Radiology - Bowel obstruction & Ileus

1. Dilated loops of bowel?
2. Transition point (CT)
3. Air in rectum or sigmoid? (plain films)
key questions in assessing bowel gas pattern on imaging studies
functional ileus
one or more loops of bowel lose their ability to propagate the peristaltic waves of the bowel (usually due to some local irritation or inflammation) – obstruction proximal to affected loops
We will write a custom essay sample on
Radiology – Bowel obstruction & Ileus
or any similar topic only for you
Order now
localized
generalized adynamic
2 kinds of functional ileus
localized ileus
affects *only one or two loops* of usually *small bowel* (a.k.a. *sentinel loops*)
generalized adynamic ileus
affects *all loops* of large and small bowel and frequently the stomach
mechanical obstruction
a physical, organic, obstructing lesion prevents the passage of intestinal content past the point of either the small or large bowel blockage
SBO
LBO
2 kinds of mechanical obstruction
mechanical obstruction
the loops that will become the most dilated will either be the loop of bowel with the *largest resting diameter* before the onset of the obstruction (e.g., the cecum) or the loops of bowel *just proximal to the obstruction*
transition point
site of obstruction and the location where the bowel changes in caliber from dilated to collapsed
mechanical obstruction
Presentation:
Abdominal pain
Abdominal distension
Constipation
Vomiting
proximal SBO
vomiting early in course
distal SBO
vomiting later in course
Vascular compromise
Necrosis
Perforation
Bowel sounds become hypoactive or absent
Prolonged obstruction with persistently elevated intraluminal pressures can lead to:
normal
localized ileus
generalized ileus
(abnormal gas patterns)
Air in rectum or sigmoid
all but LBO (unless ileocecal valve incompetence)
(abnormal gas patterns)
air in small bowel
generalized ileus
SBO
multiple dilated loops of air in small bowel
normal
1-2 loops air in small bowel
localized ileus
2-3 dilated loops air small bowel
LBO
no loops of air in small bowel
LBO
Generalized ileus
Dilated air in LB
normal
localized ileus
air in large bowel – rectum and/or sigmoid
localized ileus
sentinel loops
localized ileus
some gas continues to pass through the defunctionalized bowel past the point of ileus
localized ileus
Air reaches and is visible in the rectum/sigmoid on AXR
abdominal CT
Cause of functional ileus is frequently visible on what?
cholecystitis
Causes of localized ileus – RUQ
pancreatitis
Causes of localized ileus – LUQ
Appendicitis
Causes of localized ileus – RLQ
Diverticulitis
Causes of localized ileus – LLQ
ulcer
kidney/ureteral calculus
Causes of localized ileus – Midabdomen
functional ileus (localized)
* one to two persistently dilated loops of small bowel
* Air-fluid levels seen in sentinel loops
* Gas in rectum or sigmoid
persistently dilated
– same loops remain dilated on multiple views of the abdomen (supine, prone, upright) or on serial studies done over time
>2.5 cm
small bowel loops that are dilated
Single, persistently dilated loops of small bowel is seen in the LUQ on both supine and prone AXR
sentinel loops from pancreatitis
(functional localized ileus)
Single, persistently dilated loops of small bowel is seen in the LUQ on both supine and prone AXR
abdominal CT
If having difficulty differentiating between ileus and early SBO, what will demonstrate the underlying pathology?
generalized adynamic ileus
Entire bowel is aperistaltic or hypoperistaltic
generalized adynamic ileus
*Almost always the result of abdominal or pelvic surgery*, in which the bowel is manipulated during the surgery or electrolyte imbalance as w/ *DKA*
generalized adynamic ileus
– *Entire bowel is usually air-containing and dilated*
– *Many long air-fluid levels*
– Gas in rectum or sigmoid
– *No transition point* on CT
– BS absent or hypoactive
aerophagia
intestinal pseudoobstruction
can be mistakenly identified as having a generalized ileus on AXR
SBO
Peristalsis continues and may increase in an effort to overcome the obstruction
SBO
If complete and if enough time has elapsed since the onset of symptoms, there is usually no air in the rectum or sigmoid
postsurgical adhesions
(appendectomy, colorectal surgery, pelvic surgery)
*Most common cause of SBO*
*postsurgical adhesions*
Malignancy
Hernia
GS ileus
Intussusception
IBD
causes of mechanical SBO
inguinal
Hernia that can cause SBO
inguinal hernia
air-containing loops of bowel over obturator foramen
GS ileus
air in biliary tree (AXR & CT)
ileocolic
most common form of intussusception
– produces SBO
terminal ileum
Thickening of the bowel may compromise the lumen in patients with Crohn’s – causing SBO
– most common where?
