Concepts in Internal Medicine: Clinical Reasoning, History, Examination and Diagnosis

DCM 3101 • LWA 1 • Concepts in Internal Medicine Internal medicine is the disciplined assessment and non-operative management of disease in adolescents and adults. It is not memorising disease lists. It is a method: define the patient’s problem, understand the mechanism, gather discriminating evidence, estimate risk, make a working diagnosis, treat safely, and review the response.

1. What internal medicine means

Internal medicine deals with the whole adult patient and the interaction of organ systems. The physician or clinical officer does not examine a heart, lung or kidney in isolation; they ask how symptoms, physiology, medicines, infections, nutrition, occupation, family history and social circumstances combine to produce the patient’s current state.

Good internal-medicine practice moves from a symptom to a syndrome, from a syndrome to a mechanism, and from a mechanism to a diagnosis. For example, breathlessness may be caused by airway obstruction, alveolar infection, pulmonary vascular disease, anaemia, cardiac failure, metabolic acidosis or anxiety. The first task is to identify immediately dangerous causes while continuing to refine the diagnosis.

Core competencies in the medical clerkship

Medical terminology: the language of clinical practice

Medical terminology is not decorative vocabulary. It is a compact system for describing anatomy, symptoms, investigations, procedures and diagnoses with enough precision that another clinician can understand the patient without repeating the entire encounter. In clerkship, accurate terminology improves the history, problem list, request forms, ward-round presentation, referral letter and discharge summary. Most terms are built from Greek or Latin roots, prefixes, combining forms and suffixes.

How a medical word is built

High-yield roots and combining forms

Suffixes: recognise the clinical action or condition

Prefixes that change the meaning

Rules for combining and defining terms

1. When a suffix begins with a vowel, usually attach it directly to the root: gastr + itis = gastritis.
2. When a suffix begins with a consonant, use the combining vowel: neur/o + logy = neurology; cardi/o + megaly = cardiomegaly.
3. When joining two roots, the combining vowel commonly remains: gastroenterology means stomach and intestine study.
4. To decode a word, start with the suffix, then the prefix, then the root(s): pericarditis is inflammation (-itis) around (peri-) the heart (cardi).
5. Do not confuse a symptom with a diagnosis: haematuria describes blood in urine; it does not by itself identify the cause.

Pronunciation, spelling and plurals

Pronunciation varies between regions, but accurate spelling and meaning are essential. In many terms ph sounds like f, pn at the beginning is commonly pronounced n, and ch may sound like k in Greek-derived words. Common singular-to-plural changes include vertebra/vertebrae, bronchus/bronchi, diagnosis/diagnoses, appendix/appendices, thorax/thoraces, ovary/ovaries and diverticulum/diverticula. When unsure, consult a reliable medical dictionary rather than inventing a plural.

2. Essential terms used in internal medicine

Disease, illness and syndrome

Disease refers to a demonstrable pathological process; illness is the patient’s experience of symptoms and reduced wellbeing; and syndrome is a recognisable pattern of signs and symptoms that may have several causes. A patient can be seriously ill before a precise disease label is available, so stabilisation must not wait for perfect diagnostic certainty.

3. Causes and mechanisms of disease

Clinical reasoning becomes clearer when the cause is separated from the mechanism. The aetiology may be malaria, but the immediate mechanism of severe illness may be haemolysis, microvascular obstruction, acidosis, hypoglycaemia or shock. The same mechanism can arise from several diseases, and one disease can produce different mechanisms at different stages.

Predisposing, precipitating and perpetuating factors

A predisposing factor increases vulnerability, such as HIV infection, malnutrition, pregnancy, old age or chronic kidney disease. A precipitating factor triggers deterioration, such as pneumonia, missed insulin or gastrointestinal bleeding. A perpetuating factor prevents recovery, such as ongoing exposure, poor adherence, resistant infection or an uncorrected obstruction. Identifying all three prevents a narrow treatment plan.

4. From pathophysiology to clinical presentation

Symptoms are the patient’s report; signs are findings detected by the clinician. Link each finding to a mechanism. Fever may reflect cytokine-mediated resetting of the hypothalamic set point; oedema may reflect raised hydrostatic pressure, low oncotic pressure, sodium retention or lymphatic obstruction; jaundice may reflect excess bilirubin production, impaired hepatic processing or cholestasis.

5. Symptomatology by organ system

General and constitutional symptoms

Fever, weight loss, night sweats, fatigue, anorexia and malaise occur in infection, malignancy, inflammation, endocrine disease and advanced organ failure. Record measured temperature, amount and time course of weight change, appetite, functional decline and exposure history. Unintentional weight loss with persistent fever or lymphadenopathy needs deliberate evaluation rather than reassurance.

