Can a bariatric surgeon be sued for negligence after weight loss surgery in NSW?
Many people who undergo bariatric surgery feel that their surgeon did not fully explain what could go wrong. Others believe their surgeon failed to monitor them properly in the months and years that followed. If you are in that position, this article explains what the law expects of bariatric surgeons in NSW — and what it means when those expectations are not met.
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1GP referral and first consultationThe surgeon reviews the patient’s full medical history, discusses obesity treatment options, and explains the differences between available procedures.
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2Informed consent processThe surgeon explains the specific risks of the chosen procedure — including malabsorption, vitamin deficiency, bowel changes, and dietary requirements — both verbally and in writing.
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3Surgery and immediate post-operative careThe surgical team monitors the patient closely for complications such as pulmonary embolism, infection, or early signs of malabsorption.
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4Ongoing post-operative monitoringThe surgeon schedules regular blood tests — typically every six months — to check vitamin levels, nutritional markers, and organ function. Deficiencies are identified and treated promptly.
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5Long-term follow-up and dietary supportThe surgeon and a dietitian provide ongoing guidance on diet, supplementation, and lifestyle to prevent malnutrition and protect the patient’s long-term health.
Understanding biliopancreatic diversion surgery: what normally happens
Biliopancreatic diversion — often called BPD surgery — is a form of bariatric surgery. Bariatric surgery is weight loss surgery performed on people with severe obesity. BPD surgery works by rerouting the digestive system so that the body absorbs fewer fats and starches from food.
Unlike gastric banding or gastric sleeve surgery, BPD does not simply restrict how much a person can eat. Instead, it changes how the body digests food. Bile and pancreatic juices — the fluids that break down fats — are diverted away from most of the small intestine. Food passes through the gut more quickly and with less absorption.
This makes BPD one of the most effective bariatric procedures for long-term weight loss. But it also carries significant risks. Because the body absorbs fewer fats, it also absorbs fewer fat-soluble vitamins — particularly vitamins A, D, E and K. Patients must take specialised vitamin supplements for life and follow a strict low-fat, high-protein diet.
A competent bariatric surgeon explains all of this before the patient agrees to surgery. The surgeon also arranges regular blood tests after surgery — typically every six months — to check vitamin and nutritional levels. Early detection of deficiencies allows the surgeon to adjust supplements and prevent serious harm. For general information about bariatric procedures, Healthdirect Australia provides accessible, evidence-based health information.
A common pattern — where care can break down in bariatric surgery
Bariatric surgery cases that end up in court often share a recognisable pattern. The failure is rarely a single dramatic event. More often, it is a series of smaller gaps in care that compound over months or years.
Failure to warn about specific risks
Before any surgery, a patient must give informed consent. Informed consent means the patient understood the real risks of the procedure — not just a vague acknowledgement that surgery carries risks. A bariatric surgeon must explain the specific risks of BPD surgery, including frequent and malodorous bowel movements, fat malabsorption, vitamin deficiency, and the possibility of malnutrition if the patient does not follow dietary advice.
Some patients report that their surgeon gave them only brief or general information. Others say they received documents they did not understand. When a surgeon fails to explain material risks in a way the patient can genuinely comprehend, that failure may support a claim of negligence.
Failure to compare available procedures
A surgeon who recommends BPD surgery must also explain why that procedure is appropriate for this particular patient — and how it compares to alternatives such as gastric banding or Roux-en-Y gastric bypass surgery. Each procedure carries different risks and suits different patients. A surgeon who does not discuss alternatives may deprive the patient of a genuine choice.
Failure to monitor after surgery
Post-operative monitoring is not optional. After BPD surgery, the surgeon must arrange regular blood tests to check vitamin levels, protein levels, and other nutritional markers. When a surgeon fails to schedule these tests, or fails to act on borderline results, deficiencies can develop silently over months. By the time symptoms appear, the harm may already be serious.
Failure to treat identified deficiencies
Identifying a deficiency is only the first step. A surgeon who notes a borderline vitamin level and takes no action — or who does not refer the patient to a dietitian or specialist — may fall below the standard of care. The Australian Commission on Safety and Quality in Health Care sets national standards for clinical monitoring and follow-up care that apply across all surgical specialties.
When things start to go wrong after bariatric surgery
Some complications after BPD surgery are expected and unavoidable. Others are warning signs that something has gone wrong with the care provided. Understanding the difference matters — both for your health and for any legal question you may later face.
