BOWEL ADHESIONS: DETECTING THE HIDDEN EVIL

Paul Tung, D.O.

Michael Mousa, MD

Roozbeh Houshyar, MD

Chandana Lall, MD

Disclosure

Authors do not have any financial or other relevant disclosures.

Clustered bowel Segments

Coronal contrast enhanced CT image shows closely clustered small bowel loops in the right lower quadrant consistent with

high grade entero-enteric adhesions (green arrows) . No thickened overlying peritoneum to suggest abdominal cocoon.

Clustered or unusual crowded appearance of bowel

segments is typically seen with entero-enteric or

inter-loop adhesions, classically referred to as

“matted bowel”.

This finding has a high predictive value for bowel

adhesions.

This finding can also be seen with intra-abdominal

infections such as with abdominal tuberculosis.

Overview & Content Organization

– Review the etiologies, timeline and clinical significance of bowel adhesions

– Complications that can result secondarily

– Review spectrum of imaging findings related to bowel adhesions on multi-detector computed

tomography (MDCT) and MRI

– Emphasis on recognition of specific patterns and signs for bowel adhesions

– Assessment of severity as pertains to future risk of obstruction and possible bowel injury

during surgical procedures, due to underlying adhesions

• Role of the radiologist in identifying & reporting significant adhesions

Adhesions: Facts not fiction

• The most frequent cause of abdominal adhesions is abdominal surgery. Other etiologies include

trauma, peritoneal dialysis, infection such as tuberculosis

• Almost all patients who undergo abdominal surgery will develop adhesions of varying degree;

minimal to significant

• The risk is greater after lower abdomen and pelvic surgeries when compared to upper abdominal

surgeries eg: bowel & gynecologic procedures

• IMPORTANT POINT: Adhesions can become larger and tighter over time causing problems,

years after surgery

• Causes of abdominal adhesions include surgery and contact of tissues with foreign materials, such as

gauze, surgical gloves, and sutures as well as retained blood

– Gynecological surgeries, such as hysterectomy, are more prone to adhesion development

than most general abdominal surgeries

• A less common cause is inflammation such as ruptured appendicitis, inflammatory bowel disease,

abdominal TB and other infections, radiation treatment for cancer among others

• Rarely, abdominal adhesions form without apparent cause, ie de novo!

CAUSES OF BOWEL ADHESIONS

Types of bowel adhesions on cross-sectional imaging

Entero-Enteric

Adhesions between

adjacent bowel

loops

Entero-Visceral

Adhesions between

bowel and adjacent

organs

Entero-peritoneal

or Entero-Parietal

Adhesions between

bowel and parietal

peritoneum

Bowel Findings of Adhesions

1. Unchanged location of bowel segments on successive exams(inertia)

2. Loss of fat planes behind the rectus sheath and anterior peritoneum

3. Focal clustering or crowding of bowel loops

4. Kinking and angulation of bowel loops

5. Caliber change of bowel

6. Asymmetric thickness of the bowel wall

7. Fat notch sign

8. Localized stasis within bowel segments

9. “Star sign” of adhesions which may also signify underlying fistulization

10. Enteric-Organ adhesions

Mesenteric Findings

of underlying

adhesions

Focal increased

attenuation of

mesentery

Mesenteric Vascular

crowding Focal localized fluid

Peritoneal Changes associated with Adhesions

Focal or diffuse peritoneal thickening and enhancement

Peritoneal calcifications and Sclerosing Peritonitis

Loculated fluid in between loops of bowel

Peritoneal inclusion cyst

Entero-peritoneal adhesions with unchanged bowel location over time

Axial CT images were obtained almost 2 years apart : Note location of small bowel loops in the same

location, abutting the right anterior abdominal wall with obliteration of the right post-rectus fat plane (yellow

arrows). Normal left post rectus fat plane( green arrows)

CT: 3/2/14 CT: 11/7/15

Loss of fat planes posterior to the rectus sheath and anterior peritoneum

Normal bowel segments are nearly

always separated from the posterior

aspect of the rectus muscles by

mesenteric and omental fat. Following

intra-abdominal and pelvic surgeries,

the tissue disturbance at the level of

the visceral peritoneum results in

closely applied adherence of the small

bowel with resultant loss of the retro-

rectus fat planes.

50 year old female patient status post cholecystectomy, shows unchanged location of bowel loops along the anterior

peritoneum on studies over a period of 9 months with loss of posterior rectus sheath fat plane (yellow arrows).

Clustered bowel Segments

Coronal contrast enhanced CT image shows closely clustered small bowel loops in the right lower quadrant consistent with

high grade entero-enteric adhesions (green arrows) . No thickened overlying peritoneum to suggest abdominal cocoon.

Clustered or unusual crowded appearance of bowel

segments is typically seen with entero-enteric or

inter-loop adhesions, classically referred to as

“matted bowel”.

This finding has a high predictive value for bowel

adhesions.

This finding can also be seen with intra-abdominal

infections such as with abdominal tuberculosis.

