B5-090 CBCL: Bowel Obstruction Flashcards
sudden occlusion of the SMA causes loss of what parts of intestines?
3
jejunum
ileum
right colon
watershed locations
2
- Griffith’s point: junction of middle and left colic arteries
- Sudek’s point: junction of hypogastric and left colic a.
what is the significance of watershed points?
they have low perfusion, so in hypoperfusion states it becomes critically low and these areas of bowel will become ischemic first, can cause scarring and obstruction
why is the small bowel more susceptible to obstruction?
longer
more mobile
can rotate on it’s axis to obstruct
colon
cecal or sigmoid volvulus
the blood supply for the anorectum originates from
iliac arteries
rectum usually preserved despite blockage of other vessels
is the deep external spinchter under voluntary or involuntary control?
voluntary
is the internal spinchter under voluntary or involuntary control?
involuntary
normally contracted
most common sites of obstruction from foreign bodies
4
- esophagogastric junction
- pylorus
- ileocecal valve
- rectosigmoid junction
narrowest points
a foreign object that passes through the […] will almost always pass into the stool
which site of obstruction
ileocecal valve
physiologic impacts of GI obstruction
6 (general)
volume related: AKI, acute renal failure
alteration of blood flow: perforation, sepsis
aspiration: respiratory compromise, sepsis, MOF
what causes hypovolemia in obstructed patients?
2
- inability to ingest sufficient fluid to maintain volume
- sequestration of fluid within the bowel lumen and wall
a patient with a high obstruction can develop a volume deficit of […] liters within 24 hours
4-8 L
a patient with a low obstruction can develop a 10 liter volume deficit in […]
timespan
2 days
volume must be corrected prior to […] to prevent cardiac collapse
induction of anesthesia
very high obstructions result in the loss of what electrolytes?
K, Cl
cause alkalosis
reason for urgency in treating volume/electrolyte imbalances
to avoid acute kidney injury
increases the mortality of obstruction 10x
perforation
most common cause of performation
ischemia causing infarction, bowel disintegrates and leaks
how does bowel ischemia develop in close loop obstructions?
venous hypertension -> occlusion -> arterial occlusion
how does ischemia develop in rotational obstructions?
physical twisting of venous or arterial supply
more commonly venous
crucial aspects of ischemic pain
3
- constant pain
- out of proportion to physical findings
- may develop hours after initial findings
indicates surgical emergency
- drooling
- pain on swallowing
- chest pain
- no bile in emesis
- dry heaves
esophageal obstruction
- projectile vomiting
- epigastric pain
- non-bilious vomitus
gastric obstruction
- nausea and vomiting
- intermittent cramping pain
- relief of pain with vomiting
- loud borborgmi with pain
proximal small bowel obstruction
- less vomiting
- distension more likely
distal small bowel obstruction
- distention very common
- intermittent cramping
- little or no vomiting
colonic obstruction
signs of late mechanical obstruction
2
- silent abdomen
- development of ischemic pain
what type of obstruction?
- non-surgical
- post operative after laparotomy,severe stress states, vertebral fractures
- hypoactive to silent bowel sounds
- mild pain to palpation
- large and small diffuse gas pattern on xray
ileus
treatment for ileus
supportive: fluids, NG, K+
hypokalemia from GI loss or overuse of diuretics is a common cause of […] in a non-surgical patient
ileus
what type of obstruction?
- seen in elderly, bedridden patients
- distension in right colon and cecum
pseudo-obstruction (Ogilivie’s)
neurogenic causes of obstruction
ileus
pseudo-obstruction (Ogilivie’s)
toxic megacolon
treatment of pseudo obstruction (Ogilivie’s)
- pro-cholingeric (prostigmine)
- if bowel diameter >12 cm may require surgery
what type of obstruction?
- confined to colon
- associated with ulcerative colitis, c. diff
- distension, signs of SIRS are common
toxic megacolon
treatment of toxic megacolon
emergent total colectomy
causes of congenital obstructions
5
- congenital hernias
- malrotation
- hypoplasia/atresia
- Hirschsprung’s
- imperforate anus
most common pediatric hernias causing obstruction
inguinal
umbilical
signs of strangulation of hernias
2
- erythema
- extremely painful mass
requires emergent surgery
treatment of hernias without evidence of ischemia
manual reduction
what type of obstruction?
