Masquerading in the midgut: a rare diagnosis in a patient with recurrent abdominal pain

Abstract

A 38-year-old woman who had been previously diagnosed with irritable bowel syndrome was seen in the outpatient clinic with a 2-year history of intermittent cramp-like abdominal pain which was often followed by watery diarrhoea. She had presented several times previously to the emergency department with episodes of severe pain and collapse although on arrival examination findings were mostly unremarkable other than some mild lower abdominal tenderness. On each occasion, the symptoms resolved spontaneously with conservative management. She had been extensively investigated by her general practitioner to establish the cause of her symptoms but all laboratory findings, cross-sectional imaging, ultrasound and oesophagogastroduodenoscopy to date were unremarkable. After being seen in gastroenterology outpatients’ clinic, a colonoscopy was performed and was described as being macroscopically normal but microscopic evaluation of colonic biopsies suggested a possible ‘resolving infection’. She was treated symptomatically, but within 6 months she represented to hospital with progressively worsening symptoms of severe abdominal pain, now associated with vomiting, followed by watery diarrhoea and then resolution of the symptoms. An abdominal CT scan was performed which showed a small intraluminal-filling defect in the mid-terminal ileum. A wireless capsule endoscopy was organised to further characterise the lesion although this was reported as showing no abnormality. Prior to any further outpatient investigations, she represented as an emergency to hospital in small bowel obstruction, underwent further cross-sectional imaging followed by surgical resection of the lesion. Histological characterisation revealed a small bowel inflammatory fibroid polyp.

Case report

A 38-year-old woman who had been previously diagnosed with irritable bowel syndrome (IBS) and fibromyalgia was seen in the outpatient clinic with a 2-year history of intermittent cramp-like abdominal pain which was often followed by watery diarrhoea. She had presented several times previously to the emergency department with episodes of severe pain and collapse, although on arrival, examination findings were mostly unremarkable other than some mild lower abdominal tenderness. On each occasion, the symptoms resolved spontaneously with conservative management. She denied any weight loss or any other symptoms. Her medical history included uterine fibroids having a hysterectomy 5 years ago, after which she felt her symptoms of pain had worsened. She had been extensively investigated by her general practitioner to establish the cause of her symptoms but all laboratory findings, cross-sectional imaging, ultrasound and oesophagogastroduodenoscopy to date were all unremarkable. After being seen in gastroenterology outpatients clinic, a colonoscopy was performed and was described as being macroscopically normal but microscopic evaluation of colonic biopsies suggested a possible ‘resolving infection’. On review of her history, she had no recent travel history of note. She was diagnosed with post-infectious IBS and was reassured and given dietary advice together with the antispasmodic agent mebeverine. Initially, she responded well to this; however, within 6 months, she re-presented to hospital with progressively worsening symptoms of severe abdominal pain, now associated with vomiting, followed by watery diarrhoea and then resolution of the symptoms. An abdominal CT scan was performed (figure 1) which showed a small filling defect in the mid-terminal ileum.

Figure 1.

An axial section through the lower abdomen demonstrating a 1.9 cm rounded soft tissue mass (arrow) within the mid-terminal ileum. The intraluminal location of the mass is confirmed by a crescent of oral contrast medium which surrounds it.

Question

What is the cause of her symptoms? What is the underlying diagnosis?

Answer

The findings on the CT scan suggested a possible intraluminal lesion within the ileum precipitating episodes of intussusception and episodes of subacute small bowel obstruction. The initial major differentials related to a possible gastrointestinal stromal tumour (GIST) or small bowel lymphoma. A wireless capsule endoscopy (WCE) was organised to further characterise the lesion although this was reported as showing no abnormality, although bowel preparation was reported as suboptimal. Prior to any further outpatient investigations, she re-presented as an emergency to hospital in small bowel obstruction, underwent further cross sectional imaging followed by segmental resection of the lesion. Histological characterisation (figure 2) revealed that this was a small bowel inflammatory fibroid polyp (IFP).

