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USMLE Step 2 CK High-Yield Renal Topics
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Renal
High Yield USMLE Step 2 CK Notes
Welcome to the Renal High-Yield Notes for Step 2 CK.
These are the most commonly tested topics on the exam—ideal for quick review in your last 2 weeks before the exam, when you’re short on time, or when you’re just starting out and want to focus on what is high yield. Created and peer-reviewed by physicians who scored 260+ on Step 2 CK in a Q&A style to reinforce active learning.
How to use this file
- Read the question ➔ cover the answer ➔ self-quiz before revealing.
- Review the NOTES ➔ they include high-yield details you don’t want to miss.
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- Don’t forget to watch the video lessons that go with this file. Learn more here.
Table of Contents
Acute kidney injury
1. A 30-year-old man is found confused. Labs show a creatinine of 2.1 mg/dL, bicarbonate 13 mEq/L, and a high anion gap metabolic acidosis. Urinalysis reveals envelope-shaped crystals. What is the most likely cause?
➔ Ethylene glycol poisoning
- Note: All forms of alcohol toxicity → confusion, CNS depression, and high anion gap metabolic acidosis. Use the features below to differentiate between them.
- Alcohol toxicity:
| Substance | Typical Source | Key Clinical Features |
|---|---|---|
| Ethanol | Beer, wine, liquor | CNS depression, confusion |
| Methanol | Windshield washer fluid, homemade liquor | Vision loss, optic disc hyperemia |
| Ethylene glycol | Antifreeze | Calcium oxalate crystals in urine |
2. A 19-year-old woman with fever, rash, and malaise one week after taking TMP-SMX for a UTI. Urinalysis shows WBC casts, eosinophils, and mild proteinuria. What is the most likely diagnosis?
➔ Acute interstitial nephritis (AIN)
- Note: Classic causes of AIN: NSAIDs, diuretics, PPIs, rifampin, penicillins, sulfa drugs (TMP-SMX).
- Biopsy: Mononuclear cell infiltrate
- Symptoms: Fever, rash, pyuria (eosinophils + WBC casts), CVA tenderness.
- Management: Stop the causing medication, systemic glucocorticoid (if severe)
3. A 65-year-old man with a history of nocturia and weak urinary stream presents with rising serum creatinine. Digital rectal exam shows a smooth, enlarged prostate. What is the next best step?
➔ Renal ultrasound
- Note: Older men with lower urinary tract symptoms (LUTS) and elevated creatinine → postrenal obstruction from benign prostatic hyperplasia (BPH). Renal ultrasound is used to detect hydronephrosis.
- Note: In most cases, you can diagnose postrenal kidney injury based on the clinical scenario. To ensure the diagnosis, perform a pelvis ultrasound or catheterize the patient to assess the residual urine volume.
4. A 60-year-old woman develops acute kidney injury after surgery for multiple fractures. She had received fluids and blood products for hypotension. Her BUN/Cr ratio is 12. What is the most likely finding on urinalysis?
➔ Muddy brown granular casts
- Note: In a lot of questions, we have to differentiate between prerenal kidney injury from acute tubular necrosis (ATN). Remember, severe hypotension can cause both, so the clinical scenario doesn’t help.
- ATN: BUN/Cr ratio < 20, Urine Na > 20mEq/L, FENa > 2%, Muddy brown casts
- Prerenal AKI: BUN/Cr ratio > 20, Urine Na < 20mEq/L, FENa < 1%
- Phases of ATN:
Initiation ➔ Injury: Ischemia or toxins.
Maintenance ➔ Oliguria, ↑ Creatinine, ↑K, ↑P, Acidosis
Recovery ➔ ↑ diuresis, electrolyte wasting as K.
5. A 72-year-old man undergoes coronary angiography. His baseline creatinine is 1.5 mg/dL but rises to 2.8, two days after the procedure. What intervention before the procedure could best reduce the risk of acute kidney injury?
➔ Administering intravenous 0.9% saline
- Note: Contrast-induced acute kidney injury (CI-AKI):
- Risk factors: High contrast load, history of CKD, use of nephrotoxic drugs
- Prevention: IV saline. Avoidance of nephrotoxic medications (NSAIDs). Minimize Contrast.
- Pathophysiology: Prerenal azotemia + acute tubular necrosis
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6. A 22-year-old man with viral encephalitis is treated with IV acyclovir. Two days later, creatinine rises from 1 to 2.5 mg/dL. What is the likely cause of the kidney injury?
