Functional colonic obstruction in an adult as a presenting feature of thymoma

Abstract

Functional colonic obstruction is a colonic motility disorder with a number of causes. One cause is myenteric ganglionitis, which may result from paraneoplastic processes. We present the case of a previously healthy 53-year-old man who presented with a week’s history of functional colonic obstruction. A transverse loop colostomy failed to resolve his symptoms and he subsequently underwent an extended right hemicolectomy. Histology demonstrated lymphocytic myenteric ganglionitis that was felt to be of paraneoplastic origin. The patient later developed bilateral ptosis and was diagnosed with ocular myasthenia gravis. Further investigation revealed the presence of a thymoma that was resected, resulting in an improvement to his symptoms. We present this case and a review of the literature to illustrate the importance of seeking out a paraneoplastic cause for functional colonic obstruction in adults as early resection of the tumour may help alleviate symptoms and avoid bowel surgery.

Functional colonic obstruction is a term used to describe a number of colonic motility disorders. One cause is myenteric ganglionitis, which may result from a paraneoplastic process. It is important to recognise this condition and identify a paraneoplastic cause if possible as resection of the tumour may result in alleviation of symptoms. Our patient presented with acute functional colonic obstruction for which he required surgery. He later developed ocular myasthenia gravis and was found to have a thymoma, which was resected. We present this case and a literature review to illustrate the importance of considering paraneoplastic processes in the differential of functional colonic obstructions in adults.

Case history

A previously healthy 53-year-old gentleman was admitted acutely to the surgical assessment unit at a teaching hospital in West Yorkshire. He presented with a week’s history of abdominal pain, distension, vomiting, constipation and a weight loss of 20kg over three months. Abdominal radiographs showed dilated loops of small and large bowel. Computed tomography (CT) demonstrated gross dilation of the small and large bowel with an apparent obstructing distal sigmoid lesion. Soft faeces were noted in the colon and small bowel, in keeping with subacute obstruction (Fig 1). The patient underwent a transverse loop colostomy to alleviate his symptoms and, initially, the colostomy functioned well. Subsequent flexible sigmoidoscopy could not identify the obstructing lesion noted on CT.

Figure 1.

Plain abdominal radiograph (left) and a section from computed tomography demonstrating dilated loops of small and large bowel with the appearances of obstruction

Postoperatively, the patient developed abdominal distension and vomiting, and his stoma stopped functioning. CT demonstrated distension of the entire small bowel with right colonic faecal loading up to the point of the stoma, suggestive of high grade obstruction due to faecal loading (Fig 2). A colonoscopy and lavage of his right colon failed to resolve his impaction. Repeat CT showed increased dilation of the small bowel. After much deliberation the patient underwent an extended right hemicolectomy with formation of an end ileostomy.

Figure 2.

Abdominal computed tomography demonstrating gross faecal loading of the right colon and dilated small bowel loops, suggestive of small bowel obstruction secondary to faecal impaction

Macroscopic examination of the resected specimen revealed a distended, thin walled large bowel. Histological examination showed submucosal fibrosis, most pronounced in the distal part of the specimen, and diffuse ganglionitis affecting the submucosal and myenteric plexuses (Fig 3). Myenteric neurons were reduced in number. Submucosal and myenteric plexuses throughout the bowel showed infiltration by inflammatory cells, predominantly lymphocytes and plasma cells, with associated degenerative changes of nerves and neurons. Ganglion cells appeared vacuolated and displayed cytoplasmic irregularities, with swollen, vacuolated axons. Immunocytochemistry for cytomegalovirus and herpes simplex virus was negative and no other infective cause was determined. The diagnosis of ganglionitis was made and paraneoplastic syndrome was raised as one of the possible causes.

Figure 3.

Histology slides demonstrating chronic inflammatory cells closely associated with submucosal ganglion cells (top; haematoxylin and eosin stain; x50 magnification) and severe ganglionitis (bottom; haematoxylin and eosin stain; x200 magnification): The myenteric plexus is infiltrated with lymphocytes and plasma cells. The ganglion cells appear vacuolated.

The patient made a good recovery but four months later began to have difficulty with his vision and developed bilateral ptosis. His symptoms were felt to be compatible with ocular myasthenia gravis. He had a positive edrophonium test and antinuclear antibodies were positive. Acetylcholine receptor antibodies were not detected. Tumour markers were negative but CT demonstrated an anterior mediastinal mass of 6.6cm by 3.4cm that was felt to be a thymoma (Fig 4). It was noted retrospectively that this thymoma was visible on CT at his initial presentation. He was started on pyridostigmine and prednisolone, with an improvement in symptoms.

Figure 4.

Thoracic computed tomography demonstrating an anterior mediastinal mass, later found to be a thymoma

Positron emission tomography and magnetic resonance imaging of his head and orbits did not demonstrate any other abnormalities. The patient underwent a thymectomy and histology demonstrated a type B1/B2 invasive thymoma at clinical stage 2 (modified Masaoka system). His myasthenia has since improved, he is currently medication free and he has successfully undergone a reversal of his end ileostomy.

Discussion

Functional colonic obstruction, or pseudo-obstruction, is a motility disorder of the colon mimicking the clinical and radiological features of intestinal obstruction, without a mechanical cause. It is thought to occur as a result of the impairment of the autonomic nerve supply to the intestine, which is mediated by the ganglion cells in the myenteric plexus. Myenteric ganglionitis occurs when the myenteric plexuses become infiltrated by inflammatory mediators, either lymphocytes or eosinophils, resulting in a progressive neuropathy with impaired intestinal peristalsis ultimately leading to pseudo-obstruction. Although the pathology of ganglionitis is frequently idiopathic, it may be caused by viral infections as a result of molecular mimicry or paraneoplastic syndromes.¹

Functional colonic obstruction has been previously reported as a paraneoplastic process in the setting of small cell lung carcinoma. Other syndromes of intestinal dysmotility have also been reported in the literature in association with myasthenia gravis and thymoma.^2–4 These case reports have suggested that intestinal dysmotility and pseudo-obstruction can occur as a paraneoplastic process associated with a thymoma. Thymomas also have an established, paraneoplastic association with ocular myasthenia gravis and are implicated in a variety of other paraneoplastic syndromes. The mechanism is thought to be related to the unique role of the thymus in the production of T lymphocytes, particularly CD4 T cells.⁵

Our patient presented with a thymoma that had not been diagnosed on the initial CT. He presented with increasing constipation as a result of rapidly progressive ganglionitis. The functional obstruction could not be rectified non-surgically and resulted in mechanical obstruction due to faecal impaction. It was not till a few months later that he developed signs and symptoms of myasthenia and the thymoma was discovered and resected. His symptoms then began to improve, confirming the diagnosis.

Although thymomas are well known to cause paraneoplastic syndromes and intestinal dysmotility has previously been reported in the setting of a thymoma, in previously reported cases the patients were managed medically. To our knowledge this is the first reported case where a patient with functional colonic obstruction in association with a thymoma has required surgery. The histology we have obtained suggests that the pathogenesis of the intestinal dysmotility in these cases is due to lymphocytic myenteric ganglionitis.

Conclusions

It is important to consider a paraneoplastic cause for functional colonic obstruction in an adult as resection of the tumour will result in improvement of the patient’s symptoms and may help avoid bowel surgery.