BEIRUT When the dialysis center in the Syrian rebel town of Douma ran out of supplies last month, three people died.
"Soon after, a convoy with 250 dialysis sessions arrived, so the rest made it," said Abou Bassel, a surgeon in the local hospital. "The same thing happened last year."
The hospital's six machines make up the only dialysis facility in Eastern Ghouta, rebel-held suburbs of Damascus that government forces have blockaded since 2013.
Six years into Syria's war, doctors there are under increasing pressure from a new army offensive, while President Bashar al-Assad looks increasingly unassailable. Medics are struggling to obtain the supplies they need to save lives.
Without their disposable kits, the dialysis machines are effectively useless. "We've sent many requests to the United Nations," but erratic aid deliveries barely last a few months, said Abou Bassel, who declined to give his full name, in an internet phone call with Reuters.
"Every time these sessions run out, a patient dies."
The United Nations says Syrian authorities have removed life-saving medicines from aid convoys sent to Douma and other besieged areas.
The U.N. aid chief, reporting to the security council last year, said this was "deliberately and cynically" designed to cause more suffering among civilians. The Syrian government has rejected such accusations.
Physicians for Human Rights, in a report on Tuesday, said authorities removed dialysis supplies from several convoys headed to Douma last year.
Few doctors remain in besieged towns like Douma, where they often treat the wounded on the floors of hospitals that have run out of supplies.
Abou Bassel said conflict had bred expertise in battlefield medicine in rebel strongholds. But as their hospitals overflow with injuries and emergencies, medics have had to neglect those with chronic conditions.
"We are in a war zone, with civilians bombed regularly for years," he added, and so doctors in Douma must ration dialysis supplies.
War has battered Syria's once robust healthcare system. Hundreds of medical staff have been killed, and more than half the country's 30,000 doctors have fled, according to Physicians for Human Rights.
The New York-based group has documented at least 400 attacks on medical facilities over the past six years, blaming most on the Syrian government and its Russian allies. Islamic State and various rebel groups have also hit hospitals, it says.
Aid groups and western countries have accused Syria's government and Russia of deliberately bombing medical facilities. Moscow and Damascus say they only target militants.
"The healthcare system in all of Syria has deteriorated since the uprising, even in regime areas," Abou Bassel said. "Resources are scarce, specialists left, medicine is more expensive."
In rebel-held parts of Aleppo, Hama and the Damascus suburbs, doctors say this means many patients with common diseases have died.
Antibiotics and vaccines often run out, while cancer treatment and dialysis are too expensive and too difficult to come by, medical workers said.
Thousands have died from untreated cancer, kidney failure, and diabetes, according to the Syrian American Medical Society, a nonprofit that supports medics mostly in opposition areas.
A few chronic patients were smuggled out of the besieged suburbs across front lines to Damascus, Abou Bassel said. But most do not try, fearing arrest at checkpoints, pricey medical bills, or a long wait for treatment, he added.
Medical services have fared better in rebel-held pockets of northern Syria, where supplies arrive in trucks from Turkey.
"But there's a huge shortage of specialists. We have no kidney specialist or oncologists ... no chemo or radiotherapy," said Abdallah Darwish, head of the healthcare authority for the rebel-held part of Hama province.
There are no cancer treatment centres in rebel-held Syria, said Darwish, who also runs a hospital in a cave 17 meters underground in rural Hama.
Beyond surgery to remove tumors, the doctors cannot do much, said Mohammad Yasser Tabbaa, co-founder of the Syrian Expatriate Medical Association, which funds hospitals in opposition areas. "They give palliative surgery or pain-killers, to try to reduce suffering while the person is dying," he said.
"It's a difficult thing to say, but with the cost of one cancer patient's treatment, we can open up a clinic that treats hundreds of kids," said Tabbaa, a Syrian doctor in Saudi Arabia.
"There are children dying of fever. Even our doctors are being killed," he added. "We have continuous drainage of resources, continuous bleeding. Sometimes we have to make tough decisions."
Doctors are fighting the collapse of medical infrastructure in rebel-held swathes of Syria, home to thousands of civilians who fear Assad's rule.
In Eastern Ghouta and Idlib, they have tried to fill the gap with training schools for nurses and paramedics. Under the threat of air strikes, they have relied heavily on field hospitals, makeshift facilities and mobile clinics.
"Many are substandard, in school buildings or underground basements," Tabbaa said. Still, medical services in opposition enclaves under attack hold out the longest because they are vital to survival, he said. "There are hospitals that we've rebuilt or repaired or relocated five times."
(Editing by Tom Perry and Giles Elgood)