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%). Left-sided 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.