Differential Diagnosis

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The Challenge: What is a Ddx?

• Recognize a collection of signs and symptoms

• Recall basic pathophysiology

• Restate in terms of disease

• Reconnect with the initial complaint

• Framing: pre-/post-test probability

– Reframing: Reconsidering ddx when there is a progression of unusual natural history

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How many times have you done this?

• Premature closure of diagnosis – “Hm, this is the cardio unit and they have chest

pain. Duh. It’s a heart attack.”

• The crazy “House” diagnosis – “Chest pain and shortness of breath?!? They could

have a worm like Strongyloides stercoralis that went up their gut into their lungs and then to their bloodstream!”

• The LI of the MINDNUMBING table of differentials A-Z + 1,2,3,4,5,6,7,8,9,10…

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Cognitive Diagnostic Errors

Examples:

• “Umm… trauma or cancer?”

• “80 years old? I thought you said 18 years old.”

• “Psh. It’s just a little ____.”

• “The ___ is (+) so it is ____.”

• “The __ is (-) so it is not __.”

• “It’s gotta be a ____.”

Errors

• Faulty hypothesis generation

• Faulty context formulation

• Faulty information gathering/processing – Inaccurate assessment of

prevalence or severity

– Wrong interpretation of test

– Overrreliance on clinical axiom

• Faulty verification – Premature closure of diagnosis

• “No-fault” errors

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Many diagnostic errors occur because we try to fit the data to our hypothesis rather than

fitting the hypothesis to our data.

http://www.flickr.com/photos/epublicist/ 5

http://www.medrants.com/?p=3629 http://hlwiki.slais.ubc.ca/index.php?title=Long_tail#Impact_in_medicine

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House, MD. White board

http://differentialdiagnosi.proboards.com/index.cgi?

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Sherlock Holmes

• "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."

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DeGowin’s Quotable:

• Disease is a four-dimensional story, which follows the biologic imperatives of its particular pathophysiology in specific anatomic sites as influenced by the unique characteristics of this patient.

• Your task is not verbal, but cinematic; construct a pathophysiologic and anatomic movie of the onset and progression of the illness: the words are generated from the images, not the images from the words.

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http://www.agraphia.net/zac-fact-10-bigot-your-way-to-success/

Race/Ethnicity African Americans have sarcoid and sickle cell. White kids have cystic fibrosis Japanese people have stomach cancer

Lifestyles

Women are always pregnant. No matter how careful they were. Coke Addicts had an MI Patients with a swollen knee are female, young, hot, and caught gonorrhea from their last boyfriend.

Etc…

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The BALM

• By systems

• Acute vs Chronic

• Local vs Systemic

• MEDICINE DOC

• Great tier system for starting off your ddx

• Where is it?

• Will it kill the patient?

• What else can it do?

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Framework

• Acute vs Chronic

• Local vs Systemic

• High Probability – Incidence – (the most difficult part of the frame as a medical student)

– What is most likely? Rare Common

• High Utility – Morbidity/Mortality – What do you want to

make sure you never miss? Benign Serious 12

The Systems Approach MEDICINE

• Metabolic/Medications

• Endocrine

• Degenerative

• Infection/Ischemia/Infarction

• Congenital

• Iatrogenic/Idiopathic

• Neoplastic

• Electrical (Neuro/Psych)

Alternatively, • I VINDICATE AID • DIRECTION • VITAMIN C,D

PE organ systems list • Neuro • Lung • CV • GI • Renal/GU/GYN • Heme/ID • Endo

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The Systems Approach VITAMIN C, D & E

• Vascular

• Infection/Ischemia/Infarction

• Trauma/Toxin

• Autoimmune

• Metabolic/Medications

• Iatrogenic/Idiopathic

• Neoplastic

• Congenital

• Degenerative

• Electrical (Neuro/Psych)

Alternatively, • I VINDICATE AID • DIRECTION • MEDICINE

PE organ systems list • Neuro • Lung • CV • GI • Renal/GU/GYN • Heme/ID • Endo

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By discipline

OB/GYN Peds IM/FM Surg Geri Psych

ABD pain Abnormal menses Dysuria

Fever Jaundice Growth problems Wheeze URI complaints Rash

Cough Headache Chest Pain SOB Back pain Knee pain Leg swelling

ABD pain GI bleeding Bowel obstruction Trauma

Altered mental status Falls Fractures

Sadness Anxiety Agitation Drug abuse/ Dependence

Hint hint… 15

Assessment and Diagnosis of Pain Disorders

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Pain Assessment: Goals

• Characterize the pain

• Identify pain syndrome

• Infer pathophysiology

• Evaluate physical and psychosocial comorbidities

• Assess degree and nature of disability

• Develop a therapeutic strategy

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Comprehensive Pain Assessment

• History

• Physical examination

• Appropriate laboratory and radiologic tests

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Pain and Disability

Nociception

Other physical symptoms

Physical impairment

Neuropathic Psychologic Social isolation

mechanisms processes Family distress

Sense of loss or inadequacy

Pain

Disability

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Pain History

• Temporal features—onset, duration, course, pattern

• Intensity—average, least, worst, and current pain

• Location—focal, multifocal, generalized, referred, superficial, deep

• Quality—aching, throbbing, stabbing, burning

• Exacerbating/alleviating factors—position, activity, weight bearing, cutaneous stimulation

