18 Differential Diagnoses You Must Know by Dr. Sam Gharbi
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The differential diagnosis is at the core of medicine. Without a good differential to start off with, your approach to the history, physical, and investigations will be incomplete. In essence, your entire assessment of the patient begins with your differential diagnosis in regards to the presenting complaint. This e-book is a collection of 18 differential diagnoses that address commonly encountered medical problems. These 18 differentials in particular were chosen because they are, in my opinion, the major ones that you encounter and will be required to know on any internal medicine rotation, particularly in an inpatient setting. However, these differentials can also be generally applicable to most fields of medicine. This e-book is meant to be a user friendly educational guide with the purpose of bestowing a general framework for medical learners. It is not meant to be a clinical reference guide to be used for medical decision making, nor is it meant to be a complete list of every different possible pathology that may be contributing to a differential diagnosis.
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18 Differential Diagnoses You Must Know by Dr. Sam Gharbi
- 1. Differential Diagnoses You Must Know 18 Understanding Internal Medicine Sam Gharbi, MD
- 2. i Differential Diagnoses You Must Know 18
- 3. ii Disclaimer Extensive effort has been exerted in order to make this book as accurate as pos- sible. However, the accuracy and completeness of the information provided cannot be guaranteed. This book is to be used as an educational guide only, and healthcare professionals should use sound clinical judgement and individu- alize therapy to each specific patient care situation. The author makes no claims whatsoever, expressed or implied, about the authenticity, accuracy, reliability, completeness, or timeliness of the material presented in this book. In no event shall the author be liable to any party for indirect, direct, special, incidental, or consequential damages, including but not limited to lost profits arising out of the use of this book, even if the author has been advised of such damage. By having read the above, or by use of this book, be it partially or in its en- tirety, you have explicitly consented your agreement to the above disclaimer.
- 4. COPYRIGHT iii © Copyright 2013 Sam Gharbi. All Rights Reserved.
- 5. To Dr. Iain Mackie, for all your years of mentorship & support. iv DEDICATION
- 6. The differential diagnosis is at the core of medicine. Without a good differential to start off with, your approach to the history, physical, and investigations will be incom- plete. In essence, your entire assessment of the patient begins with your differential diagnosis in regards to the presenting complaint. This e-book is a collection of 18 differential diagnoses that address commonly encoun- tered medical problems. These 18 differentials in particular were chosen because they are, in my opinion, the major ones that you encounter and will be required to know on any internal medicine rotation, particularly in an inpatient setting. However, these dif- ferentials can also be generally applicable to most fields of medicine. This e-book is meant to be a user friendly educational guide with the purpose of be- stowing a general framework for medical learners. It is not meant to be a clinical refer- ence guide to be used for medical decision making, nor is it meant to be a complete list of every different possible pathology that may be contributing to a differential diagno- sis. In such situations I would recommend referring to your usual medical references of choice. I hope you, the reader, find it to be a helpful educational resource. Sincerely, Sam Gharbi v PREFACE
- 7. Of the 18 differential diagnoses that are outlined in this e-book, for most of the differ- entials I have outlined 2 different ways in which they can be approached. The first page of each section outlines the differential diagnosis list that, in my humble opinion, a good clinician should have memorized. On the left hand side of the table are outlined broad categories, and on the right side of the table you will find spe- cific illnesses. This list is not meant to be a complete list of every possible etiology to the pre- senting complaint, but instead a list that you should have in mind as a start- ing point to guide your assessment of the patient. This list is what will often be expected of you to know particularly in your oral examinations, as well as when quizzed by staff physicians. vi USER GUIDE
