Pellerin v Balfour: Negative Imaging, Differential Diagnosis, and ER Discharge

Some malpractice claims arise from the kind of clinical situation that is genuinely hard. A patient presents to the emergency department with abdominal pain. The differential diagnosis is broad: appendicitis, ovarian cyst, gastroenteritis, urinary tract pathology, ectopic pregnancy, kidney stones, inflammatory bowel disease, and several others depending on age, sex, and risk factors. The physician’s clinical task is to work through the differential with history, examination, and investigations, narrow it to the most likely cause, treat appropriately, and discharge with return precautions where outpatient management is appropriate. When this works, the patient feels better and the encounter is unremarkable. When it does not, the next step in the differential reveals itself days later, sometimes catastrophically.

Pellerin v Balfour, 2024 BCSC 2135, is a case in the second category that the Supreme Court of British Columbia decided in favour of the defendant. Ms. Wray attended Kelowna General Hospital with abdominal pain on November 30, 2016. The emergency physician, Dr. Balfour, ordered an ultrasound including an endovaginal study. The ultrasound showed a normal appendix. Given Ms. Wray’s known endometriosis, Dr. Balfour diagnosed a likely ruptured ovarian cyst, prescribed pain medication, gave return-to-ED instructions, and discharged her. Four days later she returned to hospital by ambulance with a perforated appendix and underwent surgery. The trial proceeded with multiple expert witnesses on each side. The court dismissed the claim, finding that Dr. Balfour’s conclusion that appendicitis was not the cause of the abdominal pain was reasonable and logical on the evidence available to him at the time.

The decision is doctrinally useful as a clean illustration of several recurring frameworks. It demonstrates the operation of the “differential diagnosis with imaging support” pattern in ER decision-making. It applies the “negative imaging substantially lowers probability” principle to appendicitis specifically. It rejects an anchoring bias allegation on documented evidence that the physician did not in fact anchor — both diagnoses were on the documented differential. It illustrates the importance of return precautions as part of safe ER discharge. And it adds a substantive appendicitis case to a cluster that previously did not have one.

A reminder before going further. This commentary is on a BC Supreme Court decision. The substantive principles of Canadian malpractice law it engages — the standard of care for emergency physicians; the use of imaging in differential diagnosis; the framework for assessing anchoring bias allegations; the discharge instructions framework — operate consistently across Canadian common law jurisdictions. The case is directly relevant to Ontario practice even though the decision is from a different province.

The case in summary

The patient. Ms. Wray was a woman of reproductive age with a known history of endometriosis. She had a long-standing relationship with her family physician. On November 30, 2016 she developed abdominal pain that brought her to the emergency department at Kelowna General Hospital.

The ED assessment. Dr. Balfour was the emergency physician on duty. He assessed Ms. Wray, took her history, examined her, and ordered investigations. The differential diagnosis he documented included both appendicitis and a ruptured ovarian cyst. He also documented that her pelvic pain was “not yet diagnosed” — an honest acknowledgement that he had not yet settled on the cause.

The investigations. Dr. Balfour ordered an ultrasound of the abdomen and pelvis, including an endovaginal study. The ultrasound showed:

• A normal appendix
• Findings consistent with a ruptured ovarian cyst (or at least findings that did not contradict that hypothesis)

The diagnosis. Based on the history (including the past history of endometriosis), the physical examination, and the ultrasound findings, Dr. Balfour concluded that the abdominal pain was likely due to a ruptured ovarian cyst rather than appendicitis. The normal appendix on imaging made appendicitis substantially less likely.

The discharge. Ms. Wray was discharged with seven days of pain medication. The discharge instructions included a recommendation to follow up with her family physician and to return to the ED or clinic if the pain continued or worsened.

The subsequent presentation. On December 4, 2016, four days after the index ED visit, Ms. Wray returned to hospital by ambulance with significant clinical deterioration. She was diagnosed with a perforated (or “punctured”) appendix and underwent surgery. She was discharged on December 11, 2016 after a multi-day hospitalization.

