Answer : B. Small bowel dilatation

Plain abdominal radiograph shows :

• Several dilated loops of gas filled bowel with diameter more than 3 cm
• Valvulae conniventes are visible - confirming this is small bowel
  
  -> Small bowel obstruction

Etiology

• 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(75%)
• In the developing countries incarcerated hernias are much more common(80%)

Extrinsic bowel lesion :

• Fibrous adhesions
• Abdominal hernia
• Volvulus
• Masses
  • Extrinsic neoplasm
  • Intra-abdominal abscess
  • Aneurysm
  • Hematoma
  • Endometriosis

Intrinsic bowel wall lesion :

• Intussusception
• Tumor (rare) such as lipoma
• Strictures such as surgical, irradiation

Luminal occlusion:

• Neoplasm such as adenocarcinoma, carcinoid, lymphoma
• Inflammation such as Crohn's, Tuberculosis
• Intestinal ischemia
• Intramural hemorrhage such as trauma, Henoch-Schonlein purpura, over-anticoagulation
• Swallowed such as foreign body, bezoar
• Gallstone : gallstone ileus
• Meconium ileus or meconium ileus equivalent)

Congenital : found in younger age group

• Jejunal atresia
• Ileal atresia or stenosis
• Enteric duplication
• Midgut volvulus
• Mesenteric cyst
• Meckel diverticulum

Radiographic features : abdominal radiograph

• Dilated loops of small bowel
• Three instances of dilatation over 3 cm
• However high grade mechanical obstruction may present:
  • Gasless abdomen : presented with fluid fill bowel
  • String-of-beads sign: presented in upright position, in case of more fluid-fill in small bowel

Radiographic features : Computer Tomography

•  CT criteria for SBO are the presence of dilated small bowel loops (diameter >2.5 cm from outer wall to outer wall) proximally to collapsed loops distally