Describes the radiological guidelines for imaging of acute abdomen and small and large bowel obstruction .

1. DR SAKHER AL-KHADERI
CONSULTANT RADIOLOGIST AMC

16. Obscured psoas outline due to
retroperitoneal fluid

35. The small bowel has a
wall pattern that is
known as valvulae
conniventes (white
arrow).The muscular
bands encircling the
small bowel are usually
seen to traverse the
bowel wall at right
angles to the long axis
of the bowel
NORMAL SMALL
INTESTINE

44. Clinical presentation
Classical presentation is constipation, increasing abdominal
distension with nausea and vomiting.
Small bowel obstruction (SBO) accounts for 80% all mechanical intestinal
obstruction; the remaining 20% result from large bowel obstruction. It has a mortality
rate of 5.5%.
Aetiology
Causes can be divided into congenital and acquired. Acquired causes may be extrinsic
causing compression, intrinsic or luminal.
In the developed countries, adhesions are by far the most common cause, accounting
for ~75% of obstructions while in developing countries incarcerated hernias are much
more common accounting for 80% of obstructions 3.

45. Congenital
jejunal atresia
ileal atresia or stenosis
enteric duplication
midgut volvulus
mesenteric cyst
Meckel diverticulum
CAUSES OF SBO
Extrinsic bowel lesion
fibrous adhesions
abdominal hernia
volvulus
masses
extrinsic neoplasm
intra-abdominal abscess
aneurysm
Haematoma ,endometriosis
Intrinsic bowel wall lesion
intussusception
tumour (rare), e.g. lipoma
strictures, e.g. surgical, irradiation
Luminal occlusion
neoplasm, e.g. adenocarcinoma, carcinoid, lymphoma
inflammation, e.g. Crohn's,Tuberculosis
intestinal ischaemia
intramural haemorrhage, e.g. trauma, Henoch-Schonlein purpura, over-anticoagulation
swallowed, e.g. foreign body, bezoar
gallstone: gallstone ileus
meconium ileus (or meconium ileus equivalent)

46. Radiographic features
Abdominal radiograph
Abdominal radiographs are only 50-60% sensitive for small bowel
obstruction 3. In most cases, the abdominal radiograph will have the
following features:
-dilated loops of small bowel proximal to the obstruction
-predominantly central dilated loops
-three instances of dilatation over 3 cm
-valvulae conniventes are visible
-fluid levels if the study is erect (non-standard technique)
However, obstruction (which may be high grade mechanical obstruction)
may also present with the following features:
-a gasless abdomen: gas within the small bowel is a function of vomiting,
NG tube placement and level of obstruction
the string-of-beads sign: small pockets of gas within a fluid-filled small
bowel

47. Cases Of Small
Bowel Obstruction

51. Small bowel obstruction (string of pearls sign)

52. Abdominal adhesionsare bands of scar tissue (fibrous or fibrous
fatty), most often occurring as a complication of previous abdominal surgery.
Radiographic features
CT
Abdominal adhesions are rarely visible on CT, however, CT has
proven to be a valuable diagnostic modality in the detection of
adhesion-related complications, such as bowel obstruction or bowel
ischaemia. In the absence of concomitant diseases, an abrupt
transition from dilated to collapsed bowel segments may be the only
hint of the presence of adhesions that can be depicted on CT scans.

53. Adhesive small bowel
obstruction

56. The findings of the CT images compatible
with small bowel obstruction due to mesenteric
volvuluswhich presented with whirl or whirlpool
sign.
Small bowel volvulus refers to the abnormal twisting
of a loop of bowel around the axis of its own
mesentery.This twisting may produce mechanical
obstruction, vascular compromise, or both.
Small bowel obstruction with mesenteric volvulus

57. Ileal sticture due to crohns disease with small bowel
obstruction

59. Incarcerated umbilical hernia

60. Small bowel closed loop obstruction

61. Closed loop obstructionis a specific type of small bowel
obstruction in which two points along the course of a bowel are obstructed
at a single location thus forming a closed loop.Closed loop usually rotates
around its axis, forming a small intestinal volvulus.
Radiographic features
CT
Some or all of the following signs may be demonstrated on CT:
marked distension of a segment of small bowel
radially distributed, C or U-shaped small bowel loops
"beak sign": of the tapering bowel loops at the point of obstruction
"whirl sign": of the tightly twisted mesentery
two adjacent collapsed loops of bowel
if strangulation is present, signs of bowel ischaemia

62. Ileo-ileal
intussusception

68. Clinical presentation
Presentation is typically with abdominal pain, distension and
failure of passage of flatus and stool. Eventually signs
of peritonism, sepsis and shock develop, when perforation
occurs.
LARGE BOWEL OBSTRUCTION
Aetiology
malignancy
colorectal carcinoma (most common, 50-60%)
pelvic tumours; direct spread or metastatic disease
colonic diverticulitis
volvulus
caecal volvulus (1-3%)
sigmoid volvulus (3-8%)
ischaemic stricture (see ischaemic colitis)
faecal impaction/faecoloma (most common cause in debilitated elderly)
hernias (uncommon) 5

69. Radiographic features
Plain film
colonic distension: gaseous secondary to gas-producing
organisms in faeces
collapsed distal colon
small bowel dilatation, depends on
duration of obstruction
incompetence of the ileocaecal valve
In advanced cases one may see the stigmata of an ischaemic
colon, namely:
intramural gas (pneumatosis coli)
portal venous gas
free intra-abdominal gas (pneumoperitoneum)

70. Cases Of Large
Bowel Obstruction

73. Caecal volvulus
Caecal volvulusdescribes torsion of the caecum around its
own mesentery which often results in obstruction. If unrecognised
can result in bowel perforation and faecal peritonitis.

74. Sigmoid volvulus
Sigmoid volvulus is a cause of large bowel obstruction and occurs when
the sigmoid colon twists on the sigmoid mesocolon.
large gas-filled loop without haustral markings, forming a closed-
loop obstruction 6,

82. THE END