From Reuters, writer Jeremy Clarke describes Amnesty's statement.
About 60 percent of Nairobi residents, or some 2 million people, live in shantytowns with limited access to water, sanitation and other vital services. Sewage runs though ditches and pathways are littered with garbage and human waste.
"Women and girls in Nairobi's slums live under the constant threat of sexual violence," Amnesty International said in a statement attached to its new report on Kenyan women in slums.
"Unable to leave their one-roomed houses after dark, many women in informal settlements resort to 'flying toilets' - using plastic bags thrown from the home to dispose of waste."
Amnesty International said these women were at high risk of communicable diseases such as cholera and dysentery.
The group criticised the slum's lack of police and the government's failure to enforce planning laws and regulations in the settlements.
"There is a huge gap between what the government commits to do, and what is going on in the slums everyday," said Godfrey Odongo, Amnesty International's east Africa researcher.