Small Intestine, C44 P286-293 Flashcards
SMALL BOWEL ANATOMY What comprises the small bowel? P286
Duodenum, jejunum, and ileum
SMALL BOWEL
ANATOMY
How long is the duodenum?
P286
≈12 inches—thus the name: duodenum!
SMALL BOWEL ANATOMY What marks the end of the duodenum and the start of the jejunum? P286
Ligament of Treitz
SMALL BOWEL ANATOMY What is the length of the entire small bowel? P286
≈6 meters (20 feet)
SMALL BOWEL ANATOMY What provides blood supply to the small bowel? P286
Branches of the superior mesenteric
artery
SMALL BOWEL
ANATOMY
What does the small bowel do?
P286
Major site of digestion and absorption
SMALL BOWEL ANATOMY What are the plicae circulares? P286
Plicae means “folds,” circulares means
“circular”; thus, circular folds of mucosa
(a.k.a. valvulae conniventes) in small bowel
lumen
SMALL BOWEL ANATOMY What are the major structural differences between the jejunum and the ileum? P287
Jejunum—long vasa rectae, large plicae
circulares, thicker wall
Ileum—shorter vasa rectae, smaller
plicae circulares, thinner wall
(Think: Ileum = Inferior vasa rectae,
Inferior plicae circulares, and
Inferior wall thickness in comparison
to the jejunum)SMALL BOWEL ANATOMY What does the terminal ileum absorb? P287
B12, fatty acids, bile salts
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is small bowel obstruction (SBO)? P287
Mechanical obstruction to the passage of
intraluminal contents
SMALL BOWEL SMALL BOWEL OBSTRUCTION What are the signs/ symptoms? P287
Abdominal discomfort, cramping,
nausea, abdominal distention, emesis,
high-pitched bowel sounds
SMALL BOWEL SMALL BOWEL OBSTRUCTION What lab tests are performed with SBO? P287
Electrolytes, CBC, type and screen,
urinalysis
SMALL BOWEL SMALL BOWEL OBSTRUCTION What are classic electrolyte/ acid-base findings with proximal obstruction? P287
Hypovolemic, hypochloremic,
hypokalemia, alkalosis
SMALL BOWEL SMALL BOWEL OBSTRUCTION What must be ruled out on physical exam in patients with SBO? P287
Incarcerated hernia (also look for surgical scars)
SMALL BOWEL SMALL BOWEL OBSTRUCTION What major AXR findings are associated with SBO? P287 (picture)
Distended loops of small bowel air-fluid
levels on upright film
SMALL BOWEL
SMALL BOWEL OBSTRUCTION
Define complete SBO.
P288
Complete obstruction of the lumen;
usually paucity or no colon gas
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the danger of complete SBO? P288
Closed loop strangulation of the bowel
leading to bowel necrosis
SMALL BOWEL
SMALL BOWEL OBSTRUCTION
Define partial SBO.
P288
Incomplete SBO; some colon gas
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is initial management of all patients with SBO? P288
NPO, NGT, IVF, Foley
SMALL BOWEL SMALL BOWEL OBSTRUCTION What tests can differentiate partial from complete bowel obstruction? P288
CT with oral contrast, small bowel
follow-through
SMALL BOWEL
SMALL BOWEL OBSTRUCTION
What are the ABCs of SBO?
P288
Causes of SBO:
- Adhesions
- Bulge (hernias)
- Cancer and tumors
SMALL BOWEL
SMALL BOWEL OBSTRUCTION
What are other causes of SBO?
P288
The acronym “GIVES BAD CRAMPS”:
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
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is superior mesenteric artery (SMA) syndrome? P288
Seen with weight loss—SMA compresses
duodenum, causing obstruction
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the treatment of complete SBO? P288
Laparotomy and lysis of adhesions
SMALL BOWEL
SMALL BOWEL OBSTRUCTION
What is LOA?
