Common Postoperative Complications
Postoperative complications are problems which arise as a result of you having had surgery, which were not an intentional effect of the surgery.
What are postoperative complications?
Complication is a term used by health professionals to refer to something which was not intended to happen. Postoperative complications are problems that can happen after you have had surgery but which were not intended. Doctors are aware of the risk of complications and take steps before, during and after surgery to reduce this risk. However, some complications are common and occur frequently despite precautions. Some postoperative complications are related to the exact surgery that you have had, but many (such as wound infection) may occur after any kind of surgery.
Some complications listed here are very serious but most people having surgery will not experience them. Planned (elective) surgery is particularly safe because both you and the doctors taking care of you can take steps beforehand to reduce your risk of problems. This includes stopping medicines which make clot formation more likely, arriving for surgery with an empty stomach, and stopping smoking.
When do postoperative complications occur?
Postoperative complications include immediate complications (up to three days after the surgery), early complications (most likely in the few weeks after your surgery) and late complications (up to years afterwards). The most common postoperative complications are:
- Bleeding (from the wound or internally).
- Lung blockage or collapse.
- Heart problems.
- Pulmonary embolism (PE).
- Severe infection (septicaemia).
- Acute kidney injury.
- Feeling sick (nausea) and being sick (vomiting).
- High temperature (fever).
- Wound breakdown.
- Deep vein thrombosis (DVT).
- Acute urinary retention - inability to pass urine.
- Infections: pneumonia, wound infection, urinary tract infection.
- Pressure sores.
- Bowel problems.
- Bowel blockage due to scarring inside the tummy.
- Incisional hernia.
- Persistent sinus.
- Thickening or tightening of scar.
- The original problem coming back.
It seems obvious that surgery will be painful, but modern expertise with painkillers and pain-blocking techniques means that most pain should be well controlled, so pain that is not well controlled is seen as a complication rather than as an expected side-effect.
Some kinds of surgery are more likely to be painful, particularly surgery to the chest and tummy (abdomen). It is important for doctors to give you enough pain relief, without giving you so much that your recovery is slowed.
- Medicines you take by mouth, such as paracetamol, codeine or oral morphine.
- Medicines which are injected or infused into a vein, such as paracetamol (again) or pethidine. Sometimes you will be able to control your own pain medication using a 'patient demand' system.
- Medicines which are anaesthetic and are infused around the nerves in the spine, or into the wound, to add numbness temporarily.
Some painkillers tend to be avoided after some types of surgery. Anti-inflammatory painkillers have traditionally been widely avoided as they were thought to slightly increase the risk of bleeding, but doctors now feel that in many types of surgery these are safe.
Confusion is quite common after surgery, particularly in elderly patients. It can be caused by the anaesthetic or by other medicines which may have been given, including painkillers. Confusion can occur for several other reasons, including pain, disturbed sleep, infection, constipation and abnormalities of fluid balance (ie you are lacking in fluid in the body (dehydrated) or you have been given too much fluid).
Nausea and vomiting
Feeling sick (nausea) and being sick (vomiting) are a common reaction to an anaesthetic. Doctors usually give you medicines to combat this at the same time as your anaesthetic, but this is not always enough.
Nausea and vomiting can also occur because of infection, or as a side-effect of medication, particularly painkillers. These symptoms are more likely if you have had surgery to your bowel.
A raised temperature after surgery may be caused by many of the conditions described below, including infection in the surgical wound, infection in lungs, cystitis, deep vein thrombosis (DVT), after blood transfusion, and as a reaction to medication. A raised temperature (fever) is a symptom, not a cause. Your temperature will be checked regularly in the postoperative period and if it is found to be raised, you will be closely examined to discover the cause.
Septicaemia is an uncommon complication of surgery. It is widespread, overwhelming infection spreading through the body, carried in the blood. It is a serious complication which can also lead to other problems. It usually results from the spread of infection from somewhere more localised, like the wound, the lungs (pneumonia) or the bladder. (The word sepsis, which you may also hear, describes the state or reaction of the body when septicaemia is present).
Septicaemia is more likely after surgery which carried a higher infection risk, particularly abdominal surgery involving cutting the bowel, surgery after trauma where wounds may be contaminated, and severe burns. It is more likely if your immune system is suppressed (such as if you are on long-term steroid treatments, if you have diabetes, or if you are very young or very elderly).
