Education Library
Deep Dives
Pathophysiology, clinical reasoning, and the nuance behind the numbers. For when you want to understand the why — not just remember the answer.
98 deep dives
Behavioral Health / Sleep
2 topicsAnxiety / Depression Medication Basics
Anxiety and depression are among the most common conditions in primary care. The clinical skill is selecting the right medication and setting realistic expectations.
Insomnia — Treat the Cause Before the Sedative
Insomnia is the most common sleep disorder. The clinical skill is identifying and treating the underlying cause before reaching for a sedative-hypnotic.
Cardiac / Vascular
9 topicsAtrial Fibrillation — Rate, Rhythm, Stroke Risk, Stability
AF is three decisions: hemodynamic stability, rate vs rhythm strategy, and stroke prevention. Anticoagulation is based on stroke risk — not on whether the patient is in sinus rhythm.
BNP
BNP and NT-proBNP reflect myocardial wall stress. They can support heart failure, but they do not diagnose heart failure by themselves.
D-dimer
D-dimer is a rule-out tool, not a rule-in test. Pre-test probability determines whether the result is useful.
Heart Failure
Heart failure management starts with phenotype and current state. Treating decompensation without understanding the underlying profile leads to incomplete care.
Hypertension Management — Diagnose It, Treat the Risk, Follow the Response
Hypertension is diagnosed by confirmed elevated readings. Treatment targets and medication choices are guided by cardiovascular risk, comorbidities, and patient-specific factors.
Orthostatic Hypotension
Orthostatic hypotension is a sign, not a diagnosis. The clinical work is finding the cause.
Peripheral Edema
Laterality and time course are the first clinical questions. Bilateral edema and unilateral edema have different differentials.
Tachycardia & Bradycardia
Rate is not rhythm. The first question is whether the rate is the problem — or the response to one.
Troponin
Serial troponins, delta changes, and the clinical reasoning behind interpreting a rising or falling troponin in context.
Dermatology / Skin
15 topicsAbscess vs Cellulitis — When Drainage Matters More Than Antibiotics
Abscesses require drainage — antibiotics alone will not resolve a walled-off collection of pus. The distinction determines whether the patient needs a procedure, a prescription, or both.
Acne / Rosacea — Same Face, Different Inflammation
Acne and rosacea both cause facial redness and papules — but the pathophysiology, triggers, and treatment are fundamentally different. Treating rosacea like acne makes it worse.
Cellulitis vs Its Mimics — Most Unilateral Leg Redness Is Not Cellulitis
Cellulitis is overdiagnosed. Bilateral lower extremity erythema is almost never cellulitis. Unilateral, acute, with systemic signs and a portal of entry — that is cellulitis.
Contact Dermatitis vs Atopic Dermatitis
Contact dermatitis maps to an exposure. Atopic dermatitis has a chronic relapsing course with flexural predilection and atopy history. Both can be secondarily infected.
Fungal Skin Infections — Tinea vs Candida
Tinea prefers dry keratinized surfaces. Candida prefers warm, moist, occluded skin folds. KOH confirms both. Avoid empiric topical corticosteroids when the diagnosis is uncertain — particularly with a scaly, annular, asymmetric, or pustular eruption.
Intertrigo — Irritant vs Fungal vs Bacterial
Intertrigo is a location, not a diagnosis. Satellite lesions mean Candida. Coral-red fluorescence means erythrasma. Moisture control is the foundation of treatment.
Petechiae / Purpura / Nonblanching Rash — When Appearance Changes the Urgency
Nonblanching rash demands immediate assessment. Fever + petechiae = meningococcemia until proven otherwise. Palpable purpura = vasculitis. Thrombocytopenia + schistocytes = TTP.
Pressure Injuries / Wounds — Stage It, Off-Load It, Treat the Cause
Pressure injuries are caused by sustained pressure over a bony prominence. Staging guides treatment. Off-loading is the intervention — without it, no wound care will succeed.
