DR SAKHER AL-KHADERI CONSULTANT RADIOLOGIST AMC

Obscured psoas outline due to retroperitoneal fluid

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

Clinical presentationClassical 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.

Congenitaljejunal atresiaileal atresia or stenosisenteric duplicationmidgut volvulusmesenteric cystMeckel diverticulum

CAUSES OF SBO Extrinsic bowel lesionfibrous adhesionsabdominal herniavolvulusmasses

extrinsic neoplasmintra-abdominal abscessaneurysmHaematoma ,endometriosis

Intrinsic bowel wall lesionintussusceptiontumour (rare), e.g. lipomastrictures, e.g. surgical, irradiationLuminal occlusionneoplasm, e.g. adenocarcinoma, carcinoid, lymphomainflammation, e.g. Crohn's, Tuberculosisintestinal ischaemiaintramural haemorrhage, e.g. trauma, Henoch-Schonlein purpura, over-anticoagulationswallowed, e.g. foreign body, bezoargallstone: gallstone ileusmeconium ileus (or meconium ileus equivalent)

Radiographic featuresAbdominal radiographAbdominal 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 obstructionthe string-of-beads sign: small pockets of gas within a fluid-filled small bowel

Cases Of Small Bowel

Obstruction

Small bowel obstruction (string of pearls sign)

Abdominal adhesions are bands of scar tissue (fibrous or fibrous fatty), most often occurring as a complication of previous abdominal surgery.

Radiographic features

CTAbdominal 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.

Adhesive small bowel

obstruction

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

Ileal sticture due to crohns disease with small bowel obstruction

Incarcerated umbilical hernia

Small bowel closed loop obstruction

Closed loop obstruction is 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 featuresCTSome or all of the following signs may be demonstrated on CT:marked distension of a segment of small bowelradially 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 mesenterytwo adjacent collapsed loops of bowelif strangulation is present, signs of bowel ischaemia

Ileo-ileal intussusception

Clinical presentationPresentation 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

Aetiologymalignancy

colorectal carcinoma  (most common, 50-60%)pelvic tumours; direct spread or metastatic disease

colonic diverticulitisvolvulus 

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

Radiographic features

Plain filmcolonic distension: gaseous secondary to gas-producing organisms in faecescollapsed distal colonsmall bowel dilatation, depends on

duration of obstructionincompetence 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)

Cases Of Large Bowel

Obstruction

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

Sigmoid volvulusSigmoid 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, 

THE END