If you develop septicaemia you will be collapsed, confused and unwell. Treatment is with oxygen therapy, antibiotics, fluids and other medicines, and you will usually need to go to intensive care.
Other bodily injury
There is a small risk of injury whilst under general anaesthetic. Anaesthetic damage can include scratches to the inside of your throat from the passage of breathing tubes, and damage to dental crowns. Muscle aches and pains are common for a few days afterwards and can be due to your positioning for surgery, particularly if your surgery was long. Some neck pains are quite common after surgery.
There is a small risk of surgical injury, when the surgeon accidentally harms other tissues and has to repair them. In the past there were episodes in which people had the wrong operation. Thankfully this is now almost unheard of, as careful steps are taken to prevent confusion, including marking your body before you are put under anaesthetic, to identify exactly which part of you is being operated upon.
Bleeding, wound and skin complications
Bleeding of any sort is more common after very long and very major operations, and after operations in which you have needed blood transfusions. It is also more common if you have a tendency to bleed easily or clot poorly, and more likely if you are on anticoagulant medicine (which is used to prevent blood clots).
Bleeding which hasn't stopped since surgery or starts straight afterwards usually means that tiny blood vessels around the area of surgery are leaking very slightly. If the bleeding is slight it may just be 'oozing' from the wound and this usually settles quickly. However, if it is more than this then you may have to go back into theatre (under anaesthetic) for the surgeon to find the source of the bleeding, and stop it.
This is much less common, as your surgeon will take great care to make sure large blood vessels, which can bleed heavily, are sealed off before the end of your operation. If heavy bleeding does occur this may mean stitches have burst, or that your blood is not clotting well as an effect of the surgery. This is an emergency, as losing blood may lead to shock and collapse. You will need to go straight back to theatre and you may need a blood transfusion.
Heavy bleeding is mainly seen after more major operations, when large blood vessels may have been cut or damaged. This is more likely to happen after surgery to large blood vessels, large joint replacements, surgery after you have experienced serious trauma (such as a road accident), and surgery associated with cancer, when there may be abnormal blood vessels present.
A haematoma is a trapped pocket of blood in the body which has leaked from a wound or blood vessel. It may be just under the skin, where it may form a bluish lump, close to the wound (where it may leak but won't completely empty, as it will have partially clotted), or inside the body where it can't be seen. The blood in a haematoma is outside your circulation, trapped in the body tissues.
Haematomas can be uncomfortable, particularly if large; if you develop one your surgeon may want to drain it. They can leave a small lump even after healing has occurred, as the trapped blood may leave behind a bit of fibrous tissue as it is reabsorbed. They can also become a site of infection, particularly if large.
Bruising is the leakage of blood from cut or damaged blood vessels into the subcutaneous tissues. It is more obvious in pale-skinned people, whose skin is more transparent and who may appear more bruised than others even if they are not.
Most people will have some bruising after surgery but some people seem to bruise particularly easily. This includes:
- People who are taking anticoagulant medications.
- A person with one of the Ehlers-Danlos syndromes.
- People with red hair.
- Elderly people.
- People with nutritional deficiencies.
- People with vitamin K deficiency.
- People with clotting disorders.
- People with liver disease.
Bruising after surgery can be surprising, as blood can track deep beneath the skin then find its way to the surface in unexpected places. For example, after knee surgery, bruising may appear right down the leg and into the ankle and the sole of the foot. After dental surgery (particularly extraction of wisdom teeth) bruising may make the face swell and track down the front of the chest, and after surgery to the nose it is common to have two black eyes.
Bruising is not usually painful, although bruises may be tender when you press them. The length of time a bruise takes to resolve is highly variable, as it depends on how much blood is in the bruise. Bruises can take anything from a few days to several weeks to clear, as the body has to slowly reabsorb the blood and the coloured pigments in it from your skin. Bruises can go almost all colours of the rainbow before they disappear, as the different pigments present in the blood cells are reabsorbed by the body at different rates.
Very extensive bruising around a surgical wound may slow healing a little, but whilst bruising can look dramatic, it does not usually leave any lasting effects.
