Meckel's diverticulum causing acute intestinal obstruction: A case report and comprehensive review of the literature

Introduction Meckel's diverticulum is a congenital anomaly that is often detected incidentally. When it presents symptomatically, it causes painless gastrointestinal bleeding. Nevertheless, in rare instances, it can cause acute intestinal obstruction, often obscuring the true clinical picture. Case presentation A 31-year-old male presented to the emergency department with a 24-h history of unremitting nausea, biliary emesis, abdominal distension, and absolute constipation. After ruling out the most common etiologies of acute bowel obstruction, radiological imaging was obtained and was suggestive of meckel's diverticulum. Laparoscopic meckel's diverticulectomy was performed, with the subsequent histopathological analysis confirming ectopic gastric tissue. Discussion Meckel's diverticulum occurs consequent to incomplete obliteration of the vitelline or omphalomesenteric duct, which connects the developing intestines to the yolk sac. It is found in roughly 2% of the population, of which only about 4% may become symptomatic due to any number of complications. Specifically, small bowel obstruction (SBO) and diverticulitis secondary to ectopic gastric or pancreatic tissue are the most common presentations of symptomatic MD. Conclusion Although relatively rare in adults, MD should be considered in the list of differentials in patients with intussusception leading to SBO, especially on a background history unremarkable for the most common etiologies causing SBO including post-operative adhesions and hernias.


Introduction
Acute intestinal obstruction continues to be a medical and surgical emergency that warrants an emergency intervention. Acute bowel obstruction usually presents with a vague constellation of symptoms, often characterized by bilious/non-bilious emesis, nausea, vomiting, anorexia, and abdominal pain [1]. While postoperative adhesions and tumors afflicting the bowel remain leading causes of acute intestinal obstruction, rarer entities, such as Meckel's diverticulum, can seldom be the source, often obscuring the true clinical picture [2,3]. In gastroenterology literature, post-operative adhesions and hernias are frequently cited as being the leading causes of small bowel obstruction. However, rare congenital abnormalities such as meckel's diverticulum are not routinely thought to be the source of acute small bowel obstruction [2,3]. Meckel's diverticulum (MD) is defined as a congenital anomaly that ensues in the wake of partial closure and persistence of the vitelline, or the omphalomesenteric, duct during embryogenesis [1,2]. This usually occurs in the fifth week of development and causes a true outpouching of the small intestine, located approximately two feet from the ileocecal valve [2,3]. It is the most common congenital abnormality afflicting the gastrointestinal tract and has been reported in up to 1-3% of patients [2]. MD, a true diverticulum, involves all layers of the small intestine and is known to contain ectopic gastric mucosa [1]. It is generally asymptomatic and is usually discovered incidentally during surgical exploration of other diseases or less commonly through diagnostic imaging [1]. However, hemorrhagic, inflammatory, and obstructive complications can arise [1][2][3]. Additionally, MD can present with painless bleeding due to ectopic gastric acid and pepsin production in the diverticulum (gastric mucosa or pancreatic differentiation in MD mucosa), further complicating the clinical picture [3,4]. In patients presenting with painless gastrointestinal bleeding of unknown etiology, MD may be suspected [2,3]. Nonetheless, acute intestinal obstruction consequent to the presence of meckel's diverticulum in the adult population remains a clinical enigma [3,4]. Herein, we elucidate the case of a 31-year-old male who presented with chief complaints of nausea, biliary emesis, and abdominal distension on a background of unremarkable medical and surgical history. Further investigative workup divulged the presence of meckel's diverticulum, with subsequent diverticulectomy resulting in prompt abatement of the patient's symptoms. The overarching objective of the present paper is to prompt clinicians to recognize MD as a potential cause of acute small bowel obstruction. Although the patient's age at presentation can yield imperative diagnostic cues, MD should nevertheless be considered in the list of differentials in patients presenting with acute small bowel obstruction regardless of age.

