Electrolytes
CBC
Type and screen
Urinalysis
What are the classic acid-base/electrolyte findings with proximal SBO?
Hypovolemic, hypochloremic, hypokalemic alkalosis
What must be ruled out on physical exam in patients with SBO?
Incarcerated hernia
Also look for surgical scars - increased risk of adhesions
What are major AXR findings are associated with SBO?
Distended loops of small bowel
Air-fluid levels on upright film
Define a complete SBO
Complete obstruction of the lumen
Little to know colon gas
What is the danger of a complete SBO?
Closed loop strangulation of the bowel leading to bowel necrosis, and potential perforation
Define parial SBO
Incomplete SBO
Some colon gas (may still be passing gas)
What is the initial treatment of patients with SBO?
NPO
NGT
IVF
Foley
What test can differentiate partial from complete bowel obstruction?
C with oral contrast and small bowel follow-through
What are the causes of SBO?
The ABCs
- Adhesions
- Bulge (hernias)
- Cancer and tumors
What are lesser cause of SBO?
After adhesions, hernias and cancer:
- Gallstone ileus
- Intussusception
- Volvulus
- External compression
- SMA syndrome
- Bezoars, bowel wall hematoma
- Abscesses
- Diverticulitis
- Crohn’s disease
- Radiation enteritis
- Annular pancreas
- Meckel’s diverticulum
- Peritoneal adhesions
- Stricture
‘GIVES BAD CRAMPS’
What is the superior mesenteric artery (SMA) syndrome?
SMA compresses the duodenum causing obstruction
Seen with weight loss
What is the treatment of complete SBO?
Laparotomy and lysis of adhesions
What is the treatment of incomplete SBO?
Initially, conservative treatment with close observation plus NGT decompression
How do you, intraoperatively, determin the level of obstruction in a SBO?
Transtion from dilated bowel proximal to the decompressed bowel distal to the obstruction
What is the most common indication for abdominal surgeyr in patients iwth Crohn’s disease?
SBO
Can a patient have a complete SBO and bowel movements/flatus?
Yes - the bowel distal to the obstruction can clear out gas and stool taht was there already
After a small bowel resection, why should the mesenteric defect always be closed?
To prevent an internal hernia
What ma cause SBO if patient is on coumadin?
Bowel wall hematoma
What is the #1 cause of SBO in adults in industrialized nations?
Postoperative adhesions
What is the #1 cause of SBO around the world?
Hernias
What is the #1 cause of SBO in children?
Hernias
What are the signs of strangulated bowel with SBO?
Fever, severe/continuous pain, hematemesis, shock, gas in teh bowel wall or portal vein, abdominal free air, peritoneal signs, acidosis (increased lactic acid)
What are the clinical parameters that will lower the threshold to operate on a partial SBO?
Increasing WBC
Fever
Tachycardia/tachypnea
Abdominal pain
What is an absolute indicateion for operation with partial SBO?
Peritoneal signs
Free air on AXR
What condition commonly mimics SBO?
Paralytic ileus
AXR reveals gas distention throughout, including the colon
What is the different diagnosis of paralytic ileus (nonobstructive)?
Postop ileus after abdominal surgery (resolves in 3-5 days)
Electrolyte abnormalities (hypokalemia)
Medications (anticholinergics, narcotics)
Inflammatory intra-abdominal process
Sepsis/shock
Spine injury
Retroperitoneal hemorrhage
What tumor classically causes SBO due to ‘mesenteric fibrosis’?
Carcinoid tumor
What are the different small bowel tumors?
Leiomyoma Lipma Lymphangioma Fibroma Adenomas Hemangiomas
What are the signs and symptoms of small bowel tumors?
Abdominal pain
Weight loss
Obstruction
Perforation
Most common benign small bowel tumor?
Leiomyoma
Most common malignant small bowel tumor?
Adenocarcinoma
What is the work up fof a small bowel tumor?
UGI with small bowel follow-through
Enteroclysis
CT scan
Enteroscopy
What malignancy is classifcally associated with metastasis to small bowel?
Melanoma
What is a Meckel’s diverticulum?
Remnant of the omphalomesenteric duct/vitelline duct, which connects the yolk sac the preimitive midgut in the embryo
Where is a Meckel’s diverticulum located?
Within 2 feett of the ileocecal valve on the antimesenteric border of the bowel
Possible complications of Meckel’s diverticulum?
Intestinal hemorrhage (painless) Intestinal obstruction Inflammation+/- perforation
What heterotopic tissue type is found in Meckel’s diverticulum?
Gastric mucosa (60%) Duodenal, pancreatic, colonic mucosa
What is a Meckel’s scan?
Can for ectopic gastric mucosa in Meckel’s diverticulum
Uses technetium pertechnetate IV
Preferentially taken up by gastric mucosa
What is the most common cause of small bowel bleeding?
Small bowel angiodysplasia