➔ Crystal-induced tubular obstruction
- Note: Crystal-induced AKI:
- Common causes: Acyclovir, Ethylene glycol, Uric acid (tumor lysis syndrome), contrast
- Management: Discontinue drug, IV fluids, Loop diuretic
7. A 42-year-old man with a history of binge drinking and cocaine use presents with leg swelling, weakness, and dark urine. CK is 2,000 U/L. What is the most likely cause?
➔ Rhabdomyolysis
- Note: Rhabdomyolysis: Crush injury, seizure, statin, heroin
- A common scenario: an IV drug user or alcohol abuser, found unresponsive by relatives.
- ↑ creatinine + ↑K, ↑P, ↓Ca + myoglobinuria (In urine: blood +, RBC −), serum CK > 1,000.
- Management: Aggressive IV Fluid, treat electrolyte abnormalities
8. A 72-year-old man presents with fatigue and weight loss. Exam shows an S4 heart sound. Labs show elevated creatinine, and ultrasound reveals small kidneys. What is the most likely cause?
➔ Hypertensive nephrosclerosis
- Note: In cases of high creatinine, ask yourself: Is this acute or chronic? In most cases, the clinical scenario is enough for differentiation. But if the clinical scenario didn’t help, perform an abdominal ultrasound. If the kidneys are small and atrophic, it is a chronic kidney disease.
- S4 heart sound → Diastolic dysfunction → Seen in cardiac hypertrophy → Seen in chronic uncontrolled hypertension.
- Uncontrolled hypertension can result in hypertensive nephrosclerosis, which is a clinical diagnosis, and renal biopsy is unnecessary.
9. A 68-year-old woman on dialysis for 15 years presents with shoulder pain and hand tingling. Exam shows enlarged shoulders and thenar atrophy. What is the most likely diagnosis?
➔ Dialysis-related amyloidosis (DRA)
- Note: ESRD patient on dialysis → ↓clearance of β2-Microglobulin → Amyloidosis
- Clinical Scenario: ESRD patient + Carpal tunnel syndrome +/- Shoulder pain.
10. A 66-year-old man is hospitalized with acute diarrhea and diagnosed with Clostridium difficile infection. He has been started on antibiotics. Two days later, labs show rising creatinine. What is the best next step?
➔ Bolus of isotonic saline
- Note: Prerenal acute kidney injury
- Features: Urine output < 0.5 cc/kg/hour. BUN/Cr > 20. FeNa < 1%
- Causes: Volume Depletion, ↓ effective arterial volume (heart failure, Cirrhosis), Sepsis, NSAIDS, ACEi in bilateral renal artery stenosis.
- Treatment: restore renal perfusion. In this case (volume depletion), bolus of IV isotonic saline.
11. A 71-year-old man undergoes hernia repair surgery. Over the first 12 hours, his urine output is <100 mL despite adequate IV fluids. Vitals are stable, and lung sounds are clear. What’s the next step for diagnosis?
➔ Pelvic ultrasound (or urinary catheter to assess postvoid residual volume)
- Note: Postoperative urinary retention (POUR):
- Oliguria after surgery, due to anesthesia-related inhibition of bladder contractility and outlet resistance. Sometimes, it is mentioned that the bladder is distended and palpable. POUR can be a cause of postoperative agitation and delirium in some elderly.
- Risk factors: Benign prostatic hyperplasia, pelvic surgery, spinal anesthesia, male gender, opioid use.
- Management: First, we should make sure hydration is adequate, and this is not a case of prerenal AKI. Then, to assess the postvoid residual volume, we perform bedside pelvic ultrasound or urinary catheterization. In severe cases, a catheter is preferred because it can also relieve the obstruction.
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Electrolyte and Acid-Base
12. A 70-year-old man presents with confusion, nausea, and abdominal pain. His calcium level is 14.1 mg/dL. What is the most appropriate initial treatment?
➔ Normal saline infusion
- Note: Signs of Hypercalcemia: Weakness, GI Distress, confusion, stupor.
- Management of hypercalcemia (if Ca > 14 or symptomatic):
1: Normal Saline infusion
2: Loop diuretic
3: Bisphosphonate (for long-term use)
4: Treat the underlying condition
13. An old man with a history of heavy smoking presents with weakness, hypercalcemia (Ca²⁺ 14 mg/dL), and 2 months history of cough. What can we see in the lab results?
