The WikiLeaks founder applied to have a warrant for skipping bail quashed, which would free him to leave the embassy, where he has hidden since June 2012, without fear of arrest.
Arguments were made by Assange's legal representatives that the warrant should be dismissed as it had "lost its objective and function" following an investigation into a sex-related allegation being dropped.
But under British authorities Assange remains in breach of his bail conditions - a separate offence.
"[Assange] has spent five-and-a-half years in conditions which, on any view, are akin to imprisonment, without access to adequate medical care or sunlight, in circumstances where his physical and psychological health have deteriorated and are in serious peril", Summers wrote in court papers, as quoted by the Guardian.
Assange sought asylum in the embassy because he fears he will eventually be extradited to the United States and prosecuted over WikiLeaks' publication of thousands of secret military documents in 2010.
MPS Kensington and Chelsea tweeted: "Police attended the Ecuadorian Embassy in SW1 following reports of a small suspicious package".
It is not publicly known whether there is a sealed US indictment against Assange.
"The British authorities' failure to provide assurance against that risk is the reason he sought asylum in the embassy in the first place", she said.
US officials haven't confirmed whether a request for Assange's extradition has been made.
Ahead of Tuesday's ruling, a small group of Assange supporters gathered outside the court in central London. Earlier this month, he was granted Ecuadorean citizenship. Britain refused, saying "the way to resolve this issue is for Julian Assange to leave the embassy to face justice".
But she said that would usually only be considered if somebody were brought to court to explain their failure to surrender to bail.