Explanations for the 2016-2017 Official Step 2 CK Practice Questions

Here are the explanations for the updated 2016-17 official “USMLE Step 2 CK Sample Test Questions” PDF, which can be found here.

Overall, the June 2016 update removes 21 questions as a result of the decrease in block size taking effect this year. There are exactly two new questions in this year’s set (#19 and #117), but the question order has been completely scrambled. The explanations for last year’s set can still be found here (I’ve expanded a few of the repeat explanations, just for fun).

Helpful reader Jarrett has made a list converting the question order from the online FRED version to the pdf numbers.

Block 1

  1. E – Intermittent polyarthritis with positive ANA (sensitive but not specific) and anti-DNA (very specific) means lupus. You don’t even need the non-painful mouth ulcers.
  2. C – Anesthesia to the anterolateral thigh is the distribution of the lateral femoral cutaneous nerve. LFC neuropathy can be caused by compression near the inguinal ligament (say, from a hematoma). Note that it’s the compression of the nerve that causes decreased sensation, not the hematoma itself.
  3. H – Recurrent infections with abscesses should raise the suspicion of chronic granulomatous disease. Suppurative arthritis does even more, if you’re likely to remember that. The real diagnosis is made from the Step 1 style question. Nitroblue tetrazolium is the test used to diagnose CGD, which is a defect in NADPH oxidase (the oxidative burst that kills Staph aureus).
  4. D – Unstable and hypotensive patients after blunt trauma get laparotomies (don’t put an unstable patient in the CT scanner). In addition to saline and blood products, definitive surgery is how you address the C in ABC.
  5. B – Alcohol raises GGT. The other liver enzyme lab to remember is the 2:1 or greater AST/ALT ratio associated with alcoholic liver disease.
  6. D – The patient has a small bowel obstruction, likely due to adhesions from prior surgery, evident clinically and confirmed by radiograph (grossly dilated small bowel without distal colonic dilation to suggest paralytic ileus). Conservative treatment in a stable patient involves NG tube decompression and NPO. A CT can be obtained for further characterization and to look signs of bowel compromise (and would be in real life), but there is no reason to delay appropriate care to get it.
  7. A – Proximal muscle weakness + skin findings = dermatomyositis. Yes, kids can get this. In this case, they’ve gone to the trouble of describing Gottron’s papules (“flat-topped red papules over all knuckles”) and the heliotrope rash (purple-red discoloration over the eyelids). Please note the USMLE will never actually say things “heliotrope” on the actual exam. They always describe.
  8. A – Autonomy matters. If a patient has the capacity to make medical decisions (i.e. understands the risks) and is not an imminent harm to self or others (i.e. suicidal or homicidal), then he cannot be held against his will. We don’t institutionalize people just for noncompliance with medical treatment.
  9. A – These questions can be a true pain of biochemistry on the Step 1 or relatively straightforward depending on how well you know it. This patient has classical Galactosemia, caused by a deficiency in galactose-1-P uridyl transferase deficiency, the enzyme that converts galactose and lactose to glucose. Intolerance to dairy, hepatomegaly/liver disease/jaundice with hypoglycemia due to decreased gluconeogenesis, and reducing substances in urine are classic. Listlessness and lethargy ensue with mental retardation and eventually death if untreated. Cataracts are also common. If you didn’t get to galactosemia (or thought it was Von Gierke’s disease, which isn’t all that unreasonable), the answer is still A. By process of elimination, given the serum hypoglycemia but no urine glucose, the issue is the inability to make glucose from stores (not to absorb it).
  10. C – Meningitis/encephalitis symptoms (fever, headache, altered mental status) with monocytic predominance and only mildly elevated protein on CSF studies go along with viral meningitis, such as HSV.
  11. D – Microcytic anemia is essentially always iron-deficiency unless there is a reason to suspect a thalessemia. In this case, extensive surgery has removed nutrient absorbing small bowel (the duodenum and proximal jejunum absorb iron).
  12. D – First-line treatment for panic disorder (and all anxiety disorders) is SSRI therapy. The only time you answer “benzodiazepine” (which wasn’t offered as a choice, because it would be arguable) for a panic disorder question is when they ask you what drug is “most likely to treat the episode” or something along those lines. BZDs work immediately; SSRIs take time.
  13. C – Polycystic ovarian syndrome (PCOS) is treated with estrogen-containing birth control (OCPs). Metformin would be an additional appropriate pharmacotherapy.
  14. D – Euvolemic hyponatremia means SIADH. Both brain and lung insults are common causes. Nonphysiologic secretion is “inappropriate,” of course.
  15. A – Repetitious vomiting leads to the classic hypokalemic hypochloremic metabolic alkalosis, as well as run of the mill dehydration (hyponatremic hypovolemia). So—low sodium, low potassium, low chloride, high bicarbonate.
