Internal hernia (IH) is an acute or chronic protrusion of viscera through a hernia orifice formed by the peritoneum or mesentery¹. It is considered a rare cause of bowel obstruction in adults, with an incidence between 0.2 and 0.9%; < 10% is caused by transmesenteric hernias², which may be congenital or acquired (e.g., after surgery). Postoperative internal hernias are the most common type.

We report the case of a 20-year-old otherwise healthy male patient with no previous surgeries who had an acute bowel obstruction secondary to a congenital transmesenteric IH. The patient presented to the emergency department with generalized abdominal pain that started 72 hours before, was moderate in intensity and worsened while eating. Other symptoms included abdominal bloating, bilious vomiting, and inability to pass stool and gas. He complaint of a similar episode between 30 and 40 days before that solved spontaneously. On admission, the vital signs were within normal ranges. On physical examination the abdomen was distended, and metallic, high-pitched and frequent bowel sounds were heard, suggestive of obstruction. There was generalized tenderness on palpation, predominantly in the periumbilical region with no signs of rebound tenderness, and tympanitic sound on percussion. There were no palpable masses or hernias. The rectal examination was normal.

The laboratory tests did not show any abnormality. A plain abdominal X-ray showed dilated small bowel loops with air-fluid levels. A CT scan of the abdomen and pelvis with oral and intravenous contrast agent was ordered (Fig. 1). The small bowel loops were dilated, the bowel walls were preserved, but it was not possible to detect any area of stenosis or organic lesions. A small amount of free fluid was interposed between the bowel loops and in the hypogastrium.

Figure 1 CT scan showing distension of small bowel loops without obstruction. 

We decided to perform an exploratory laparotomy. Free serosanguineous fluid was observed within the cavity with distension of the bowel loops caused by a transmesenteric IH close to the ileocecal valve (Fig. 2A). There were no other abnormalities. The hernial orifice, formed by the mesentery of the distal jejunum, was identified and the hernia was reduced. As the bowel loop presented good viability (Fig. 2B), there was no need to perform bowel resection. The peritoneal defect was closed with absorbable suture. The patient had a favorable outcome, with good tolerance to oral intake and was discharged on postoperative day 3. Longterm follow-up was favorable without recurrences.

Figure 2 A: Transmesenteric internal hernia (arrows). B: Small bowel stenosis after the hernia was reduced (arrows). 

Internal hernias are a rare cause of bowel obstruction in adults² and account for 0.6 to 5.8% of all cases of small bowel obstruction in autopsy studies¹. Among internal hernias, transmensenteric (TM) hernias are uncommon, with an incidence of about 5-10%. These hernias are usually the main cause of IH in children resulting from a congenital defect in the small bowel mesentery, usually near the ileocecal valve. However, in adults they are usually acquired and caused by previous surgical procedures or secondary to trauma³. Congenital mesenteric defects are very rare in adults but can cause IH followed by bowel incarceration or strangulation⁴.

In 2013, Butterworth et al. reported that only 13 cases of adults with bowel obstruction secondary to congenital defects of the mesentery had been published to that date⁵. Our patient had no history of previous trauma or surgery, so the mesenteric defect was considered congenital. Although the causes of congenital defects remain uncertain, a few hypotheses have been reported, such as regression of the dorsal mesentery, rapid lengthening of a segment of mesentery and developmental enlargement of a hypovascular area⁴.

The clinical presentation includes periumbilical abdominal pain, vomiting, and inability to pass stool and gas. Some patients have a history of similar episodes that solved spontaneously, as in the case of our patient who reported similar symptoms 30 days before which solved without treatment. Physical examination reveals diffuse abdominal pain and bloating. An abdominal mass is rarely palpated³. Transmesenteric hernias usually occur in the small bowel mesentery, specifically in the ileocecal mesentery⁴ as in our patient with a hernial orifice located in the distal jejunal mesentery. The preoperative diagnosis is still a challenge for the surgeon due unspecific symptoms and the low sensitivity of imaging tests to detect IH.

Computed tomography (CT) scan has high specificity and sensitivity (> 90%) for the diagnosis of bowel obstruction, but the specificity for the diagnosis of IH is < 80%². Nevertheless, CT scan is the best method for the diagnosis of IHs. Blachar et al. described the characteristic findings of transmesenteric IH, as dilatation of small bowel loops, clustering of small bowel loops and displacement of the mesenteric trunk⁶. However, the diagnosis of transmesenteric IH is still an intraoperative finding in most cases, as was the case in our patient. Surgical intervention is the recommended treatment due to the high risk of strangulation of the incarcerated intestine. Surgery includes hernia reduction, bowel resection in case of necrosis and suture of the defect. Laparoscopy is another possible approach. Before Hussein’s report in 2012, laparoscopy had been successfully performed in 16 patients². There is no evidence in the literature about the best approach: both conventional surgery and laparoscopy have been used, without recurrence or postoperative complications³. Delays in the diagnosis and treatment of internal hernias can lead to ischemia, necrosis of the segment involved and, in the final stage, patients’ death.

Transmesenteric hernias are a rare cause of bowel obstruction in adults. The diagnosis should be suspected in patients without a history of surgeries or trauma. The preoperative diagnosis is still a challenge for the surgeon due unspecific symptoms and the low sensitivity of the complementary imaging tests; the diagnosis is usually intraoperative. Early surgery is crucial to reduce morbidity and mortality because delaying surgery can lead to bowel necrosis and finally to death.