Psoriasis — Treat the Skin, Screen the Joints
Psoriasis is a systemic immune-mediated disease, not just a skin condition. Up to 30% of patients develop psoriatic arthritis. Skin severity does not predict joint involvement.
Rash First-Pass Assessment — Describe It Before You Diagnose It
The most common error in rash assessment is naming the diagnosis before completing the description. Morphology, distribution, blanching, evolution, and host context come first.
Scabies / Lice — Treat the Patient AND the Exposure Network
Scabies and lice are contact-transmitted infestations. Treating only the index patient guarantees reinfestation. The entire household and close contacts must be treated simultaneously.
Shingles vs HSV — Vesicular ≠ Automatically Shingles
Dermatomal pain may precede a zoster rash. Once the rash appears, start antiviral therapy promptly, ideally within 72 hours. Hutchinson's sign means ophthalmology consultation today.
Skin Cancer Warning Signs / Suspicious Lesions — Know What Not to Watch
The clinical skill in skin cancer is recognizing the features that demand biopsy rather than watchful waiting. When in doubt, biopsy. For a lesion suspicious for melanoma, complete full-thickness sampling that permits accurate Breslow-depth assessment is preferred.
Urticaria vs Anaphylaxis — Hives Alone ≠ Anaphylaxis
Hives alone are not anaphylaxis. Anaphylaxis requires multi-system involvement or cardiovascular compromise. Epinephrine IM is the only first-line treatment.
Viral Exanthem vs Drug Eruption vs Allergic / Inflammatory Rash
These three categories overlap clinically. Timeline, medication history, systemic features, and morphology distinguish them — not any single finding.
End of Life / Advance Care Planning
6 topicsAdvance Care Planning — Have the Conversation Before You Need the Decision
Advance care planning is not a checkbox or a code-status question. It connects prognosis, values, goals, and future treatment decisions.
Advance Directives — Document the Wishes Before the Crisis
Advance directives preserve patient preferences when future decisions may need to be made without the patient's participation.
Healthcare Power of Attorney — Who Speaks When the Patient Can't?
A healthcare agent does not replace the patient's voice while the patient retains decision-making capacity.
Hospice Appropriateness — Recognize the Trajectory, Not Just the Diagnosis
Hospice appropriateness is based on prognosis, disease trajectory, functional decline, and goals — not a single diagnosis or laboratory value.
Palliative Care vs Hospice — Similar Goals, Different Timing
Palliative care can begin alongside disease-directed treatment. Hospice is a specific model of end-of-life care with eligibility requirements.
POLST — Medical Orders, Not Just Another Advance Directive
A POLST is a medical order for patients with serious illness or frailty — not a replacement for an advance directive.
Endocrine / Metabolic
6 topicsA1c vs Serum Glucose
A1c reflects average glucose over 2–3 months — not current glucose. Hemolytic anemia and recent transfusion falsely lower it. A1c targets should be individualized — 7% is not universal.
Diabetes Management — Beyond the A1c
Treat the patient, not just the A1c. Glycemic targets and medication choices change with comorbidity, hypoglycemia risk, kidney function, weight goals, cost/access, and life expectancy.
Glucose Abnormalities — Hyperglycemia vs Hypoglycemia
Euglycemic DKA occurs with SGLT2 inhibitors — check ketones even when glucose is near normal. HHS has higher glucose and osmolality than DKA with minimal ketosis.
Hypercalcemia / Hypocalcemia
Primary hyperparathyroidism and malignancy account for 90% of hypercalcemia. PTH level distinguishes them. Albumin affects total calcium interpretation — ionized calcium provides a more direct assessment when accurate measurement matters.
Hypothyroidism / Hyperthyroidism Management
TSH and free T4 tell you the biochemical pattern. Management starts after you decide whether the patient truly has thyroid dysfunction, why, and how urgently it matters.
TSH + Free T4
TSH makes more sense when you know what Free T4 is doing. Interpret them as a pair — then check whether the pattern fits primary thyroid disease, central disease, medication effects, or acute illness.
