In a statement published on his Facebook page, Anwar said that he decided to proceed with the surgery as a as part of his recovery for his condition.
He said he has lumbar central stenosis, where the spinal canal narrows, causing pain and numbness. Anwar also has central disk herniation, also known as a slipped disc, that can cause severe neck or lower back pain.
"I had to undergo a follow-up spinal surgery operation at Medipol Mega University Hospital, Istanbul," said Anwar.
"Alhamdulillah, my health condition has improved after the surgery and I am scheduled to undergo another surgery on Thursday on the right side of my shoulder due to rotator cuff injuries.
"Appreciate everyone's doa (prayers) and well wishes in seeing it go smoothly," he said.
Anwar shared photos of him with doctors and his two daughters at the hospital.
In one photo, presumably taken after the surgery, Anwar was seen standing up with a brace wrapped around his lower back.
Anwar was rushed to University Malaya Medical Centre (UMMC) last month after he complained of shoulder and back pain upon returning from his trip to Turkey.
Anwar said that an examination and angiogram at UMMC found that his chronic back pain and shoulder pain has not yet caused an obstructive coronary disease.
The PKR leader has been suffering from continuous pain in his right shoulder, which worsened after a car accident on Sept 22 last year.
Anwar also tweeted that Turkish president Recep Tayyip Erdogan and his wife paid him a visit during his post-surgery recovery in Istanbul.
"Their visit was greatly appreciated even though their time was limited due to their recent victory in the election," he said.
Erdogan was re-elected as president on June 24.
Anwar said that he expressed desire to strengthen the bond and cooperation between Malaysia and Turkey during the meeting.
"President Erdogan responded positively. May this close friendship remain strong and unbroken," said Anwar.