A 16-year-old boy presents to the emergency department with abdominal pain and tenderness. The pain began approximately 2 days ago in the area just above his umbilicus and was crampy in nature. Earlier this morning, the pain moved laterally to his right lower abdomen. At that time, the pain in the right lower quadrant became severe and constant and woke him up from sleep. He decided to come to the hospital. The patient is nauseous and had a low-grade fever of 37.8°C (100.1°F). Other vitals are normal. Upon physical examination, the patient has rebound tenderness but a negative psoas sign while the remaining areas of his abdomen are non-tender. His rectal exam is normal. Laboratory tests show a white cell count of 15,000/mm3. Urinalysis and other laboratory findings were negative. What conclusion can be drawn about the nerves involved in the transmission of this patient’s pain during the physical exam?

His pain is transmitted by right somatic nerve fibers.

His pain is transmitted bilaterally by somatic afferent nerve fibers of the abdomen.

His pain is transmitted by somatic afferent nerve fibers located in the right flank.

His pain is transmitted by the pelvic nerves.

His pain is mainly transmitted by the right splanchnic nerve.

A 75-year-old woman presents to her primary care physician with her son because she is convinced that people are stealing from her. Her son claims she has been misplacing her medications and money throughout the house. She recently lost her husband to old age and has become reclusive and no longer wants people to visit. Physical examination is unremarkable and the patient is oriented to person, time, and place. A mini-mental status examination (MMSE) is performed and she has difficulty recalling words after 5 minutes and also has problems with serial subtraction. Which of the following is the most likely diagnosis in this patient?

Histrionic personality disorder

A 72-year-old woman comes to the emergency department 4 hours after the sudden onset of a diffuse, dull, throbbing headache. During this time, she also reports blurred vision, nausea, and one episode of vomiting. She has a history of hypertension and type 2 diabetes mellitus. Her medications include hydrochlorothiazide, lisinopril, atorvastatin, and metformin. She has smoked 1 pack of cigarettes daily for the past 30 years and drinks 1–2 glasses of wine per day. Her temperature is 36.6 °C (97.9 °F), pulse is 90/min, respirations are 14/min, and blood pressure is 185/110 mm Hg. Fundoscopic examination shows bilateral blurring of the optic disc margins. Physical and neurologic examinations show no other abnormalities. A complete blood count and serum concentrations of electrolytes, urea nitrogen, and creatinine are within the reference range. Urinalysis shows 2+ protein but no WBCs or RBCs. Which of the following is the most likely diagnosis?

Idiopathic intracranial hypertension

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A previously healthy 33-year-old woman comes to the physician because of pain and sometimes numbness in her right thigh for the past 2 months. She reports that her symptoms are worse when walking or standing and are better while sitting. Three months ago, she started going to a fitness class a couple times a week. She is 163 cm (5 ft 4 in) tall and weighs 88 kg (194 lb); BMI is 33.1 kg/m2. Her vital signs are within normal limits. Examination of the skin shows no abnormalities. Sensation to light touch is decreased over the lateral aspect of the right anterior thigh. Muscle strength is normal. Tapping the right inguinal ligament leads to increased numbness of the affected thigh. The straight leg test is negative. Which of the following is the most appropriate next step in management of this patient?

Advise patient to wear looser pants

Blood work for inflammatory markers

Symptom-based differential diagnosis approach for USMLE Step 2 CK: High-Yield Diagnosis Lessons

DDx Framework - Blueprint for Thinking

A systematic approach to a patient's chief complaint is crucial for diagnostic accuracy. Instead of random recall, use a structured framework like the VINDICATE mnemonic to build a comprehensive differential diagnosis (DDx). This ensures all major categories of disease are considered, minimizing cognitive errors.

📌 VINDICATE Mnemonic: A classic tool to organize potential diagnoses systematically.

⭐ While Occam's razor (the simplest explanation is best) is useful, always consider Hickam's dictum in complex cases: "A patient can have as many diseases as they damn well please." This is especially true for elderly patients with multiple comorbidities.

Chest Pain DDx - Cracking the Code

📌 PET MAC: Pulmonary embolism, Esophageal rupture, Tension pneumothorax, Myocardial infarction (ACS), Aortic dissection, Cardiac tamponade.

Can't-Miss Cause	Pain & Radiation	Key Signs & Diagnostics
ACS	Crushing, substernal → jaw/arm	EKG changes, ↑Troponins
Aortic Dissection	Tearing, ripping → back	Asymmetric BPs, widened mediastinum
PE	Pleuritic, sudden	Tachycardia, hypoxia, S1Q3T3 on EKG
Tension Pneumo.	Unilateral, sharp	Tracheal deviation, ↓breath sounds
Esophageal Rupture	Retrosternal, severe	Post-emesis, Hamman's crunch

Abdominal Pain DDx - Gut Instincts

Abdominal Quadrants & Regions

RUQ: Cholecystitis, Hepatitis, Cholangitis, Fitz-Hugh-Curtis
Epigastric: Pancreatitis, Peptic Ulcer Disease, GERD, MI
LUQ: Splenic infarct/rupture, Gastritis
RLQ: Appendicitis, Ectopic Pregnancy, Ovarian Torsion, IBD
LLQ: Diverticulitis, Ectopic Pregnancy, Ovarian Torsion
Suprapubic: Cystitis, Prostatitis, PID
Diffuse/Periumbilical: Bowel Obstruction, Gastroenteritis, DKA, AAA rupture

⭐ In appendicitis, vague periumbilical visceral pain (T8-T10) precedes sharp, localized somatic pain in the RLQ as inflammation irritates the parietal peritoneum. This migration is a classic diagnostic clue.

Headache DDx - Mind the Gaps

Primary vs. Secondary: The first step is to rule out dangerous secondary causes by looking for red flags.
📌 SNOOP Mnemonic (Red Flags):
- Systemic symptoms (fever, myalgia)
- Neurologic signs (focal deficits, papilledema)
- Onset sudden (e.g., thunderclap headache)
- Older age of onset (>50 years)
- Pattern change from previous headaches

CT scan: Subarachnoid Hemorrhage vs. Normal

Headache Type	Onset & Timing	Quality & Location	Associated Signs
SAH	Sudden, "thunderclap"	"Worst headache of life"	Meningismus, ↓LOC
Migraine	Gradual, 4-72 hrs	Pulsating, unilateral	Aura, photophobia
Cluster	Abrupt, cyclical	Excruciating, periorbital	Lacrimation, ptosis
Tension	Gradual, variable	Band-like, bilateral	Pericranial tenderness

High‑Yield Points - ⚡ Biggest Takeaways

Start with the most common causes for a given symptom, then consider life-threatening ones.

Always prioritize and rule out "can't-miss" diagnoses that pose an immediate threat.

Use patient demographics (age, sex) and risk factors to narrow the differential list.

The history and physical exam are the most powerful tools to shorten the list.

Structure differentials by organ system or use a mnemonic like VINDICATE.

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