The action. Ms. Wray (initially named with surname Wray; the case is styled Pellerin v Balfour) commenced a malpractice action against Dr. Balfour alleging that the index ED visit fell below the standard of care.

The plaintiff’s allegations

The plaintiff advanced a multi-ground case against Dr. Balfour. The principal allegations:

Failure to take appropriate history. That the history-taking at the November 30 visit was inadequate; that key features of the presentation were not elicited or were not documented.

Failure to conduct appropriate physical examination. That the examination was not sufficiently thorough; that signs suggestive of appendicitis (rebound tenderness, McBurney’s point tenderness, Rovsing’s sign, psoas sign, obturator sign) were not adequately tested for or documented.

Anchoring bias for the ovarian cyst diagnosis. That given Ms. Wray’s known endometriosis, Dr. Balfour anchored on a gynecological explanation for her abdominal pain and failed to maintain appropriate consideration of alternative diagnoses including appendicitis.

Inadequate record-taking. That the chart was not sufficient to document the clinical reasoning and the workup.

Failure to undertake further investigation. Specifically:

• Failure to order a CT scan
• Failure to order further lab tests including C-reactive protein (CRP)
• Failure to conduct a further assessment including vital signs
• Failure to keep Ms. Wray in hospital for observation when she was still in significant pain and appendicitis had not been definitively ruled out

Premature discharge with inappropriate amounts of medication and misleading instructions. That seven days of pain medication was excessive; that the discharge instructions did not adequately convey the importance of returning to the ED in the case of clinical deterioration.

The cumulative effect, the plaintiff argued, was that the standard of care of an emergency medicine physician was not met. The harm — the perforated appendix requiring surgery — was the consequence.

The expert evidence

The trial proceeded with multiple expert witnesses for each side. The plaintiff called three experts: a family physician qualified to provide opinion evidence on the standard of care of an emergency physician in the assessment of acute abdominal pain; a second family physician who had been the plaintiff’s treating family physician since 2001 and who provided both fact and expert evidence; and a radiologist qualified to provide opinion evidence on the assessment of pelvic ultrasounds. The defence called an emergency physician with 27 years of experience qualified to provide opinion evidence on the standard of care of an emergency physician in this clinical context, and a general surgeon (regional medical director and department head of surgery for a major BC health authority, with a clinical professorship at the University of British Columbia) qualified to provide opinion evidence on the surgical management of suspected appendicitis.

The expert evidence on the operational question — what does the standard of care require when an emergency physician evaluates a patient with abdominal pain and a normal-appendix ultrasound? — was the operative material for the decision. The defence expert evidence, accepted by the court, supported the proposition that:

• Appendicitis is one of several diagnoses on the differential for acute abdominal pain in a woman of reproductive age
• A normal appendix on ultrasound substantially lowers the probability of appendicitis
• Where the ultrasound is normal and the clinical picture supports an alternative explanation, the physician is entitled to act on that alternative
• The clinical reasoning does not require ruling out every possibility with exhaustive investigation; it requires a reasonable assessment based on the evidence available

The court found Dr. Balfour’s clinical approach met that standard.

The court’s analysis

The court worked through several specific findings.

Both diagnoses were on the differential. Dr. Balfour had documented both appendicitis and ovarian cyst on his differential diagnosis. He had also documented that pelvic pain was “not yet diagnosed.” This documented thinking was important. It refuted the allegation that he had anchored on a single diagnosis.

The diagnostic reasoning was supported by the evidence. Dr. Balfour reached his conclusion based on:

• Ms. Wray’s past medical history including endometriosis
• His own history-taking at the visit
• His physical examination
• The results of the ultrasound, including the endovaginal study showing a normal appendix

The “negative imaging substantially lowers probability” principle. The court accepted that when an ultrasound is negative showing a normal appendix, a diagnosis of appendicitis becomes extremely unlikely. The principle reflects the underlying medicine: ultrasound for appendicitis has reasonable sensitivity and specificity; a normal study in the right clinical context substantially shifts the probability away from appendicitis. The physician who relies on the imaging is exercising reasonable clinical judgment.