➔ ↓ PTH, ↑PTHrP, ↓Phosphate (squamous cell carcinoma of lung)
- Note: In most cases of hypercalcemia, you’ll be able to diagnose based on the history:
Chronic cough ➔ lung problems (sarcoidosis or Squamous carcinoma of lung). Heavy smoking➔ Squamous carcinoma of lung producing PTHrP . - PTHrP has all the effects of PTH (↑calcium, ↓phosphate), while in a negative response, PTH ↓.
14. An old man with CKD. His serum calcium is high and PTH level is high. What’s the diagnosis?
➔ Tertiary hyperparathyroidism
- Note: Tertiary hyperparathyroidism: long standing secondary hyperparathyroidism ➔ autonomous parathyroid gland hyperplasia ➔ persistent PTH elevation even after correction of phosphate and calcium levels.
- Result: Very high PTH with hypercalcemia and hyperphosphatemia.
| Feature | Secondary HPT | Tertiary HPT |
|---|---|---|
| Cause | Response to CKD-induced hypocalcemia | Autonomous PTH secretion after prolonged stimulation |
| PTH | Increased | Greatly increased |
| Calcium | Low or normal | High |
| Phosphate | High | High |
15. An old man with back pain, Cr: 3, and Hb: 9. The calcium level is 12. What’s the mechanism of hypercalcemia?
➔ Calcium release from bone
- Note: Hypercalcemia of Malignancy:
- Bone Metastases: Seen in a lot of cancers. Remember multiple myeloma as a high yield cause. Associated with bone pain, fractures, and lytic bone lesions. Lab findings: ↓ PTH, ↓ PTHrP, ↓ Vitamin D
- PTHrP Secretion: Squamous cell lung carcinoma and renal cell carcinoma commonly secretes PTHrP, mimicking PTH and causing hypercalcemia. Lab findings: ↓ PTH, ↑ PTHrP
- Overactivation of Vit D: Seen in lymphoma (also in sarcoidosis). Vitamin D activation ➔ ↑ intestinal calcium absorption. Lab findings: ↓ PTH, ↑ 1,25 (OH)2 Vit D, normal 25OH Vit D
16. A 29-year-old woman is hospitalized after pelvic trauma. Following blood transfusions, she develops perioral numbness and hand cramping. What is the most likely cause?
➔ Hypocalcemia
- Note: Hypocalcemia:
- Common Causes: Parathyroidectomy, severe pancreatitis, tumor lysis syndrome, Chelation (through massive blood transfusion)
- Clinical Features: Muscle cramps, Chvostek sign, trousseau sign, seizure, hyperreflexia.
- Treatment: IV Calcium if symptomatic, oral calcium if asymptomatic.
17. A woman receiving carbamazepine is brought in for altered mental status. She is euvolemic, has a sodium of 119 mEq/L, low serum osmolality, high urine osmolality, and high urine sodium concentration. What is the most likely cause of her hyponatremia?
➔ Syndrome of inappropriate antidiuretic hormone (SIADH)
- Note: Syndrome of inappropriate anti-diuretic hormone (SIADH) causes hyponatremia with low serum osmolality and concentrated urine with high osmolality and sodium. Clinical signs include confusion, nausea, and euvolemia (no edema or JVD).
- It can result from CNS disease, such as hemorrhage or tumors, drugs (carbamazepine, SSRIs), lung infection, or cancer (small-cell lung carcinoma).
- Tip: Any form of CNS or Lung pathology + hyponatremia ➔ think of SIADH
- Note: When the plasma sodium is low, the normal response from the kidneys is to create a dilute urine to get rid of excess water. In this case, the kidneys aren’t excreting the excess water, so something is preventing the normal response.
18. A patient presents with seizures and confusion. Labs show sodium of 148 mEq/L and urine osmolality of 78 mOsm/kg. Water deprivation testing shows minimal increase in urine osmolality, but a sharp rise occurs after desmopressin administration. What is the most likely diagnosis?
➔ Central diabetes insipidus (insufficient ADH production)
- Note: Diagnosing a patient with polyuria and polydipsia:
1- Check Urine osmolality: it should be low because the patient produces a lot of urine with a small amount of electrolyte (normal response from the kidney).