Respiratory symptoms

Characterise cough, sputum, haemoptysis, dyspnoea, wheeze, pleuritic pain, orthopnoea and paroxysmal nocturnal dyspnoea. Ask about smoking, biomass fuel, occupational dust, tuberculosis contact, HIV risk, asthma triggers and heart disease. Respiratory rate, oxygen saturation, work of breathing, ability to speak and mental state help identify severity before imaging.

Cardiovascular symptoms

Clarify chest pain using site, character, radiation, duration, provoking and relieving factors, associated sweating, nausea and dyspnoea. Ask about palpitations, syncope, exercise tolerance, orthopnoea and leg swelling. Sudden chest pain with shock, hypoxia or a new neurologic deficit is an emergency until dangerous vascular causes are excluded.

Gastrointestinal and hepatic symptoms

Assess dysphagia, odynophagia, reflux, nausea, vomiting, abdominal pain, diarrhoea, constipation, melaena, haematemesis, jaundice, pruritus and change in stool or urine colour. Ask about water and food exposure, travel, alcohol, medicines, previous surgery, pregnancy possibility and family history of liver or bowel disease.

Neurologic symptoms

Determine whether weakness, numbness, speech change, visual loss, seizure, headache, dizziness or altered behaviour was sudden or gradual. Establish the last-known-well time for acute focal deficits. Examine glucose, airway, breathing, circulation, pupils, language, power, sensation, coordination and gait as appropriate.

Genitourinary and endocrine symptoms

Ask about dysuria, frequency, flank pain, haematuria, reduced urine, polyuria, polydipsia, menstrual and sexual history, heat or cold intolerance, tremor and change in weight. Ask sensitively about pregnancy, contraception, sexually transmitted infection risk and intimate partner violence when clinically appropriate.

Musculoskeletal and skin symptoms

Characterise joint pain, swelling, stiffness, weakness, muscle pain, rash, ulcers, itch, colour change and photosensitivity. Distribution, symmetry, morning stiffness, systemic symptoms and medication exposure help separate infection, inflammatory disease, crystal arthritis, connective-tissue disease and malignancy.

6. The internal-medicine history

Opening and presenting complaint

Introduce yourself, confirm identity, obtain permission, provide privacy and ask an open question: “What brought you to hospital today?” Record the patient’s words as the presenting complaint, then clarify the duration. Do not interrupt the opening narrative unnecessarily; it reveals the patient’s priorities and chronology.

History of the presenting illness

Build a timeline. For pain use site, onset, character, radiation, associated features, timing, exacerbating and relieving factors and severity. For fever ask onset, pattern, rigors, exposures and antipyretic response. For breathlessness ask exertional level, posture, wheeze, cough, chest pain and nocturnal symptoms. Include relevant negatives that change the differential.

Past medical, surgical and treatment history

Ask about previous admissions, chronic illnesses, operations, transfusions, tuberculosis, HIV testing and treatment, immunisation, allergies and adverse drug reactions. Record all medicines with dose, frequency, adherence, recent changes, traditional remedies and non-prescription drugs. A medication reconciliation is part of diagnosis, not an administrative task.

Family, social and exposure history

Ask about inherited disease, premature cardiovascular disease, cancers, sickle-cell disease, sudden death and recurrent infections. Assess occupation, housing, ventilation, water and sanitation, travel, animals, food, tobacco, alcohol and other substances. Ask who supports the patient, whether treatment is affordable and whether there are barriers to follow-up.

Review of systems and patient perspective

Use a targeted review to find symptoms not volunteered. Explore the patient’s ideas about the illness, concerns, expectations, explanatory model and preferred involvement in decisions. Use an interpreter when required and avoid using children as interpreters for sensitive or complex information.

7. Physical examination in internal medicine

Wash hands, introduce the examination, obtain consent, expose only what is necessary and maintain dignity. Begin with general appearance: distress, hydration, nutrition, pallor, jaundice, cyanosis, clubbing, lymphadenopathy, oedema, rash, consciousness and mobility. Record temperature, pulse, blood pressure, respiratory rate, oxygen saturation, capillary refill, pain score and bedside glucose when indicated.

Perform a focused examination guided by the history, but complete a systemic examination when the patient is ill, the diagnosis is uncertain or multi-organ disease is possible. Reassess after intervention: respiratory rate, work of breathing, perfusion, mental status, pain, urine output and vital signs are dynamic data.

8. Investigations and interpretation

Choose investigations to answer a clinical question. A test result changes probability; it does not replace history and examination. Consider sensitivity, specificity, predictive value, likelihood ratios, specimen quality, timing, pre-analytic error and local reference ranges. In resource-limited settings, prioritise tests that change immediate management and use referral pathways when a specialist test is needed.