SBO
– Multiple dilated loops of small bowel proximal to the point of obstruction
– *step-ladder* appearance
the fewer the dilated loops
the more proximal the SBO
intermittent (partial or incomplete) SBO
one that sometimes allows some gas to pass the point of obstruction
– usually from adhesions
CT
should be able to demonstrate a partial SBO or identify the abnormality producing the sentinel loops
SBO
SB disproportionately dilated compared to the LB
CT (+/- oral contrast)
most sensitive study for diagnosing the site and cause of a mechanical SBO
oral contrast
(but might obscure important findings displayed with IV contrast)
may help in identifying dilated loops of bowel and in finding the transition point between the proximal dilated bowel and the distal collapsed bowel
IV contrast
used for detecting complications of obstruction such as ischemia and strangulation
SBO (CT)
small bowel *feces sign*
feces sign
Proximal to the transition point, intestinal debris and fluid may accumulate, producing the appearance of fecal material in the small bowel. [not feces]
– dilated/fluid-filled loops prox to obstruction
– *transition point*
– collapsed SB or colon distal
– *feces sign*
– *closed-loop obstruction*
– *strangulation*
CT imaging can show what with SBO
closed-loop obstruction
higher risk of strangulation
closed-loop obstruction
When 2 points of the same loop of bowel are obstructed at a single location
volvulus
large bowel, a closed loop obstruction
strangulation
circumferential thickening of the wall of bowel with absence of normal wall enhancement following IV contrast
strangulation
edema of the mesentery and ascites
spigelian hernia
occurs at the lateral edge of the rectus abdominis muscle at the semilunar line
cecum
LBO – frequently obtains largest diameter
tumor (carcinoma)
most common cause of LBO
tumor
hernia
volvulus
diverticulitis
intussusception
Causes of LBO
diverticulitis
Uncommon cause of colonic obstruction
colocolic intussusception
usually occurs because of a tumor acting as a lead point
LBO
bowel loops tend not to overlap since limited number
ast air-containing segment of the colon
Sometimes possible to identify the site of obstruction as what?
>12-15 cm
cecum dilation – danger of rupture
LBO
Small bowel is not dilated
LBO
(later SBO)
Rectum contains little or no air
LBO
Usually no or very few air-fluid levels
suspected LBO
No oral contrast
cecum w/ air and dilated
Clue that it is LBO w/ incompetent ileocecal valve
ID cause
Assess for free air
ID associated lesions (mets to liver or lymph nodes)
CT obtained for what with LBO
LBO
CT: Large bowel is dilated to the point of obstruction, then normal in caliber distal to the obstructing lesion
sigmoid volvulus
Volvulus – more common and tends to occur in older men
*coffee bean*
sigmoid volvulus
*coffee bean*
volvulus
can produce massively dilated loops of sigmoid colon
cecum
volvulus – usually moves across the midline into the left upper quadrant producing loops of bowel forming a line that characteristically points from the right lower to the left upper quadrant
contrast enema
cecum volvulus – can be both diagnostic (the obstructed sigmoid produces a beak sign⚠️ ) and therapeutic
cecal volvulus
beak sign
(Contrast enema)
ogilvie syndrome
may occur in older individuals who are usually already hospitalized or at chronic bed rest
– drugs with anticholinergic effects
ogilvie syndrome
Massively dilated large bowel + CT or barium enema shows no obstructing lesion
Marked abdominal distension + NORMAL-Hyperactive BS
Older individual/chronic bedrest
×

Hi there, would you like to get such a paper? How about receiving a customized one? Check it out