See also: [[HIV]] - A wide range of gastrointestinal pathogens cause diarrhoea in HIV-infected patients. Patients should be asked about recent travel or antibiotic use. - [[Gastroenteritis#Bloody vs non-bloody diarrhoea DDx table|Bloody]] small-volume diarrhoea with cramping lower abdominal pain is suggestive of a **large bowel pathogen**, such as cytomegalovirus, Entamoeba histolytica or Clostridium difficile, whereas profuse watery diarrhoea suggests an infection of the small bowel, such as cryptosporidiosis. - However, clinical features are often of limited diagnostic value and the specific diagnosis rests on identification of the pathogen in a faecal or biopsy specimen. - Prominent anal pain or tenesmus suggests the possibility of proctitis due to a sexually acquired infection, such as gonorrhoea, Chlamydia (including lymphogranuloma venereum) or herpes.