Anatomic Considerations

Left Paraduodenal Hernias

Although nine normal and aberrant paraduodenal folds

and fossae have been classically described, there is only one fossa to the left of the duodenum capable of developing into the sac of a hernia, termed the paraduodenal fossa (fossa of Landzert)26 (Fig. 16-2). This fossa, present in about 2% of autopsy cases,20 is situated at some distance to the left of the ascending or fourth portion of the duodenum and is caused by the raising up of a peritoneal fold by the inferior mesenteric vein as it runs along the lateral side of the fossa and then above it. Small intestine may herniate through the orifice posteriorly and downward toward the left, lateral to the ascending limb of the duodenum, extending into the descending mesocolon and left portion of the transverse mesocolon. The free edge of the hernia thus contains the inferior mesenteric vein and the ascending left colic artery. Confusion can be minimized if it is understood that the her-nial orifice is in a paraduodenal location but the her-niated loops present at a distance—more clearly, as a hernia into the descending mesocolon23 (Fig. 16-3).

The hernia may contain only a few loops and be spontaneously reducible. Evaluation during symptomfree intervals is likely to be misleadingly negative. Since the afferent loop enters the sac from behind where the duodenum emerges from its fixed retroperitoneal position, only the efferent loop of the intestine truly passes through the hernial orifice.

Right Paraduodenal Hernias

The mesentericoparietal fossa (fossa of Waldeyer)28 is in the first part of the mesentery of the jejunum, immediately behind the superior mesenteric artery and inferior to the transverse duodenum (Figs. 16-2 and 16-4). The fossa's orifice looks to the left, its blind extremity to the right and downward, directly in front of the posterior parietal peritoneum. This fossa is present in 1% of cases.20 Right paraduodenal hernias most commonly

Fig. 16—2. The paraduodenal fossa of Landzert and the mesentericoparietal fossa of Waldeyer.

The transverse colon and mesocolon have been elevated and the proximal jejunal loop deflected medially in order to identify the fossae clearly. Behind the fossae lie the parietal peritoneum and retroperitoneal organs.

(Reproduced from Meyers.27)

Fig. 16—2. The paraduodenal fossa of Landzert and the mesentericoparietal fossa of Waldeyer.

The transverse colon and mesocolon have been elevated and the proximal jejunal loop deflected medially in order to identify the fossae clearly. Behind the fossae lie the parietal peritoneum and retroperitoneal organs.

(Reproduced from Meyers.27)

Mesenterico Parietal Fossa Waldeyer

involve the mesentericoparietal fossa (Fig. 16-5), representing an entrapment of the small bowel behind the ascending mesocolon and the right half of the transverse mesocolon, more accurately conceived therefore as hernias into the ascending mesocolon. The superior mes-enteric and ileocolic arteries are then in the free edge of the sac.9,23 Because both afferent and efferent loops pass through the hernial orifice, right paraduodenal hernias are usually more massive and fixed than those occurring on the left side.16,17

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