The “reasonable and logical” conclusion. The court found that Dr. Balfour’s conclusion that Ms. Wray did not have appendicitis was reasonable and logical given the available evidence. The standard of care does not require certainty. It requires the conclusion to be one that a reasonable emergency physician would reach in the same circumstances. The defence expert evidence supported the proposition that the conclusion fell within that range.

The anchoring bias allegation rejected. The plaintiff’s anchoring bias argument required showing that Dr. Balfour had latched onto an ovarian cyst diagnosis to the exclusion of other possibilities. The documented evidence showed the opposite: both diagnoses were on the differential, the pelvic pain was acknowledged as “not yet diagnosed,” and the ultrasound was specifically ordered to investigate both possibilities. The argument that Dr. Balfour anchored on endometriosis-related pathology failed on the documented record.

The discharge framework was appropriate. Discharge with pain medication and return precautions is a recognized component of safe ER management for cases where outpatient management is appropriate and the working diagnosis is one that does not require hospital admission. The instructions to follow up with the family physician and to return to the ED if pain continued represented appropriate care. The plaintiff’s argument that the instructions were misleading or inadequate was rejected.

The further-investigation argument rejected. The plaintiff argued that Dr. Balfour should have ordered a CT scan, CRP, additional vital signs, or hospital observation. The court accepted that none of those further investigations was required by the standard of care in the circumstances. The ultrasound had been ordered and was negative for appendicitis. The clinical picture was consistent with the alternative diagnosis. The further investigations would have been responsive to a clinical picture that did not exist on the available evidence.

The conclusion. The court found Dr. Balfour did not breach the standard of care of an emergency physician. The action was dismissed.

Doctrinal anchors

Several doctrinal points emerge from the case.

The differential diagnosis with imaging support framework. Emergency medicine practice routinely involves working through a differential diagnosis using clinical assessment plus selective investigations including imaging. The standard of care does not require ruling out every possibility with exhaustive investigation. It requires reasonable clinical reasoning supported by appropriate investigations. Where the imaging is negative for a particular diagnosis, the physician is entitled to act on the negative result subject to clinical judgment about the residual probability and the appropriate return precautions.

The framework parallels what I covered in the Communication Failures, Continuity of Care, and Medical Malpractice commentary on the importance of structured clinical reasoning. The documented differential is part of the structure that supports defensible care. The physician who documents the differential, documents the workup, and documents the reasoning can demonstrate the standard of care met in a way that the physician who does not cannot.

The “negative imaging substantially lowers probability” principle. The principle applies wherever investigations are used to narrow a differential. Where a test is reasonably sensitive for a condition and the test is negative, the post-test probability of the condition is lower than the pre-test probability. The physician is entitled to act on that lower probability subject to the clinical context.

The principle is not absolute. False negatives occur. Test performance varies by patient factors, by operator experience, by the timing of the test relative to the disease process. The framework requires the physician to consider these factors and to calibrate the clinical response accordingly. But where the imaging is negative and the clinical picture is consistent with an alternative diagnosis, the framework supports the physician’s decision to act on the alternative.

The anchoring bias allegation framework. Anchoring bias is a recognized cognitive error in clinical reasoning where the physician latches onto an early hypothesis and fails to maintain appropriate consideration of alternatives. The framework is well-established in the patient safety and clinical decision-making literature.

The legal framework for assessing anchoring bias allegations:

• The plaintiff has the burden of proof
• Evidence of documented differential diagnosis weighs against the anchoring allegation
• Evidence of investigations directed at multiple diagnoses on the differential weighs against the anchoring allegation
• Evidence of clinical reasoning that explicitly considered the alternative diagnoses weighs against the anchoring allegation

In Pellerin v Balfour, all three of these factors operated in the defendant’s favour. The differential was documented. The ultrasound was directed at both gynecological and appendiceal pathology. The clinical reasoning explicitly addressed both. The anchoring bias allegation failed on the documented record.