Figure 2.

(A) Coronal CT scan through the abdomen and pelvis demonstrating the soft tissue mass within the lumen of the small bowel. The loop of bowel lies adjacent to the dome of the urine-filled bladder. (B) H&E staining of the inflammatory fibroid polyp (IFP) composed of spindle shaped, bland stromal cells which are arranged in an onion-skin (arrow) pattern around blood vessels. The inflammatory infiltrate is dominated by eosinophils (original magnification ×20). (C) CD34 immunostaining of IFP is positive in spindle cells (arrow) (original magnification ×20).

Small bowel IFPs are rare, active benign lesions originating from the submucosa of the gastrointestinal tract^{1 2} which can rarely present as a cause of intussusception in adults.³ Vanek first described them in 1949 as ‘gastric submucosal granuloma with eosinophilic infiltration’.⁴ Histologically, an IFP is characterised by a localised proliferation of mononuclear spindle-shaped cells arranged around vasculature with an inflammatory infiltrate dominated by eosinophils.^{3 4} The exact pathogenesis of IFP has not yet been identified, however, suggestions include intestinal trauma, eosinophilic gastroenteritis or an inflammatory process caused by an unknown irritant.^1–3 In the majority of cases, patients are asymptomatic, or present with symptoms of anaemia, weight loss or bowel obstruction although the presentation is dependent on the anatomical position of the polyp (stomach 70%, small bowel 20%).² Histological diagnosis is vital in differentiating IFPs from other tumours, in particular GISTs which stain positive for CD34. IFPs are usually positive for CD34 also, but negative for S-100 protein, P53 and Bcl- 2.⁵ The IFP also stained negative for both CD117 and DOG-1 immunostaining, which are strong GIST markers. Therefore, the combination of the morphological features, CD34 immunohistochemical staining and negative staining with other markers excludes other lesions that commonly enter the differential diagnosis, for example, GIST, Schwannoma. Recent studies have identified activating mutations of the platelet-derived growth factor receptor-α gene (PDGFRA) in as many as 70% of gastric and small intestinal inflammatory fibroid polyps. PDGFRA mutations are more often located within exon 12 in small intestinal polyps, while exon 18 mutations are more common in gastric polyps. We did not perform further genomic testing in this case however.^{6 7}

In patients, recurrent abdominal pain attributed to functional disease, it is essential to reassess the patient if symptoms change, or if there are alarm symptoms develop such as vomiting in this patient and the presence of obstructive symptoms.⁸ Plain abdominal radiography has been shown to be as accurate as abdominal CT scan in diagnosing low-grade and high-grade small bowel obstruction⁹ and should be utilised acutely to aid diagnosis in such patients.¹⁰ The diagnostic yield of WCE in patients with recurrent abdominal pain with or without diarrhoea (with or without raised inflammatory markers) can be as high as 90.1% and therefore is a useful investigative tool in patients with recurrent abdominal pain.¹¹ However, as in this case, bowel preparation can be suboptimal in patients undergoing WCE, and even with good bowel preparation, the sensitivity of WCE specifically for small bowel tumour/polyp detection is as low as 83.3% indicating significant pathology can still be missed.^{12 13} Management of IFPs typically includes endoscopic (double balloon enteroscopy) or surgical resection, which is often determined by size and location of the polyp.^{1 5}

This patient presented with recurrent abdominal pain, which could easily have been attributed to her previous diagnosis of IBS without careful examination of the obstructive symptomology the patient re-presented with, requiring further investigations, which ultimately led to the diagnosis. As this case highlights, an awareness of the more unusual causes of small bowel obstruction in adults (such as IFPs), in addition to the reassessment and further investigation of patients with functional bowel disorders with worsening symptomology are both important to avoid missing subtle pathology which may initially masquerade as non-significant diagnoses.