Mild odour changes related to fat malabsorption
Need for lifelong vitamin supplementation
Dietary adjustment period requiring support from a dietitian
Gradual, sustained weight loss over 12–24 months
No blood tests arranged in the 12 months after surgery
Vitamin deficiency identified but not treated or referred
Neurological or psychiatric symptoms developing without investigation
Surgeon unavailable or unresponsive to reported symptoms
Not every difficult experience after bariatric surgery means something went wrong legally. But if your surgeon did not monitor you, did not warn you, or did not respond to symptoms you reported, those facts are worth examining carefully.
Why this matters legally
Every surgeon in NSW owes their patient a duty of care. A duty of care is a legal obligation to act with reasonable skill and competence. When a surgeon falls below that standard and causes harm, the law may treat that as negligence.
But not every complication equals negligence. Surgery carries inherent risks — risks that exist even when the surgeon does everything correctly. Under section 5I of the Civil Liability Act 2002 (NSW), a surgeon is not liable for harm caused by an inherent risk of a procedure. An inherent risk is one that cannot be avoided even with the best possible care.
The legal question is not whether something went wrong. The question is whether the surgeon’s conduct fell below what a competent peer would have done in the same circumstances. Section 5O of the Civil Liability Act 2002 (NSW) provides that a professional is not negligent if they acted in a way that was widely accepted by peer professional opinion as competent practice.
This means that a patient who suffers vitamin deficiency after BPD surgery does not automatically have a legal claim. The patient must show that the surgeon failed to meet the standard of care — for example, by not arranging blood tests, not warning about risks, or not treating a known deficiency. For a broader explanation of how medical negligence law works in NSW, see Reframe Legal — Medical Negligence.
The negligence framework — when a care failure becomes a legal claim
A patient develops malodorous stools after BPD surgery — this is a known inherent risk that the surgeon warned about before the procedure
A surgeon arranges no blood tests after BPD surgery, a vitamin deficiency develops undetected, and the patient suffers neurological harm that earlier treatment could have prevented
This is a general educational framework only. Each case is assessed on its individual facts.
When bariatric surgery may amount to medical negligence
Several specific failures can give rise to a legal claim after BPD surgery. Each must be examined against the facts of the individual case.
If the surgeon did not explain the risks of malabsorption before surgery, and you would have made a different decision had you understood those risks, that failure may support a claim for lack of informed consent. The Civil Liability Act 2002 (NSW) — a law that sets out the rules for negligence claims in this state — requires that a patient receive enough information to make a genuine choice.
If the surgeon did not compare BPD surgery with alternative procedures, such as gastric banding or Roux-en-Y bypass, you may not have had the information needed to choose between them. A surgeon who recommends only one option without explaining why alternatives were unsuitable may fall below the standard of care.
If the surgeon failed to arrange regular blood tests after surgery, and a vitamin or nutritional deficiency developed as a result, the surgeon may have breached their duty of post-operative care. The key legal question is whether a competent bariatric surgeon in the same position would have arranged those tests.
If the surgeon identified a deficiency and did not treat it, or did not refer you to a specialist, that inaction may also constitute a breach. Causation — the legal link between the breach and your harm — must also be established. You must show that the deficiency caused the harm you suffered, and that earlier treatment would have prevented it.
When harm becomes long-term or permanent
Vitamin and nutritional deficiencies after bariatric surgery can cause serious long-term harm if they go undetected and untreated. The physical consequences depend on which nutrients are depleted and for how long.
Deficiencies in B vitamins — particularly thiamine (B1) and B12 — can affect the nervous system. Severe thiamine deficiency can cause a condition called Wernicke’s encephalopathy, which damages the brain. Deficiencies in vitamins A, D, E and K can affect vision, bone density, immune function, and blood clotting. Protein malnutrition can cause muscle wasting, fatigue, and organ damage.
Psychological and cognitive consequences
Some patients report mood changes, memory difficulties, and cognitive problems after bariatric surgery. Whether these symptoms result from nutritional deficiency, pre-existing conditions, or other causes is a question that requires careful expert analysis. Courts in NSW have considered this question carefully. Expert neurologists, neuropsychologists, and psychiatrists may all give evidence about the likely cause of a patient’s symptoms.
Proving that a cognitive or psychiatric injury was caused by a nutritional deficiency — rather than by pre-existing depression, anxiety, or other factors — is one of the most complex challenges in bariatric negligence cases. The plaintiff carries the burden of proving causation on the balance of probabilities.
