Journal Reading: CT of Internal Hernias RadioGraphics 2005; 25:997–1015 ~NCKUH, Jan. 17th, 2006~ Presented by Intern 洪健齡

Introduction Internal hernia: protrusion of the viscera through the peritoneum or mesentery and into the compartment in the abdominal cavity Pre-operative diagnosis is difficult due to wild range of clinical symptoms Silent: easily reducible Intermittent digestive complaint, abdominal discomfort Incarceration: small bowel obstruction (SBO) normal or abnormal apertures: Pathologic defects of the mesentery and visceral peritoneum, which are caused by congenital mechanisms, surgery, trauma, inflammation, and circulation, are also potential herniation orifices Most common presentation: acute obstruction of small bowel loop

Diagnosis with CT Anatomic location CT findings: evidence of small bowel obstruction Bowel configuration: saclike mass or cluster of dilated bowel loop Mesenteric change: mesenteric vascular pedicle that is engorged, stretched, and displaced Converging vessels at the entrance of the hernial orifice

E: pericecal hernia F: transomental hernia G: intersigmoid hernia H: supravesical hernia I : hernia through the broad ligament 1= vesicouterine pouch 2= Douglas (rectouterine) pouch 3= perirectal fossa A: foramen of Winslow hernia B: left paraduodenal hernia C: right paraduodenal hernia D: transmesenteric hernia

Foramen of Winslow hernia Anatomy: Aperture communicate the lesser sac and the greater peritoneal cavity Beneath the upper part of the right border of the lesser sac, cephalad to the duodenal bulb and deep to the liver Anterior to the IVC and posterior to the hepatoduodenal ligament, Including the portal triad

Foramen of Winslow hernia Predisposing factors: Enlarged foramen of Winslow Excessively mobile intestinal loop due to long mesentery or persistence ascending mesocolon Involvement: Small intestine(60~70%) Terminal ileum, cecum, A-colon (25~30%) Rare: T-colon, GB, omentum

Foramen of Winslow hernia CT findings: Two or more bowel loops in the high subhepatic space Air-fluid collection in the lesser sac with a beak toward foramen of Winslow Mesentery between IVC and portal vein Absence of the A-colon

H: hepatoduodenal ligament I : inferior vena cava D: duodenum P: panceatic head

Paraduodenal Hernia Anatomy: Superior duodenal fossa (50%) Inferior duodenal fossa (fossa of Treitz) (75%) Paraduodenal fossa (fossa of Landzert) (2%)-left PDH Intermesocolic fossa (fossa of Broesike) Mesentericoparietal fossa (fossa of Waldeyer) (1%)-right PDH originate as congenital peritoneal anomalies owing to failure of mesenteric fusion with the parietal peritoneum and an associated abnormal rotation during imprisonment of the small intestine beneath the developing colon

Paraduodenal Hernia Features: Congenital peritoneal anomalies: Three-fourths occur on the left Male predominant (M:F=3:1) Congenital peritoneal anomalies: Abnormal rotation during imprisonment of the small intestine beneath the developing colon Failure of mesenteric fusion with the parietal peritoneum

Paraduodenal Hernia Left PDH: Dilated small bowel loops between the pancreas and stomach Mesenteric vessels crowded, engorged, and stretched Mass effect to the stomach, duodenal flexure and transverse colon IMV and left colic artery above the encapsulated bowel loops The fossa of Landzert is located at the duodenojejunal junction, which is a zone of confluence of the descending mesocolon, transverse mesocolon, and small bowel mesentery. Mass effect: displaces the posterior wall of the stomach, the duodenal flexure inferiorly, and the transverse colon inferiorly.

P: pancreatic head D: descending mesocolon L: fossa of Lanzert J : jejunal loops S: stomach Arrowhead: IMV

Paraduodenal Hernia Right PDH: Tends to the right and downward directly to the posterior peritoneum, in to the ascending mesocolon with a right colic vein anteriorly SMA and right colic vein which are located at the anterior-medial border of the hernial sac as landmark Right PDH involves the fossa of Waldeyer is located immediately behind the superior mesenteric artery and inferior to the transverse segment of the duodenum. Right PDH occurs most frequently in cases of a nonrotated small intestine and a normally or incompletely rotated colon.