Common interpretation traps

• A normal result may be falsely reassuring if the test was taken too early or from the wrong specimen.
• An abnormal result may be incidental, age-related, treatment-related or caused by pre-analytic error.
• Reference ranges describe populations; they do not automatically define health or disease in one patient.
• A positive rapid test may require confirmation, while a negative test may not exclude disease when pre-test probability is high.

9. Diagnosis and differential diagnosis

State a working diagnosis in one sentence using the syndrome, severity and likely cause: for example, “severe community-acquired pneumonia with hypoxaemic respiratory failure, likely bacterial, while tuberculosis and pulmonary embolism remain important alternatives.” This statement guides immediate treatment while acknowledging uncertainty.

Rank differentials by probability, danger and treatability. Ask what finding supports each option, what finding argues against it, and what test or bedside action will distinguish it. Avoid anchoring on the first label, availability bias from a memorable case and premature closure after one abnormal result.

10. Initial management plan

Management begins with safety. Use an ABCDE approach, call for help early, monitor vital signs, obtain intravenous access when needed, check glucose, treat immediately reversible threats and reassess. Then treat the most likely cause while awaiting confirmatory information. Document the indication, dose, route, frequency, contraindications, monitoring and response for every treatment.

11. Infection-specific reasoning for DCM 3101

When infection is possible, identify the source, likely organism, route of transmission, host risk factors, severity and complications. Ask about contact with sick people, food and water, travel, animals, insect bites, sexual exposure, healthcare exposure, previous antibiotics and immunosuppression. Do not wait for fever: older adults, severely immunosuppressed patients and neonates may have serious infection without a high temperature.

Separate colonisation from infection and infection from sepsis. A positive culture from a non-sterile site may represent colonisation. Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection; assess perfusion, mental status, urine output, respiratory function and lactate or other local severity markers. Start appropriate antimicrobials and source control according to current local guidelines, then review the diagnosis and narrow therapy when data return.

Internal-medicine clerkship: from first contact to a defensible plan

Clerkship is the structured process of collecting the patient’s particulars, understanding the presenting problem, examining the patient, interpreting findings, forming a provisional and differential diagnosis, and developing a safe treatment plan. The sequence is not a ritual: each step reduces uncertainty and identifies danger early.

Before touching the patient

• Review the referral, triage information, observation chart and previous results.
• Clean your hands, introduce yourself by name and role, confirm the patient’s identity with at least two identifiers, and explain what you need to do.
• Obtain consent, ensure privacy and adequate exposure, offer a chaperone when appropriate, and adapt communication for language, hearing, cognition and distress.
• Ask about immediate danger before a long history: airway or breathing difficulty, shock, altered consciousness, severe pain, active bleeding, seizures or rapidly progressive illness.

Particulars and the chief complaint

Record age, sex, residence, occupation, source and reliability of the history, and the date and time of assessment. Write the chief complaint in the patient’s words with duration, for example, “shortness of breath for three days,” rather than beginning with an assumed diagnosis. If there are several complaints, list them in order of importance or chronology.

History of presenting illness: make the symptom usable

Allow an uninterrupted opening narrative, then clarify each complaint systematically. Establish the mode and cause of onset, exact site, character, severity, timing, course, aggravating and relieving factors, associated symptoms, effects on nearby structures and constitutional symptoms. Ask what the patient thinks is happening, what they fear, what they expected, and what treatment has already been tried. Purposeful negative answers are valuable when they reduce the likelihood of a dangerous alternative.

Relevant background history

• Past medical and surgical history: record important illnesses chronologically, especially diabetes, hypertension, heart disease, tuberculosis, asthma, epilepsy, bleeding disorders, renal or liver disease, previous admissions, operations, trauma, transfusions and infusions.
• Medication and allergy history: include prescribed drugs, over-the-counter medicines, herbal remedies, steroids, antihypertensives, contraceptives, antiretroviral therapy and recent antimicrobials. Record the reaction, not merely “allergy.”
• Family history: ask about similar illness, diabetes, hypertension, peptic ulcer disease, cancers, sudden death, sickle-cell disease and other inherited conditions; distinguish shared genes from shared environment.
• Personal, social and economic history: diet, smoking, alcohol, other substances, occupation, housing, water and sanitation, finances, support, marital status, sleep, bowel and urinary habits, and ability to access or continue treatment.
• Sexual, gynaecological and obstetric history: ask sensitively when clinically relevant, using confidentiality and non-judgmental language.
• Review of systems: use it to find overlooked symptoms, not to replace a focused history. General, respiratory, cardiovascular, gastrointestinal, neurological, genitourinary, endocrine, musculoskeletal and skin review should be guided by the case.

