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Numbness and bulging at the flank scar | CION Cancer Clinics
A flank bulge after kidney surgery is usually a slack muscle, not a hernia and not the cancer returning. Small nerves between the ribs are stretched or cut on the way to the kidney, which leaves a numb patch of skin and a weaker side muscle. This page explains why it happens, how it changes over the months, and when it needs a surgeon to look. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
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Medically reviewed by Dr. Muralidhar MuddusettyConsultant Surgical Oncologist · MBBS (AIIMS), MS (Surgery, AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh) · last reviewed September 2026, next review due September 2027
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On this page
- Why is my side numb and bulging after kidney surgery?
- What else could a swelling at the scar be?
- Will the numbness and bulge get better with time?
- What do the words in the clinic letter mean?
- What do people worry about that is not true?
- What helps, and who should look at it?
- What can this page not tell you?
- Common questions about numbness and bulging after nephrectomy
The short answer
Why is my side numb and bulging after kidney surgery?
Numbness and a bulge at the flank scar are both common after open kidney surgery. They usually happen because small nerves running between the ribs were stretched or cut on the way to the kidney. Neither is a sign that the cancer has come back.
Where the numbness comes from
Nerves run around your body from the spine to the front of the belly, tucked under each rib. A cut along the side crosses some of them. The skin those nerves supply loses feeling, usually in a patch in front of and below the scar. It can feel dead, tingly, tight or oddly sensitive to clothing.
Where the bulge comes from
The same nerves also tell the side muscles of the belly to tighten. When they stop working, that part of the muscle wall goes slack. It pushes out when you stand, cough or strain, and looks like a hernia. Doctors call this a flank bulge or pseudohernia, meaning a false hernia, because there is no hole in the muscle.
A true hernia, where there is a gap in the muscle, can look the same. Only an examination, and sometimes a scan, tells them apart.Telling them apart
What else could a swelling at the scar be?
These look alike on a phone photo. They are handled very differently.
Slack muscle
An even, soft fullness along the whole side, usually appearing in the weeks after surgery. Nothing can be felt going in and out. It does not trap bowel.
A true hernia
A rounder lump over part of the scar, often with an edge you can feel. It may go back in with a gurgle when you lie down. It can occasionally trap bowel, so it needs a surgeon's review.
Fluid under the wound
A soft, squashy swelling in the first weeks, sometimes called a seroma. It often settles by itself. If it is red, hot or leaking, the wound team should see it.
Swelling and bruising
In the first days the whole side can be swollen and discoloured. This is part of normal healing and fades gradually.
Not sure whether this applies to you?
Ask an oncologistOver the months
Will the numbness and bulge get better with time?
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The first weeks
Pain from the wound usually hides the numbness. Many people only notice the dead patch of skin once the pain settles. The side may look swollen.
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The first few months
Feeling can start to creep back from the edges of the numb patch, often with pins and needles or sharp, brief twinges. This is usually a sign of nerves recovering. A slack-muscle bulge often becomes clearer now, as the swelling goes down.
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Around the first year
Nerve recovery is slow. Some people regain most of the feeling and some of the muscle tone. Others keep a smaller numb patch and a softer side.
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Beyond that
Whatever is left by now is more likely to stay. It usually causes no harm, though some people find the look or a dragging feeling bothersome.
On your report
What do the words in the clinic letter mean?
- Flank
- The side of the body between the lowest rib and the hip bone.
- Pseudohernia or flank bulge
- A bulge caused by a weak, slack muscle, with no gap in the muscle wall.
- Incisional hernia
- A true gap in the muscle under a surgical scar, with fat or bowel pushing through it.
- Denervation
- Loss of the nerve supply to a muscle or patch of skin.
- Intercostal nerve
- A nerve that runs under a rib and supplies the skin and muscle of the side and belly.
- Seroma
- A pocket of clear fluid that collects under a healing wound.
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Commonly believed
What do people worry about that is not true?
"The lump on my side is the tumour growing back."
A soft bulge that gets bigger when you stand and flatter when you lie down is a muscle wall problem. If it worries you, your follow-up scans and an examination can settle it at the same visit.
"Numbness means a nerve was damaged by mistake."