For physicians, the practical implication is operationally important: document the differential. The documented differential is the most powerful protection against subsequent anchoring bias allegations. A physician who arrives at the right diagnosis by considering only the alternative actually faces less protection in subsequent litigation than a physician who arrived at the diagnosis through documented consideration of both. The documented thinking is the operational record of the standard of care.

The return precautions framework. Safe ER discharge typically includes return precautions: instructions to the patient about when to return to the ED if symptoms develop or worsen. The framework recognizes that outpatient management is appropriate for many ED presentations but that the patient must be empowered to recognize deterioration and to access escalation.

The legal significance of return precautions:

• Adequate return precautions support the appropriateness of discharge
• Inadequate or absent return precautions can support an argument that the discharge was unsafe
• Specific instructions about symptoms that warrant return are more protective than generic instructions

In Pellerin v Balfour, the discharge instructions included both a follow-up recommendation and a return-to-ED instruction. The court found these adequate. The plaintiff’s argument that the instructions were misleading or failed to communicate the importance of returning was rejected on the documented record.

The multi-ground dismissal pattern. Pellerin v Balfour joins a growing list of cluster cases where the plaintiff advanced multiple grounds of negligence and the court rejected all of them. The pattern includes Williamson v Y (BC anaesthesia), Papineau v Sharma (Ontario), Noel v Hawrylyshyn (Ontario birth injury / informed consent), and now Pellerin. The common doctrinal feature: where each ground of alleged breach is addressed individually and rejected on the evidence, the cumulative effect is dismissal of the action even where the plaintiff has identified multiple potential vulnerabilities in the defendant’s care.

The pattern is important for plaintiff counsel: a kitchen-sink approach to pleading and proof is not necessarily protective. A concentrated case on the strongest ground may produce a better outcome than a diffuse case on multiple grounds. Each ground requires evidentiary support. Grounds that are not adequately supported can undermine the credibility of the stronger grounds.

The “bad outcome alone” principle in ER misdiagnosis

The case is also a clean illustration of the principle that a bad outcome does not by itself establish negligence. Ms. Wray genuinely had appendicitis. Her appendix did rupture four days after the ED discharge. From her perspective, the consequence was unambiguous: the system did not catch the disease that was developing.

The legal framework requires more than the bad outcome. The framework requires the trier of fact to assess whether the care met the standard at the time it was provided, on the evidence available then, with the clinical reasoning that a reasonable physician would apply. The retrospective knowledge that the patient turned out to have a condition the physician did not diagnose is not in itself evidence that the physician breached the standard.

The principle is the subject of substantial cluster discussion. See Dallner v Gladwell for the principle applied (with appropriate bounds) in a plaintiff-success surgical case, and see Six Common Misunderstandings About Medical Malpractice in Ontario for a foundational treatment of the “bad outcome equals malpractice” misunderstanding.

Why this case matters

For prospective clients. Cases involving missed appendicitis are emotionally difficult. The disease is well-recognized, the consequence of missed diagnosis (perforation, peritonitis, sometimes worse) is serious, and the retrospective knowledge often makes the index visit look obviously deficient. The legal framework requires more than retrospective scrutiny. It requires showing that the care at the index visit fell below what a reasonable emergency physician would have provided on the evidence available at the time.

Key assessment questions for a missed-appendicitis claim:

• What was the documented clinical picture at the index visit? Specifically, what were the vital signs, what were the examination findings, what was the documented history?
• What investigations were ordered? If imaging was ordered and was negative, the physician’s reliance on the imaging is typically defensible. If no imaging was ordered when the clinical picture warranted it, that is a different analysis.
• What was the documented differential? A physician who documented appendicitis on the differential and worked through it to a defensible conclusion has substantial protection. A physician who never considered appendicitis at all in a presentation that should have included it is in a weaker position.
• What were the discharge instructions? Specific, clear return precautions support the discharge. Absent or inadequate return precautions undermine it.
• What is the time interval between the index visit and the presentation with the missed diagnosis? A patient who returns within hours with a substantially deteriorated picture engages a different legal analysis than a patient who returns days later.

