Kidney Disease & Surgery

Why kidney disease matters for surgery

Your kidneys do three jobs that surgery puts under strain: they clear waste and many medicines from your blood, they balance your fluids and salts, and they help control your blood pressure. When kidney function is reduced, drugs can build up, fluids given during surgery have to be judged carefully, and minerals like potassium can drift to unsafe levels.

A high potassium level matters because it affects the heart's rhythm, and anaesthesia plus surgery can push it higher. This is why we measure it close to your operation and treat it before you go to sleep if needed. The goal throughout is simple: protect the kidney function you have and avoid anything that strains it further.

What's checked and optimised beforehand

Before surgery you'll usually have:

• Blood tests for kidney function (creatinine and eGFR), potassium and other salts, and your blood count — anaemia is common in kidney disease and is corrected where possible.
• A review of your blood pressure and fluid status — whether you're carrying extra fluid or are on the dry side.
• For dialysis patients, confirmation of when your last and next sessions are, and protection of your fistula or line arm (no blood pressure cuffs or drips on that side).
• A heart check (ECG, sometimes more) because heart and kidney problems often travel together.

If your potassium is high or your fluid balance is off, your operation may be delayed a short while so it can be corrected — this is done for your safety, not as a setback.

Medicines that are adjusted

Several common medicines are paused or re-timed around surgery when kidneys are involved:

• Metformin is usually held around the operation, as it relies on the kidneys to clear it. See metformin before surgery.
• SGLT2 inhibitors (drugs ending in -gliflozin, such as dapagliflozin or empagliflozin) are stopped a few days beforehand. See SGLT2 inhibitors before surgery.
• ACE inhibitors and ARBs (blood pressure medicines like ramipril, lisinopril or candesartan) and diuretics (water tablets) are often held on the morning of surgery to protect blood pressure and the kidneys. See ACE inhibitors before surgery and diuretics before surgery.
• NSAID painkillers (ibuprofen, naproxen, diclofenac) are usually avoided because they can reduce blood flow to the kidneys. See NSAIDs before surgery.
• Blood thinners — the timing of when to stop depends heavily on your kidney function, because reduced kidneys clear some of these drugs more slowly. See blood thinners before surgery.

Always follow the specific instructions your pre-assessment team gives you, as these are tailored to your medicines and kidney level.

Dialysis timing, fluids and contrast dye

If you're on dialysis, your session is usually scheduled for the day before surgery rather than the same day. This leaves you with balanced salts and a good fluid level without being freshly dialysed and on the dry side, which can make blood pressure unstable under anaesthetic.

During the operation, fluids given through your drip are measured carefully — too little risks the kidneys, too much can overload someone who can't pass urine normally. If your surgery involves an X-ray contrast dye, the team weighs up whether it's necessary, uses the smallest helpful amount, and keeps you well hydrated, because dye can be hard on vulnerable kidneys.

The anaesthetic and the day of surgery

Your anaesthetist adjusts which drugs are used and at what dose, choosing ones that don't rely heavily on the kidneys to leave your body, so they don't build up. Where suitable, a regional or spinal anaesthetic may be offered, which can reduce the amount of drug needed.

On the day, you'll have a fresh potassium and sometimes a blood-sugar check. Drips and blood pressure cuffs are kept off any fistula or dialysis-access arm. Throughout the operation your fluids, blood pressure and salts are watched closely, and your bladder may be monitored to track how your kidneys are doing in real time.

Recovery and what to watch for

After surgery the team keeps a close eye on your fluid balance, urine output and potassium for a day or two. Pain relief is planned around your kidneys — NSAIDs are avoided, and opioid painkillers are chosen and dosed with care: some, such as morphine, have by-products that build up when the kidneys are weak and can cause heavy or prolonged drowsiness and slow breathing, so they are often avoided or used only at a reduced dose with longer gaps and closer monitoring, while opioids that the body handles more safely in kidney disease may be preferred instead.

Your usual kidney and blood pressure medicines are restarted in a planned order once you're eating, drinking and stable — not all at once. If you're on dialysis, your next session is arranged to fit around your recovery. Tell your team promptly if you feel breathless, very swollen, unusually drowsy, or notice you're passing much less urine than normal.