  16. B – Endometriosis is a common cause of infertility and is associated with chronic pelvic/abdominal pain and excruciating periods. Gold standard for diagnosis is laparoscopy (visualization of “chocolate cysts”).
  17. D – Consider bacterial sinusitis to be analogous to bacterial pneumonia. All are possible, but Strep pneumo is the most common.
  18. B – Diabetes get diabetic nephropathy. Don’t over-think things.
  19. B – A cohort study (as opposed to a randomized controlled trial) is ripe for selection bias, which occurs when the treatment and control groups are not truly comparable. Matching for some factors (age, gender) doesn’t mean you’ve controlled for all possible confounders. That’s what randomization does!*
  20. D – Atopic dermatitis (eczema) is the “itch that rashes.” It’s one leg of the allergic triad: asthma, allergic rhinitis, and atopic dermatitis. Treatment is with topical steroids and rigorous emollient therapy.
  21. B – Repetitive vomiting (be it due to viral gastroenteritis or bulimia) leads to hypokalemic hypochloremic metabolic alkalosis. Alkalosis means elevated bicarbonate, which in this case is created as the byproduct of increased stomach acid production.
  22. D – Abscessed Bartholin’s cysts get incised and drained. When recurrent, they can be marsupialized, which isn’t as fun as it sounds.
  23. B – Catecholamines, such as those released by a functioning pheochromocytoma, are made by the chromaffin cells of the adrenal medulla. Episodic headache/hypertension is the tip-off here.
  24. A – Even if you forget the signs/symptoms of Kawasaki’s disease, which you shouldn’t (strawberry tongue is a giveaway), just remember it’s essentially the diagnosis for any child with 5 days or more of fever. Treatment is aspirin (the one time it’s okay in children, otherwise let’s avoid Reye’s syndrome) and IVIG.
  25. C – Macrocytic anemia with sensory changes is indicative of B12 deficiency. Causes include the classic pernicious anemia, but don’t forget the complications of GI surgery. Intrinsic factor is made by the stomach’s parietal cells.
  26. B – This patient has chronic (6 weeks) symptomatic hypotension while not coincidentally on three BP meds: a diuretic, a beta blocker, and an ACE inhibitor. The most likely explanation and easiest/fastest intervention is to reduce her polypharmacy.
  27. F – Premature babies get neonatal respiratory distress syndrome due to surfactant deficiency.
  28. B – Multiple lytic bone lesions equals multiple myeloma. Blastic/sclerotic lesions should make you think of metastatic prostate cancer (in men) and breast cancer (in women).
  29. B – Two things make this aortic dissection instead of a heart attack or pulmonary embolism. First, the diastolic murmur is that of aortic insufficiency/regurgitation, which is happening because the dissection is involving the aortic root. Second, the presence of diminished femoral pulses implies that the dissection also involves the descending thoracic aorta distal to the takeoff of the brachiocephalic and left subclavian arteries (which supply the arms). Only an issue in the aorta can cause that constellation of symptoms.
  30. F – TTP always seems like too many disparate symptoms but just remember the pentad: thrombocytopenia, microangiopathic hemolytic anemia, neurologic symptoms, renal failure, and fever. If the symptoms list seems super long, keep TTP in mind.
  31. A – An egg allergy is the most common contraindication to receiving the flu vaccine.
  32. G – Pleuritic chest pain and hypoxia with a normal chest x-ray should lead you to pulmonary embolism. There’s usually enough total lung and blood flow, but it’s the VQ mismatch that’s the issue.
  33. F – SIGECAPS+. Patient has MDD and developing panic disorder. Both of these can be treated first-line with SSRI therapy, such as paroxetine (Paxil).
  34. E – An acutely swollen painful great toe means gout (podagra). Gout is an inflammatory crystalline arthropathy. Aspiration reveals white cells and negatively-birefringent needle-shaped crystals. Pseudogout, which has rhomboid positively-birefringent crystals, more commonly affects the knee.
  35. F – Vasculitides like Wegener’s granulomatosis, microscopic polyangiitis, and others can cause poly-symptom disease and glomerulonephritis (hence the hematuria and proteinuria). Positive ANCA, (either P-ANCA or C-ANCA depending on the variant) is the key laboratory finding.
  36. E – LLQ pain with fever equals diverticulitis. The test of the choice is a CT scan of the abdomen with contrast.
  37. C – Bipolar disorder is the only reasonable answer, as evidenced by the increased energy, elevated mood, labile affect, and poor judgment and focus. You don’t develop ADHD at 32.
  38. A – Sudden respiratory failure after rupture of membranes means amniotic fluid embolism (it’s not like a fat embolism; it’s actually an allergic reaction). Can happen during labor or secondary to trauma. Hypotension and coagulopathy ensue.
  39. D – Fever, pain, and swelling behind the ear means mastoiditis (remember the mastoid air cells?). The cause is nearly universally direct spread from otitis media.
  40. E – Exfoliative and blistering drug reactions come in three severities of the same mechanism: erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis. Diffuse involvement (>30%) is consistent with toxic epidermal necrolysis (TEN), which carries a 30-40% mortality.