- 8. I find that most experienced staff physicians even- tually develop a shortened differential diagnosis list that they then expand upon as necessary. From this stemmed the idea for the second page of most sections, which is entitled "The Big Ones". Essentially this is a list that I have put together of the most common etiologies to the presenting complaint. This list is formulated based on my clinical experience over the years, and is in no way based on any hard evidence or statistical analysis of patient data unfortunately. I have found that many students and junior resi- dents struggle with learning their differentials, mainly because the lists can often be somewhat large and overwhelming. It may be better to instead layer that learning, and to start with this foundation in the form of "The Big Ones". This was my main impetus for putting together "The Big Ones" lists, to be used as a starting point for medical learners early in their careers to then build upon. These lists may be particularly helpful if you are in an oral exam situation and you blank on your differential. It's always nice to have a go to short list. Hopefully this will be of some help. vii
- 9. During the course of my medical training, I of- ten found it quite frustrating to not have a sin- gle integrated source for all my information during the course of my medical training. I re- member that most of us were spending as much time (if not more) with data gathering than actual studying. From this stemmed the idea for an interactive component to this e-book. On most pages, you will find the following yellow clipboard icon. If you press on it, a notepad will appear. It is de- signed so that you may add your own notes and have all your information integrated into one source. Once you have finished writing your notes, press on the "x" at the top left hand corner to close the notepad screen and return to the e- book. Overall, the hope with the notepad functional- ity is that you can be a bit better organized in having all your study notes regarding differen- tials in one source. It may be particularly help- ful if you are sitting in lectures, or during grand rounds, where you may follow along with the e-book while adding notes as neces- sary. Then later when you are studying, you have all the information you need in a single re- source. viii
- 10. I would love to hear your feedback on what you liked about this book, and what you think could be improved. Please click on the icon below to send feedback. Any and all con- structive comments are greatly appreciated. ix FEEDBACK
- 11. DIFFERENTIAL DIAGNOSES OVERVIEW CHAPTER 1 10 Symptoms (on history): • Chest Pain • Shortness of Breath • Abdominal Pain • Gastrointestinal bleeding • Syncope • Confusion • Arthritis Signs (on exam): • Hypotension & Shock • Hypertension Laboratory Abnormalities: • Anemia • Thrombocytopenia • Hyponatremia • Acute Kidney Injury • Anion-Gap Metabolic Acidosis • Transaminitis (Elevated AST & ALT) • Elevated Biliary Enzymes (ALK) • Coagulopathy (Elevated INR & PTT) • Thrombophilia
- 12. CHEST PAIN SECTION 1 11 Differential Diagnoses 1
- 13. Coronary Artery Disease Acute Coronary Syndrome Aortic Dissection Pericarditis GERD Chostochondritis 12 Differential Diagnoses CHEST PAIN THE BIG ONES 1
- 15. COPD/Asthma Pneumonia Pneumothorax Pulmonary Embolism Congestive Heart Failure Pericardial Tamponade 14 Differential Diagnoses 2 DYSPNEA THE BIG ONES
- 16. ABDOMINAL PAIN SECTION 3 15 Differential Diagnoses 3
- 17. Gastroenteritis Colitis (infectious or ischemic) Peritonitis (SBP or surgical) Inflammatory Bowel Disease Pancreatitis Note that ultimately the DDx for abdominal pain is very much dependent on its location, as well as the reality that many of the etiologies on the previ- ous page can ultimately present as generalized abdominal pain. 16 Differential Diagnoses 3 Generalized ABDOMINAL PAIN THE BIG ONES
- 18. GI BLEED SECTION 4 17 Differential Diagnoses 4
- 19. 4 Peptic Ulcer Disease Variceal bleed Angiodysplasia Gastric cancer Diverticulosis Angiodysplasia Bowel Ischemia Inflammatory Bowel Disease Colon cancer 18 Differential Diagnoses GI BLEED THE BIG ONES Upper GI Bleed Lower GI Bleed
- 21. Neurogenic Cardiogenic Vasovagal Orthostatic Hypoglycemia 20 Differential Diagnoses SYNCOPE THE BIG ONES 5
- 23. Drugs Infectious Metabolic Structural 22 Differential Diagnoses CONFUSION THE BIG ONES 6 Remember the "DIMS" Mnemonic