2- Water deprivation: if water deprivation increases the urine osmolality → Primary polydipsia → Treat with water deprivation. No need for next steps
3- Administer Vasopressin: If vasopressin increases the urine osmolality → Central DI (↓ ADH production) → Treat with Vasopressin (synthetic ADH).
4- If nothing works: Nephrogenic DI (important risk factor: lithium use) → Treat with Thiazide diuretics
19. A man with end-stage renal disease misses dialysis for 3 days and presents with weakness. ECG shows bradycardia with widened QRS and absent P waves. What is the next best step?
➔ IV calcium gluconate
- Note: ECG findings in hyperkalemia: Peaked T wave, Prolonged QRS, Sine wave
Treatment of Hyperkalemia:
1- Prevent arrhythmia by stabilizing the myocytes ➔ IV Calcium (doesn’t affect the level of K)
2- Shift K into cell: - Insulin
- Beta-adrenergic (albuterol)
- Treat underlying acidosis
3- Excrete K: - Into Urine: Diuretic (most commonly loop-diuretics)
- Into the intestine: Kayexalate, Patiromer
- Hemodialysis
20. A 55-year-old man with COPD presents with an acute exacerbation and is treated with nebulized albuterol and corticosteroids. The next day, labs show potassium of 2.8 mEq/L. What explains this finding?
➔ High dose Albuterol
- Note: Common scenarios of hypokalemia:
A hospitalized asthma patient, after taking a lot of albuterol ➔ Intracellular shift
A patient with severe diarrhea ➔ Gastrointestinal loss
A new-onset hypertension with hypokalemia ➔ Think of hyperaldosteronism (RAAS activation)
A Diabetic ketoacidosis patient, receiving insulin ➔ Intracellular shift - Common scenarios for hyperkalemia:
Patient with chronic kidney disease
Patient after chemotherapy (Tumor lysis syndrome: hyperkalemia, hypocalcemia, hyperphosphatemia, hyperuricemia)
Rhabdomyolysis
21. A man with fever and productive cough is found to have pH 7.49, PaCO₂ 30 mm Hg, and HCO₃⁻ 24 mEq/L. What is the acid-base disorder?
➔ Uncompensated respiratory alkalosis
- Note: Interpretation of arterial blood gas:
- This patient has an alkalosis, and the PaCO2 is low. ➔ Respiratory alkalosis.
- In respiratory alkalosis, we expect a decrease in HCO₃⁻ to compensate for the PH change. But here, the HCO₃⁻ is normal. ➔ There’s an uncompensated respiratory alkalosis.
- Commonly asked with pregnancy, post-operative atelectasis, and pulmonary emboli
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22. A 16-year-old girl is brought to the ED after ingesting a large number of aspirin tablets. She is alert but complains of ringing in her ears and nausea. What is the expected acid-base disturbance?
➔ Mixed respiratory alkalosis and anion gap metabolic acidosis
- Note: Salicylate poisoning is a very high-yield mixed acid-base disorder: direct stimulation of respiratory centers leads to respiratory alkalosis, and increased salicylic acid accumulation leads to anion-gap metabolic acidosis. A keyword for salicylate poisoning is ringing in the ear.
- In case of an arrow question: ↓HCO₃⁻, ↓PaCO2, and pH will remain normal. To check whether respiratory compensation is appropriate, use this formula:
Expected PaCO₂ = (1.5 × HCO₃⁻) + 8 ± 2 - In aspirin poisoning, the PaCO2 is going to be lower than expected ➔ There’s also an underlying respiratory alkalosis.
23. An elderly woman with a small bowel obstruction has persistent NG suction. Labs show hypokalemia, hypochloremia, and elevated bicarbonate. What is the best initial treatment?
➔ Normal saline infusion
- Note: Gastric loss (from severe vomiting or NG suctioning) leads to volume depletion, activation of RAAS, and loss of H⁺, K⁺, and Cl⁻. This causes hypokalemic, hypochloremic metabolic alkalosis.
- Management: Chloride repletion with saline and addressing the underlying cause.
- Remember: Urine chloride is <20 mEq/L in these patients (normal kidney response to hypochloremia).
24. A 64-year-old man with Sjögren syndrome presents for follow-up. Labs show pH: 7.33, bicarbonate: 15, serum sodium: 140, and chloride: 115. What is the most likely diagnosis?
