Umbilical hernia arises from a cicatrized umbilical scar due to various abdominal conditions that increase intra abdominal pressure. The European Hernia Society (EHS) classifies umbilical hernias based on location, width, and content [3]. Finding mucinous material in an otherwise asymptomatic patient’s hernia is rare. PMP is a condition characterized by the presence of mucinous ascites within the peritoneal cavity, often secondary to a ruptured mucinous tumour, typically originating from the appendix or ovary [2]. Given the rarity of this condition (1 to 4 in a million annually) [1], we present this case report. 
 
Case Report 
A 73-year-old patient presented to the surgical clinic with complaints of a gradually progressing umbilical hernia with excoriation of overlying skin for the past two years. The patient reported mild discomfort associated with the hernia but denied significant pain, changes in bowel habits, or weight loss. He had no history of prior abdominal surgeries. On physical examination, a 6x4 cm reducible umbilical hernia (PM3W1) with excoriated hyperpigmented skin changes was observed. The abdomen was mildly distended without palpable organomegaly, and shifting dullness suggested ascites. 
 
Investigations: 
• Laboratory findings: Normal complete blood picture (CBP), liver function, and renal function tests. 
• Ultrasound: Confirmed moderate ascites and an umbilical hernia without evidence of bowel obstruction. 
• CT scan: Revealed a significant amount of hypodense fluid within the peritoneal cavity, with fluid projecting through the umbilicus into the subcutaneous planes, without solid organ or bowel abnormalities. 
• Upper GI Endoscopy: Performed to rule out oesophageal varices due to suspected portal hypertension but showed no abnormalities. 
Given these findings, the patient was scheduled for elective surgical repair of the umbilical hernia due to excoriation of 
overlying skin. 

Intraoperative Findings 
During surgery: 
• A 2 cm hernial defect was identified and corrected. 
• 1.5 litres of yellowish, gelatinous ascitic fluid was aspirated from the peritoneal cavity. 
• The peritoneum appeared diffusely thickened with mucinous deposits on the omentum, bowel surfaces, and diaphragm. 
• No primary tumour was identified after examining the appendix, colon, and pancreas. 
• An appendectomy was performed. Peritoneal biopsies and aspirated fluid were sent for cytological and histopathological analysis. 

Histopathology Report 
• Peritoneal biopsy revealed abundant acellular mucin with reactive mesothelial hyperplasia, confirming a low-grade mucinous neoplasm without invasive carcinoma. 
• Appendix histopathology was normal.

Tumour Markers: 
• Carcinoembryonic antigen (CEA): 390.70 (elevated, suggesting potential malignancy) [4]. 
• CA-19-9: 0.90 (within normal range).

Further Workup 
• PET Scan: Suggested increased metabolic activity in the hepatic flexure and adjacent ascending colon, possibly due to an inflammatory or infective aetiology. 
• Colonoscopy: No significant findings or lesions in the hepatic flexure/ascending colon. 
• Oncology Consultation: Given the patient’s age and comorbidities, palliative chemotherapy was recommended following repeat PET-CT evaluation. 

Umbilical hernias account for approximately 6-14% of all abdominal wall hernias [3]. Common contents include bowel, omentum, fat, or fluid [5]. However, mucinous content is extremely rare. PMP has an estimated incidence of 1 to 4 in a million annually [1]. The most common primary site is the appendix (63.3%), followed by the ovaries (16.6%), while 16.6% remain of undetermined origin [6]. In this case, the patient presented with an umbilical hernia and ascites, initially masking the underlying pathology. The diagnosis of PMP was confirmed through histopathological findings of the ascitic fluid and peritoneal biopsy. The primary tumour remained unknown, as the appendix was clinically and pathologically normal, and imaging did not reveal any malignancy in other abdominal organs. The absence of a primary tumour in PMP cases is not uncommon, as the lesion may be small or already ruptured [7].  Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is the optimal treatment option to remove mucinous deposits and control disease progression [8]. However, given the patient’s advanced age and comorbidities, surgical candidacy was assessed, and palliative care was chosen.

This case highlights the importance of considering PMP in the differential diagnosis of patients presenting with umbilical hernia and ascites, especially when imaging reveals peritoneal thickening or mucinous ascites. Early recognition and accurate diagnosis enable timely referral and appropriate management. Although acellular mucin in PMP suggests a more indolent course, vigilant evaluation is necessary to rule out underlying neoplastic processes. 

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