For more on the general framework for evaluating these cases, see Suing for Medical Malpractice in Ontario: What You Need to Know and the firm’s ER Delay practice page.

For emergency physicians and clinical leaders. A few practical observations.

Document the differential. This is the recurring theme of defensible ER practice. The differential diagnosis is the operational expression of structured clinical reasoning. Documented appropriately, it protects against subsequent anchoring bias allegations and demonstrates that alternative diagnoses were considered.

Document the reasoning, not just the conclusion. A chart entry that says “ruptured ovarian cyst” is much weaker than one that says “given history of endometriosis, normal-appendix ultrasound, and clinical picture consistent with ruptured ovarian cyst, working diagnosis is ruptured ovarian cyst.” The reasoning is the standard of care; the documentation is the evidence.

Use return precautions explicitly. Generic discharge instructions are weaker than specific ones. Instructions that articulate the symptoms that should prompt return, the appropriate destination (ED vs family physician), and the timeline for follow-up are stronger than instructions that say only “follow up with your doctor.”

Consider the residual probability. A negative imaging study lowers the probability of a particular diagnosis but does not eliminate it. The physician’s clinical reasoning should incorporate the residual probability and calibrate the return precautions accordingly. Where the residual probability is meaningful, more specific return precautions are appropriate.

Document the patient’s understanding. Where the discharge instructions include specific return precautions, documenting that the patient understood the precautions is a useful protective practice.

Cluster integration

The ER misdiagnosis cluster:

• Sutherland v Toronto (stroke ER defeat)
• Williamson v Y (BC anaesthesia ED context)
• Pellerin v Balfour (appendicitis ED defeat)

The multi-ground dismissal pattern:

• Papineau v Sharma (Ontario)
• Williamson v Y (BC)
• Noel v Hawrylyshyn (Ontario)
• Pellerin v Balfour (BC)

The “negative imaging substantially lowers probability” framework (new for the cluster):

• Pellerin v Balfour establishes the principle in the cluster
• Generally applicable to any case involving imaging-supported differential narrowing

The anchoring bias allegation framework (new for the cluster):

• Pellerin v Balfour is the principal cluster authority
• The documented differential as protection against the allegation

The discharge / return precautions framework (new for the cluster):

• Pellerin v Balfour establishes the principle
• Connects to the broader ER discharge framework discussed in Hallway Medicine in Ontario

The “bad outcome alone” doctrine (recurring):

• Pellerin v Balfour illustrates the doctrine applied successfully for the defence
• Complements Dallner v Gladwell where the doctrine had bounded application (bad outcome plus rarity supports inference)

NEW substantive practice area: appendicitis / acute abdomen ED misdiagnosis.

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Decision Date: November 22, 2024

Jurisdiction: Supreme Court of British Columbia

Citation: Pellerin v Balfour, 2024 BCSC 2135 (CanLII)

Outcome: Action dismissed. The court found that the defendant emergency physician did not breach the standard of care in the assessment, investigation, diagnosis, treatment, and discharge of the plaintiff with abdominal pain on November 30, 2016, despite the subsequent diagnosis of perforated appendicitis on December 4, 2016. The court accepted that the physician’s documented differential diagnosis included both appendicitis and ovarian cyst; that the ultrasound was a reasonable investigation; that the normal appendix on imaging substantially lowered the probability of appendicitis; that the working diagnosis of ruptured ovarian cyst was reasonable and logical on the available evidence; and that the discharge with pain medication and return precautions was appropriate. The anchoring bias allegation was rejected on the documented record showing both diagnoses were on the differential.

Key authorities (implicit in the BCSC analysis): The standard of care framework articulated by the Supreme Court of Canada in ter Neuzen v Korn, [1995] 3 SCR 674; the standard of practice of emergency physicians as established through expert evidence; the principle that a bad outcome alone does not establish negligence; the framework for assessing allegations of cognitive bias including anchoring bias in clinical reasoning.