Block 2

  1. E – Pseudogout (calcium pyrophosphate deposition disease) is an inflammatory arthritis with a predilection for the knee that causes synovial calcifications.
  2. A – Low pH means acidemia. Renal failure causes metabolic acidosis (hence low bicarb). Low CO2 is the respiratory compensation. If it was vice versa, the pH would be high (alkalemia).
  3. A – Lisinopril and especially spironolactone (a K-sparing diuretic) can both cause hyperkalemia. Renal failure (severe AKI or ESRD) is also a major cause of hyperkalemia, but not in this case with the only mildly elevated Cr and BUN levels.
  4. A – The differential for chronic diarrhea in an AIDS patient includes bacterial, viral, and parasitic causes as well as HIV enteropathy. Cryptosporidium is a protozoa that classically causes watery diarrhea in AIDS patients, especially those exposed to unclean water sources (hence the traveling to Asia). CMV is a reactivation infection and MAC is ubiquitous; disease caused by either of these pathogens is due to severely depressed immunity (i.e. CD4 < 50).
  5. A – Headache and stiff neck clues you to meningitis. In a college student, that’s enough for the diagnosis of meningococcal meningitis. Stop reading. The treatment is ceftriaxone.
  6. F – Weight loss and worsening lung symptoms in a smoker means lung cancer. Non-small cell is by far the most common variety. The small cell variety on tests will usually have fun paraneoplastic syndromes.
  7. B – Wide split fixed S2 is an ASD.
  8. C – Weight loss and iron deficiency anemia are concerning for colon cancer with occult blood loss. Colonoscopy is required. Parasitic causes of iron deficiency (e.g. hookworm) are first tested with stool ova & parasite screening.
  9. A – Dermatomal rash means zoster (a chickenpox/varicella reactivation disease). Immune insults, like chemotherapy, predispose to zoster flares.
  10. D – Transillumination of a scrotal mass equals a hydrocele, which is due to a patent processus vaginalis.
  11. E – Working up serious hypoglycemia involves measurement of both insulin and C-peptide (the cleaved by-product of endogenous proinsulin) to assess for hyperinsulinemia and distinguish endogenous (e.g. insulinoma) from exogenous (e.g. Munchausen’s) causes. “Nurse” is a common Munchausen tip-off (someone with the know-how and skills to pull it off well).
  12. C – Interstitial nephropathy (also known as tubulointerstitial nephritis) is most commonly an allergic-type reaction to medications, typified by eosinophils in the urine. The nonspecific maculopapular reaction is also the common type of drug reaction rash and is seen in a minority of cases, as is low-grade fever (not critical to the question). Several medications can cause this: penicillins, cephalosporins, and NSAIDs are the most common.
  13. D – Pinpoint pupils are a classic tip-off for opioid use (caused by parasympathetic activation). Additionally, neither alcohol nor barbiturates would be likely choices in this context because they have similar effects (along with benzodiazepines).
  14. C – Patients who have the capacity to make medical decisions are allowed to refuse life-saving medical treatment. You should offer it but accept her refusal.
  15. B – A p-value less than 0.05 means that the results are statistically significant. However, most would agree that roughly 7 hours difference in cold duration is clinically insignificant.
  16. E – ABCs. Patient has an airway (evidenced by breath sounds without mention of other complicating factors like unconsciousness). Move on to breathing. Asymmetry implies a hemo-, pneumo-, or hemopneumothorax, which requires a chest tube immediately.
  17. E – Crescents mean rapidly progressive glomerulonephritis (RPGN—bad news bears). Immune complexes along the basement membrane mean Type II, such as seen with lupus, IgA nephropathy, acute proliferative glomerulonephritis, and Henoch-Schönlein purpura. Treated with immune suppression, which in the acute phase always means steroids.
  18. A – Cough is often the only sign of asthma. Exercise-induced asthma is exercise-induced asthma.
  19. E – Bronze diabetes and arthritis means hemochromatosis. They never say the words “bronze diabetes” on board questions, but it doesn’t mean it’s not there. You don’t want an awesome tan on the boards.
  20. A – Repeated microtrauma from repetitive stress can cause thrombosis. DVT leads to erythema and venous engorgement, the other choices do not. For bonus points, the eponym for effort-induced upper extremity DVT is “Paget–Schroetter disease” (for those keeping track at home).
  21. D – The radiograph is showing complete collapse of the left lung (2/2 mucous plugging) with resultant severe ipsilateral mediastinal shift. An acute shift can have the same effect as any other “tension”-type process, causing impaired venous return to the heart and decreased cardiac output via the Starling mechanism.
  22. E – Weight gain, fatigue, and constipation go with hypothyroidism. High LDL cholesterol actually does too, but the question is doable even when ignoring the lab values.
  23. A – Organ donation is a complex organizational dance, and the regional procurement organization manages the nitty-gritty aspects.
  24. A – They’ve listed the criteria for ADHD. Note that conduct disorder is the kid-version of antisocial behavior. If the kid breaks rules and messes up but doesn’t seem evilthen it’s not conduct disorder.
  25. D – Abdominal pain is a common presenting complaint for DKA, which is a common presentation of new-onset type 1 diabetes. Note the glucose of 360.
  26. E – Abnormal vaginal bleeding in a woman over 35 requires an endometrial biopsy to rule out endometrial cancer.
  27. A – It’s not clear that the glucose is a fasting value or not, but it’s clear that the patient has symptoms of diabetes in the context insulin resistance (obese kid with acanthosis nigricans). Diet and exercise are always necessary in DM2 and can reverse many early cases. With a 10% weight loss, for example, the patient may not require pharmacotherapy.
  28. B – Marfan syndrome (you know, hinted at by the familial tall stature and weak hypermobile joints) is associated with a dilated/aneurysmal aortic root, which can worsen, dissect and/or rupture if not monitored.
  29. D – Meniere disease is characterized by recurrent vertigo attacks associated with ear fullness, tinnitus, and hearing loss.
  30. C – Follow your ABCs. Tachycardia and hypotension mean severe volume loss necessitating aggressive intravenous fluid resuscitation.
  31. A – Totally healthy people with indirect hyperbilirubinemia means Gilbert syndrome (which causes decreased bilirubin conjugation due to reduced glucuronyltransferase activity).
  32. D – Mitral valve stenosis is a sequela of rheumatic heart disease that can lead to LAE and left-sided heart failure if left untreated.
  33. B – Folic acid prevents neural tube defects. End stop.
  34. B – The primary mechanism by which beta-blockers reduce angina is via decreased contractility, which reduces the oxygen demand of the myocardium (which has a constrained supply due to coronary artery disease). Lowering heart rate also helps, but that isn’t one of your choices.
  35. B – One of the in SIGECAPS is for suicidality. Depression is extremely common, and it’s also underdiagnosed and undertreated in cancer patients.
  36. C – Again, acute RUQ pain (especially in an obese woman) should set off the gallstone alarms. Fever and other systemic signs, white count, etc lead you down the acute cholecystitis. Simple pain leads you to symptomatic cholelithiasis. Either way, the first step is to get a RUQ sono to see those stones! HIDA is used as an adjunctive study in cases of cholelithiasis to assess for cystic duct obstruction (and thus likely acute cholecystitis) in equivocal cases.
  37. D – Walking pneumonia is treated with macrolide antibiotics as first line. Patchy infiltrates in a patient with clinical pneumonia symptoms who otherwise young, healthy, and walking around…think mycoplasma.
  38. B – They describe claudication and vascular insufficiency with strong flow in the groin and no palpable flow distally in the dorsalis pedis, placing the level of stenosis somewhere in between (i.e. femoropopliteal). Diabetes and smoking are two big risk factors for peripheral arterial disease (PAD).
  39. C – We can only put the laboratory tests into context if we have an accurate gestational age. Since her LMP is unreliable (totally unknown), we need an ultrasound to date her pregnancy. The most common cause of an abnormal MSAFP is wrong dates.
  40. B – Post-traumatic AV fistula! Just like dialysis AV fistulae have bruits and thrills, so do non-purposefully created ones. These can take a long time to form but can be associated with steal syndromes due to decreased perfusion to the distal extremity, venous incompetence, varicosities, and eventually stenoses due to unreasonably high flow, and even high-output heart failure.