P288
Lysis Of Adhesions
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the treatment of incomplete SBO? P289
Initially, conservative treatment with close
observation plus NGT decompression
SMALL BOWEL SMALL BOWEL OBSTRUCTION Intraoperatively, how can the level of obstruction be determined in patients with SBO? P289
Transition from dilated bowel proximal to
the decompressed bowel distal to the
obstruction
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the most common indication for abdominal surgery in patients with Crohn’s disease? P289
SBO
SMALL BOWEL SMALL BOWEL OBSTRUCTION Can a patient have complete SBO and bowel movements and flatus? P289
Yes; the bowel distal to the obstruction
can clear out gas and stool
SMALL BOWEL SMALL BOWEL OBSTRUCTION After a small bowel resection, why should the mesenteric defect always be closed? P289
To prevent an internal hernia
SMALL BOWEL SMALL BOWEL OBSTRUCTION What may cause SBO if patient is on coumadin? P289
Bowel wall hematoma
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the #1 cause of SBO in adults (industrialized nations)? P289
Postoperative adhesions
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the #1 cause of SBO around the world? P289
Hernias
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the #1 cause of SBO in children? P289
Hernias
SMALL BOWEL SMALL BOWEL OBSTRUCTION What are the signs of strangulated bowel with SBO? P289
Fever, severe/continuous pain, hematemesis, shock, gas in the bowel wall or portal vein, abdominal free air, peritoneal signs, acidosis (increased lactic acid)
SMALL BOWEL SMALL BOWEL OBSTRUCTION What are the clinical parameters that will lower the threshold to operate on a partial SBO? P289
Increasing WBC
Fever
Tachycardia/tachypnea
Abdominal pain
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is an absolute indication for operation with partial SBO? P290
Peritoneal signs, free air on AXR
SMALL BOWEL SMALL BOWEL OBSTRUCTION What classic saying is associated with complete SBO? P290
“Never let the sun set or rise on complete
SBO”
SMALL BOWEL SMALL BOWEL OBSTRUCTION What condition commonly mimics SBO? P290
Paralytic ileus (AXR reveals gas distention throughout, including the colon)
SMALL BOWEL SMALL BOWEL OBSTRUCTION What is the differential diagnosis of paralytic (nonobstructive) ileus? P290
Postoperative ileus after abdominal
surgery (normally resolves in 3–5 days)
Electrolyte abnormalities (hypokalemia is
most common)
Medications (anticholinergic, narcotics)
Inflammatory intra-abdominal process
Sepsis/shock
Spine injury/spinal cord injury
Retroperitoneal hemorrhageSMALL BOWEL SMALL BOWEL OBSTRUCTION What tumor classically causes SBO due to “mesenteric fibrosis”? P290
Carcinoid tumor
SMALL BOWEL SMALL BOWEL TUMORS What is the differential diagnosis of benign tumors of the small intestine? P290
Leiomyoma, lipoma, lymphangioma,
fibroma, adenomas, hemangiomas
SMALL BOWEL SMALL BOWEL TUMORS What are the signs and symptoms of small bowel tumors? P290
Abdominal pain, weight loss, obstruction
(SBO), and perforation
SMALL BOWEL SMALL BOWEL TUMORS What is the most common benign small bowel tumor? P290
Leiomyoma
SMALL BOWEL SMALL BOWEL TUMORS What is the most common malignant small bowel tumor? P290
Adenocarcinoma
SMALL BOWEL SMALL BOWEL TUMORS What is the differential diagnosis of malignant tumors of the small intestine? P290
- Adenocarcinoma (50%)
- Carcinoid (25%)
- Lymphoma (20%)
- Sarcomas (<5%)
SMALL BOWEL SMALL BOWEL TUMORS What is the workup of a small bowel tumor? P291
UGI with small bowel follow-through,
enteroclysis, CT scan, enteroscopy
SMALL BOWEL SMALL BOWEL TUMORS What is the treatment for malignant small bowel tumor? P291
Resection and removal of mesenteric
draining lymph nodes
SMALL BOWEL SMALL BOWEL TUMORS What malignancy is classically associated with metastasis to small bowel? P291
Melanoma
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is it?