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Pathophysiology

• Nociceptive pain

• Neuropathic pain

• Idiopathic pain

• Psychogenic pain

• Commensurate with identifiable tissue damage

• May be abnormal, unfamiliar pain, probably caused by dysfunction in PNS or CNS

• Pain, not attributable to identifiable organic or psychologic processes

• Sustained by psychologic factors

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Pain Assessment Tools

• Pain intensity scales – Verbal rating

– Numeric scale

– Visual analogue scale

– Scales for children

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Pain Syndromes

• Acute pain

• Chronic pain

• Breakthrough pain

• Recent onset, transient, identifiable cause

• Persistent or recurrent pain, beyond usual course of acute illness or injury

• Transient pain, severe or excruciating, over baseline of moderate pain

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Neuropathic Pain: Clinical Assessment

• A comprehensive diagnostic approach to patients affected by neuropathic pain – Medical history – Examinations: general,

neurologic, regional – Diagnostic workup:

imaging studies, laboratory tests, nerve/skin biopsies, electromyography/nerve-conduction velocity (EMG-NCV) studies, selected nerve blocks

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Medical History

Ask patient about complaints suggestive of

• Neurologic deficits: persistent numbness in a body area or limb-weakness, for example, tripping episodes, inability to open jars

• Neurologic sensory dysfunction: touch-evoked pain, intermittent abnormal sensations, spontaneous burning and shooting pains

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Neurologic and Regional Examinations

In patients with neuropathic pain, examination should focus on the anatomic pattern and localization of the abnormal sensory symptoms and neurologic deficits

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Diagnostic Workup: Lab Tests

• Complete blood cell count with differential, erythrocyte sedimentation rate, chemistry profile

• Thyroid-function tests, vitamin B12 and folate, fasting blood sugar, and glycosylated hemoglobin

• Serum protein electrophoresis with immunofixation

• Hepatitis B and C, HIV screening

• Antinuclear antibodies, rheumatoid factor, Sjögren’s titers (SS-A, SS-B), antineutrophil cytoplasmic antibody

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Diagnostic Workup: Lab Tests

• Cryoglobulins

• Antisulfatide antibody titers, anti-HU titers

• Heavy metals serum and urine screens

• Cerebrospinal fluid study for demyelinating diseases and meningeal carcinomatosis

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Diagnostic Workup: Electrophysiologic Studies

EMG-NCV and QST

• To localize pain-generator/nerve or root lesion

• To rule out

– Axonal vs focal segmental demyelination

– Underlying small-fiber or mixed polyneuropathy

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Biopsies

• Nerve (eg, sural nerve): to diagnose vasculitis, amyloidosis, sarcoidosis, etc.

• Skin: to evaluate density of unmyelinated fibers within dermis and epidermis

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Back Pain and Sciatica: Comprehensive Assessment

• History – Medical

– Psychosocial

– Family

– Previous trials

• General examination – Musculoskeletal

– Neurologic

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Back Pain and Sciatica: Pain Assessment

• Description

• Duration

• Intensity

• Alleviating factors

• Aggravating factors

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Assessment of Patients With Low Back, Hip, and Leg Pain

• Neurologic exam – DTRs, strength,

sensitivity, gait

• Regional exam of spine and leg – Inspection for scoliosis or

skin rash, palpation for bone tenderness

• Sciatic- and femoral-nerve stretching tests – SLR, reverse and

contralateral SLR maneuver

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Assessment of Patients With Low Back, Hip, and Leg Pain

• Provocative mechanical joint tests

– Truncal flexion for discogenic pain or spine instability

– Truncal extension for facet joint disease

– Patrick’s maneuver for hip disease (FABER test of both hips for SI joint disease)

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Back Pain and Sciatica: Imaging Evaluation

• Lumbosacral x-ray studies with flexion/ extension/oblique views

• MRI of the spine

• CT with 3-D reconstruction

• CT plus myelography

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Assessment of Acute Back Pain and Sciatica: “Red Flags”

• Nighttime pain, fever, weight loss, history of cancer

• Fever, IV drug abuse

• Bladder, bowel dysfunction; leg weakness

• Trauma

• Neoplasm

• Infection (diskitis, epidural abscess)

• Cauda-equina syndrome

• Compression Fx

History Possible Diagnosis

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Headaches

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Headache Evaluation

• History (duration, onset, frequency)

• Is there a family history of headache?

• Are there any known causes of headache?

• What is the typical location(s)?

• What does the pain feel like?

• What makes it worse?

• What makes it better?

• What are the results of past evaluations?

• Are there associated symptoms? Exam findings?

• What is the patient’s sex?

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Headache: Diagnostic Red Flags

• Rash, meningeal signs, or fever

• Onset after age 50

• Onset in a person with HIV or cancer

• Abrupt onset

• Worsening pain

• Signs of focal neurologic disease

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