Pseudomyxoma peritonei overview

# Overview
Pseudomyxoma peritonei is a very rare tumor characterized by the presence of abundant mucus in the abdominal cavity, consisting of intraperitoneal mucinous tumors and ascites, most commonly arising from mucinous tumors of the appendix, however, the ovary or the colon may be the primary site of origin. The tumor is not harmful by itself, but the mucus accumulation in abdominal cavity compresses vital organs such as spleen, kidney, colon. On 1842, Carl F. Rokitansky described the first case of pseudomyxoma peritonei.  Pseudomyxoma peritonei may be divided into two pathological subtypes with different etiology and prognosis, these two subtypes are peritoneal adenomucinosis and peritoneal mucinous carcinoma. The K-Ras and p53 genes are involved in the oncogenesis. Pseudomyxoma peritonei must be differentiated from peritoneal carcinomatosis without mucinous ascites, peritoneal sarcomatosis, and tuberculosis peritonitis. The incidence of pseudomyxoma peritonei is approximately 0.1 person per 100,000 individuals worldwide. Females are more commonly affected with pseudomyxoma peritonei than males. The median age at diagnosis is 50 years. There are no established risk factors for pseudomyxoma peritonei. Patients with pseudomyxoma peritonei may develop abdominal or pelvic pain, bloating, abdominal distension, weight change, and infertility symptoms if left untreated. Common physical examination findings of pseudomyxoma peritonei include abdominal tenderness, abdominal distention. On abdominal CT scan, pseudomyxoma peritonei is characterized by low attenuation, loculated ascitic mucinous fluid in the peritoneum, omentum and mesentery with scalloping of visceral surfaces of the liver. On abdominal MRI, pseudomyxoma peritonei is characterized by a mass which is hypointense on T1-weighted MRI and hyperintense on T2-weighted MRI. Finding on ultrasound scan suggestive of pseudomyxoma peritonei are echogenic peritoneal masses or ascites which is not mobile. Cytoreductive surgery combined with hyperthermic intraperitoneal chemoperfusion is the optimal way of treatment for pseudomyxoma peritonei.

# Historical Perspective
The first case of pseudomyxoma peritonei was described by Carl F. Rokitansky in 1842.

# Pathophysiology
Pseudomyxoma peritonei is a rare poorly understood neoplasm which may be divided into two pathological subtypes: Disseminated peritoneal adenomucinosis (DPAM), and Peritoneal mucinous carcinomatosis (PMCA).

# Causes
Pseudomyxoma peritonei is caused by a pre-existing intraperitoneal mucinous neoplasm. The K-Ras and p53 genes may be involved in the oncogenesis.

# Differentiating Pseudomyxoma peritonei from other Diseases
Differential diagnosis of pseudomyxoma peritonei include peritoneal carcinomatosis without mucinous ascites, peritoneal sarcomatosis, Peritonitis, peritoneal mesothelioma.

# Epidemiology and Demographics
The incidence of pseudomyxoma peritonei is approximately 0.1 per 100,000 individuals worldwide. Females are more commonly affected with pseudomyxoma peritonei than males. The median age at diagnosis is 50 years.

# Risk Factors
There are no established risk factors for pseudomyxoma peritonei.

# Natural History, Complications and Prognosis
Patients with pseudomyxoma peritonei may develop abdominal or pelvic pain, bloating, abdominal distension, weight change, and infertility. Prognosis is generally good and the 10-year survival rate of patients with pseudomyxoma peritonei is approximately 63%.Overall risk of complications after surgery such as urinary tract involvement due to tumor seeding in pelvis is very low.

# History and Symptoms
Symptoms of pseudomyxoma peritonei include: abdominal pain, bloating, abdominal distention, Shortness of breath, Weight change, Menstrual irregularities in women.

# Physical Examination
Common physical examination findings of pseudomyxoma peritonei include: Abdominal tenderness, Abdominal distention.

# Laboratory Findings
The laboratory findings associated with pseudomyxoma peritonei include: increased levels of tumor markers such as carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), carbohydrate antigen 125 (CA125).

# CT
Findings on abdominal CT scan of patients with pseudomyxoma peritonei include: accumulation of fluid throughout the peritoneum, omentum and mesentery seen as low attenuation mucin depositis on CT scan, scalloping of visceral organs.

# MRI
On abdominal MRI, pseudomyxoma peritonei is characterized by a mass which is hypointense on T1-weighted MRI and hyperintense on T2-weighted MRI, it can further clarify the cystic structure of mass.

# Ultrasound
Abdominal ultrasound scan may be helpful in the diagnosis of pseudomyxoma peritonei. Finding on ultrasound scan suggestive of pseudomyxoma peritonei are echogenic peritoneal masses or ascites with echogenic particles which do not move.

# Medical Therapy
The predominant therapy for pseudomyxoma peritonei is surgical resection and debulking. Supportive therapy for pseudomyxoma peritonei includes chemotherapy which can be used as adjuvant treatment. The treatment of choice is complete tumor excision named cytoreductive surgery (CRS) combined with Hyperthermic intraperitoneal chemoperfusion (HIPEC).

# Surgery
Surgery is the mainstay of treatment for pseudomyxoma peritonei. The feasibility of surgery depends on the stage of pseudomyxoma peritonei at diagnosis.