Internal hernia is an abnormal protrusion of abdominal viscera through a defect, which may be congenital or acquired, within the peritoneum or mesentery. ¹ Internal hernias cause 0.6 to 6.0 percent of small bowel obstructions. ² Types of internal hernia (in decreasing frequency) include paraduodenal, pericecal, Winslow foramen, transmesenteric and transmesocolic, pelvic, intersigmoid, retroanastomotic, and transomental hernia. ¹

Paraduodenal hernia is a rare congenital abnormality caused by a malrotation of the midgut. It is the most common type of internal herniation (53%) with left-sided dominance (left to right ratio is 3:1). ³ Paraduodenal hernia occurs when the small intestine becomes trapped beneath the colon because of anomalous rotation of the mesentery of the developing colon in utero. The duodenum and small intestine become trapped in a sac lined by peritoneum, behind the mesentery of the colon, either to the left or to the right of the midline. ⁴ Treatment of paraduodenal hernia is laparotomy or laparoscopy with reduction of the herniated loops and closure of the hernial orifice. ⁵ We present a case of right paraduodenal hernia presenting in an emergency department with symptoms consistent with acute small bowel obstruction (SBO). Subsequently, supine and erect abdomen x-ray was suggestive of small bowel obstruction at the level of the ileum. The patient underwent open surgery, paraduodenal hernia was diagnosed and entrapped intestinal loops were reduced. The patient tolerated the procedure well without complications. The treatment of internal hernias needs to be prompt as the delay may lead to ominous outcome.

A 45-year-old male presented in the emergency department of B P Koirala Institute of Health Sciences, Dharan, Nepal (a tertiary care hospital in Eastern Nepal) with complaints of non-radiating dull pain in the central abdomen, moderate to severe in intensity with mild abdominal distension and not passing stool and flatus for three days’ duration. He did not receive any treatment for the condition prior presenting to emergency department. He also gave a history of on and off epigastric pain for five years that would otherwise subside after getting some over the counter analgesics (Paracetamol) and proton pump inhibitors (Pantoprazole). The patient did not have a past history of abdominal trauma or surgical intervention. The patient was non-diabetic, non-alcoholic and non-vegetarian. The psychosocial, medical and family history were not significant.

On physical examination, his pulse rate was 100 beats/minute (Normal, 60-100), respiratory rate was 18 cycles/minute (Normal, 14-20), temperature was 98°F, and blood pressure was 100/60 mmHg (Normal, <120/80). An abdominal examination showed distended abdomen with mild tenderness and peritonism without any sign of free fluid or free air in the peritoneal cavity and absent bowel sounds. Groin examination and digital rectum examination were normal.

Blood investigation was done and all routine parameters were within normal limits (total leukocyte count (TLC) (8,0000, differential count (DC) (Neutrophil 60, Lymphocyte 28, Monocytes 5, Eosinophils 1, Basophils 0), random blood sugar (RBS) (115 mg/dl), urea (20 mg/dl), creatinine (0.8 mg/dl), sodium (138 mEq/L), potassium (4.1 mEq/L)). During radiological investigation, a plain X-ray of abdomen was done (supine and erect) and it was suggestive of small bowel obstruction at the level of the ileum. A computed tomography (CT) scan with contrast was not available in the emergency room so it was not done.

On the basis of history, clinical examination and investigation, exploratory laparotomy was planned for the patient. The patient was placed in supine position, general anaesthesia was given. Abdominal cavity was entered through a mid-line incision. Intraoperative findings revealed a 10 × 6 cm ² defect in the right paraduodenal area and the whole of the small intestine was herniating through the defect ( Figure 1). The small bowel was reduced and the defect was repaired with silk 2/0 round body suture in an interrupted fashion ( Figures 2 and 3). The rest of the abdominal findings were normal.

The patient was admitted to the surgical ward and their post-operative course was uneventful. Post-operative analgesic (Tramadol), anti-emetic (Ondansetron) and venous thromboembolism prophylaxis were provided. The patient was discharged on the 6 ^th post-operative day. He was followed every month for couple of months and then 6 monthly. Routine investigations deemed necessary were carried out and no major diagnostic test was needed. He has been fit and healthy for 24 months of follow up with no active complaints.

Paraduodenal hernia, also referred to as internal, congenital, retroperitoneal, or meso-colonic hernia, was first described at autopsy by Neubauer in 1786. ⁶ Subsequently, Treitz (in 1987) provided a precise scientific description of the condition and considered it as a retroperitoneal protusion of abdominal viscera. Right paraduodenal hernias protrude into the ascending mesocolon, involving the fossa of Waldeyer, behind the superior mesenteric artery and inferior to the third portion of the duodenum. ⁶ In 1889, the classification of hernias into the distinct left and right types was made by Jonnesco. ⁷

Paraduodenal hernia may present at any age, but is usually observed between the 4th and 6th decade of life. ⁸ It is more common in men than women, with a ratio of 3:1, ² and is more frequent on the left than right, with a ratio of 3:1. ⁴ Fifty percent of paraduodenal hernias cause obstruction; the remainder are diagnosed incidentally at exploratory laparotomy or at necropsy. ^{2 , 8}

The rare prevalence and the variable symptoms make the clinical diagnosis of paraduodenal hernia a diagnostic challenge. The clinical presentation is entirely nonspecific. It remains completely asymptomatic or found accidentally during surgery or post-mortem as an acute bowel obstruction observed in around 50% of cases with the risk of gangrene and puncture. ^{9 , 10} Such a myriad of clinical features often leads physicians to misdiagnose/misinterpret paraduodenal hernia as biliary disease or peptic ulcer resulting in delay in diagnosis and management and also patients receiving unnecessary therapeutic interventions only to discover obstructive and ischemic complications later.

As the lifetime risk of incarceration or strangulation is as high as 50% with 20%-50% mortality risk, surgical treatment of paraduodenal hernia is of paramount importance once diagnosed. Also the future risk of SBO is high, paraduodenal hernia detected incidentally should be repaired in same settings. ¹¹ In the present case, the diagnosis of right paraduodenal hernia was made intraoperatively as additional investigations such as CT scan with contrast was not available in the emergency room and thus not performed after the diagnosis of acute small bowel obstruction was made in emergency ward. In the present case, the defect was repaired using silk 2-0 round body sutures. Some authors have tried prosthesis placement, especially when the defects are larger. ^{12 , 13} As per the literature, complete removal of sac is not advised due to potential massive blood loss from injury of nearby superior mesenteric artery and its branches. ¹⁴

All data underlying the results are available as part of the article and no additional source data are required.

Written informed consent was obtained from the patient for the publication of the case report and any associated images.