Case presentation
A 31-year-old male presented to the emergency department with a 24-h history of unremitting nausea, biliary emesis, abdominal distension, and absolute constipation. Notably, the patient's last regular bowel movement had been three days prior to the current presentation, with the patient erroneously attributing his altered bowel habits to his recent onset of anorexia of unknown origin. The patient reported no red flag symptoms, affirmatively denying recent fevers, previously altered bowel habits, infectious urinary symptoms, or weight loss. The patient's prior medical and surgical histories were unimpressive, and he reported no other comorbidities. Pertinently, the patient had had an episode similar to the current one four years ago; at the time, his condition was managed conservatively and resulted in a prompt resolution of his symptoms within 24 hours of his presentation to the hospital. The patient remained asymptomatic thereafter with no consequent episodes till the current presentation.
Upon clinical examination, the patient appeared profusely unwell, with excruciating, 7/10, vague, non-localized abdominal pain that caused significant distress to the patient. Abdominal examination revealed a soft, distended abdomen that was non-tender with no evidence of rigidity, peritonitis, or guarding. Pertinently, bowel sounds were audible and were noted to be tinkling in nature, raising the initial suspicions for an obstructive etiology underlying the patient's clinical presentation. The murphy's sign, along with the psoas, obturator, and rovsing's signs, were all negative and unimpressive, effectively ruling out acute cholecystitis and acute appendicitis as plausible etiologies. The patient's past surgical history was also unimpressive, further precluding post-operative adhesions as the likely etiology. Upon clinical examination, there was no evidence of hernial protrusions, and the genital orifices were unremarkable. Furthermore, clinical examination of the abdomen did not reveal any rigidity or guarding, and no signs of peritonitis were appreciated. The patient's C-reactive protein was raised to 15; however, his remaining labs were unremarkable for any pertinent derangements. In order to better delineate the etiology underlying the patient's presentation, an abdominal x-ray was obtained and revealed multiple air-fluid levels in the small bowel (Fig. 1).
Based on the patient's x-ray findings, an obstructive pathology was deemed plausible. However, given that the patient demonstrated an unremarkable surgical history and did not show signs of a possible gastrointestinal malignancy, adhesions, and tumor as causes of acute intestinal obstruction were effectively ruled out. Further radiological investigation through the means of a computed tomography (CT) scan divulged a transition point in the terminal ileum, with mesenteric band cut-off, strongly alluding to the presence of a diverticulum in the specified region (Fig. 2).
The CT imaging of the abdomen further revealed the presence of the classical meckel's loops, thereby confirming the presence of meckel's diverticulum (Fig. 3).
Considering the impression obtained from the patient's radiological work-up, a multidisciplinary team meeting (MDT) was conducted. The presence of meckel's diverticulum due to an acute small bowel obstruction was deemed exceedingly plausible. Consequently, the patient was managed using conservative measures for the next 24 hours; however, the patient refused a nasogastric tube, which would have been pivotal in relieving the obstruction. During this time, the patient had an episode of nominal bowel motion once but did not pass any flatus. Conservative treatment was thus continued, and the patient was prepared for a laparoscopic diverticulectomy.
During the operation, meckel's diverticulum in close proximity to the ileocecal valve was confirmed. Per-operative evaluation divulged meckel's diverticulitis with the tip attached to the ileal mesentery through the means of a band (Fig. 4).
Given this intraoperative finding, tip and band release was performed (Fig. 5).
Additionally, given the presence of meckel's diverticulitis and the fact that the patient had been symptomatic four years prior to the current episode, meckel's diverticulectomy was performed (Fig. 6).
The surgery was conducted unremarkably, with no intra-or perioperative complications encountered during the process. Postoperatively, the patient remained well and symptom-free except for a minor wound infectious from the hypogastric port used for specimen delivery during the surgery. Daily wound dressings were advised without the need for antibiotics.
The subsequent histopathology report confirmed the presence of diffusely inflamed ectopic gastric mucosa in close proximity to the ileocecal valve, reinforcing meckel's diverticulum as the culprit etiology underlying the patient's episode. The present paper was reported in line with the SCARE guidelines [5].