P291 (picture)
Remnant of the omphalomesenteric duct/
vitelline duct, which connects the yolk sac
with the primitive midgut in the embryo
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is its claim to fame?
P291
Most common small bowel congenital
abnormality
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is the usual location?
P291
Within ≈2 feet of the ileocecal valve on
the antimesenteric border of the bowel
SMALL BOWEL MECKEL’S DIVERTICULUM What is the major differential diagnosis? P291
Appendicitis
SMALL BOWEL
MECKEL’S DIVERTICULUM
P291
Is it a true diverticulum?
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is the incidence?
P291
≈2% of the population at autopsy
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is the gender ratio?
P292
Twice as common in men
SMALL BOWEL MECKEL’S DIVERTICULUM What is the average age at onset of symptoms? P292
Most frequently in the first 2 years of
life, but can occur at any age
SMALL BOWEL MECKEL’S DIVERTICULUM What are the possible complications? P292
Intestinal hemorrhage (painless)—
50%; accounts for half of all lower
GI bleeding in patients younger than
2 years
Bleeding results from ectopic gastric
mucosa secreting acid → ulcer →
bleeding
Intestinal obstruction—25%; most
common complication in adults;
includes volvulus and intussusception
Inflammation ( ± perforations)—20%SMALL BOWEL MECKEL’S DIVERTICULUM What are the signs/ symptoms? P292
Lower GI bleeding, abdominal pain, SBO
SMALL BOWEL MECKEL’S DIVERTICULUM What is the most common complication of Meckel’s diverticulum in adults? P292
Intestinal obstruction
SMALL BOWEL MECKEL’S DIVERTICULUM In what percentage of cases is heterotopic tissue found in the diverticulum? P292
>50%
SMALL BOWEL MECKEL’S DIVERTICULUM What heterotopic tissue type is most often found? P292
Gastric mucosa (60%), but duodenal,
pancreatic, and colonic mucosa are also
found
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is the “rule of 2s”?
P292
2% of patients are symptomatic Found ≈2 feet from the ileocecal valve Found in 2% of the population Most symptoms occur before age 2 years Ectopic tissue found in 1 of 2 patients Most diverticula are ≈2 inches long 2 to 1 male:female ratio
SMALL BOWEL MECKEL’S DIVERTICULUM What is the role of incidental Meckel’s diverticulectomy (surgical removal upon finding asymptomatic diverticulum)? P292
Most experts would remove in children
very controversial in adults
SMALL BOWEL
MECKEL’S DIVERTICULUM
What is a Meckel’s scan?
P293
Scan for ectopic gastric mucosa in
Meckel’s diverticulum; uses technetium
pertechnetate IV, which is preferentially
taken up by gastric mucosa
SMALL BOWEL MECKEL’S DIVERTICULUM What is the treatment of a Meckel’s diverticulum that is causing bleeding and obstruction? P293
Surgical resection, with small bowel
resection as the actual ulcer is usually
on the mesenteric wall opposite the
diverticulum!
SMALL BOWEL MECKEL’S DIVERTICULUM What is the name of the hernia associated with incarcerated Meckel’s diverticulum? P293
Littre’s hernia (Think alphabetically:
Littre’s, then Meckel’s)
SMALL BOWEL MECKEL’S DIVERTICULUM In patients with guaiacpositive stools and a negative upper- and lower- GI workup, what must be ruled out? P293
Small bowel tumor; evaluate with
enteroclysis (small bowel contrast study)
SMALL BOWEL MECKEL’S DIVERTICULUM What is the most common cause of small bowel bleeding? P293
Small bowel angiodysplasia