Block 3

  1. A – This patient has urge incontinence, which is commonly caused by detrusor instability (and can be treated with anticholinergics like oxybutynin). This is opposed to stress incontinence, the other most common type, which is worsened by abdominal pressure/coughing/laughing/etc and can be caused by pelvic floor prolapse secondary to multiple childbirths etc. Neurogenic bladder can cause overflow incontinence.
  2. B – Lumbar strain doesn’t require specific treatment or workup. Bed rest (old school idea) has actually been shown to worsen outcomes.
  3. A – Most common palpable breast mass in women less than 30 is fibroadenoma. In women between 30-50, it’s a cyst (or fibrocystic changes of the breast). Greater than 50, malignancy.
  4. E – The thing you do with things that look like skin cancer is excise them completely.
  5. D – A boot-shaped heart means Tetrology of Fallow on board exams. Outside of that rare straight-up buzzword giveaway, TOF is by far the most common cause of cyanotic heart disease.
  6. A – Via urinalysis and renal ultrasound, we’ve excluded serious/treatable causes of renal hypertension including Conn’s disease (hyperaldosteronism) and renal artery stenosis such as due to fibromuscular dysplasia. That leaves her obesity.
  7. B – Asymptomatic bacteriuria is never treated, except in pregnancy, when it should always be treated due to its association with preterm labor. Treat with an oral antibiotic that covers gram negatives (like E coli), such as amoxicillin or nitrofurantoin.
  8. D – You know what causes sudden onset headache and neck stiffness? Subarachnoid hemorrhage. The first episode can be transient, the so-called sentinel bleed before a catastrophic aneurysmal bleed.
  9. D – The description of a primary lung cancer with associated muscle weakness is leading you to Lambert-Eaton myasthenic syndrome, a paraneoplastic autoimmune condition where antibodies attack the presynaptic calcium channels of the neuromuscular junction. Lung-cancer paraneoplasias are test favorites.
  10. A – Frequent turning prevents the development of pressure ulcers in patients with decreased mobility.
  11. A – PTSD symptoms that begin within 4 weeks of a traumatic event and last 4 weeks or less is acute stress disorder (ASD).
  12. B – The drugs of choice for Alzheimer’s-type dementia (i.e. general dementia without specific factors to make you consider other diagnoses) are the cholinesterase inhibitors, the most important of which is Donepezil.
  13. D – Painless uterine bleeding goes with placenta previa. Painful uterine bleeding goes with placental abruption. Ruptured vasa previa results in rapid loss of the fetus.
  14. F – Septic arthritis (rapidly warm swollen joint +/- fever) must be tapped, followed by antibiotics. Untreated, the joint can be destroyed in days. Minor trauma can predispose to hematogenous bacterial spread.
  15. B – The first imaging test in acute stroke is a noncontrast CT scan of the head. At 12 hours out, it may show ischemic strokes, but more importantly, it will diagnose hemorrhagic strokes, for which reperfusion and antiplatelet therapies are contraindicated.
  16. B – Myocardial infarction causes heart muscle death (as the name implies). Lose enough muscle and you get systolic heart failure.
  17. B – Thick, white, and acidic means candidal vulvovaginitis (aka a yeast infection). Bacterial vaginosis typically only causes foul/fishy odor (and is alkaline, has a positive whiff test, clue cells on wet mount, etc).
  18. E – Thrombocytopenia without antiplatelet antibodies or splenomegaly implies a platelet production problem (e.g. myelofibrosis). History of radiation therapy is a risk factor. The only way to know what’s happening at the factory is a bone marrow biopsy.
  19. C – Multinodular goiter! Say it five times fast. Feels good, doesn’t it? The first half describes blatant hyperthyroidism. The thyroid scan is now demonstrating an enlarged gland with multiple nodules (“areas”), some avid/hyperfunctioning and other relatively depressed (either not “hyper”-functioning and thus relatively cold or actually cold, most commonly filled with colloid).
  20. C – Obstructive sleep apnea (OSA) is diagnosed exclusively by polysomnography (aka a sleep study).
  21. E – Everyone should get a flu shot. Diabetics are relatively immune suppressed and deserve it even more.