- 26. Septic Arthritis Gout/Pseudogout Osteoarthritis Hemarthrosis Septic Arthritis Gout/Pseudogout Osteoarthritis Rheumatoid Arthritis SLE Reactive Arthritis 25 Differential Diagnoses ARTHRITIS THE BIG ONES 7 Monoarthritis Polyarthritis
- 30. Essential Hypertension Chronic Kidney Disease Thyroid Disease Meds - NSAIDs, OCPs, Steroids Drugs - Alcohol, Cocaine, Amphetamines Obstructive Sleep Apnea 29 Differential Diagnoses HYPERTENSION THE BIG ONES 9
- 33. Iron Deficiency Anemia of Chronic Disease Blood Loss Hemolysis Anemia of Chronic Disease Liver disease Alcohol abuse 32 Differential Diagnoses ANEMIA THE BIG ONES 10 Microcytic Macrocytic Normocytic
- 35. 11 Sepsis Cirrhosis Hematological malignancy HUS-TTP DIC HIT ITP Splenomegaly 34 Differential Diagnoses THROMBOCYTOPENIA THE BIG ONES Decreased Production Increased destruciton Sequestration
- 37. Hypovolemia SIADH Low solute diet Psychogenic polydipsia Hypervolemia 36 Differential Diagnoses HYPONATREMIA THE BIG ONES 12
- 38. ACUTE KIDNEY INJURY SECTION 13 37 Differential Diagnoses 13
- 39. 38 Differential Diagnoses ACUTE KIDNEY INJURY13
- 40. Hypovolemia Congestive Heart Failure Sepsis Shock Drugs ATN (from pre-renal) AIN (from drugs) BPH Blocked Foley Catheter 39 Differential Diagnoses ACUTE KIDNEY INJURY THE BIG ONES 13 Pre-Renal Renal Post-Renal
- 41. AG METABOLIC ACIDOSIS SECTION 14 40 Differential Diagnoses 14
- 42. Ketoacidosis Lactic Acidosis Renal Failure Drugs 41 Differential Diagnoses AG METABOLIC ACIDOSIS THE BIG ONES 14
- 44. 15 Alcohol Tylenol overdose Hepatitis B & C Hemochromatosis Fatty Liver Disease 43 Differential Diagnoses TRANSAMINITIS THE BIG ONES
- 45. ELEVATED BILIARY ENZYMES SECTION 16 44 Differential Diagnoses 16
- 46. Choledocholithiasis Cholangitis Biliary stricture Pancreatic cancer Sepsis 45 Differential Diagnoses 16 ELEVATED BILIARY ENZYMES THE BIG ONES
- 49. Malignancy APS DIC HIT OCPs Immobilization Recent Surgery 48 Differential Diagnoses THROMBOPHILIA THE BIG ONES 18
- 50. SUMMARY SECTION 19 49 Differential Diagnoses Finding Differential Chest Pain •Coronary Artery Disease •Acute Coronary Syndrome •Aortic Dissection •Pericarditis •GERD •Chostochondritis Dyspnea •COPD/Asthma •Pneumonia •Pneumothorax •Pulmonary Embolism •Congestive Heart Failure •Pericardial Tamponade Generalized Abdominal Pain •Gastroenteritis •Colitis (infectious or ischemic) •Peritonitis (SBP or surgical) •Inflammatory Bowel Disease •Pancreatitis Gastrointestinal Bleed Upper GI Bleed: •Peptic Ulcer Disease •Variceal bleed •Angiodysplasia •Gastric cancer Lower GI Bleed: •Diverticulosis •Angiodysplasia •Bowel Ischemia •Inflammatory Bowel Disease •Colon cancer
- 51. 50 Differential Diagnoses Finding Differential Syncope •Neurogenic •Cardiogenic •Vasovagal •Orthostatic •Hypoglycemia Confusion •Drugs •Infectious •Metabolic •Structural Arthritis Monoarthritis: •Septic Arthritis •Gout/Pseudogout •Osteoarthritis •Hemarthrosis Polyarthritis: •Septic Arthritis •Gout/Pseudogout •Osteoarthritis •Rheumatoid Arthritis •SLE •Reactive Arthritis Hypotension & Shock •Hypovolemic •Cardiogenic •Obstructive •Distributive •Drugs Hypertension •Essential Hypertension •Chronic Kidney Disease •Thyroid Disease •Meds - NSAIDs, OCPs, Steroids •Drugs - Alcohol, Cocaine, Amphetamines •Obstructive Sleep Apnea
- 52. 51 Differential Diagnoses Finding Differential Anemia Microcytic: •Iron deficiency •Anemia of chronic disease Normocytic: •Blood loss •Hemolysis •Anemia of chronic disease Macrocytic: •Liver disease •Alcohol abuse Thrombocytopenia Decreased production: •Sepsis •Cirrhosis •Hematological malignancy Increased destruction: •HUS-TTP •DIC •HIT •ITP Sequestration: •Splenomegaly Hyponatremia •Hypovolemia •SIADH •Low solute diet •Psychogenic polydipsia •Hypervolemia
- 53. 52 Differential Diagnoses Finding Differential Acute Kidney Injury Pre-renal: •Hypovolemia •CHF •Sepsis •Shock •Drugs Renal: •ATN (from pre-renal) •AIN (from drugs) Post-renal: •BPH •Blocked foley catheter Anion-Gap Metabolic Acidosis •Ketoacidosis •Lactic acidosis •Renal failure •Drugs Elevated Transaminases •Alcohol •Tylenol OD •Hepatitis B&C •Hemochromatosis •Fatty Liver Disease Elevated Biliary Enzymes •Choledocholithiasis •Cholangitis •Biliary stricture •Pancreatic cancer •Sepsis
- 54. 53 Differential Diagnoses Finding Differential Coagulopathy Increased INR: •Warfarin •Vitamin K deficiency •Factor inhibitor Increased PTT: •Heparin •Hemophilia A or B •Factor inhibitor Increased INR & PTT: •Liver disease •DIC •Heparin & Warfarin Thrombophilia •Malignancy •Antiphospholipid Antibody Syndrome (APS) •Heparin Induced Thrombocytopenia (HIT) •DIC •OCPs •Immobilization •Recent surgery