Wound infection can happen after any surgery but is particularly a problem after abdominal surgery which involves opening the bowel. To try to prevent this, you may be given antibiotics before your operation; however, drug-resistant bugs (pathogens) are an increasing problem and this does not always work.
- The most common type of infection is surface (superficial) wound infection occurring within the first week. It causes soreness and localised pain, redness and, sometimes, a slight sticky discharge. It usually responds to antibiotics, sometimes as ointment.
- Deeper infections are most likely after bowel-related surgery. They can occur any time from immediately after surgery to up to three weeks later. They cause a high temperature, sometimes with confusion, nausea and feeling unwell. If skin or muscle is affected, you may develop a red, swollen area which is hot and sore. If the infection is internal you may not see anything but will develop a temperature and, probably, some increased pain.
- Abscess is a collection of pus inside the body, where infection has collected. It is more common after abdominal surgery. Abscesses cause swinging fever - a temperature that goes up and down. Confusion and nausea are common. If an abscess is suspected, you may be given an ultrasound scan or an X-ray so that the surgeon can localise it. Abscesses need to be drained, so this may mean going back to theatre.
- Wound sinus is a late infection from a deep but undetected abscess that finds a way of discharging through the skin. You may have a mild temperature but otherwise symptoms may not be marked. However, there will be a sticky discharge, often through the surgical scar, hinting at the infection hidden inside.
Poor wound healing
Most wounds heal without complications. However, some things make the job of healing harder for the wound:
- If skin or subcutaneous tissue has been removed then the two sides that are being closed together will not have absolutely matching blood vessels any more. This makes healing a little slower, as the small blood vessels will take longer to 'knit' together.
- A poorer blood supply slows healing. Diabetes, obesity and smoking all reduce skin blood supply.
- Over-tight stitches can slow healing.
- Long-term steroid medicines and immunosuppressants, particularly taken by mouth, make healing slower and the resulting scar thinner and less strong.
- Some patients with Ehlers-Danlos syndromes heal poorly and make poor scars as part of their condition.
- Some hormonal problems, including diabetes and hypothyroidism, tend to cause slower and less strong wound healing.
- Coughing may strain your wound and slow healing, especially if the wound is in your tummy (abdomen).
- Vitamin C deficiency (scurvy) slows wound healing.
- Radiotherapy damages the small blood vessels in the skin, so that it no longer heals as readily. Cancer can also affect wound healing.
- Wounds that are tightly stretched, such as over joints, may heal more slowly.
- Wounds that are in moist, airless areas, like under the breast or in the genital area, can be slow to heal as they are more likely to develop wound infection. An exception to this is episiotomy (after childbirth), which tends to heal very quickly as the blood supply is so good.
In most cases healing will still occur but stitches may need to be left in for longer and may need additional support, such as Steri-strips® or bandages.
Wound dehiscence occurs when your wound comes partially or completely open again. This is obviously very upsetting and it can be shocking, particularly if an abdominal wound is involved. If it happens to you then you should cover the open wound with a clean cloth and seek medical help urgently.
Dehiscence is uncommon, affecting about 1 out of every 100 large tummy wounds. Sometimes there is leakage of pink liquid from the wound just beforehand. If you have wound dehiscence your wound will need to be re-stitched, usually under anaesthetic.
Wound re-opening is more likely if you have reasons for poor wound healing, such as nutritional deficiency, infection in the wound, or stitches which were not adequately secured. It is also more likely if you are or were very overweight and it can occur when the skin integrity is not good, such as when stretched extra skin has been removed following weight loss. Dehiscence is more likely after longer operations, if you are coughing a lot (putting strain on your stitches).
Incisional hernia develops as a late (it can be years afterwards) complication of about 1 in 10 tummy operations. Usually, the hernia is a bulge in the tummy wall near the surgical scar. It is not usually painful and will not usually block (strangulate); however, incisional hernias do tend to get steadily larger and they may need to be repaired.
The things that make wound dehiscence and poor healing more likely also make incisional hernia more likely. They include obesity, weak tummy muscles, wound infection and repeated re-operations through the same site (such as caesarean sections).
Damage to other tissues may occur during many types of surgery. If nerves are damaged these can take a particularly long time to heal and they may never completely recover. Some nerve damage may be impossible to avoid during surgery: for example, tumours of the parotid gland (a salivary gland on the side of the face) tend to be wrapped around the nerve, so that when the tumour is removed the nerve is cut out with it. Other nerve damage can sometimes, but not always, be avoided.