  22. D – A nagging persistent dry cough is a common side effect of ACE-inhibitors due to bradykinin accumulation (bradykinin is normally degraded by ACE). Along with angioedema, it’s an important reason for discontinuation; the solution for both is to switch to an angiotensin II-receptor blocker (ARB) like losartan, which does not affect ACE activity directly.
  23. A – RUQ pain and nausea after meals is concerning for symptomatic cholelithiasis. The test of choice is RUQ sono to assess for stones.
  24. A – It’s a cholesteatoma, which can be congenital (rare) or acquired (much more common). Even if you have no idea what that is (look it up), it’s the only answer with “proliferation” to go along with the mass. None of the others mention anything remotely mass-like.
  25. A – The most common cause of hypothyroidism in developed countries is Hashimoto’s thyroiditis. In developing countries, it’s iodine deficiency.
  26. D – If environmental, food, or exposure allergies ever include shortness of breath, hoarseness, or anything remotely airway-involving or anaphylaxis-like, then carry an epi-pen.
  27. D – STDs are always double-treated for both chlamydia and gonorrhea, as coinfection is extremely common, and clearance is crucial to prevent reinfection and continued spread. That means anyone with cervicitis or urethritis gets azithromycin or doxycycline with ceftriaxone.
  28. D – The majority of twins are born premature, which is even more true for triplets. Only monochorionic twins experience twin-twin transfusion syndrome (as they have to share a blood supply in order for the problem to occur).
  29. B – Confusion and tremulousness a few days after an unexpected hospital admission on the USMLE means alcohol withdrawal (unanticipated detox).
  30. B – The STD that forms a painful ulcer aka chancroid = H ducreyi (ducreyi makes you cry, as they say).
  31. D – The lungs are clear. Location, JVD, and lack of heart sounds mean cardiac tamponade from hemorrhage into the pericardium. Pericardiocentesis is the next step. Don’t forget, if you see tension pneumothorax or a water-bottle heart (from tamponade) on chest xray, you’ve already delayed life-saving therapy.
  32. D – The inclusion bodies signify that this patient has a CMV infection of the renal transplant, which can originate from either the donor or recipient but are activated/unmasked by immune suppression. CMV is an important cause of morbidity and mortality in renal transplants and both the donor/recipient are routinely screened.
  33. E – Don’t let the carpal tunnel history fool you. Numbness of the pinkie and half of the ring finger is ulnar entrapment (cubital tunnel syndrome, which happens at the elbow); carpal tunnel syndrome is the median nerve at the wrist (affecting thumb, index, middle, and half of the ring)
  34. E – Genital warts don’t hurt and they turn white with vinegar (acetic acid). No systemic therapy works (although there is now a vaccine), but cryotherapy (as well as laser and electrocautery) can help. HPV will remain however, and the lesions can recur.
  35. C – Remember cystic fibrosis in young people with worsening obstructive lung disease and frequent infections. The infertility in males is secondary to failure of the vas deferens to develop properly (in women, it’s due to thick cervical mucus). Sweat chloride test makes the diagnosis.
  36. D – Fever, AMS, and muscle rigidity in a patient on antipsychotics (aka ‘neuroleptics’) means neuroleptic malignant syndrome (NMS). Very rare, very dangerous.
  37. B – IBS is a “functional” G.I. problem, which means that it is a diagnosis of exclusion (must rule out IBD, Celiac, etc). You may have enjoyed its recent popular appearance on television as a disturbing anthropomorphized walking bowel. Common symptoms include diarrhea, constipation, pain relieved by defecation, and flatulence, often subject to a degree of emotional valence. As such, like headaches, IBS symptoms can be improved by TCA therapy, such as nortriptyline.
  38. D – They hit you over the head with hypocalcemia symptoms before giving the value. Hidden in there is the pancreatic insufficiency causing steatorrhea and fat-soluble vitamin deficiency (A, D, E, and K).
  39. B – The patient has rhabdomyolysis from a prolonged visit with the floor. The ridiculously high CK confirms the diagnosis. Rhabo causes renal failure and requires aggressive fluid resuscitation.
  40. B – Type II error is the possibility of producing a false negative (a negative result when it should be positive). A smaller sample size may not be able to detect a small (but real) treatment effect and thus increases the chance of type II error.

