Hematology, Neuroanatomy, Psychiatry, and Renal Mnemonics

A ValueMD community study resource, originally shared on our forums and preserved here for students working through hematology, psychiatry, and renal physiology.

This set covers a handful of frequently tested topics that don’t always get grouped together: the oxygen-hemoglobin dissociation curve, temporal lobe function, the diagnostic criteria for depression, acid-base disorders, and the causes of digital clubbing.

Educational note: these are student-built memory aids for exam review, not a substitute for your course material or a clinical reference. A few entries below have been corrected or completed from the original forum thread for accuracy.

Hematology

Oxygen-Hemoglobin Dissociation Curve: Shift to the Right

DAT: the curve shifts right (hemoglobin releases oxygen more readily) whenever DPG, Acidity, or Temperature increases. This is a shorter version of the fuller “CADET, face right” mnemonic, which also includes CO2 and exercise as factors that shift the curve right.

Neuroanatomy

Temporal Lobe Function: HELM

Think of a helmet covering the side of the head:

• Hearing
• Emotion
• Learning
• Memory

Psychiatry

Symptoms of Major Depression: SIG E CAPS

A classic way to remember the DSM criteria for major depressive disorder, framed as “writing a prescription for Energy Capsules”:

• Sleep changes
• Interest loss (anhedonia)
• Guilt
• Energy decreased
• Concentration difficulty
• Appetite change
• Psychomotor changes (agitation or retardation)
• Suicidal ideation

(Depressed mood or loss of interest, plus at least four more of the above, present most of the day for at least two weeks, are required for a diagnosis of major depressive disorder.)

Renal and Acid-Base

HUS/TTP: CRAFTY

Hemolytic uremic syndrome and thrombotic thrombocytopenic purpura share overlapping features, remembered as CRAFTY:

• CNS symptoms
• Renal failure
• Anemia (microangiopathic hemolytic anemia, or MAHA)
• Fever
• Thrombocytopenia
• Y: no one fully knows why it occurs

Normal Anion-Gap Metabolic Acidosis: USED CAR

• Ureterosigmoidostomy
• Saline administration (in the setting of renal dysfunction)
• Endocrine causes (Addison’s disease, spironolactone, triamterene, amiloride, primary hyperparathyroidism)
• Diarrhea
• Carbonic anhydrase inhibitors
• Ammonium chloride
• Renal tubular acidosis

A shorter alternative groups the same categories as RAGE: Renal tubular acidosis, Acetazolamide/ammonium chloride, GI losses (diarrhea, enteroenteric fistula, ureterosigmoidostomy), Endocrine causes.

Increased Anion-Gap Metabolic Acidosis: MUDPILES

• Methanol
• Uremia
• Diabetic ketoacidosis
• Paraldehyde
• Iron tablets or Isoniazid (INH)
• Lactic acidosis
• Ethylene glycol
• Salicylates

A shorter alternative, DULSI, groups these into fewer categories: Diabetic ketoacidosis, Uremia, Lactic acidosis, Salicylate poisoning, Intoxicants (methanol, ethanol, ethylene glycol). MUDPILES is the more complete version, since it separates out iron and isoniazid toxicity as their own distinct, clinically important cause.

Miscellaneous: Causes of Digital Clubbing

• Cardiac (right-to-left shunt)
• Lung (tumor, pulmonary fibrosis)
• Ulcerative colitis (also Crohn’s disease, less commonly)
• Bronchiectasis
• Benign fibrous tumor of the pleura
• Inherited or idiopathic
• Neurogenic tumors
• GI disease (cirrhosis)

Clubbing may also be accompanied by Hypertrophic Pulmonary Osteoarthropathy (HPOA), a related syndrome involving periosteal new bone formation, joint pain, and swelling.

Frequently Asked Questions

1. What causes the oxygen dissociation curve to shift right?
   Increases in DPG, acidity (lower pH), temperature, CO2, and exercise all shift the curve right, meaning hemoglobin releases oxygen more readily to tissues.
2. What does SIGECAPS stand for?
   Sleep, Interest, Guilt, Energy, Concentration, Appetite, Psychomotor changes, and Suicidal ideation, the core symptom checklist for major depressive disorder alongside depressed mood or anhedonia.
3. What’s the difference between MUDPILES and USED CAR?
   MUDPILES lists causes of an increased anion-gap metabolic acidosis (methanol, uremia, DKA, paraldehyde, iron/INH, lactic acidosis, ethylene glycol, salicylates). USED CAR lists causes of a normal anion-gap metabolic acidosis (ureterosigmoidostomy, saline administration, endocrine causes, diarrhea, carbonic anhydrase inhibitors, ammonium chloride, renal tubular acidosis). They apply to two different categories of metabolic acidosis, not the same one.
4. What are the main causes of digital clubbing?
   Cardiac right-to-left shunts, lung disease (tumors, fibrosis, bronchiectasis), inflammatory bowel disease, benign pleural tumors, and idiopathic or inherited causes are the classic categories.

Want to Know More?

These are just a few of the mnemonics our community has put together across hematology, psychiatry, renal, and neuroanatomy. Visit our USMLE student community to find more, share your own, or ask a question about a topic you’re stuck on.