ENT / Upper Respiratory
3 topicsOtitis Media / Otitis Externa — Same Ear Pain, Different Treatment
Otitis media and otitis externa both cause ear pain — but the anatomy, pathogens, and treatment are completely different. Pulling the tragus or pinna distinguishes them at the bedside.
Pharyngitis — Viral vs Strep
Most pharyngitis is viral and self-limited. Group A Streptococcus causes 5–15% of adult cases. The clinical skill is identifying who needs testing and treatment — not treating every sore throat.
URI / Acute Sinusitis — Viral vs Bacterial
The vast majority of upper respiratory infections and acute sinusitis are viral. Antibiotics do not shorten the course of viral URI. The clinical skill is identifying the minority that are bacterial.
Hematology / Coagulation
8 topicsAnemia — First-Pass Interpretation
MCV organizes the differential. Reticulocyte count separates hypoproliferative from hyperproliferative. Use the pattern — not a single value — to find the mechanism.
Anticoagulation + Bleeding
Identify the agent first. Reversal is agent-specific. Not all bleeding requires reversal — and reversing anticoagulation carries its own thrombotic risk.
Hemoglobin & Hematocrit
The trend often tells you more than the value. Trend first, assess the patient, then classify with indices, reticulocytes, kidney function, and loss or destruction clues.
INR / PT / PTT
PT/INR and PTT measure different parts of the cascade. An isolated prolongation points to different causes than both prolonged together. DOACs are largely invisible to both.
Iron Studies
Ferritin, serum iron, TIBC, and transferrin saturation each tell a different part of the story. No single value is sufficient — interpret the panel together.
MCV
Small, normal, or large — let MCV narrow the differential, not end it. Use MCV to organize the workup, then use RDW, reticulocytes, smear, and targeted labs to identify the mechanism.
Platelets
Trend first. Panic second. Verify the count, assess trajectory, examine the other cell lines, and identify the mechanism.
WBC
Leukocytosis does not equal infection. Use trajectory, differential, medications, stressors, symptoms, and other cell lines before calling it infection.
Infection
8 topicsBacterial vs Viral vs Fungal Infection
Classify the syndrome before the organism. Neutrophilia does not prove bacterial disease. Green sputum is not a bacterial test. Tempo, host, exposure, and trajectory narrow the cause.
Blood Cultures — Positive ≠ Automatically True Bacteremia
A positive bottle may represent true bloodstream infection or contamination. Organism, number of sets, timing, and patient context determine significance.
C. difficile Infection — Test the Right Stool, Treat the Clinical Infection
A positive C. diff assay can reflect infection or colonization. Test the patient with a compatible diarrheal syndrome — not every patient with a positive test needs treatment.
Lactate — Elevated ≠ Automatically Sepsis
Lactate is a marker of altered production and/or clearance. Beta-agonists, seizures, liver dysfunction, and intense exertion can all elevate lactate without tissue hypoperfusion.
Procalcitonin
Procalcitonin modifies probability; it does not replace the patient. Start with the clinical syndrome and pretest probability before looking at the biomarker.
Pyelonephritis — When a UTI Is No Longer Just a Bladder Infection
Pyelonephritis is a UTI that has ascended to the kidney. Obstructed infected kidney is a urologic emergency — decompression cannot wait for antibiotics alone.
Sepsis — Infection ≠ Sepsis
Sepsis requires organ dysfunction — not just infection with fever and leukocytosis. In outpatient and telehealth settings, recognition and escalation is the clinical imperative.
UTI vs Asymptomatic Bacteriuria
Asymptomatic bacteriuria should not be treated in most patients. Pyuria indicates inflammation — not infection. CAUTI requires symptoms, not just a positive culture.
Liver / GI
11 topicsAlkaline Phosphatase + Bilirubin — Recognize the Pattern
Pattern first: hepatocellular, cholestatic, mixed, or nonhepatic. Alk phos may originate from bone. Conjugated vs unconjugated bilirubin changes the differential entirely.