Corrections, clarifications, copy/paste errors etc can be made/asked/mocked in the comments below.


S.G. 07.10.16 Reply

CK in 2 weeks. Thank you for this!

Daniil 07.16.16 Reply

Awesome to be able to go over explanations for these Qs. Thank you so much.

alex 07.20.16 Reply

thanks, much appreciated!

NG 07.26.16 Reply

Thank you so much! This really helped. My test soon. You’re a life saver!

thankful 09.01.16 Reply

thank you so, so much for doing this. it helped me a bunch on step 1 and it’s helping on step 2. so nice of you!!

Gertie 03.31.17 Reply

Kudos to you! I hadn’t thuohgt of that!

Ben 09.01.16 Reply

You’re welcome everyone. Good luck!

Aisha 11.15.16 Reply

My question sequence was completely different :(. got pretty confusing but thank you for this

Aisha 11.15.16 Reply

also some answers were missing. so maybe they updated it again.

Ben 11.15.16

I’m guessing you used the new fangled web-based FRED software. My numbers/order are based on the PDF I linked to (which has a different order and also does not include the multimedia questions).

val 07.11.17 Reply


nagisafurukawa 11.26.16 Reply

Again, your answer explanations are wonderful and even has comedic value, and have contributed greatly towards my prep for both Step 1 and Step 2 CK. Keep up the amazing work!

ash 02.17.17 Reply

this is great!! u should be a teacher. you hammer the concept right into the head.. good work!!

bre 04.24.17 Reply

would you be willing to comment on the few multimedia questions in the newest version on their website? one is about a 27 yo woman with shortness of breath with moderate exertion and a non-productive cough. another is a 14 year old boy who is trying out for basketball.

thank you so much for your help!

Ben 04.27.17 Reply

Do you remember which questions they are in the online version?

rebecca 05.28.17

18 on block 2

Lauren 05.28.17 Reply

Both are in Block 2: the 14 y.o. basketball boy question is #18, and the 27 y.o. SOB woman is #33. Thank you!

Mohammed 05.29.17 Reply

I think the 14 y.o boy one was just simply a normal physical exam, the heart sounds on the media players always get me too but I did not hear any specific HOCM murmur at the left sternal border on re-listening(I got it wrong too). I don’t like we would be looking for anything else at 14 y/o or else we would have had some history. Long QT syndrome is another that might prohibit sports but that can be seen on EKG.

Ben 05.30.17 Reply

As with most of these types of questions, you don’t really need the multimedia component to arrive at the correct answer.

18. A – I’m going to point out that a normal healthy kid with no cardiac history or symptoms and no family history of sudden cardiac death for a pre-sports physical is probably going to have a benign exam no matter what you think you hear. HOCM is what you want to exclude theoretically, but here we don’t have a real systolic murmur, just a little vibratory flow murmur at LLSB.

