Small bowel obstruction is a common cause of surgical emergencies, especially one that requires an operation. In the United Kingdom, SBO was the most frequent indication for which emergency laparotomies were performed, accounting for 37.3% of all emergency laparotomies [1]. Accounting for 0.6–5.8% of cases of SBO, internal hernia is a relatively uncommon cause for this common presentation [2]. An internal hernia can be defined as the protrusion of viscus through a normal or abnormal peritoneal or mesenteric aperture within the confines of the abdominal cavity [3]. These openings may be related to congenital peritoneal defects, or they may be acquired through trauma, postinflammatory adhesions, or surgery [4]. Here, we present a unique case of SBO due to internal herniation of small bowel through a defect formed by a torted left fallopian tube which had become adherent to the sigmoid colon. To our knowledge, this is the first case in the literature to describe this mechanism of internal hernia formation leading to small bowel obstruction.

A 76-year-old female patient was brought in by the ambulance to the Emergency Department with a 12-hour history of central colicky abdominal pain and multiple vomits. Her medical history included a previous ischemic stroke in 2006 with residual dysphagia and left-sided hemiparesis, type 2 diabetes, and dyslipidemia. Her surgical history consisted of previous open appendectomy and laparoscopic cholecystectomy.

On clinical assessment, she had a heart rate of 90 beats per minute, blood pressure of 134/84 mmHg, respiratory rate of 16 breaths per minute, oxygen saturation of 97% on room air, and a temperature of 36.8°C. She had a mildly distended abdomen with tenderness in her lower abdomen without features of peritonism.

Her laboratory investigations showed leukocytosis with a white cell count of 13.0 × 10⁹/L with an elevated neutrophil count of 10.3 × 10⁹/L. She had a serum lactate level of 2.0 mmol/L. Her electrolytes, renal function, and liver function tests were unremarkable. Findings of computed tomography (CT) scan of her abdomen and pelvis were consistent with that of small bowel obstruction with a transition point in the left lower quadrant (Figure 1). There was no CT evidence of perforation, ischemic small bowel, intraperitoneal free fluid, or portal venous gas.

A diagnosis of SBO was made, and an adhesive etiology was thought to be most likely. A nasogastric tube was inserted, and the patient was admitted for a trial of conservative management. However, the patient did not show any signs of improvement over the next 36 hours, as there was ongoing high output from the nasogastric tube. A Gastrografin follow-through study also failed to demonstrate progress of contrast through to the large intestine after 24 hours of administration.

Hence, the patient was taken for a laparoscopy which revealed a loop of ileum that had been incarcerated through an internal hernia defect in the left pelvis created by a torted left fallopian tube which had become adherent to an epiploic appendage of the sigmoid colon. It appeared that an isolated torsion of the left fallopian tube led to its infarction and had subsequently become adherent to the adjacent sigmoid epiploic appendage (Figure 2). The incarcerated loop of ileum, which was still viable, was successfully reduced. A left salpingo-oophorectomy was performed, therefore eliminating the defect which had caused the internal herniation.

The patient made a good recovery postoperatively with a return of her bowel function, and was discharged from the hospital three days after surgery. Histopathologic findings of the left salpingo-oophorectomy specimen were consistent with hemorrhagic necrosis.

In females, a defect whereby an internal herniation may occur can be created by abnormalities of the female reproductive organs in the pelvis. These are rare occurrences, however, and examples of such cases reported in the literature are sparse. They include cases of incarceration of small bowel through a defect in the broad ligament [5], strangulated small bowel caused by an ectopic fallopian tube [6], and a case of incarcerated cecum due to an abnormally elongated fallopian tube where the distal end of the abnormal fallopian tube had become adherent to the parietal peritoneum in the left lower abdominal quadrant [7]. Our case reported here describes another mechanism of internal herniation, which has not been previously described in the literature to the best our knowledge, whereby a defect was created by an isolated fallopian tube torsion followed by necrosis and subsequent formation of an inflammatory adhesion to the adjacent sigmoid colon.

Torsion of the fallopian tube is also a rare entity with a reported incidence of 1 in 1,500,000 women [8]. It most commonly affects women in the reproductive age [9], and the torsion is usually associated with an anatomical predisposition, such as ovarian cysts, paratubal cysts, unusually long mesosalpinx, hydrosalpinx, or previous pelvic surgery [10]. Another interesting observation about our case is that the fallopian tube torsion occurred in a postmenopausal patient in the absence of any obvious predisposing anatomical abnormality.

Computed tomography imaging plays a key role in the assessment of patients presenting with SBO, as CT scans can identify a transition point with dilatation of bowel proximally and collapsed bowel distally. It can also detect features of bowel ischemia, such as reduced bowel wall enhancement with intravenous contrast, bowel wall thickening, mesenteric venous congestion, mesenteric fluid, and unusual course of the mesenteric vasculature [11]. In our case, the CT scan correctly identified a transition point in the left lower quadrant without any features of bowel ischemia, although the presence of an internal hernia was not obviously apparent.

The Eastern Association for the Surgery of Trauma (EAST) guideline for evaluation of management of small bowel obstruction recommends early operative intervention for patients presenting with SBO together with features of bowel strangulation and ischemia [11]. Patients with bowel strangulation and ischemia may present with radiological features on CT as previously mentioned, as well as clinical signs which include tachycardia, fever, peritonitis, systemic inflammatory response syndrome (SIRS), leukocytosis, and metabolic acidosis. In the absence of clinical or radiological indicators of bowel ischemia, patients may be safely observed for a trial of nonoperative management, which can be successful in 65–80% of patients [11]. It should be stressed that if a decision for initial nonoperative management is elected, patients should be monitored closely with serial clinical examinations and laboratory investigations. Clinicians should have a low threshold to consider the need for an operation if the patient does not improve with nonoperative management or if they develop signs of bowel ischemia.

We present a case of SBO due to herniation of small bowel through an internal hernia defect created by torsion of the left fallopian tube, which had formed an inflammatory adhesion to the adjacent sigmoid colon. This case describes an uncommon etiology for a commonly encountered presenting problem. Our case highlights the importance of close monitoring and considering the need to operate on those who fail to progress with initial nonoperative management. Our patient’s intestinal obstruction would have been unlikely to resolve spontaneously due to the presence of an internal hernia, and further delays may have led to bowel strangulation, ischemia, and perforation.