📚 Internal Medicine Osce Clinical Skills Clinical Cases Diabetes

📚 Lecture Overview

This lecture covers the essential clinical skills required for evaluating and managing patients with diabetes mellitus in an OSCE (Objective Structured Clinical Examination) setting. It details the structured diabetic history, comprehensive lower limb physical examination (vascular and neurological), and the clinical principles of managing acute and chronic complications, insulin therapy, oral antidiabetics, and dyslipidemia.

🎯 Key Concepts & Definitions

• Diabetic Neuropathy: Symmetric, length-dependent nerve damage caused by chronic hyperglycemia, typically presenting in a "glove-and-stocking" pattern.
• Charcot Arthropathy: A progressive, non-infectious joint destruction characterized by bone softening, fracture, and deformity, triggered by repetitive microtrauma in a neuropathic limb.
• 10g Monofilament: A calibrated nylon wire used to assess protective sensation in the foot; loss of sensation identifies patients at high risk for ulceration.
• Lipodystrophy: Localized hypertrophy or atrophy of subcutaneous fat at insulin injection sites, which impairs insulin absorption when used repeatedly.
• Ankle-Brachial Index (ABI): The ratio of the systolic blood pressure in the ankle to that in the arm, used to screen for peripheral arterial disease (PAD).

📖 Main Content

1. The Diabetes History (Diabetic Sheet)

A structured clinical history for a patient with diabetes must screen for glycemic control, risk factors, and target organ damage.

• Presenting Symptoms: Screen for polyuria, polydipsia, unexplained weight loss, and fatigue.
• Microvascular Complications Screen:
  • Retinopathy: Ask about blurry vision, floaters, or sudden vision loss.
  • Nephropathy: Ask about foamy urine or bilateral lower limb swelling (edema).
  • Neuropathy: Ask about numbness, tingling, burning pain, or a "walking on cotton wool" sensation.
• Macrovascular Complications Screen:
  • Coronary Artery Disease (CAD): Ask about exertional chest pain, tightness, or dyspnea.
  • Cerebrovascular Disease: Ask about sudden weakness, numbness, or speech difficulties.
  • Peripheral Arterial Disease (PAD): Ask about calf pain brought on by walking and relieved by rest (intermittent claudication).
• Treatment History: Document current medications, compliance, glucose monitoring logs, and injection site rotation. Screen for history of hypoglycemia (sweating, palpitations, tremors, confusion).

2. Physical Examination of the Lower Limb (Vascular & Inspection)

Diabetic foot complications are a major cause of morbidity. A systematic physical exam is critical.

Inspection

• Skin Changes: Note dryness, loss of hair, shiny skin, hyperpigmentation, or necrobiosis lipoidica diabeticorum.
• Nails: Look for fungal infections (onychomycosis) or ingrown toenails.
• Deformities: Inspect for claw toes, hammer toes, prominent metatarsal heads, and Charcot joint (rocker-bottom foot).
• Ulcers: Look for ulcers, particularly on pressure points (plantar surface, tips of toes). Inspect the interdigital spaces carefully.

Vascular Palpation (Pulsation)

• Femoral Pulse: Located at the mid-inguinal point.
• Popliteal Pulse: Located deep in the popliteal fossa, palpated with the knee slightly flexed.
• Posterior Tibial Pulse: Located posterior and inferior to the medial malleolus.
• Dorsalis Pedis Pulse: Located lateral to the extensor hallucis longus tendon on the dorsum of the foot.

3. Neurological Examination of the Lower Limb

This exam assesses the sensory and motor integrity of the peripheral nerves.

Sensory Testing

• 10g Monofilament Test:
  • Show the patient how the filament feels on their hand first.
  • Instruct the patient to close their eyes and say "yes" when they feel the touch.
  • Apply the filament perpendicular to the skin until it bends.
  • Test key sites on the plantar surface: the distal hallux, 1st, 3rd, and 5th metatarsal heads. Avoid calluses or open wounds.
• Vibration Sense: Use a 128 Hz tuning fork. Place it on the bony prominence of the great toe (interphalangeal joint). If absent, test proximally at the medial malleolus and tibial tuberosity.
• Proprioception: Hold the lateral aspects of the great toe and move it up or down. Ask the patient to identify the direction with their eyes closed.

Reflexes

• Knee Jerk (L3-L4): Strike the patellar tendon.
• Ankle Jerk (S1-S2): Strike the Achilles tendon while keeping the foot in slight dorsiflexion.
• Note: Use the Jendrassik maneuver (reinforcement) if reflexes are difficult to elicit.