Minor damage to nerves in the skin is very common, as tiny surface nerves will be cut when the incision is made. These nerves will usually grow back; however, if they become caught up in the scar tissue, you may be left with small localised areas which are numb or where the sensation is not quite normal. Nerves grow back very slowly - it can take a couple of years for sensation to fully return around a surgical scar.
A pressure sore (pressure ulcer) is an ulcerated area of skin caused by irritation and continuous pressure on part of your body. Pressure ulcers are more common over places where your bones are close to your skin (bony prominences), such as your heels, the lower part of your back and your bottom, and your risk of developing a pressure ulcer is increased if you are spending long periods lying in bed or sitting in a chair, particularly if you are not moving very much.
Pressure sores affect between 1 to 5 in every 100 people admitted to hospital. They are more likely it you are seriously ill, have had a spinal cord injury, or have had a poor diet. They are more common in people who smoke, in those with diabetes or heart failure and in those with neurological diseases.
Pressure sores are prevented by good nursing care - in particular helping you change your position as much as possible and the use of pressure-relieving devices such as cushions and mattresses. They are treated with antibiotics and painkillers, dressings and surgery. See separate leaflet called Pressure Ulcers.
Breathing and lung complications
This is very common and involves a blockage and then a collapse (atelectasis) of a part of one of your lungs, usually at the bottom, so that it no longer fills with air when you inhale. It is particularly common after surgery to the tummy (abdomen) or the chest. Lung collapse occurs when the finer airways get blocked with trapped mucus. Once air can't get in or out, the air that is already behind the blockage is absorbed by the body and the fine tubes collapse. These collapsed sections of lung easily become infected due to trapping of germs (bacteria). Atelectasis is more likely if you are overweight, are a smoker, are in a lot of pain and can't cough, or if you are having a very high level of painkillers (which tends to suppress coughing). The condition makes you breathless and you may develop a painful cough and start to become hot.
Treatment is usually with physiotherapy, including breathing exercises to help you clear the blockage, together with antibiotics for any infection. You may be given extra oxygen (through nasal prongs or a mask) for a day or two to compensate for the area of lung that isn't working.
Infection in the lungs (pneumonia) can occur after surgery. It is fairly common, although much less common than atelectasis. You may have a cough or abdominal pain and you are likely to be hot and running a high temperature (feverish), and possibly be short of breath.
Pneumonia often follows atelectasis and is treated with antibiotics. Sometimes additional oxygen is needed. It is more likely to happen if you are a smoker, if you are older, or if you have had surgery to your lungs.
Deep vein thrombosis and pulmonary embolism
Deep vein thrombosis (DVT) occurs when clots form in the large veins in your legs and pelvis, and pulmonary embolism (PE) occurs when bits of those clots come loose, enter the circulation and end up in your lungs. PE is very serious and can be fatal. There is an increased risk of PE and DVT any time from surgery until you are fully mobilised again; however, the risk is highest in the first two to three days after your operation.
Clots in veins are more likely to form after surgery because you are not moving around, and because the body's response to the (intentional) injury of surgery is to increase its tendency to form blood clots. The risk is greatest for surgery affecting the pelvis.
The risk of clotting is increased by long periods of being immobile, by being on hormones, if you are overweight, by certain medicines (including hormone replacement therapy (HRT) and the combined oral contraceptive (COC) pill), by pregnancy and, particularly, by being a smoker.
DVT is not always detected but it causes painful swelling of the leg (particularly the calf). Smaller pulmonary emboli cause sudden breathlessness, chest pain and confusion, while large ones cause collapse and may be fatal. Doctors try to reduce the risk of DVT and PE by stopping drugs which increase your clotting risk well before high-risk surgery, by getting you to wear compression stockings to keep blood from pooling in the deep veins of the legs and by getting you up and mobile as soon as possible after surgery. If you are particularly at risk you will be given blood-thinning medicines for the period of your surgery.
Aspiration pneumonitis (also called aspiration pneumonia) is a rare complication of surgery. It is a chemical inflammation of the lungs which occurs because acidic stomach contents are inhaled, usually due to being sick (vomiting) or regurgitation followed by inhalation whilst you are under anaesthetic. Aspiration pneumonia is more likely in emergency surgery where you did not have a period of starvation to empty your stomach beforehand. It is an extremely serious condition which needs treatment with antibiotics, ventilation and suction of the lung, and often steroids.
