The aim of this presentation is to provide a pictorial exhibit of abdominal internal hernias; a rare but important differential to consider in closed loop small bowel obstructions, which are a surgical emergency. This presentation will describe and demonstrate some of the key imaging findings for radiological diagnosis, the relevant imaging anatomy and a discussion on the different types of internal hernias with a series of case studies.

Cases are from hospital presentations from Brisbane, Queensland between 2017-2021, obtained from the Metro North imaging PACS. Abdominal internal hernias are defined as a protursion of abdominal viscera through peritoneum or mesentery while remaining within the abdominal cavity (as opposed to external hernias, which are a prolapse extending outside of the abdominal cavity).[1] Internal hernias require an intra-abdominal aperture for abdominal viscera (e.g. small or large bowel) to herniate through. These apertures can be congenital or acquired. Congenital apertures may be normal anatomical apertures (such...

Types: Paraduodenal hernias: [Figure 9, Figure 11] [Fig 9] [Fig 11] Two subtypes: right and left paraduodenal hernias. Herniation is into abnormal apertures around the duodenum which arise from congenital failures of mesenteric fusion. [1-3,5,6] Most common type of internal hernia (approximately 55%), with left being more common than right (approximately 75% to 25%). More common in males than females (ratio of approximately 3:1). Left paraduodenal hernia: [Figure 8, Figure 11, Figure 14] [Fig 14] From a congenital fossa of Landzert anomaly, which is failure...

Small bowel obstruction is a potential surgical emergency, and the various types of internal hernia (both congenital and acquired) should be considered as an important differential along with adhesions, particularly after Roux-en-Y anastamosis. Increased understanding of the different types and presentations of the various internal hernias may help in detection and aid surgical management.

Doishita, S, et al. Internal Hernias in the Era of Multidetector CT: Correlation of imaging and surgical findings. Radiographics: 2015. Martin LC, et al.Review of internal hernias: radiographic and clinical findings.AJR Am J Roentgenol2006;186(3):703–717. Takeyama N, et al.CT of internal hernias.RadioGraphics2005;25(4):997–1015. Federle MP. CT of the acute (emergency) abdomen. Eur Radiol. 2005;15(4):100-4. Newsom BD,et al.Congenital and acquired internal hernias: unusual causes of small bowel obstruction.Am J Surg1986;152(3):279–285. Mathieu D,et al. Internal abdominal herniations.AJR Am J Roentgenol2004;183(2):397–404.