AST / ALT Elevation — Reading the Pattern, Not Just the Numbers
AST and ALT are markers of cellular injury, not liver function tests. AST is not liver-specific. Pattern, magnitude, trajectory, companion tests, and synthetic function tell you what the elevation means.
Constipation — Build the Bowel Regimen, Do Not Just Add Another Laxative
Constipation is a symptom, not a diagnosis. The clinical skill is identifying the underlying cause, ruling out alarm features, and building a rational bowel regimen.
Dehydration / Volume Depletion
Volume status is a clinical synthesis. Do not diagnose dehydration from a BUN/creatinine ratio, dry mouth, or one sodium value. Water deficit and extracellular volume depletion are not identical.
Diarrhea — Acute vs Persistent
Most acute diarrhea is self-limited and does not require antibiotics. The clinical skill is distinguishing inflammatory from noninflammatory diarrhea.
Diverticulitis — Uncomplicated vs Complicated Changes Everything
Uncomplicated diverticulitis can often be managed outpatient without antibiotics. Complicated diverticulitis — abscess, perforation, fistula — requires a fundamentally different approach.
GERD / Peptic Ulcer Disease — Treat the Acid, Find the Alarm Feature
GERD and PUD are common and treatable — but alarm features demand endoscopic evaluation before empiric acid suppression. Do not treat your way past a cancer.
GI Bleed — Clues Before the Obvious Bleed
GI bleeding is not always hematemesis or bright red blood. Early clues: fatigue, tachycardia, orthostasis, melena, falling hemoglobin, or the medication list. Stability first, source second.
Lipase & Acute Pancreatitis — Elevated Lipase ≠ Automatically Pancreatitis
Diagnose pancreatitis from the 2-of-3 framework, not the enzyme alone. Lipase height does not grade severity. After diagnosis, stop chasing lipase and start managing severity, cause, and complications.
Low Albumin — Not Just Nutrition
Low albumin is a context marker, not a standalone nutrition test. Inflammation, renal protein loss, liver synthetic failure, GI losses, and fluid shifts all lower albumin independently of nutritional intake.
Nausea / Vomiting — Treat the Symptom Without Missing the Cause
Nausea and vomiting are symptoms, not diagnoses. The clinical skill is identifying the underlying cause before reaching for an antiemetic.
Medication Safety / TOC
2 topicsMedication Reconciliation / Polypharmacy — The Post-Discharge Safety Check
Medication errors at transitions of care are a leading cause of preventable harm. The clinical skill is systematic medication reconciliation and deprescribing.
Post-Discharge Fever / Persistent Infection Symptoms
Persistent symptoms after discharge require reassessment — not automatic extension of the original treatment. Determine trajectory, verify source control, and ask whether this is expected recovery, treatment failure, a complication, or a new process.
Musculoskeletal
3 topicsGout — Treat the Flare, Then Treat the Uric Acid
Gout is the most common inflammatory arthritis in adults. The clinical skill is managing the acute flare without causing harm, then addressing hyperuricemia.
Low Back Pain — When Imaging Is and Is Not Needed
Most acute low back pain is nonspecific and self-limited. The clinical skill is identifying the minority with serious underlying pathology.
Osteoarthritis — Pain Management Beyond "Take Tylenol"
Osteoarthritis is the most common joint disease worldwide. The clinical skill is building a rational management plan starting with exercise and weight loss.
Neurologic
2 topicsDizziness / Vertigo — Not All Dizziness Is BPPV
In appropriately selected patients with acute vestibular syndrome and nystagmus, HINTS performed by a trained clinician can be highly sensitive for posterior circulation stroke. HINTS is not a general screening exam for all patients with dizziness.
Headache — Primary vs Secondary
Most headaches are primary. The clinical skill is identifying the minority that are secondary to a dangerous underlying cause.
Pulmonary
9 topicsAcute Bronchitis — Cough ≠ Antibiotics
Acute bronchitis is almost always viral. Antibiotics do not shorten the course, reduce complications, or prevent pneumonia. The clinical skill is distinguishing bronchitis from pneumonia.