Discussion
Meckel's diverticulum (MD) is one of several congenital abnormalities that can result from incomplete obliteration of the vitelline or omphalomesenteric duct, which connects the developing intestines to the yolk sac during development, and is a true diverticulum composed of all intestinal layers [6]. It is found in roughly 2% of the population, of which only about 4% may become symptomatic due to any number of complications [6]. Specifically, small bowel obstruction (SBO) and diverticulitis secondary to ectopic gastric or pancreatic tissue are the most common presentations of symptomatic MD [7]. When it does present with obstructive symptoms, subsequent complications may arise in up to 36.5% of cases via a vast myriad of mechanisms [8]. Obstruction can commonly occur due to volvulus or torsion of the intestine around a fibrous band from MD to the umbilicus; intussusception or inversion of the MD into the ileum or cecum; or mesodiverticular band trapping the small bowel under the vascular supply of the MD and potentially leading to strangulation [9]. With symptomatic MD patients representing only 0.08% of the total population, the exceeding rarity of the condition leads to poor rates of pre-operative diagnosis, thereby obscuring the true clinical picture [9]. Early recognition is of paramount importance since a delay in surgery of 36 hours or more can triple the mortality rate from 8% to 25% in patients presenting with strangulation [10]. In this context, it is imperative that clinicians are aware of MD, its associated clinical findings, and the best practices for its diagnosis and management.
The present study elucidates a case of a 31-year-old male patient with acute onset of symptoms consistent with obstruction. The patient presented with the classical tetrad of bowel obstruction involving nausea, emesis, abdominal distension, and constipation [11]. Diagnostic imaging showed multiple air-fluid levels, which indicate pathological accumulation of fluid and gas and are a hallmark finding in X-ray and CT of SBO [12]. Ultrasound for Meckel's Diverticulum is feasible and can identify mesodiverticular bands as a hyperechoic line, particularly in pediatric patients. However, CT scan was found to be more accurate in determining the cause of small bowel obstruction in adults [13]. In cases with ectopic mucosa in the diverticular outpouch, a Meckel's radionuclide scan, which injects technetium-99 m as a dye to detect gastric tissue, can be performed [14]. A previous study found the transition zone was located near the midline in 80% of patients. In our case, the transition point was identified in the terminal or distal ileum [15].
Interestingly, volvulus of the MD was not suspected as a mechanism of obstruction in our case as there was no fibrous band connecting the MD to the umbilicus. We also did not suspect intussusception of the small bowel due to the absence of inversion of the diverticular outpouching into the ileum or cecum. The subsequent histopathology report showed unremarkable intestinal tissue. The lack of ectopic tissue thus suggests diverticulitis as a cause of inflammation, and subsequent obstruction was not a likely differential. Instead, the tip of the Meckel's diverticulum with a band attached to the ileal mesentery was discovered per-operatively during the diverticulectomy. Thus, mesodiverticular band (MDB) of Meckel's diverticulum was determined to be the cause of SBO in this patient. The MDB is a remnant of the vitelline artery, which supplies Meckel's Diverticulum and provides a bridge for bowel loops to        [16,17]. Surgery, in specific meckel's diverticulectomy, remains the mainstay of treatment in such cases. The most common forms are diverticulectomy, wedge, or segmental resection, and the rationale for which procedure to form depends largely on the integrity of the diverticular base and proximal ileum and the location of ectopic tissue if any [3]. Wedge or segmental resection is recommended for MD with SBO; however, diverticulectomy was performed in our patient with full recovery and resolution of symptoms [3]. Generally, prophylactic removal of MD found incidentally is still a controversial topic, with one systematic review of 244 cases divulging reduced postoperative consequences for uncomplicated and asymptomatic Meckel's Diverticulum left alone [13].
In order to better elucidate the etiology underlying the obstructive symptoms seen in our case, we conducted a literature search using the digital databases (PubMed/MEDLINE, CINAHL, and Web of Science) to search for relevant material and articles implicating MD as a cause of SBO. The literature search in our search was conducted using the terms (s): "small bowel obstruction" AND "meckel's diverticulum" OR "diverticulitis" OR "volvulus" OR "intussusception". The symptomatology, imaging findings, treatment employed, and the follow-up are delineated by Table 1 below .

Limitations
The present study discusses a case report and delineates a singlecenter experience dealing with an unusual etiology underlying acute small bowel obstruction. While the study yields important evidence surrounding this etiology and prompts the clinicians to aptly recognize this congenital aberration as a cause of acute small bowel obstruction, it is limited by its sample size. Further multi-centric cross-sectional studies evaluating the true, unadjusted incidence of MD as the causative etiology underlying acute small bowel obstruction will further yield robust data to support the presented conclusions.

Conclusion
MD is the most common congenital abnormality of the gastrointestinal tract, presenting in 1-3% of patients, of which about 4% may become symptomatic. When asymptomatic, it is discovered incidentally during surgical exploration or through diagnostic imaging. Various hemorrhagic, inflammatory, and obstructive complications can arise, leading to an array of presentations. Nevertheless, the presence of MD as the causative etiology underlying acute SBO remains a clinical enigma, with most cases erroneously attributed to post-operative adhesions and/ or abdominal hernias. Early diagnosis and a high index of suspicion are imperative to deliver the most optimal treatment. Although relatively rare in adults, MD should be considered in the list of differentials in patients with intussusception leading to SBO, especially on a background history unremarkable for the most common etiologies causing SBO.

Disclosure
None.

Provenance and peer review
Not commissioned, externally peer-reviewed. TA, SH, MFM, EM: Conceived the initial study idea, diagnosed the case, and gave the final approval for publication.

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Consent
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Declaration of competing interest
NA.