Financial and practical consequences
Long-term harm from bariatric surgery can affect a person’s ability to work, maintain relationships, and manage daily life. Lost income, ongoing medical costs, and the need for assistance with daily activities can all form part of a compensation claim — provided the plaintiff proves that those losses flow from the surgeon’s negligence rather than from pre-existing conditions or unrelated events.
What compensation can cover in bariatric surgery negligence cases
If a patient proves negligence in a bariatric surgery case, NSW law allows compensation for a range of losses. These include pain and suffering, loss of enjoyment of life, past and future medical expenses, lost income, and the cost of care and assistance.
The amount of compensation depends on the severity of the harm and the strength of the evidence linking that harm to the surgeon’s conduct. Courts assess each case individually. General ranges give a rough guide only.
| Level of harm | Typical compensation range |
|---|---|
| Moderate injury | $50,000–$150,000 |
| Serious injury | $150,000–$500,000 |
| Severe / life-changing injury | $500,000+ |
Each case is assessed on its own facts. These figures are general ranges only. Time limits apply to medical negligence claims in NSW. Generally, a person has three years from the date they discovered — or ought reasonably to have discovered — that they suffered harm as a result of negligence. Missing that deadline can end a claim entirely, even if the underlying facts are strong.
Bringing it together — do the pieces fit?
A bariatric surgery negligence case involves many moving parts. The facts must establish not just that something went wrong, but that the surgeon’s conduct fell below the standard of care, and that this failure caused the harm you suffered.
Courts in NSW have examined these cases carefully. In Campbell bht Mammoliti v Ritchie [2026] NSWSC 754, the NSW Supreme Court dismissed a claim against a bariatric surgeon after finding that the surgeon had warned the patient about the risks of BPD surgery, had provided adequate post-operative advice, and had acted in accordance with peer professional opinion. The court also found that the patient had not proved he suffered the nutritional deficiencies or cognitive harm he alleged. Credibility — the court’s assessment of whether a witness is telling the truth — played a central role in that outcome.
That case illustrates something important: a claim that feels compelling from the inside may face serious obstacles when tested against contemporaneous medical records, expert evidence, and the legal standards that courts apply. It also shows that pre-existing health conditions, prior injuries, and inconsistencies in a patient’s account can significantly affect the outcome.
For a detailed explanation of how negligence claims proceed in NSW, see Reframe Legal — How Medical Negligence Claims Work in NSW.
You don’t need certainty to understand your position
Many people who contact a lawyer after bariatric surgery feel uncertain. They wonder whether their experience was normal. They question whether they are remembering things correctly. Some worry that their pre-existing health problems will undermine their case.
That uncertainty is understandable. Medical negligence cases are complex. The facts that matter most — what the surgeon said, what tests were ordered, what records were kept — are often buried in documents that patients have never seen. Legal clarity does not come from certainty about what happened. It comes from examining the available evidence against the standard of care the law requires.
Informed consent is one of the most important legal concepts in bariatric surgery cases. A patient who was not given enough information to make a genuine choice about their surgery may have a claim even if the surgery itself was performed competently. For more on this area of law, see Reframe Legal — Informed Consent and Medical Negligence.
If you have concerns about the conduct of a registered health practitioner, AHPRA — Australian Health Practitioner Regulation Agency handles complaints and registration matters for surgeons and other health professionals across Australia.
About the lawyer behind this article
Dr Rosemary Listing is a NSW lawyer with a PhD focused on medical negligence. Her academic and legal work centres on the standard of care owed by clinicians — and what happens when that standard is not met.
Dr Listing has examined cases involving bariatric surgery, including claims arising from failures in pre-operative counselling, post-operative monitoring, and the management of nutritional deficiencies after procedures such as biliopancreatic diversion. She understands that the harm in these cases often develops slowly — not in the operating theatre, but in the months and years of inadequate follow-up that follow.
Her experience includes reviewing cases where patients had significant pre-existing health conditions. Those conditions do not automatically defeat a claim. What matters is whether the surgeon’s conduct — measured against the standard of a competent peer — caused harm that would not otherwise have occurred.
People who seek legal clarity after bariatric surgery are rarely looking to blame someone. Most want to understand what happened to them and whether the care they received met the standard they were entitled to expect.
Dr Listing’s role is to assess the facts against the legal standard — carefully, honestly, and without overpromising outcomes. Every case is different, and every case deserves a clear-eyed assessment of its strengths and its limits.
This article is general legal information only. It does not constitute legal advice. Each person’s circumstances are different. The law discussed applies to New South Wales, Australia. Time limits apply to legal claims.