Asthma — Control, Exacerbation, and the Treatment Step
Asthma management is step-based. The step is determined by symptom frequency, nighttime awakenings, activity limitation, and rescue inhaler use — not just whether symptoms exist.
Atelectasis vs Infiltrate vs Consolidation
Air bronchograms commonly occur with air-space consolidation but can also occur with non-obstructive atelectasis. Atelectasis shows volume loss. Consolidation has a broad differential beyond pneumonia.
COPD Exacerbation
Not every exacerbation is infectious. Purulent sputum is the best predictor of bacterial infection. Target SpO2 88–92% — not 98–100%.
Dyspnea — Don't Anchor on One System
The prior diagnosis explains the baseline. It does not explain the acute change. Maintain a broad differential until the evidence supports narrowing it.
Hypoxemia / Low SpO₂
SpO2 is an estimate with real limitations. Understand the five mechanisms, the A-a gradient, and why shunt does not respond to oxygen the way V/Q mismatch does.
Pleural Effusion
Light's criteria distinguish transudates from exudates — but have a false-positive rate in diuretic-treated heart failure. Know when to tap, what to send, and when drainage is required.
Pneumonia — Expected Recovery vs Treatment Failure
Fever and leukocytosis lag behind clinical improvement. Chest X-ray infiltrates can persist 4–6 weeks. True treatment failure means clinical deterioration — not just persistent findings.
Pulmonary Embolism — Pretest Probability + D-dimer + Imaging
D-dimer is a rule-out test — not a rule-in test. Use pretest probability first. Massive PE is defined by hemodynamic instability, not just hypoxemia.
Renal / Electrolytes
11 topicsACE/ARB & Creatinine
A creatinine bump after starting an ACE inhibitor or ARB is expected — and usually not a reason to stop.
AKI vs CKD vs Acute-on-Chronic
One creatinine does not tell you which one you are dealing with. Prior values, trajectory, and clinical context are the only way to distinguish them.
BUN/Creatinine Ratio
A clue, not a diagnosis. Interpret BUN and creatinine separately, then use the ratio as supporting context within the full clinical picture.
Chronic Kidney Disease Management — Protect the Kidney You Have
CKD management is kidney protection plus cardiovascular protection. Both eGFR and albuminuria guide risk stratification and treatment intensity — not eGFR alone.
eGFR
One eGFR does not equal CKD. Chronicity, albuminuria, and other markers of kidney damage are required — not just the number.
Hyperkalemia
The ECG, not the number, determines urgency. Cardiac membrane stabilization comes first.
Hypernatremia
Almost always a free water deficit — not a sodium excess problem. Correct it slowly and never miss diabetes insipidus.
Hypokalemia
Check magnesium before you replete. Understand the mechanism. The serum level understates the total body deficit.
Hypomagnesemia & Hypermagnesemia
The electrolyte most often checked last — but it controls potassium and calcium repletion. Refractory hypokalemia or hypocalcemia means check magnesium first.
Hyponatremia
Hyponatremia is almost always a water problem, not a sodium problem. The clinical framework starts with volume status.
Pre-Renal vs Intrinsic AKI
AKI is not a diagnosis — it is a finding. The clinical work is determining whether the kidneys are underperfused or intrinsically injured.
Women's Health
3 topicsAbnormal Uterine Bleeding — Stabilize, Classify, Then Treat
Abnormal uterine bleeding affects 1 in 3 women. The clinical skill is using the PALM-COEIN classification to identify structural vs nonstructural causes and ruling out malignancy.
Uncomplicated Cystitis — Treat the Bladder, Not the Urinalysis
Uncomplicated cystitis is a clinical diagnosis. The clinical skill is treating symptomatic patients and not treating asymptomatic bacteriuria.
Vaginitis — BV vs Candida vs Trichomonas
Vaginitis is one of the most common reasons women seek outpatient care. The clinical skill is distinguishing BV, VVC, and trichomoniasis by history, exam, and point-of-care testing.
98 deep dives across 15 categories
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