Small bowel obstruction: secondary to right inguinal hernia

Case Discussion

• Findings: Small bowel obstruction secondary to right indirect inguinal hernia

• Objectives:

  • To learn the definition of a small bowel obstruction, high grade small bowel obstruction

  • To review common etiologies of small bowel obstruction

  • To practice following small bowel to assess for severity, etiology, signs of ischemia

• Protocolling:

  • Contrast Enhanced CT, no oral contrast required

  • Can give oral contrast if suspected to be only partial obstruction

• Key points:

  • Abdominal Xray is only approximately 50% sensitive for SBO

    • Difficult to exclude - can appear as fluid filled loops or nonspecific bowel gas pattern

  • Role of CT scan is to answer the following questions:

    • Is the small bowel obstructed?

    • How severe is the obstruction? (i.e. high grade?)

    • Is an etiology apparent on imaging?

    • Are there signs of ischemia?

  • Small bowel obstruction

    • Proximally dilated loops (>2.5 - 3 cm)

    • Distally normal or collapsed small bowel loops.

    • Passage of oral contrast can distinguish complete vs. incomplete.

  • Ileus = dilatation of large and small bowel with no transition point

  • High grade obstruction

    • Distally collapsed small bowel loops less than ½ the caliber of proximally dilated loops

  • Finding the transition point:

    • Follow small bowel anterograde or retrograde, depending on suspected location of transition point

    • Use reformats to help follow small bowel

    • Don’t make any assumptions - follow bowel from loop to loop only when 100% sure that the lumens connect

    • “Small bowel feces sign” often identified just proximal to obstruction

  • Determining the etiology (assess the transition point):

    • Adhesion - most common. Diagnosis of exclusion (abrupt change of caliber without findings to suggest another cause)

    • Hernias - external (inguinal, femoral, obturator, umbilical, incisional, etc), internal (paraduodenal, transmesenteric, etc)

    • Crohn’s disease - from acute thickening, strictures, adhesions/hernias

    • Tumor - adenocarcinoma/mets. Look for focal mass, asymmetric thickening, evidence of other metastatic disease.

    • Intussusception - bowel within bowel with or without mesenteric fat

    • Gallstone Ileus - Rigler’s triad (pneumobilia, SBO, gallstone). Bouveret’s syndrome is basically proximal gallstone ileus.

    • Other: endometriosis, bezoar, radiation enteritis, etc.

  • Assess for ischemia (see intestinal ischemia case)

• Suggested resource: “Silva AC, Pimenta M, Guimaraes LS. Small Bowel Obstruction: What to look for. RadioGraphics 2009; 29;423-39.”