Clustered bowel loops

60 year-old female patient status post hysterectomy. Contrast enhanced axial and sagittal CT images

show shows matted bowel loops clustered in the lower abdomen & pelvis (green arrows)

Kinking and Angulation of Bowel Loops

42 year old female status post hysterectomy, 3 years ago, presenting with chronic lower abdominal pain. Axial CT images

demonstrate acute angulation and kinking of multiple bowel loops (red arrows).

One of the most common signs of bowel

adhesions is acute angulation of bowel.

Normal small bowel being freely mobile

normally shows smooth curved loops

usually evenly distributed in the abdomen

and pelvis. With development of either

entero-enteric adhesions or entero-parietal

adhesions, loops become fixed at certain

points, leading to acutely angulated

segments with kinking and changes in

caliber as seen in these images

Angulation of Bowel Loops

Axial CT images show multiple segments of angulated small bowel (arrows) from underlying adhesions in three different post surgical patients

Caliber change of bowel and Localized stasis within bowel

Coronal CT image demonstrates focal caliber change of a small bowel loop in the mid abdomen (white

arrow) with fecalized material present proximal to the caliber change (red arrows).

Bowel adhesions may lead to caliber

change of the bowel with slow transit times

in focal segments of bowel. These

segments may demonstrate features of

stasis including fluid accumulation and

fecalized appearance of small bowel loops.

Finding of localized stasis may be an

indirect sign of unsuspected underlying

bowel adhesions.

Asymmetric bowel wall thickening

Above contrast enhanced axial CT images show small bowel loops with asymmetric wall thickening from

underlying adhesions after bowel surgery (orange arrows).

Fat notch sign

44 year old female with past surgical history of hysterectomy presented with abdominal pain, nausea and vomiting. Axial CT

image demonstrates a fat indentation at level of adhesion, the “fat notch” sign ( arrow) along with associated dilated loops of

small bowel.

This sign reflects

insinuation of mesenteric

fat at an area of adhesions

with focal caliber change.

This has been described in

cases of small bowel

obstruction related to

adhesions and is a very

specific finding of adhesive

small bowel obstruction.

Star Sign

32 year old female with history of Crohn’s disease. Coronal MR enterography images demonstrate thick

T2 dark adhesions radiating to multiple loops of tethered small bowel in the lower abdomen (red arrows)

compatible with the “Star Sign”. Accompanying entoroenteric fistulas are suspected.

This sign develops due to

adhesions forming

between different loops of

bowel and can often be

seen in the setting of

enteroenteric or

enterocolonic fistulas.

Entero-visceral adhesions

Examples of entero-visceral adhesions. Axial CT image on the left shows adhesions between the right

ovary and adjacent bowel loop (green arrow). The middle axial CT image show an anteriorly displaced

uterus secondary to entero-visceral, and entero-peritoneal adhesions (red arrow). The sagittal CT image

on the right show an example of adhesions between small bowel loops and the bladder (yellow arrow).

Entero-visceral adhesions

Axial CT image shows entero-visceral adhesion to the right bladder wall with caliber change and stasis in

the affected loop of small bowel (green arrow). Sagittal CT image shows entero-visceral adhesions to the

bladder dome with matted appearance of small bowel loops in patient status post hysterectomy (red arrow).

Focal increased attenuation of the Mesentery

Axial contrast enhanced CT images show localized increase in mesenteric attenuation in the right abdomen

when compared to normal mesenteric fat in the left abdomen, related to mesenteric congestion (red arrow)

secondary to underlying adhesions.

Mesenteric Vascular Crowding Associated with Adhesions

Axial contrast enhanced CT image on the right and coronal MR enterography image show localized vascular

crowding in the right abdomen related to mesenteric congestion (red arrows) secondary to underlying small bowel

adhesions.

Cocoon Abdomen

56 year old male, status post colonic surgery presents with abdominal pain and vomiting. Axial and coronal CT images

demonstrate a cluster of adherent fluid filled mildly dilated small bowel loops in pelvic region, enclosed by thickened

peritoneal lining ( red arrows), consistent with “cocoon abdomen” (green arrows).

Cocoon abdomen refers to

closely clustered bowel loops

adherent within thickened

peritoneum in a sac like manner.

This finding is classically

associated with peritoneal

dialysis, with presence of

underlying entero-parietal and

entero-enteric adhesions.

Sclerosing Peritonitis with bowel adhesions

62 year old female with

history of peritoneal dialysis

presents with abdominal

pain. Sagittal CT image

demonstrates thick

peritoneal and mesenteric

surface calcifications

(green arrows) involving

multiple loops of bowel,

consistent with

encapsulating peritoneal

sclerosis.

CONCLUSION

• It is essential for radiologist to recognize the varied imaging findings and specific signs

related to presence of bowel adhesions

• Radiologists should mention the presence of non-obstructing bowel adhesions, since this

has direct implications when future surgeries, especially laparoscopic procedures are

being considered, due to high risk of inadvertent bowel injury and prolonged surgical time

• Adhesions are the most common cause of small bowel obstruction!

• Adhesions can also result in infertility and chronic abdominal pain among other issues

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