Differential Diagnoses

Introduction to Differential Diagnosis

  • Importance of obtaining a thorough history in diagnosis (80% of diagnosis).

  • Differential diagnosis can be refined through physical exam and investigations.

  • Structure the history into subsections:

    • About the symptom: what, where, when, how bad, exacerbating/relieving factors.

    • Relevant organ systems: target questions based on presenting complaints.

Risk Factors

  • Review differential diagnoses for presenting complaints.

  • Identify risk factors that heighten likelihood of certain conditions, e.g. food history and recent travel for diarrhoea.

  • Utilize lists of differential diagnoses as a guide for pertinent questioning.

Systemic Enquiry

General Questions

  • Common symptoms to inquire: fever, sweats, fatigue, malaise, appetite loss, weight loss.

Cardiovascular System

  • Symptoms: chest pain, palpitation, breathlessness (exertional, at rest), dizziness.

Respiratory System

  • Symptoms: wheeze, breathlessness, cough.

Gastrointestinal System

  • Symptoms: nausea/vomiting, abdominal pain, changes in bowel habits.

Urogenital System

  • Symptoms: urinary frequency, urgency, dysuria, loin pain.

Neurological System

  • Symptoms: cognitive impairment, headache, weakness, coordination problems.

Rheumatological System

  • Symptoms: joint pain/swelling, morning stiffness, malaise.

Diabetes and Endocrine

  • Symptoms: polyuria, polydipsia, fatigue, neck swelling.

Ear, Nose, Throat

  • Symptoms: ear pain/discharge, nasal discharge.

Common Presentations and Differential Diagnoses

Abdominal Pain

  1. Loin Pain

    • Causes: UTI, obstruction, renal carcinoma.

    • Conditions leading to pain could be surgical or medical.

  2. Groin Pain

    • Causes: renal stones, testicular torsion, hernias.

  3. Diffuse Abdominal Pain

    • Gastroenteritis is common.

  4. Referred Abdominal Pain

    • Can appear from distant sites, clinicians to assess appropriately.

Back Pain

  • Causes include muscle spasm, malignancy, infections like TB.

  • Differentiate based on age-related factors.

Blackouts

  • Common causes: arrhythmias, postural hypotension, vestibular condition.

  • Neurological considerations include epilepsy.

Breathlessness/Dyspnoea

  1. Acute Causes: PE, pneumothorax.

  2. Subacute: pneumonia, acute LVF.

  3. Chronic: asthma, COPD, cardiac disease.

Chest Pain

  1. Chest Wall: fractures, intercostal muscle pain.

  2. Pleura and Lung: pneumonia, pleurisy.

  3. Mediastinal Structures: aortic dissection, pericarditis.

Confusion

  • Common causes: hypoglycaemia, infection (e.g. meningitis), metabolic issues (e.g. liver failure).

Constipation

  • Drug-related (opiate use), GI issues, endocrine causes.

Cough

  • Consider infectious causes (e.g. URTI, TB) and chronic conditions (e.g. asthma).

Diarrhoea

  1. Bloody Diarrhoea: infectious colitis, IBD, malignancy.

  2. Non-bloody Diarrhoea: viruses, bacteria, parasites, medication effects.

Fits

  • Differentiate from other causes of seizures such as metabolic disorders and infections.

Fever

  • Common causes: infections, connective tissue diseases, malignancy.

Joint Pain/Swelling

  • Assess for infections, trauma, potential malignancy.

Leg Swelling

  • Investigate causes such as cardiac failure, renal failure, and DVT.

Muscle Weakness

  • Range of causes from congenital to infectious and neuro-conditions.

Wheeze

  • Possible causes include asthma, bronchitis, and anaphylaxis.

Conclusion

  • Accurate diagnosis relies on a structured approach to history, physical examination, and understanding of differential diagnoses for common symptoms.