A 58 year-old gentleman presented to the hospital with worsening bloating and a gradual increase in his abdominal girth. He had also noted a loss of weight of more than 10 kg over the last 2 years. The patient otherwise denied any abdominal pain or change in his bowel habit. He was known to have a history of well-controlled diabetes mellitus, hypertension, hyperlipidaemia and atrial fibrillation. There was no previous history of pancreatitis or abdominal surgery. The patient had recently undergone a gastroscopy and colonoscopy the previous year for iron deficiency anaemia. This had shown gastritis as well as the presence of pandiverticular disease and a sub-centimeter colonic polyp. Histology showed the polyp to be a tubular adenoma with low-grade dysplasia (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6).
Clinical examination showed an adequately nourished gentleman but with a large abdominal mass occupying most of his abdomen. It was possible to feel over the superior edge but the inferior edge extended into the pelvis. The mass was non-tender on palpation. Digital rectal examination was unremarkable.
In view of the above findings, the patient underwent a computed tomography (CT) of the abdomen and pelvis. This showed a large 25 x 17 x 22 cm cystic lesion extending from the mid-abdomen to the pelvis. The lesion was thin walled and contained homogenous low density fluid (14 Hounsfield unit). There was no septations, irregularity or abnormal thickening of the cyst wall. The cyst was noted to have a mass effect but not invading the surrounding bowel loops and the urinary bladder. It was found to be separate from the liver and the kidneys. The pancreas was normal in appearance. The CT scan was otherwise unable to identify the origin of the giant cyst.
As this was a thin walled cyst with no irregular or solid component, a fine needle aspiration (FNA) was not suitable as there was no specific area to target. Aspiration of the fluid was also unlikely to yield any meaningful finding for diagnosis. Further imaging such as a MRI would also not help in identifying the origin or the diagnosis of the cyst. The possibility of a mesenteric or omental cyst was therefore discussed and surgical excision was offered to the patient. Tumour markers were not performed as it would not have affected the management.
An elective exploratory laparotomy was performed via a midline incision. A giant cyst was immediately identified but was found to have multiple adhesions to the peritoneum, omentum, mesentery, urinary bladder as well as the small and large intestines. However, the cyst was not found to be originating from any of the above organs or the vas deferens. The cyst was entirely within the abdominal cavity and did not originate from within the mesentery. A controlled decompression of the cyst was made through a purse-string encircled incision in the anterior wall. This was performed to aid with retraction and visualization of the posterior surface. Thick purulent fluid was aspirated until dry. The cyst was subsequently excised in whole.
The patient underwent an uneventful recovery with a brief period of expected post-operative ileus. He was discharged on post-operative day 6. Follow-up visits showed complete resolution of his initial symptoms and a vast improvement in his appetite.
Culture of the fluid was positive for Streptococcus agalactiae. Fungal culture and tuberculosis polymerase chain reaction (TB PCR) tests were negative. Cytology of the fluid showed mainly neutrophils.
Histological examination of the cyst showed thick fibrous walls covered with coarse fibrillary strands admixed with fibrin. There were also large numbers of mature IgG plasma cells with aggregates of neutrophils and scattered lymphocytes. No viable epithelial lining was identified. The walls stained positive for AE1/3 suggesting myofibroblasts. They were negative for CD117 and DOG-1 and therefore not suggestive of a gastrointestinal stromal tumour.
This was therefore treated as a benign cyst of an undetermined origin.
The patient was last seen in clinic two months after his surgery with a significant improvement in his appetite and oral intake. He was thereafter discharged from follow-up as the likelihood of recurrence was low considering that the cyst had been excised entirely with no remnant wall left behind.