33. E – This one is a bit silly. The lung exam is normal outside of the super common basilar crackles. Everything except for PE you would expect to hear a more impressive auscultation abnormality. But for this question: B and C take longer than 3 days. D we would expect fever, productive cough etc. Bronchitis would be possible, but still more often to have at least productive cough if not fever. But PE classically has a nonproductive cough, hypoxemia, and tachycardia. All three are present. And then they mention her med: OCPs, which are an important predisposing factor for PE in young women for whom it is otherwise a rare entity.

Lauren 06.04.17 Reply

Thanks so much, Ben! :-)

Mamta 06.04.17 Reply

Haha thanks ! valuable and entertaining. Very curious about this recent anthropomorphized walking bowel you refer to ?

Ben 06.04.17 Reply

Enjoy. You can’t unsee it:


JL 06.09.17 Reply

Hi Ben,
Thank you so much for writing this blog! Are you planning to post a blog for the 2017 STEP 2CK Sample question explanation any time soon?

Ben 06.09.17 Reply

Ah, hadn’t noticed they were out yet. Yeah, I’ll try to squeeze it in.

JL 06.10.17

Thank you so much, Ben!

JL 06.13.17 Reply

Q43: I’m curious to know why C. metabolic acidosis is not correct? I thought metabolic acidosis (low HCO3-) can induce hyperkalemia.

Ben 06.13.17 Reply

1) It’s never about the other answers not being correct in some way. It’s about what is the best answer.
2) Yes, acidosis can cause a shift of K into the extracellular fluid resulting in hyperkalemia. This is usually mild, and in this case the degree of acidosis would be highly unlikely to cause massive hyperkalemia into the 7+ range.

JL 06.14.17

Ben: Thank you so much for answering my question! So out of all the answer choices, only drugs side effect can cause such a drastic increase in K+? I know this may be out of scope for this question. But I’m curious to know if there are any other causes (besides the drug side effect) that may result in significant hyperkalemia?

Ben 06.14.17

There are tons of causes, of which renal failure is one of the most clinically pertinent. The uptodate or medscape articles discuss the many etiologies, for example, as I imagine your physio book does as well.

JL 06.16.17 Reply

Q118: It makes sense based on your explanation why choice D is the answer. But I’m curious why choice A – HYPOmagnesemia is wrong? This pt is an alcoholic and his steatorrhea symptoms make him prone to magnesium depletion. According to STEP 2CK secrete, magnesium depletion also cause hypocalcemia.

Ben 06.19.17 Reply

Never forget that step questions aren’t one factually correct answer and several incorrect answers. It’s single best answer.

Hypomagnesia doesn’t need to be incorrect for it not to be the best answer. The history and timecourse are great for vitamin D deficiency, and there are no additional signs of hypomagnesemia or mention of it in the lab values.

FC 07.18.18

I initially went with VitD deficiency since you lose ADEK with diarrhea, but then I second guessed myself; the line right after that says h/o drinking 8-10 beers daily and hypoMg is classically associated with alcoholics. That along with the cahexia and chronically ill made me further think they were trying to hint at a malnourished alcoholic.

I was wondering what your thoughts were on this. Was there anything that would actively suggest otherwise?

Ben 07.18.18

The patient is chronically ill with chronic steatorrhea related to pancreatic insufficiency/chronic pancreatitis 2/2 alcohol. Vitamin D deficiency is super common, and the history is hitting you hard for ADEK malabsorption. Hypomag is certainly a possibility, but it’s more commonly seen in a more acute setting (hospitalized patients, less common over 6 months) and often has additional sxs (palpitations, tremors, etc). Vitamin D explains the situation without asking you to infer more that isn’t provided.

George 06.23.17 Reply

For Q.78, I was thinking about thromboangiitis obliterans(Buerger’s disease), given that he has claudication and smoking history. What makes answer “D.Vasculitis” wrong?

Ben 06.24.17 Reply

One, regular PAD is way more common. Two, Buerger’s usually affects younger people (say, <45). Three, BD also usually involves multiple extremities, including the uppers, and often has skin findings, ulcers, gangrene, etc.

Is it definitely wrong? Of course not. But is it the single best answer? No.

Mauricio 06.25.17 Reply

That was amazing, wish most qbanks had such fun and straight to the point explanations! I have my test on 2 days! I could answer 120 of the 140 questions, so thats kind of a relief. Thanks!!

Aaqib 07.09.17 Reply

Thank you so much…But dont you think these practice qns seemed a LOT easier than u world or anything else?..These are so direct and straightforward tell the answer. How is the real exam compared to this ? why doesnt the official usmle site keep tough qns like they ask in exam so that we learn better..this is what i dont like

Ben 07.12.17 Reply

UW is harder than the real thing. This is closer to the exam style, though the exam will have some more questions out of left field. My feeling is that if you can get most of these right, you’re in good shape. You don’t need to know all the crazy stuff for a normal solid score.

