LAUSR

Pseudomyxoma peritonei (PMP) is a rare phenomenon with an incidence of one to two per million per year worldwide. It is a progressive disease, characterized by the production of mucinous ascites and implants diffusely involving the peritoneal surfaces. It arises most commonly from a ruptured mucinous appendiceal neoplasm, although gastric, ovarian and colorectal origins are possible. Mucinous tumour accumulates within the peritoneal cavity and recesses, eventuating in extraluminal gastrointestinal obstruction. Pleural dissemination from PMP is very uncommon and thought to be secondary to transdiaphragmatic spread of the disease through the lymphatic lacunae. Generally, this occurrence carries a poor prognosis, and treatments to date including debulking surgery and systemic chemotherapy have largely been palliative. Specialized centres now perform cytoreductive surgery (CRS) with intraoperative locoregional chemotherapy with the aim of complete macroscopic and microscopic tumour eradication. CRS, with heated intraperitoneal chemotherapy (HIPEC), has demonstrated survival benefits for PMP from appendiceal tumours. Similarly, in cases of pleural dissemination from PMP, complete cytoreduction with addition of intrathoracic chemotherapy may significantly improve overall and disease-free survival in an otherwise terminal condition. We report a case of a 67-year-old female with high-volume, intra-abdominal and concomitant intrathoracic disease. The patient presented with per vaginal bleeding and a symptomatic urinary tract infection on a background of hypertension, long-standing hypodense liver lesions, thought to be cysts, and a previous mucinous right pleural effusion of unknown origin in 2018. Her inpatient workup involved a pelvic ultrasound, demonstrating free fluid, followed by a combination positron emission tomographycomputed tomography scan of the chest, abdomen and pelvis showing inferior right hemithorax pleural disease as well as intraabdominal fluid in the right subphrenic space and para-colic gutters (Fig. 1). Based on the radiological findings, PMP was suspected. Inpatient colonoscopy was unremarkable aside from uncomplicated diverticular disease. Tumour markers, including carcinoembryonic antigen, carbohydrate antigen 19-9 and cancer antigen 125, were within normal limits. A diagnostic laparoscopy was undertaken to perform a biopsy of a diseased segment of peritoneum to confirm the underlying diagnosis and quantify disease burden for operative strategy. The peritoneal carcinomatosis index (PCI) score was 18, with typical appearing PMP arising from an abnormal appendix. After multidisciplinary discussion, it was decided that the patient would undergo CRS with HIPEC. At laparotomy, the disease was found to extend through the right diaphragm into the right hemi thorax. Considering this, the patient underwent CRS with simultaneous hyperthermic thoracoabdominal chemotherapy (HITAC) for high-volume intra-abdominal and concomitant intrathoracic disease. This procedure was uncomplicated with a PCI of 28 and involved major and lesser omentectomy and bilateral diaphragmatic stripping, with 8 cm 5 cm 2.2 cm full-thickness resection of the right hemidiaphragm and pleura, transabdominally (Fig. 2). The patient also underwent cholecystectomy, porta hepatis clearance,