To reach the kidney through the side, the surgeon has to cross the area where these nerves run. Some numbness is an expected effect of the route, not a sign that something went wrong.
"Exercise will make the bulge worse."
Once your wound has healed and your team agrees, gentle core exercises can help the muscles that still work. Heavy lifting too early is the thing to avoid.
"An operation with mesh will fix the bulge."
Mesh closes a gap. A slack muscle has no gap, and mesh does not bring back its nerve supply. Some surgeons do offer repair for a large, troublesome bulge, but the results are less predictable.
Day to day
What helps, and who should look at it?
For most people, the answer is time, comfort measures and a check from the surgical team. Show the bulge at your follow-up visit even if it does not hurt, so it is recorded.
Looking after numb skin
Numb skin cannot warn you of heat. Avoid hot water bottles and heat packs on the area. Check the skin for rubbing from a tight waistband or a belt. If clothing touching the area feels unpleasant, softer fabric often helps more than creams.
Comfort for the bulge
A support binder can make the side feel more held and look flatter under clothes. Keeping your weight steady and treating a long cough or constipation reduce the push against the weak area.
When nerve pain is the problem
Some people get burning or shooting pain along the scar rather than numbness. Tell your team. There are medicines aimed at nerve pain, and a pain specialist can help if ordinary painkillers do not.
Being straight with you
What can this page not tell you?
It cannot tell you whether your own bulge is a slack muscle or a hernia, or how much feeling will return. Nerve recovery differs from person to person, and nobody can predict it reliably.
Get it seen sooner if
The swelling becomes hard, painful and will not flatten when you lie down, especially with vomiting or a swollen belly. That needs an emergency department the same day. A new lump that is firm and does not change with position should also be checked promptly, rather than at the next routine visit.
What to bring to the review
Bring your discharge summary, the operation notes if you have them, and your latest scan reports. Note when you first saw the bulge and whether it changes with standing or lying down. If you live far from the hospital that operated, a surgeon nearer home can examine you first and write to your original team.
Questions we are asked
Common questions about numbness and bulging after nephrectomy
Is it normal for my side to bulge after kidney surgery?
It is common after an open flank cut. Most bulges are a slack muscle whose nerve was affected during surgery. It still deserves a look from your surgeon, because a true hernia can look very similar and is managed differently.
Will the feeling in my skin come back?
Often some of it does, slowly, over many months. The numb patch tends to shrink from its edges. Some people are left with a small area that stays numb for good. It is not harmful, but take care with heat on that skin.
Does keyhole surgery avoid this?
Keyhole surgery crosses fewer nerves, so a large numb patch and a slack side are less common. They are not impossible. The choice of open or keyhole surgery depends on the tumour and on safety, so ask your surgeon what they recommend for you and why.
Can a scan show if it is a hernia?
Yes. An ultrasound or a CT scan can show whether there is a gap in the muscle. Your follow-up CT scans for the cancer often show it too, so ask the team to look at that area when they review your next scan.
Should I wear a belt all the time?
A binder is for comfort, not for healing the muscle. Many people wear one during the day and for travel. It should not be so tight that it hurts or marks the skin. Ask your team whether it suits your situation.
The scar area burns and shoots. Is that normal?
Sharp twinges can be nerves recovering. Constant burning pain that disturbs sleep deserves attention. Tell your team, because nerve pain often responds to different medicines from ordinary painkillers. Do not take extra painkillers on your own, especially with one kidney.
Can I go back to farm work or riding a bike?
Usually, once the wound has fully healed and your surgeon agrees. A slack side does not stop most people working. Build back up gradually, and avoid heavy lifting until you have been told it is safe. Bring your usual work into the conversation at your follow-up.
Does the bulge mean I need another operation?
Not usually. A slack-muscle bulge is mostly managed with support and time. A true hernia that is growing or painful may be repaired. Your surgeon weighs your fitness and cancer follow-up before suggesting any further surgery.
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Sources
- Cancer Research UK — Surgery for kidney cancer
- American Cancer Society — Surgery for Kidney Cancer
- NHS — Hernia
- Macmillan Cancer Support — Kidney cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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Tell us what you have noticed and send your discharge summary. A surgical oncologist will help you work out whether it needs checking and how soon. One helpline serves every CION centre.