4. Acute and Chronic Complications

5. Pharmacological Management

Insulin Therapy

• Rapid-acting (e.g., Lispro, Aspart): Taken right before meals.
• Short-acting (e.g., Regular): Taken 30 minutes before meals.
• Intermediate-acting (e.g., NPH): Provides basal coverage, often dosed twice daily.
• Long-acting (e.g., Glargine, Detemir): Once-daily basal insulin with no peak.

Oral Antidiabetics (OADs) and Injectables

• Metformin (Biguanide): Decreases hepatic glucose production. First-line. Key side effects: Gastrointestinal upset, lactic acidosis (rare). Hold prior to IV contrast studies.
• Sulfonylureas (e.g., Gliclazide, Glimepiride): Stimulate pancreatic beta-cell insulin secretion. Key side effects: Hypoglycemia, weight gain.
• SGLT2 Inhibitors (e.g., Empagliflozin, Dapagliflozin): Promote glucose excretion in urine. Cardioprotective and renoprotective. Key side effects: Genital mycotic infections, urinary tract infections, euglycemic DKA.
• GLP-1 Receptor Agonists (e.g., Liraglutide, Semaglutide): Injectable incretin mimetics. Delay gastric emptying and promote weight loss. Cardioprotective.

Dyslipidemia Management

• Patients with diabetes are at high cardiovascular risk.
• Statins (HMG-CoA reductase inhibitors) are first-line therapy to lower LDL cholesterol.
• Target LDL levels are strictly managed (typically <70 mg/dL for high risk, or <55 mg/dL for very high risk).

📊 Visual Learning

Diabetes Complications Overview

Monofilament Test Protocol

💡 Important Points to Remember

• DKA Management Mnemonic: Remember DKA -> Dehydration (give IV fluids first), Kalium (check potassium before starting insulin), Acidosis correction (via insulin).
• Potassium Rule: Never start insulin in DKA if the serum potassium is $< 3.3 mEq/L$. Correct the potassium level first to avoid fatal arrhythmias.
• Monofilament Technique: The monofilament must bend to apply exactly 10g of linear force. Do not bounce or slide it on the skin.
• Avoid Calluses: Never perform sensory testing directly on a callus, scar, or open ulcer, as this will yield a false-negative result.
• Contrast Dye Rule: Always hold Metformin for 48 hours after procedures involving iodinated contrast dye to prevent acute kidney injury and subsequent lactic acidosis.
• Euglycemic DKA: SGLT2 inhibitors can cause DKA with normal or only mildly elevated blood glucose levels. Always check blood ketones if a patient on an SGLT2 inhibitor presents with nausea, vomiting, or abdominal pain.
• Foot Inspection: Always inspect between the toes (interdigital spaces). This is the most common missed area for hidden tinea pedis or early neuropathic ulcers.
• Reflex Reinforcement: If you cannot elicit the ankle reflex, ask the patient to clench their teeth or hook their fingers together and pull (Jendrassik maneuver) to reinforce the reflex.

⚠️ Common Exam Questions & Traps

OSCE Traps

• The Blind Test Trap: Forgetting to ask the patient to close their eyes before starting the monofilament or vibration sense exam. Examiners will penalize this immediately.
• Missing the Back of the Foot: Forgetting to inspect the heels and the plantar aspect of the feet during a lower limb inspection.
• Pulse Misidentification: Confusing the anatomical location of the posterior tibial pulse (medial malleolus) with the peroneal or lateral areas.

MCQ Traps

• First Step in DKA: Examiners often ask for the immediate next step in managing a patient with DKA. "Insulin infusion" is a common trap option. The correct answer is always aggressive IV fluid resuscitation (normal saline).
• SGLT2 Inhibitor DKA: A diabetic patient presents with classic symptoms of DKA but has a normal blood glucose level of $140 mg/dL$. Students often rule out DKA. If the patient is taking an SGLT2 inhibitor (e.g., empagliflozin), this is euglycemic DKA.
• Metformin Contraindication: Testing when to hold Metformin. It is contraindicated in patients with severe renal impairment (eGFR $< 30 mL/min$) and must be held before contrast media injection.

📝 Quick Review Checklist

I can list the key screening questions for diabetic microvascular and macrovascular complications.
I can locate and palpate all four lower limb pulses (Femoral, Popliteal, Posterior Tibial, Dorsalis Pedis).
I know how to correctly perform and document a 10g monofilament test.
I understand the immediate management priorities for DKA, HHS, and hypoglycemia.
I can identify the mechanism of action and major side effects of Metformin, Sulfonylureas, and SGLT2 inhibitors.
I can recognize the clinical signs of a Charcot joint and a diabetic neuropathic ulcer.