Examination: general, vital signs and focused systems

Begin with the general impression: distress, consciousness, orientation, hydration, nutrition, pallor, jaundice, cyanosis, clubbing, lymphadenopathy, oedema, rash, body habitus and mobility. Measure and interpret temperature, pulse, respiratory rate, blood pressure, oxygen saturation, pain score, weight and bedside glucose where indicated. A number without context is incomplete: record the position, oxygen delivery, device and time when relevant.

Examine the symptomatic system and then other systems that could explain the problem or reveal complications. Use inspection, palpation, percussion and auscultation deliberately. Compare sides, describe positive and important negative findings, and examine the abdomen, chest, cardiovascular system, nervous system, musculoskeletal system and skin according to the clinical question.

Assessment, provisional diagnosis and differentials

After the examination, summarise the case in one sentence containing the patient’s context, time course, key positives and key negatives. Convert findings into a prioritised problem list. The provisional diagnosis is the working explanation formed from the history and examination; it is allowed to change. A differential diagnosis is a short, ranked list of plausible alternatives with the evidence for and against each.

Investigations: ask a clinical question

Investigations should confirm or refute a diagnosis, exclude a dangerous alternative, assess severity, guide treatment or monitor response. Choose tests in a logical sequence: bedside tests and samples first when urgent, then laboratory studies such as full blood count, inflammatory markers, renal and liver function, glucose, urinalysis and microbiology; imaging such as radiographs, ultrasound, CT or MRI; and endoscopy or specialised tests when indicated. Check specimen quality, timing, pre-test probability, reference ranges and whether a result changes what you will do.

From result to treatment plan

• Stabilise first using an ABCDE approach and treat immediately reversible threats.
• State the working diagnosis and severity; start supportive, definitive or empiric treatment according to risk and local guidance.
• Write drug name, dose, route, frequency, duration, indication, contraindications and monitoring. Review renal/hepatic function, pregnancy possibility and allergies.
• Set measurable monitoring targets: observations, urine output, mental state, pain, oxygen requirement, glucose, laboratory trends and adverse effects.
• Decide disposition: admission, observation, referral, discharge with safety-net advice or urgent transfer. Explain warning symptoms and the exact follow-up plan.

Documentation and communication in the ward

A clear admission note should allow another clinician to reconstruct what happened and what must happen next. Include date/time, patient identifiers, source and reliability, history, examination, problem list, assessment, differentials, investigations requested and reviewed, treatment, response, outstanding tasks and review time. A SOAP structure can be used where accepted locally: Subjective symptoms and patient concerns, Objective examination and results, Assessment clinical interpretation, and Plan actions and monitoring.

For handover, use a structured format such as SBAR: Situation, Background, Assessment and Recommendation. State urgency, code status where applicable, current oxygen or infusions, allergies, pending results, escalation triggers and who is responsible for the next action. Never assume that “review later” is a plan.

Common clerkship errors and how to correct them

Clerkship and OSCE checklist

1. Hand hygiene, introduction, identity, consent, privacy and chaperone.
2. Immediate danger screen and baseline observations.
3. Chief complaint and a chronological, symptom-focused HPI.
4. Past illness, surgery, medication, allergies, family, social and exposure history.
5. Relevant review of systems and the patient’s ideas, concerns and expectations.
6. General, vital-sign, focused and relevant-system examination.
7. One-sentence summary, prioritised problem list and provisional diagnosis.
8. Ranked differential diagnoses with discriminating evidence.
9. Purposeful investigations with interpretation plan.
10. Safe treatment, monitoring, disposition, safety-netting, documentation and handover.

12. Documentation and handover

A safe medical note records the date and time, patient identifiers, presenting complaint, relevant history, examination and vital signs, investigations, assessment, differential diagnosis, management, response, pending results and follow-up. A handover should state the current problem, severity, what has been done, what is still concerning, what must happen next and when to call for help.

13. Examination and OSCE focus

In an OSCE, greet and identify the patient, obtain consent, explain the process, use a structured history, summarise aloud, identify red flags, perform a relevant examination, interpret the provided results, give a differential and propose a safe plan. Examiners reward clinical reasoning and patient safety, not merely the number of questions asked.

14. Summary

Internal medicine is a method of solving patient problems. Define the terms, identify the syndrome, understand the mechanism, take a chronological history, examine systematically, choose purposeful investigations, rank differential diagnoses, stabilise first, treat the cause, prevent complications and arrange review. In infectious disease, always add source, organism, host, transmission, severity, specimen quality and antimicrobial stewardship.

References

• SlideShare: Medical Terminology — roots, combining forms, prefixes, suffixes, pronunciation and pluralisation.
• SlideShare: Clerkship — particulars, history, examination, provisional/differential diagnosis, investigations and treatment planning.
• WHO: Integrated management and clinical care resources.
• NCBI Bookshelf: History and Physical Examination.
• NCBI Bookshelf: Clinical Reasoning.
• WHO clinical services and systems resources.