Introduction Case presentation: A 68-year-old man presented with a 3-month history of anorexia, weight loss and increasing abdominal girth. He was known to have type 2 diabetes mellitus and no history of alcohol excess was obtained. Physical examination revealed tense ascites in the absence of stigmata of chronic liver disease. Cardiovascular examination was normal. The serum-ascites albumin gradient (SA-AG) was 5 g/l.

Methods Initial bloods revealed normal full blood count, clotting, renal and liver function excepting a low albumin of 34 g/l. Ascitic fluid amylase was normal, cytological examination revealed lymphocytes, macrophages, mesothelial cells, pools of mucin and a negative gram stain. Ultrasound of the abdomen confirmed portal, hepatic and splenic vein patency, normal liver size with no focal lesions and ascites of varying density.

Results A computed tomographic (CT) scan revealed a discrete, low attenuation mass in the right iliac fossa with a central area of calcification, consistent with an appendiceal mucinous tumour. Scalloping of the liver surface occurs secondary to mucinous intraperitioneal loculi. Laparoscopy showed mucinous deposits on the peritoneal surface. Pathological examination of the omental biopsies revealed abundant extracellular mucin with epithelial cells being CK20 positive, consistent with an appendiceal origin. This patient had primary appendiceal mucinous tumour with mucinous ascites (pseudomyxoma peritionei).

Conclusion Case discussion: Pseudomyxoma peritionei is a rare malignant condition that may also present with altered bowel habit and infertility in women. It is more common in women, usually secondary to mucinous ovarian tumours. It is characterised by a large volume of mucinous ascites (“jelly-belly”) and is a histological diagnosis. Ultrasound-guided biopsy of the greater omentum has a high sensitivity (95.6%) and specificity (93.8%) in distinguishing malignant ascites from benign ascites. Treatment is primarily surgical peritonectomy (cytoreductive surgery) with intraoperative hyperthermic intraperitoneal chemotherapy.