Mohammad 08.02.17 Reply

Great Great Great, you strategy for answering is impressing, but the question of the breathing sound, I heard harsh breathing and crackles in the lung bases mainly, so I picked Hypersensitivity pneumonitis, also I thought that Dyspnea and chest pain together are very important features of PE, so I’m still confused regarding this question

Ben 08.02.17 Reply

Chest pain is variable. There is nothing else in the history to suggest HSP, and lung auscultation findings would never lead you to that dx in real life. This is why I believe the multimedia stuff isn’t usually important; you’re overthinking it. The history alone tells the tale.

Danielle 08.23.17 Reply

Thank you so much for taking the time to write these explanations. I take Step 2 CK in just two days and would be lost on some of the questions without this.

Jarrett Lever 02.06.18 Reply

Is there any conversion list between the online Fred question list and the the PDF question list (i.e. this FRED # = this PDF#)? This would help a lot for those of us who did the FRED first.

Jarrett 02.06.18 Reply

Yes! Since I couldn’t find one anywhere, I made a conversion list in an Excel file and here is a link to the page. Hopefully this helps all those students who do the FRED first and then realize that Dr. White’s great explanation resource/blog exists. Here is a link to it on my Google Drive:

Ben 02.07.18 Reply

That’s awesome!

awe 02.12.18 Reply

74 answer is A, explanation is correct, but that is one of the answer choices — decreases myocardial contractility

Ben 02.13.18 Reply

I’m confused. The answer is B, as described.

Z 05.20.18

I am confused as well – how do Beta Blockers dilate coronary arteries (answer B) as their primary mechanism? I thought their primary mechanism was to decrease contractility (answer A)?

Ben 05.20.18

Seems like you’ve both misread the answer choice order or are reading a different version where the order is swapped? In the PDF version linked to for these explanations, the correct answer is B, which is “decreasing myocardial contractility.” Whichever letter is showing up, the correct answer is decreasing contractility.

guy 05.22.18

Hi ben, the answer on the online version is wrong. It is selecting B as the correct answer.

B. F. 05.08.18 Reply

I had a question about #26 on the PDF sheet. It seems as though they are just glossing over the right to left blood pressure discrepancy with steal. Is that just a distraction?

Ben 05.08.18 Reply

Pretty much. Steal is demand-dependent, but she’s got sinus brady with positive orthostatics, so that’s her primary issue.

Bonnie 07.10.18 Reply

Dirty question, in my opinion. Getting us young, eager medical students all hot and concerned about subclavian steal. :(

Ben 07.17.18

It all boils down to the real concept behind “single best answer.” The other answers don’t have to be uninteresting or even wrong to not be the best :)

Nikhitha Chandrashekar 08.07.18 Reply

This was so incredibly helpful Ben White! I was so dreading the enormous time waste of googling and searching on forums for these answers. God bless you for updating it every year with each new set of questions, had to just split my screen and finished the answers in a jiffy.

If you could make an answer key like this for the NBMEs there would be nothing like it !

ronnell 08.28.18 Reply

hey, does the score you get on these practice questions have any correlation/predictive value to the exam? even loosely?

Ben 08.29.18 Reply

I’m confident it does, but I don’t think anyone has acquired data to do a conversion for Step 2 CK like there’s been for the Step 1 free questions (e.g. here). It’s possible the conversion is similar, so feel free to check out that link.

Ali Doruk Yalçıntepe 11.09.18 Reply

A very big service for the community, thank you for that.
But some explanations doesn’t contain sufficient amount of details:
83. A – This patient has urge incontinence, which is commonly caused by detrusor instability (and can be treated with anticholinergics like oxybutynin). This is opposed to stress incontinence, the other most common type, which is worsened by abdominal pressure/coughing/laughing/etc and can be caused by pelvic floor prolapse secondary to multiple childbirths etc. Neurogenic bladder can cause overflow incontinence.

Ok. NBME answer tells you that this person has detrussor instability, then it’s not hard not to know that it causes urge incontinence.
Question clearly specifies that our patient doesn’t have stress incontinence.
But why urge is a better option? why not neurogenic bladder? (not uti as it cannot last for 20 years)
Only symptom: she has incontinence while shopping. How it is related to one over another?

Ben 11.09.18 Reply

You’ve read the question incorrectly. It’s not incontinence only while shopping. She has incontinence while doing normal activities like shopping (as opposed to specifically with activities of increased abdominal pressure like laughing).

There is no history provided to suggest neurogenic bladder. This usually manifests in the reduced feeling of bladder fullness with incomplete emptying or inability to void and often frequent UTIs. She has no history of injury, stroke, diabetes, or neurological disorder, no history of frequent UTIs or incomplete voiding, no mention of self-cathing, no dribbling of overflow incontinence, etc etc etc.

On the flip side, urge incontinence is extremely common, especially in the elderly.

Soniya 07.14.19 Reply

Thank you

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