Background Pseudomyxoma peritonei (PMP) is a disease involving the peritoneum characterized by the production of large quantities of mucinous ascites. PMP has a low incidence, is difficult to diagnose, and has a guarded prognosis. PMP induced by low-grade appendiceal mucinous neoplasm is extremely rare, and PMP accompanied by rectal cancer is even rarer. Case presentation We present a unique case of a 70-year-old male with PMP induced by low-grade appendiceal mucinous neoplasm accompanied by rectal cancer. The patient’s clinical, surgical, and histologic data were reviewed. The patient had persistent distended abdominal pain without radiating lower back pain, abdominal distension for 1 month, and no exhaustion or defecation for 4 days. A transabdominal ultrasound-guided biopsy was performed on the first day. The patient received an emergency exploratory laparotomy because of increased abdominal pressure. We performed cytoreductive surgery, enterolysis, intestinal decompression, special tumour treatment and radical resection of rectal carcinoma. The postoperative course was uneventful. The postoperative histological diagnoses were PMP, low-grade appendiceal mucinous neoplasm and rectal medium differentiated adenocarcinoma. At the 1-year follow-up visit, no tumour recurrence was observed by computed tomography (CT). We also performed a literature review. Conclusions We should be aware that PMP can rarely be accompanied by rectal cancer, which represents an easily missed diagnosis and increases the difficulty of diagnosis and treatment. Additionally, there are some typical characteristics of PMP with respect to diagnosis and treatment.

Background Paragangliomas (PGLs) are extremely rare neuroendocrine tumours arising from extra-adrenal chromaffin cells. PGLs are clinically rare, difficult to diagnose and usually require surgical intervention. PGLs mostly present catecholamine-related symptoms. We report a case of Acute abdomen as the initial manifestation of haemorrhagic retroperitoneal PGL. There has been only one similar case reported in literature. Case presentation We present a unique case of a 52-year-old female with acute abdomen induced by haemorrhagic retroperitoneal PGL. The patient had a 5-h history of sudden onset of serve right lower quadrant abdominal pain radiating to the right flank and right lumbar region. Patient had classic symptoms of acute abdomen. Abdominal ultrasound revealed a large abdominal mass with a clear boundary. A Computed Tomography Angiography (CTA) of superior mesenteric artery was also performed to in the emergency department. The CTA demonstrated a large retroperitoneal mass measured 9.0 × 7.3 cm with higher density inside. A provisional diagnosis of retroperitoneal tumour with haemorrhage was made. The patient received intravenous fluids, broad-spectrum antibiotics and somatostatin. On the 3rd day of admission, her abdominal pain was slightly relieved, but haemoglobin decreased from 10.9 to 9.4 g/dL in 12 h suggesting that there might be active bleeding in the abdominal cavity. Thus, we performed a midline laparotomy for the patient. Haemorrhage was successfully stopped during operation. The retroperitoneal tumour with haemorrhage was completely removed. The abdominal pain was significantly relieved after surgery. The patient initially presented with acute abdomen instead of catecholamine-related symptoms. The diagnosis of retroperitoneal PGL with haemorrhage was finally confirmed by postoperative pathological and immunohistochemical results. The postoperative course was uneventful. At the 1-year follow-up visit, no tumour recurrence was observed by Single Photon Emission Computed Tomography. A literature review was performed to further understand and analyse the aforementioned disease. Conclusion Acute abdomen as the initial manifestation of haemorrhagic retroperitoneal paraganglioma is extremely rare. Abdominal Computed Tomography is essential to locate the lesion and differentiate between other causes of acute abdomen. PGLs are hypervascular tumours. We should be aware that ruptured retroperitoneal PGL with massive bleeding could be life threatening and require emergency laparotomy.