ABDOMINAL PAIN

SUMMARY Spotting those in whom it is important to make a timely diagnosis for abdominal pain is a critical clinical skill. Particular care is needed in the elderly and in those with known Human Immunodeficiency Virus (HIV) infection. If diagnostic error arose from lack of reliable clinical evidence, care was substandard. There are definitive tests for the commonly missed life-threatening diagnoses.

Abdominal pain accounts for up to 5-10% of Emergency Room visits ¹.

In almost a third of cases, no diagnosis is made^{1, 2}. Often the cause of the pain is not serious and is self-limiting.

Spotting those in whom it is important to make a timely diagnosis for abdominal pain is a critical clinical skill. For a minority, medical or surgical intervention can preserve health and life.

Particular care is needed in the elderly and in those with known Human Immunodeficiency Virus (HIV) infection. These groups are susceptible to both atypical clinical features of disease and serious causes of life-threatening illness.

For each decade beyond age 50, misdiagnosis and mortality increase steadily ^{3, 4}. Abdominal pain arising from arterial disease is rare in the young but relatively common in the elderly:

Practice Point Arterial diseases causing abdominal pain in the elderly: 1. Aortic Aneurysm 2. Mesenteric Ischemia 3. Myocardial Infarction

The wall of a diseased aorta may lose its resistance to stretching and become ballooned (aneurysm) usually without causing symptoms. Such a weakened aorta can subsequently cause pain by leaking blood. If it ruptures without such warning, death often rapidly follows, but sometimes emergency surgery is life-saving.

Compromised blood supply (ischemia) to the bowel and its supporting tissue ( mesentery) may cause warning abdominal pain before the bowel becomes critically damaged.

Myocardial infarction (heart attack) causes upper abdominal rather than chest pain more frequently than in younger patients.

In HIV infected patients, nonspecific abdominal pain may herald the onset of life-threatening complications of undiagnosed infections and cancers that are rare in those without HIV infection ^{5, 6}.

Practice Point Life-threatening conditions that are commonly missed: 1. Abdominal Aortic Aneurysm 2. Appendicitis 3. Ectopic Pregnancy 4. Diverticulitis 5. Perforated organ 6. Mesenteric Ischemia 7. Bowel Obstruction

If diagnostic error arose from lack of reliable clinical evidence, care was substandard. In many instances of misdiagnosed abdominal pain seen by medical malpractice plaintiff counsel, the diagnostic process has been terminated prematurely by ill-advised guesswork.

Clinical medicine is not an exact science, and diagnostic errors arise because typical features of a disease are commonly not present. By analogy, there is such a variety in dogs that some look more like a typical cat or typical wolf than an "average" dog, at least at first sight.

For example, appendicitis in up to one third of women of child-bearing age is misdiagnosed ⁷, commonly as Pelvic Inflammatory Disease (PID) or Urinary Tract Infection.

Some diagnostic errors may be unavoidable, but undoubtedly others arise from failure to apply a standard and reasonably conscientious diagnostic routine when approaching patients with abdominal pain.

Once the serious diagnostic probabilities have been excluded, Abdominal pain, Not Yet Diagnosed (NYD) is a more legitimate and safer assessment than guessing at a probable diagnosis on insufficient evidence. However, the lack of diagnosis must be shared with the patient, who also should be given specific discharge instructions and advice about timely reevaluation.

Practice Point Common misdiagnoses 1. Gastroenteritis 2. Gastritis 3. Urinary Tract Infection 4. Pelvic Inflammatory Disease 5. Constipation

In some instances a confident misdiagnosis is made in the face of contrary evidence - for example, viral gastroenteritis 1) without diarrhea or vomiting, or 2) with a raised White Blood Cell Count and neutrophilia typical of bacterial infection.

In the face of unjustified diagnosis or uncertainty about the cause of abdominal pain, violation of certain principles ⁸ may strengthen the plaintiff's case:

Practice Point In misdiagnosed abdominal pain look for: 1. Differential diagnosis wrongly restricted solely by pain LOCATION 2. In the elderly, overreliance on FEVER to distinguish medical and surgical causes 3. SERIAL evaluations over several hours 4. COMPLETENESS of data collected 5. STOOL check for occult blood 6. PELVIC examination in female patients

Peritonitis cannot be excluded by presence of bowel sounds ⁹ or absence of rebound tenderness ¹⁰.

Although its omission has been used as a marker for substandard assessment in acute appendicitis, digital rectal examination is not very useful for making or excluding particular diagnoses in cases of abdominal pain ¹¹.

When a correct diagnosis has not been considered in the differential diagnosis, common, simple tests may have been omitted⁸:

Practice Point Missed tests in misdiagnosed abdominal pain: 1. ECG in elderly or if cardiac risk factors 2. Pregnancy test if childbearing potential 3. Abdominal ultrasound or C-T if age >50 4. Tests for appendicitis in women with diagnoses of PID or urinary infection

The clinician must first think of myocardial infarction in the elderly, and of pregnancy and appendicitis in women of child-bearing age.

There are definitive tests for the commonly missed life-threatening diagnoses. In other cases, the most discriminating tests may not have been undertaken.

[Consult full table⁸. Key: Colour = Colour Flow Doppler Ultrasound, CT = Computed Tomography, IVP = IntraVenous Pyelography, US = UltraSound, U- = Urine, WBC = White Blood Cell Count, XR = XRays, Ang = Angiography]

As will be seen from this considerably abbreviated table ⁸, UltraSound or, if available, Computed Tomography will provide the diagnosis in most of the serious abdominal pain conditions that are commonly missed or misdiagnosed. In other specific instances, the clinician needs continuing education in state-of-the-art diagnostic methods.

Indiscriminate use of US or CT in all new-onset abdominal pain is not economic or rational, nor can these tests substitute for competent clinical assessment.

Nevertheless, physicians and surgeons providing acute-care services should be able, by careful history and examination, to identify those patients that need a definitive diagnosis and to select the tests that will identify or exclude serious causes.

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