Dr/Ahmed BahnassyConsultant radiologistPSMMC

Importance of subjectAlthough internal hernias have anoverall incidence of less than1%, they constitute up to 5.8% ofall small-bowel obstructions,which, if left untreated, have been reportedto have an overall mortality exceeding 50%if strangulation is present

Types of herniasHernias are of two main types, external andinternal . External hernias refer to prolapseof intestinal loops through a defect in the wall of the abdomen or pelvis, and internal herniasare defined by the protrusion of a viscusthrough a normal or abnormal peritoneal ormesenteric aperture within the confines of theperitoneal cavity. The orifice can be either acquired,such as a postsurgical, traumatic, orpostinflammatory defect, or congenital, includingboth normal apertures, such as the foramenof Winslow, and abnormal aperturesarising from anomalies of internal rotationand peritoneal attachment.

Clinical presentation Clinically, internal hernias can be asymptomatic or cause significant discomfort ranging from constant vague epigastric pain to intermittent colicky periumbilical pain. symptoms include nausea, vomiting (especially after a large meal), and recurrent intestinal obstruction

FluoroscopyGeneral radiographicfeatures with barium studies includeapparent encapsulation of distendedbowel loops with an abnormal location, arrangementor crowding of small-bowel loopswithin the hernial sac, evidence of obstructionwith segmental dilatation and stasis, with additionalfeatures of apparent fixation and reversedperistalsis during fluoroscopic evaluation

CT On CT, additional findings include mesenteric vessel abnormalities, with engorgement, crowding, twisting, and stretching of these vessels commonlyfound and providing an important clue to theunderlying diagnosis

Diagrammaticillustration showsvarious types of internalhernias:A = paraduodenal,B = foramen of Winslow,C = intersigmoid,D = pericecal,E = transmesenteric, andF = retroanastomotic.Review of Internal Hernias:Radiographic and Clinical Findings:Lucie C. MartinElmar M. Merkle,William M. Thompson,Martin LC, Merkle EM, Thompson.AJR 2006; 186:703717

Paraduodenal fossaeDrawing (coronal view) shows the locationsof duodenal fossae. Arrows indicate the directionsof hernias through these fossae. The frequency withwhich each fossa is found at autopsy is given in parentheses.1. superior duodenal fossa (50%), 2.inferior duodenal fossa (fossa of Treitz) (75%), 3.paraduodenalfossa (fossa of Landzert) (2%),4.intermesocolic fossa (fossa of Broesike), 5.mesentericoparietal fossa(fossa of Waldeyer)

Left paraduodenal herniaReview of Internal Hernias:Radiographic and Clinical Findings:Lucie C. MartinElmar M. Merkle,William M. Thompson,Martin LC, Merkle EM, Thompson.AJR 2006; 186:703717Landzert's fossa

Left paraduodenal hernia

Left paraduodenal hernias have an overallincidence of approximately 40% of internalhernias. They occur when bowel prolapsesthrough Landzerts fossa, an aperturepresent in approximately 2% of the populationThese hernias therefore can beclassified as a congenital type, normal aperturesubtype. Landzerts fossa is located behindthe ascending or fourth part of theduodenum and is formed by the lifting up ofa peritoneal fold by the inferior mesentericvein and ascending left colic artery as theyrun along the lateral side of the fossa. Small bowel loops prolapse posteroinferiorly through the fossa to the left of the fourthpart of the duodenum into the left portion of the transverse mesocolon.

Left paraduodenal hernialt adrenalstretched IMV

Left paraduodenal herniaengorged vessels

Right paraduodenal heniaRight paraduodenal hernias have an overallincidence of approximately 13% andoccur when bowel herniates throughWaldeyers fossa (representing a defect inthe first part of the jejunal mesentery), behindthe superior mesenteric artery and inferiorto the transverse or third portion of theduodenum . This type of hernia occurs more frequently in the setting of nonrotated small bowel .

Right paraduodenal heniawaldeyer fossaReview of Internal Hernias:Radiographic and Clinical Findings:Lucie C. MartinElmar M. Merkle,William M. Thompson,Martin LC, Merkle EM, Thompson.AJR 2006; 186:703717

Right paraduodenal heniaOn a standard barium gastrointestinal examination,a larger and more fixed, encapsulated,ovoid collection of bowel loops is noted lateral and inferior to the descending duodenum, in the right half of the transverse mesocolon.

Right paraduodenal henia..CTSMA

Additional vascularfindings include the presence of thesuperior mesenteric artery, ileocolic artery,and right colic vein in the anterior margin ofthe neck of the hernial sac, displaced anteriorlyif there is sufficient mass effect by theencased small-bowel loops . Again, vesselengorgement may also be present andprovide a clue to the diagnosis.SMA

Lesser sac herniaReview of Internal Hernias:Radiographic and Clinical Findings:Lucie C. MartinElmar M. Merkle,William M. Thompson,Martin LC, Merkle EM, Thompson.AJR 2006; 186:703717foramen of winslow

Lesser sac herniaRisk factors for this type of hernia includean enlarged foramen of Winslow, anabnormally long small-bowel mesentery,persistence of the ascending mesocolon allowing marked mobility of bowel,

Lesser sac herniabowel loops posterior to stomach

Transmesenteric hernia

Transmesenteric herniaswirled mesenteric vesselsclusters of bowel loopsstretched vessesl

Transmesenteric herniamost common in pediatricscluster of bowel

Pericecal herniaReview of Internal Hernias:Radiographic and Clinical Findings:Lucie C. MartinElmar M. Merkle,William M. Thompson,Martin LC, Merkle EM, Thompson.AJR 2006; 186:703717paracaecal recesses

Retro-caecal

Para-caecal

Para-cecal hernia

Intersigmoid herniasigmoid mesocolondefectReview of Internal Hernias:Radiographic and Clinical Findings:Lucie C. MartinElmar M. Merkle,William M. Thompson,Martin LC, Merkle EM, Thompson.AJR 2006; 186:703717

Intersigmoid herniaIMVPsoas major

Intersigmoid hernia

Trans-Omental hernia

Trans-Omental hernia

Pelvic internal hernia

Broad ligament hernia

Broad ligament hernia

Peri-rectal fossa hernia

Trans-mesocolic internal herniano omentumdirectly on ABWdilated boweltransition point

the only statistically significant signs were relatively nonspecificfindings of small-bowel dilatation with transition point, clustering of small-bowel loops, and mesenteric vessel abnormalities (includingdisplacement of the main mesenteric trunk to the right).

Occasionally, there may even beevidence of ischemia with ascites and bowel wall thickening present .closed loopsign, twisting of the mesenteric vessels and whirl sign .

Post operative Retro-anastomotic

Adviceslocate the abnormal position of bowel.clustering , +/- encapsulation,dilatation.any transitional point Relation to other organs.Study vessels status.is it obstructed (surgical emergency)or not.discuss with the referring physician (an abnormality is present i.e.:follow up ,and presence of data in patient file is important)