Left paraduodenal hernia causing acute small bowel obstruction

Introduction 

Congenital internal hernias are an infrequent cause of intestinal obstruction [1]. They produce non-specific abdominal symptoms, and thus are often not diagnosed preoperatively [2], [3]. Paraduodenal hernia is a rare congenital anomaly that arises from an error of rotation of the midgut [2], [4]. These may be discovered as incidental finding at laparotomy or may be the cause of acute small bowel obstruction, which can progress to strangulation [5]. Imaging studies during a symptomatic episode can make the diagnosis [6]. Surgical treatment is necessary, considering the risk of incarceration and strangulation [6], [7]. We report a case of left paraduodenal hernia that had multiple episodes of undiagnosed abdominal pain before presenting with acute intestinal obstruction.

Case report 

A 32-year-old man presented to the emergency room with acute onset of upper abdominal pain associated with bilious vomiting for 2days. He had presented at our emergency room many times previously with pain and heaviness in the upper abdomen, more on the left side, associated with nausea, which was relieved without treatment each time within a short span. Ultrasound showed a small left renal stone, which was considered as the cause of his symptoms. He was treated for his symptoms with antispasmodic drugs. There was no history of any operation. On this occasion, however, a globular mass in the left upper abdomen could be seen. Bowel sounds were hyperdynamic. Erect radiograph of the abdomen showed clustering of small bowel loops along with some air–fluid levels in the left upper abdomen (Fig. 1). A nasogastric tube was inserted to drain the bilious aspirate. The patient was taken for exploratory laparotomy. Intra-operatively, proximal jejunal loops were found invaginating through a small orifice situated on left side of the fourth part of the duodenum below the transverse colon (Fig. 2A and B). A diagnosis of left paraduodenal hernia leading to acute intestinal obstruction was confirmed. The bowel loops could not be retracted into peritoneal cavity easily as the orifice of hernial sac was too narrow. The opening was enlarged by careful division of the hernial sac’s free margin, including the inferior mesenteric vein, which was ligated and divided, to reduce the bowel (Fig. 3A). The reduced bowel was healthy and there were no signs of ischaemia. The extra peritoneum was excised and the sac was obliterated by simple suturing (Fig. 3B). The postoperative course was simple and he was discharged on the fifth postoperative day. During a follow-up period of 6months, he suffered no recurrence.

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Fig. 1. Erect radiograph of the abdomen of a 32-year-old man with acute intestinal obstruction, showing clustered small bowel loops along with some air-fluid levels in the left upper abdomen; typical radiograph of left paraduodenal hernia.

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Fig. 2. Intra-operative photographs of the same patient mentioned in Fig. 1, showing a narrow orifice of left paraduodenal hernial sac (arrow) through which loops of jejunum are seen invaginating into the hernial sac. Transverse colon can be seen in upper left quadrant of (A).

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Fig. 3. (A) The opening has been enlarged by dividing the inferior mesenteric vein (here seen ligated in the free margin of the hernial sac), and bowel has been reduced. Note that hernial sac is situated below the transverse colon (TC) and to the left of the duodeno–jejunal junction (multiple arrows). (B) Obliterated sac after excising the extra peritoneum.

Discussion 

Internal hernias are rare type of hernias and account for 0.2–0.9% of all cases of intestinal obstruction [1]. Paraduodenal hernias are the most common type of internal abdominal hernias, accounting for 53% of all internal hernias, 75% of these being left sided [2], [8]. Less than 1% of all causes of small bowel obstructions are due to paraduodenal hernias, with a male-to-female ratio of 3:1 [3], [4], [7].

It is believed that they occur because of a congenital defect known as the ‘fossa of Landzert’ or ‘paraduodenal fossa’, at the confluence of the mesentery of small bowel, descending mesocolon and transverse mesocolon [4]. Thus, the fossa of Landzert is situated to the left of ascending or fourth part of the duodenum and is caused by raising up of a peritoneal fold by the inferior mesenteric vein as it runs along the lateral side of fossa and then above it [2]. It is present in 2% of autopsy cases. Small bowel loops may herniated through the opening of the fossa, to the left posteriorly and downward, lateral to the fourth part of the duodenum extending into the descending mesocolon and left part of the transverse mesocolon [2]. The herniated small bowel loops may become entrapped within this mesenteric sac [4].

Clinically, internal hernias can be asymptomatic or cause significant discomfort, ranging from constant vague epigastric pain to intermittent colicky peri-umbilical pain. Other symptoms include nausea, vomiting (especially after a large meal) and recurrent intestinal obstruction [2]. Severity of the symptoms relates to the duration and reducibility of the hernia and the presence or absence of incarceration and strangulation [5]. Postprandial pain with postural variation is a characteristic symptom [2]. Repeated episodes of herniation into the ‘paraduodenal fossa’ can increase the size of the defect and lead to development of adhesions, which can result in obstruction or circulatory compromise. Therefore, even a small paraduodenal hernia is potentially dangerous and is usually considered to be an operable condition [6].

Examination and investigations during an asymptomatic interval may not show the hernia. Even at surgery, a left paraduodenal hernia may not be evident. This may either be because of spontaneous resolution of the hernia or inadvertent operative reduction due to traction on small bowel loops [6]. These hernias have a characteristic appearance of a cluster of dilated small intestinal loops, which appear encased in a sac, and lying between the pancreatic body and/or tail and the stomach to the left of the ligament of Treitz [8], [9].

Other commonly seen signs on computed tomography (CT) scan are duodeno–jejunal junction depression, mass effect on the posterior stomach wall, engorgement and crowding of the mesenteric vessels with frequent right displacement of the main mesenteric trunk and depression of the transverse colon [4].

A person with paraduodenal hernia has a lifetime risk of over 50% for development of intestinal obstruction with associated 20% mortality rate. Surgical treatment is essential to avoid these complications [6], [7], [10]. This includes reduction of entrapped bowel loops and obliteration of the hernia defect by simple closure or by wide opening of the sac [11]. If reduction through the small orifice is not possible, the latter can be enlarged, by division of the inferior mesenteric vein [8], [12]. Bowel resection may be needed in presence of ischaemia.

In conclusion, left paraduodenal hernias are rare and have non-specific symptoms, thus a preoperative diagnosis can be challenging. The present case emphasises that these should be considered in middle-aged men presenting with features of acute intestinal obstruction. A high index of suspicion is needed to make the diagnosis. Lifetime risk of acute intestinal obstruction and the associated mortality is high, underlining the importance of considering this uncommon diagnosis while examining a patient with acute small bowel obstruction.