W: fossa of Waldeyer D: duodenum I: ileal loops Arrowhead: SMA Arrow: converging vessels

Transmesenteric Hernia Anatomy: In children (35%): congenital Close to the ligament of Treitz or the ileocecal valve Adult: the result of surgery, trauma, or inflammation Nearly 35% of transmesenteric hernias occur during the pediatric period and are probably caused by a congenital mechanism. Mesenteric defects are usually 2–5 cm in diameter and are located close to the ligament of Treitz or the ileocecal valve (a) partial regression of the dorsal mesentery, (b) fenestration during the developmental enlargement of an inadequately vascularized area, (c) an ileocecal mesentery with considerable and rapid lengthening in fetal life In adults, most mesenteric defects are probably the result of surgery, trauma, or inflammation.

Transmesenteric Hernia Absence of limiting hernia sac: mechanical SBO usually occurs Usually manifests as proximal bowel dilatation → transitional zone →normal or collapsed intestine A volvulus may further complicate the process: rapid hernial strangulation and gangrene

Transmesenteric Hernia The clustering of the small bowel loop and abnormality of the mesenteric vessels CT findings: Mesenteric vascular pedicle is engorged, stretched, and crowded Converging mesenteric vessels are located at the entrance Displacement of the main mesenteric trunk

S: small bowel loops Arrow: crowed and stretched vessels

Pericecal Hernia Anatomy: 1=superior ileocecal recess Superior ileocecal recess: bounded in front by the vascular fold of the cecum and behind by the ileal mesentery Inferior ileocecal recess is bounded in front by the ileocecal fold, above by the posterior ileal surface and its mesentery, to the right by the cecum, and behind by the upper mesoappendix The retrocecal recess, the largest of the four recesses, is bounded anteriorly by the posterior wall of the cecum, posteriorly by the posterior abdominal wall, superiorly by the reflection of the visceral peritoneum coating the posterior wall of the cecum, and medially and laterally by two cecal folds of the peritoneum Paracolic sulci are lateral depressions of the peritoneum investing the cecum 1=superior ileocecal recess 2=inferior ileocecal recess 3=retrocecal recess 4=paracolic sulci

Pericecal Hernia Most common: ileal loops herniated through the defect and occupy the right paracolic gutter CT findings: The specific CT appearance is not established Cluster of fluid-filled small bowel loops located lateral to the cecum and posterior to the ascending colon dilatation of small bowel loops with a transition zone Beaking appearance

A: ascending colon Black arrow: dilated and stretched vessels White arrow: beaking

Hernia through the broad ligament Anatomy: B: Broad ligament F: Fallopian tube M: Mesosalpinx O: Ovary R: Round ligament

Hernia through the broad ligament Clinical features: Middle-aged women Parous women(85%) Small intestine is involved (90%) Congenital: developmental peritoneal defect around the uterus Aquired: surgical trauma, pregnancy and birth trauma, and prior pelvic inflammatory disease Congenital cases have an embryologic basis due to a developmental peritoneal defect around the uterus. Acquired defects are due to surgical trauma, pregnancy and birth trauma, perforations following vaginal manipulation, and prior pelvic inflammatory disease

Hernia through the broad ligament Classification (the position of the defect): type 1: caudal to the round ligament type 2: above the round ligament type 3: between the round ligament and the remainder of the broad ligament through the mesoligamentum teres Fenestra type: through a defect in the broad ligament (most common) Pouch type, with herniation into an anterior or posterior aperture of the broad ligament

Hernia through the broad ligament CT findings: A cluster of dilated small bowel loops with air-fluid levels in the pelvic cavity Bowel loops compressing the rectosigmoid dorsolaterally and the uterus ventrally

S: small bowel loops U: uterus R: rectum S: sigmoid colon U: uterus R: rectum

Conclusion Identification of the internal hernia: Understanding of the anatomy Characteristic anatomic location of each internal hernia Characteristic CT findings Multi-director row CT+3-D reformatting Cooperation between surgeon and radiologist

Thank you for attention!!