Anaesthetists treating emergency surgery patients are very aware of the risk of vomiting and inhaling, and will use medicines and techniques to try to prevent it.
Acute respiratory distress syndrome (ARDS)
This rare condition comes on 24-48 hours after surgery, usually after multiple trauma, although it can also occur after near drownings. It causes severe breathlessness and confusion due to low oxygen levels. It is sometimes called 'shock lung'.
ARDS is a serious condition which requires intensive care. It is more common if you have widespread, generalised infection (sepsis), have inhaled harmful substances (including smoke inhalation and near-drownings) and after serious head injury and serious burns. It can also occur as a consequence of aspiration pneumonitis.
Heart problems associated with surgery most often happen in the 48 hours following surgery, although they may occur in the first six days. They include heart attacks, abnormal heart rhythms, angina and heart failure. They can sometimes go undetected, because you are on strong painkillers which mask pain and discomfort, or you are still sleepy or confused.
Heart problems occur because the physical strain and challenge of surgery, including the anaesthetic, the surgery itself and the medicines and any fluids you have been given, are an extra load on your heart. A normal, healthy heart can cope with this extra work; however, if you were already at risk of (or you already had) heart disease or cardiovascular disease, surgery may be enough to trigger a heart problem.
Your surgeon and anaesthetist will assess you carefully prior to your operation, to determine whether you are at increased risk of heart problems. If your risk is thought to be high then you may be advised against all but essential surgery. If you do want or need to go ahead with surgery then the surgeon and anaesthetist will take every precaution they can to minimise the strain on your heart, including making your operation as short and small as possible, making sure you have enough pain relief and taking extra care with medicines and with fluid replacement.
Kidney and bladder complications
This is very common after surgery, particularly to the tummy (abdomen) or pelvis. You are unable to pass urine despite a full bladder. Urinary retention is most often caused by pain and it will often settle with pain relief. It is sometimes necessary to pass a catheter to allow the bladder to drain, particularly if it is so full that it is causing you discomfort.
Urinary retention is common after surgery close to the bladder, including vaginal wall repair (for prolapse) which can cause bruising around the neck of the bladder. See separate leaflet called Urinary Retention.
Urinary tract infection (UTI, or cystitis) is very common after surgery, especially in women, and particularly if you had a catheter during your surgery. UTI often causes a high temperature (fever), although the usual symptoms of needing to pass water often, and pain on passing water, do not always occur.
Urine infection usually responds quickly to antibiotics and you will usually be given extra fluids to help 'wash' the infection out. If UTI is not treated then there is a risk of it spreading to the kidneys or to cause sepsis, particularly if you have had major surgery or are already very unwell.
Acute kidney injury
The kidneys have a difficult job to do when you have surgery, as they do most of the work of clearing medicines, painkillers and chemicals (produced by your body in response to injury) from the body. Injury to the kidneys can happen because they don't get given quite enough fluid during surgery to help them process all these materials, so that they shut down and stop working.
The kidney can also be upset by some antibiotics and painkillers. The blood supply to the kidney can be compromised by surgery to the aorta - the big blood artery in your tummy - or by a long period of very low blood pressure whilst you are in surgery.
If the kidneys are injured they stop making urine. You may be treated with fluid restriction until the kidney recovers. Rarely, dialysis is needed to do the work of the kidney until it recovers. Kidney injury is more likely to happen to older patients, those with liver disease, those having surgery to the aorta and those with severe atherosclerosis.
Complications of bowel surgery
Inability to pass a stool (constipation) is very common in the days and weeks after surgery. The medicines used in your anaesthetic tend to send the bowel to sleep initially and this in itself can be enough to trigger constipation. Other factors that lead to constipation are being dry (dehydrated), not eating (so the bowel is not stimulated) and most postoperative painkillers. Not moving around much (immobility) and a reduced diet (whilst in hospital) also contribute.