- chronic obstruction of pylorus
- high GI obstruction with profuse projectile vomiting
- hypokalemia, hypochloremia, metabolic alkalosis
2- differentiate children v adults
- pyloric stenosis (children)
- pyloric stricture from peptic ulcer (adults)
treatment for pyloric stenosis/stricture
- correct volume deficit
- correct hypokalemia
- surgery
result of failure in utero for gut to attach properly to retroperitoneum
malrotation
a whirl sign on CT indicates
obstruction of rotational cause
emergency
ulcerative colitis can cause obstruction in the
colon
leading malignant cause of small bowel obstruction
lymphoma
adenocarcinoma and NET requires resection of […] bearing area
lymph node
most common malignant cause of colon obstruction
adenocarcinoma
sigmoid most common
benign causes of colonic obstructions
3
- diverticular disease
- IBD
- ischemic stricture
in patients with a competent […] distension and ischemia is more likely to occur, more rapidly resulting in perforation
ileocecal valve
why does gastric outlet obstruction classically result in hypokalemia, hypochloremia, and alkalosis?
- loss of H+ in vomitus
- kidneys try to compensate by wasting K+ to retain H+
what order should these be done to treat gastric outlet obstruction?
* relief of obstruction
* volume replacement
* K+ replacement
- volume replacement
- K+ replacement
- relief of obstruction
in a young child with intermittent obstructive episodes without vomiting, what diagnosis should you think of primarily?
malrotation
hallmark of pyloric stenosis
vomiting
Why does the presence of a compentent ileocecal valve increase risk of perforation?
prevents venting of colonic gas
by the law of LaPlace, what part of the colon takes the least pressure to expand?
the cecum, the widest part
junction of SMA and IMA
Griffith’s point
treatment of choice for pseudo obstructions
prostigmine
ileus is caused by loss of peristalsis originating in
Auerbach’s plexus
has a characteristic diffuse gas bowel pattern
ileus
closed loop obstructions which result in rapid development of ischemia and constant pain
volvuli
why are elderly people with chronic constipation at higher risk of volvulus?
chronic constipation elongates the sigmoid colon over time
why is spinal anesthesia better than general anesthesia for rectal foreign body removal?
paralyzes internal spinchter
the internal spinchter is in a chronic state of […] normally
contraction
procholinergic agent used to treat pseudo obstructions
neostigmine
what is the primary concern of midgut volvulus due to malrotation?
infarction of the majority of the small bowel
electrolyte findings typical of gastric outlet obstruction
3
hypochloremic
hypokalemic
metabolic alkalosis
peptic ulcer disease is a common cause of what type of obstruction?
gastric outlet
early satiety, vomiting, electrolyte disturbances
gastric outlet obstruction
most common places for ischemia to occur due to hypotension
- splenic flexure
- rectal-sigmoidal junction
where the IMA and branches of iliac artery meet
recto-sigmoidal junction
where middle colic and left colic arteries meet
splenic flexure
watershed zones
- splenic flexure
- recto-sigmoidal junction
best fluid solution for an issue affecting the small bowel
Lactated Ringers
which electrolyte is associated with ileus?
potassium
may also need magnesisum
best next step for bowel perforation and developing sepsis
antibiotics
before OR
what can mitigate the risk of aspiration prior to the induction of anesthesia?
placement of NG tube
cutting the vagus nerve would result in what level of bowel obstruction?
gastric
what vital sign is the most sensitive indicator of adequate volume replacement?
pulse rate
what is the next best step for a bowel obstruction with no bowel sounds?
exploratory laparatomy
bowel is dying and perforation is imminent
in a patient with an obstruction and the esophageal level, what is the best protection against aspiration during EGD?
ET tube
decreased stool passage
constipation
absence of passage of gas or stool per rectum
obstipation
caused by failure of the bowel to roate and attach properly during gestation
malrotation
associated with midgut volvulus
which has a worse prognosis: colon or rectal cancer?
rectal
what is the last segment of the GI tract to restart normal peristalsis after ileus?
colon
what is the first segment of the GI tract to restart normal peristalsis after ileus?
small bowel
vascular obstruction of the 3rd portion of the duodenum can result from compression of which vessel?
SMA
to correc the alkalosis of gastric outlet obstruction, what electrolyte must be replaced?
K+
all obstructed patients have some form of
hypovolemia
a normal 70 kg patient typically injests up to […] liters of fluid a day
2
if the question inlcudes an amount lost through NG tube, be sure to add
LaPlace’s law
wall tension = intraluminal pressure x radius
the […] has the largest diameter of the colon and requires the least pressure to distend
cecum
increased bowel wall pressure first compromises […] flow
venous or arterial
venous
is venous or arterial pressure first affected by increased bowel wall tension?
venous
constant pain is
ischemic pain
leads to necrosis and bowel perforation
ischemia
leads to volume depletion and renal failure
obstruction
common point of obstruction in newborns due to hypertrophy
pylorus
a child, 0-5, with sudden onset of life-threatening small bowel obstruction involving the midgut likely has?
malrotation
