Studies has shown an increasingly infection rate after splenectomy, and there is a potential correlation between microbiota and immune system. investigators suppose that increasingly infection can be associated with the alteration composition of the gut microbiota after splenectomy. It's investigators' aim to discover if any difference of gut microbiota is exist in patients who suffer from traumatic splenectomy compared with normal people, ultimately aim toreduce and mitigation infection rate through controlling gut microbiota.

The spleen is crucial in regulating immune homoeostasis through its ability to link innate and adaptive immunity and to protect against infections. Asplenia refers to the absence of the spleen, a disorder that is rarely congenital and is more frequently as a result of surgery. Splenic hypofunction, as a result of asplenia can lead a series of changes in body systems. Recent study has show an increasingly infection rate after splenectomy including abdominal infection, pulmonary infection and cranial cavity infection.

The gastrointestinal tract plays host to a diverse and metabolically complex community of microorganisms. Recent literature suggests that organisms in the gastrointestinal tract, referred to collectively as gut microbiota, play an indispensable role in the maintenance of host's homeostasis. Study has proved a potential correlation between microbiota and immune system. Lymphocyte, in either peripheral circulation or mesenteric lymph node, altered can lead to an composition change in microbiota.

Investigators suppose that this phenomenon can be associated with the alteration of the resident commensal microenvironment after splenectomy compared to commensal communities. It's investigators' aim to discover if any difference of gut microbiota is exist in patients who suffer from traumatic splenectomy compared with normal people, ultimately aim toreduce and mitigation infection rate through controlling gut microbiota.

Inclusion Criteria:

• All the patients underwent an total splenectomy in the First Affiliated Hospital of Harbin Medical University from January 1st, 2015 to May 1st, 2017. Each participant provided a fresh stool sample in hospital when following-up.

Exclusion Criteria:

• Use antibiotics and probiotics 3 mouth before samples collection.
• Other severe abdomen injury
• Underwent abdomen organ resection surgery
• Other digestive system disease

Study Population are aged from 18 to 65 years，which divided into 2 groups: Splenectomy, healthy controls