Constipation is uncomfortable and most constipation is easily treated, although if you wait too long it becomes more difficult. If you have not opened your bowels within 48 hours of surgery, and particularly if you are on painkillers called opiates (including codeine and pethidine, which are both commonly used after surgery) then you should ask the doctors and nurses looking after you for something to help get things going again. Early mobilisation, and swift reduction in painkillers as the pain eases, will also help.
Constipation can sometimes be due to paralytic ileus (below). Unlike constipation (in which you typically can still pass wind (flatus), in paralytic ileus and bowel obstruction you cannot pass anything, including wind.
Sometimes the bowel takes a while to start working again after surgery - a condition called paralytic ileus. The bowel becomes still and stops its usual rhythmic contracting, so food is not pushed through it and you stop opening your bowels or passing wind. Paralytic ileus usually lasts from a few hours to a few days, but occasionally it can last much longer.
Paralytic ileus is particularly common if the surgeon has touched the bowel during surgery, as often happens with surgery to the tummy or pelvis. Painkillers (particularly opiate medicine) make it more likely and it is more likely to occur in older people, in people with an underactive thyroid gland, in people with Parkinson's disease and in people with diabetes.
If you have paralytic ileus your bowel behaves as if it were asleep. You will not feel hungry and you may feel sick (nausea), or be sick (vomiting). You will be bloated and uncomfortable. You will be taken off oral food and drink and given fluids intravenously whilst your bowel recovers. You are likely to have a nasogastric tube. This is a tube passed to your stomach via a nostril to keep the stomach empty. If the paralytic ileus is prolonged, doctors may try to stimulate normal bowel activity with simple medicines. There have been some trials of chewing gum as a 'sham' stimulus to wake up the bowel.
After bowel or abdominal surgery, the bowel can become twisted, which causes a sudden blockage. It can also be blocked by strings of scar tissue called adhesions, which can form inside the tummy (abdomen).
An obstructed bowel causes colicky tummy pain (which can be severe), constipation, nausea and vomiting. It may settle if the bowel is rested by moving you to 'nil by mouth' and giving you intravenous fluid. If it doesn't settle then you may have to go back to surgery. Doctors try to avoid this, as the more surgery you have, the more adhesions you tend to make. Adhesions can last for a long time and can intermittently interrupt the normal functioning of the bowel for many years after surgery.
If the bowel has been cut and then stitched closed (for example, in appendicectomy) or if a section of bowel has been removed, the 'join' (anastomosis) in the bowel can leak or come apart. Small leaks are common and cause small abscesses in the tummy, sometimes several weeks after surgery. Larger leaks are rare but cause severe tummy pain and widespread infection (peritonitis). This is a surgical emergency and you will need to go back to theatre for treatment..
Can postoperative complications be prevented?
Modern approaches to surgery and anaesthetics are very advanced compared to the distant past, and health professionals know a great deal about how to reduce the risk of postoperative complications. However, the risks are still there, even though they are kept as small as possible. Surgery is a serious kind of assault on the body. It is important not to go ahead if the risks of complications are felt to be too great.
Before you have an operation the surgeon will talk to you about the possible complications. He or she will be able to give you a clear idea of what the general risks are for the surgery, and also of what the risks are to you, specifically. This will help you decide whether you want to go ahead.
There are several things that you can do that will make you fitter for surgery, making complications less likely. They include:
- Stopping smoking.
- Weight control.
- Good level of fitness for age.
- Healthy diet with correction of any deficiencies such as a anaemia.
- Stopping any medication that you are advised to stop, well in advance (note, not all medication should be stopped for surgery).
- Following the surgeon's advice regarding preparation for surgery.
- Following instructions about when to have your last food and drink prior to planned surgery.
There are also several things that your surgeon and anaesthetist can do. This includes:
- Pre-operative check-ups to look for things that could be corrected before surgery, such as high blood pressure or anaemia.
- Assess and discuss fitness and risk with you and make a plan for fitness after surgery.
- Planning and action to reduce risk of thrombosis, including stopping medication where necessary and use of TED stockings.
- Use of antibiotics to 'cover' surgery where there is felt to be a risk of infection.
- Specialist postoperative nurses and doctors looking after you closely when you come out of theatre.
- Careful attention to fluid balance and pain relief during and after your surgery.
- Early mobilisation.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Patient Platform Limited has used all reasonable care in compiling the information but makes no warranty as to its accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Mary Lowth
Dr Adrian Bonsall