A case report of left paraduodenal hernia with a spontaneous reduction on follow-up: the rare demonstration on computed tomography

Left paraduodenal hernia (PDH) makes for around 40% of all internal hernias. It is due to the prolapse of bowel through fossa of Landzert, an anatomic variant that is found in around 2% of the population. This hernia is presumed to be spontaneously reducible in many patients with recurrent symptoms. The present report shows the case of this condition in a 65-year-old male presenting with recurrent abdominal pain and subacute intestinal obstruction who was unwilling for surgery and was managed conservatively. A follow-up scan after 11 months revealed complete spontaneous resolution of hernia. This represents only the second demonstration of the oft-mentioned spontaneous reduction of this condition on computed tomography. The radiologists should be aware of this uncommon entity and in the event of clinical suspicion; the imaging should be performed when the patient is symptomatic.


Background
Internal hernias have an overall incidence of around 1% and cause around 4% of all cases of intestinal obstruction [1]. Paraduodenal hernia (PDH) is the most common type of internal hernias. Left-sided PDH, where the bowel loops herniate through fossa of Landzert, makes around 75% of all PDH [2]. PDH is presumed to be spontaneously reducible in literature, leading to the chronic and recurrent symptomatology [3]. However, there is only one previous case report demonstrating the spontaneous reduction on computed tomography (CT) [4]. This report shows the case of a 65-year-old male with left-sided PDH who was managed conservatively, and a follow-up scan revealed a complete reduction of the hernia.

Case presentation
A 65-year-old male presented to the emergency department of a tertiary care center in Southern India with complaints of abdominal pain for 3 days duration. He had associated abdominal distension and two episodes of vomiting with no passage of stools over this period. Intermittent passage of flatus was present. He had no history of fever or weight loss. There was no history of previous surgery, trauma, or chronic abdominal pathology. Family and travel history were not contributory.
General examination including vital parameters was normal. Abdominal examination revealed abdominal distension and diffuse abdominal tenderness. There was no guarding or rigidity. Bowel sounds were muffled. A radiograph abdomen showed a few air-fluid levels. However, bowel loops were not dilated. There was no evidence of pneumoperitoneum. A bedside ultrasound of the abdomen and pelvis was not contributory. Routine hematological and biochemical investigations were normal.
A contrast-enhanced computed tomography (CECT) scan of the abdomen and pelvis was performed for further evaluation of suspected sub-acute intestinal obstruction. The CECT revealed anteromedial displacement of the descending colon in its entire length which was abutting the anterior parietal peritoneum. Multiple proximal jejunal bowel loops were seen to herniate posterolaterally and lie in the anterior pararenal space, to the left of the ligament of Treitz (Fig. 1a). There was crowding and stretching of the mesenteric vessels supplying these loops, but no torsion was seen (Fig.  1c). These vessels were seen to drain into the superior mesenteric vein. The herniated bowel loops did not show any evidence of obstruction or ischemia. There was no other abnormality in the abdomen and pelvis except multiple simple renal cysts. Based on these findings, the patient was diagnosed as a case of left-sided paraduodenal hernia. He was advised for surgery. However, he refused it and was managed conservatively. The patient was discharged after 5 days as his symptoms resolved.
The patient had three episodes of recurrence of symptoms before a follow-up CECT scan done at 11 months. This scan revealed complete resolution of previously seen herniation of bowel loops. The descending colon was also seen to occupy its normal position in the anterior pararenal space lying flush with anterior renal facia ( Fig. 1b and d).
The patient was managed conservatively. He was advised of surgical exploration and repair. However, he did not provide consent for the same. He is on regular follow-up with intermittent recurrence of symptoms which are managed conservatively.

Ethics approval and consent to participate
The present study was approved by the ethical board of the hospital in which the study was performed. The patient reported in this article had signed a written informed consent form. This case report was a reporting of a case in a medical educational center, in which all patients are informed that they may be subjects of scientific experiments and are informed of the ethical codes of conduct. This study was in compliance to the latest version of the Helsinki Declaration.

Discussion
Internal hernias are well-known, though uncommon, cause of intestinal obstruction. Their types, clinical features, imaging features, and complications have been well documented in the literature [2,5].
PDH is the most common type of internal hernias constituting around 53% of them [2]. It is of two types: left-sided PDH (75%) and right-sided PDH (25%). Leftsided PDH is due to failure of fusion of the part of the descending mesocolon to the posterior parietal peritoneum [4]. This leads to the formation of the fossa of Landzert, which is also known as the left paraduodenal fossa. This fossa is located at the duodenojejunal (DJ) junction, and bowel loops can herniate through it.
Its clinical features are usually non-specific ranging from vague epigastric discomfort to recurrent intestinal obstruction [6]. Chronic post-prandial pain is another feature of this condition. Some cases may be found incidentally on imaging [5].
Although findings of this entity have been well described on barium studies [4], CT is the modality of choice in current radiology practice [2]. CT shows the variable location of herniated bowel loops. They may lie at the DJ junction between the stomach and the pancreas; between the transverse colon and the left adrenal gland; posterior to the pancreatic tail; or in the left anterior pararenal space [5,7]. This may be associated with features of small-bowel obstruction in the form of dilated bowel loops and air-fluid levels. Dilated bowel loops may exert mass effect by displacing the stomach, DJ junction, or transverse colon. This may be associated with stretching, engorgement, or even torsion of mesenteric vessels. Unresolved obstruction may lead to sinister complications like ischemia and perforation.
The overall difficulty in the diagnosis of this uncommon condition is compounded further by the transient nature of herniation. This has often been hypothesized in the literature [3][4][5]. However, there is a scarcity of literature demonstrating spontaneous reduction. Parsons [3] and Meyers [4] demonstrated this on barium studies. There has been just a single report demonstrating this event on CT [8]. There, the authors repeated the CT after 5 days and found the spontaneous reduction.

Conclusion
This report shows a case of spontaneous reduction of left paraduodenal hernia which is only the second case demonstrating this phenomenon. The radiologists should be aware of this uncommon entity and in the event of clinical suspicion; the imaging should be performed when the patient is symptomatic. Our patient had a recurrent course and exemplified the clinical manifestations of spontaneous reduction and re-herniation.