Case report

A 24-year-old woman was admitted after 2 weeks of intermittent abdominal pain associated with nausea and vomiting. Pain occurred on a daily basis, lasting for 1 h at a time, and was worse with recumbency. She reported having her appendix removed at age 10 for perforated appendicitis; medical records were not available. The admission physical examination was completely normal, with the exception of a well-healed surgical scar from a previous right lower quandrant incision with medial extension. Laboratory studies and upper endoscopy were normal. Computed tomography (CT) revealed the small bowel on the right side of the abdomen and the colon on the left, suspicious for malrotation. Subsequent upper gastrointestinal series with small bowel follow-through revealed the ligament of Treitz to be on the right side with the small bowel encased within a probable hernia sac (Fig. 1). A presumptive diagnosis of right paraduodenal hernia was made.

Figure 1
figure 1

The right-sided paraduodenal hernia on upper gastrointestinal series, with small bowel follow-through. The small bowel is encased in a hernia sac on the right side with the characteristic “bunched up” appearance. The colon lies to the left of midline.

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The patient was taken to the operating room for elective repair. The patient was placed in the supine position. Access to the peritoneal cavity was obtained at the umbilicus using the Verees needle technique through a 10-mm skin incision. Survey of the abdomen revealed a large hernia sac encompassing the entire small bowel. Three 3-mm ports were placed. One port was placed in the right upper quadrant and two were placed in the left upper and lower quadrants to facilitate triangulation for retraction and exposure. With the patient in the reverse Trendelenberg position, the hernia sac was opened widely using electrocautery scissors from the duodenum to the pelvis. The sac was opened laterally to avoid injury to superior mesenteric vessels, which border the hernia orifice. The small bowel was then released into the peritoneal cavity. The entire bowel was inspected and no other abnormalities were noted. The patient had resolution of her abdominal pain and her postoperative course was uncomplicated. She was discharged home on postoperative day 3 and has since done exceptionally well.

Discussion

Paraduodenal hernia, also known as mesocolic or retroperitoneal hernia, is a rare form of internal hernia that results from abnormal rotation of the midgut during embryological development. As a result, the small intestine becomes trapped behind the developing mesocolon. Right and left paraduodenal hernias have both been described. The two entities are distinguished from each other anatomically and have different embryologic etiologies.

Normal embryologic development of the midgut consists of three phases [8]. The first phase occurs in the sixth week of development. In this phase, the midgut elongates and pushes its way out through the umbilical cord into the extraembryonic coelom. The second phase occurs in the 10th week of development when the midgut returns to the abdomen. Phase three occurs at 12 weeks and involves posterior peritoneal fixation of the midgut.

The midgut is divided into two limbs, delineated by either a proximal (prearterial) or distal (postarterial) relationship to the superior mesenteric artery (SMA). The prearterial segment will form the majority of the small intestine, and the postarterial segment will form the distal ileum and the right half of the colon. As the midgut elongates, it undergoes a 90° counterclockwise rotation around the superior mesenteric artery. The prearterial segment enters before the postarterial segment and passes inferior to the SMA. It then undergoes 180° counterclockwise rotation and the prearterial segment ends up on the left side of the SMA and the posterial segment on the right of the SMA. The midgut then becomes fixated to the posterior abdominal wall.

Andrews elucidated the etiology of a right paraduodenal hernia in 1923 [4]. The hernia is formed in the fourth week of embryological development when the prearterial portion of the midgut fails to rotate around the SMA. The majority of the small bowel remains to the right of the SMA. The cecum and proximal colon rotate in a normal manner and will fixate to the posterior peritoneum. The small bowel is then trapped in a sac created by the mesentery of the right colon. The SMA and ileocolic artery form the anterior border of the hernia opening. The orifice of the hernia is located to the right of midline.

A left paraduodenal hernia occurs secondary to a failure of fusion of the mesocolon and mesentery of the duodenum, as described first by Callender et al. in 1935 [4]. The small bowel rotates in a normal fashion to the left and invaginates into the potential space between the inferior mesenteric vein and retroperitoneum. The small bowel then becomes trapped in a sac of mesocolon, with the inferior mesenteric vein at the neck of the sac. The orifice of the hernia can be to the left of midline or displaced to the right, depending on the amount of small bowel contained in the hernia sac.

Although internal hernias account for less than 1% of all cases of intestinal obstruction, half of all patients with paraduodenal hernia eventually present with bowel obstruction [6]. Paraduodenal hernias are three times more common in men, and they are more common on the left side. Patients with paraduodenal hernias typically experience chronic, intermittent abdominal pain, which is often postprandial. In some instances, it has been described as being relieved by recumbency, which is contrary to our patient. Although the most common presentation of a paraduodenal hernia is acute small bowel obstruction, most patients have had symptoms of vague abdominal pain for years. Many patients have undergone extensive workup of the chronic pain, which has been negative for gastroesophageal reflux, gastritis, and biliary colic [5]. The chronic pain may eventually present with partial or complete obstruction. The diagnosis of paraduodenal hernia should always be considered when the cause of obstruction is unknown. The diagnosis can be made preoperatively with upper gastrointestinal series, which will show the characteristic pattern of “bunched up” small bowel on either side of midline [2]. Computed tomography findings for a right paraduodenal hernia are small bowel clustered in the right midabdomen, as was evident in our patient. The hernia sac is difficult to appreciate on CT scan. A left paraduodenal hernia may show encapsulated bowel loops between the stomach and pancreas or behind the pancreas on CT scan.

The basic principle of surgical repair, open or laparoscopic, is reduction of the hernia and repair of the defect either by closure or wide opening of the hernia orifice. Care must be taken to avoid injury to the vessels at the neck of the sac. When opening the sac of a right paraduodenal hernia, this must be done laterally to avoid injury to the superior mesenteric and ileocolic vessels [2]. These vessels lie in the neck or opening of the hernia sac. By taking down the lateral attachments of the ascending colon, the small bowel is released from the sac (Fig. 2).

Figure 2
figure 2

Right paraduodenal hernia, with line of incision for reduction of hernia.

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The left paraduodenal hernia is approached by incising the sac in an avascular plane to the right of the inferior mesenteric vein; then the intestine can be reduced through the neck of the sac. Some authors have described division of the vessels in the sac without comprising bowel viability, but most advocate preservation of the vessels [1, 3].

In our patient, we successfully applied these principles with a laparoscopic approach. The patient had an uncomplicated postoperative course and resolution of her abdominal pain. There have been two reports in the literature of left paraduodenal hernias repaired laparoscopically [5, 7]. This is the first report of laparoscopic repair of a right paraduodenal hernia. Our success demonstrates that right paraduodenal hernias can be successfully approached minimally invasively. Laparoscopic repair of left as well as right paraduodenal hernias is a feasible and practical approach.