➔ Renal tubular acidosis
- Note: 1. Check arterial PH. Normal 7.35 – 7.45:
○ ↑ PH → Alkalosis
○ ↓ PH → Acidosis - 2. Determine Primary Disorder:
○ If HCO₃⁻ changes in the same direction as PH: Metabolic
○ If HCO₃⁻ changes in the opposite direction as PH: Respiratory
This patient has metabolic acidosis. In case of compensated metabolic acidosis, check the anion gap (anion gap = serum Na+ – [serum Cl– + serum HCO3–]). If it is >12, it means there’s “unmeasured acid” in the serum. But if it’s normal (<12), it means that the cause of metabolic acidosis is loss of bicarbonate.
○ ↑ Anion Gap (>12 mEq/L):
§ Toxic Alcohols (ethylene glycol, propylene glycol, Methanol)
§ Oxoproline (chronic acetaminophen use)
§ L-lactate (lactic acidosis) commonly tested
§ Aspirin (late effect) Also results in respiratory alkalosis.
§ Renal failure
§ Ketones (diabetic, alcoholic, starvation) commonly tested
○ Normal Anion Gap (8–12 mEq/L):
§ Spironolactone
§ Hyperchloremia/hyperalimentation
§ Addison’s disease, acetazolamide use
§ Renal tubular acidosis
§ Diarrhea
§ Saline infusion
- Note: Sjogren is a common cause of RTA. For USMLE Step 2, they don’t focus on different types of RTA.
Glomerulonephritis
25. A 24-year-old man develops dark-colored urine a few days after an upper respiratory infection. Urinalysis shows RBC casts and proteinuria. What is the most likely diagnosis?
➔ IgA nephropathy
- Note: You have to differentiate between IgA nephropathy and Post-Streptococcal GN:
- IgA Nephropathy (Berger Disease): Less than 1 week after Upper resp / GI infection. Often in adults. Normal C3 & C4
- Post-streptococcal GN: More than 2 weeks after tonsillitis or skin infection. ↓Complement levels. Anti-ASO +.
26. A woman with a persistent facial rash develops edema and proteinuria. Labs reveal elevated creatinine and low complement. What is the most likely renal complication?
➔ Lupus nephritis
- Note: First, we want to check the serum complement level for this kind of question. Then look for clues from the table below:
| Serum Complement | Example | Clue |
|---|---|---|
| Low | Lupus nephritis | Signs of SLE, ANA, anti-dsDNA |
| MPGN | cryoglobulins, HCV | |
| Infection-related GN | PSGN: ASO- Staph GN: culture- Endocarditis: culture | |
| Normal | Goodpasture disease (anti-GBM Ab) | |
| Pauci-immune GN | ANCA |
27. A 55-year-old man with newly diagnosed type 2 diabetes has a normal creatinine level. What is the best test to screen for early nephropathy?
➔ Urine albumin/creatinine ratio
- Note: It takes 15-20 years for diabetic nephropathy to show an increase in creatinine. However, we can detect it earlier by using the urine albumin/creatinine ratio.
Prevention: Glycemic control, ACE inhibitor/ARB, SGLT-2 inhibitor. - Note: Diabetic nephropathy and diabetic retinopathy are both forms of microvascular complications of diabetes mellitus and are closely associated with poor glycemic control. So, if a patient is diagnosed with one, we should screen for the other.
- Microscopy in Diabetic Nephropathy: GBM thickening, Kimmelstiel-Wilson nodules, mesangial expansion.
28. A 25-year-old man with hemoptysis and worsening dyspnea a few weeks after a flu-like illness. Urinalysis: hematuria and proteinuria. Chest CT: bilateral alveolar infiltrates. What’s the diagnosis?
➔ Goodpasture syndrome (anti-GBM disease)
- Note: Goodpasture syndrome involves autoantibodies against type IV collagen found in the glomerular and alveolar basement membranes.
- It causes rapidly progressive glomerulonephritis and pulmonary hemorrhage. Immunofluorescence shows linear IgG and C3 deposition along the glomerular basement membrane (GBM). Crescent formation.
- Note: Hemoptysis + Glomerulonephritis = Goodpasture
29. A 25-year-old woman with a history of systemic lupus erythematosus (SLE) presents with weight gain, facial puffiness, and proteinuria. Kidney biopsy shows thickening of glomerular capillary walls with subepithelial spikes. What is the most likely diagnosis?
➔ Membranous nephropathy
- Note: Membranous Nephropathy: Thickened capillary walls, subepithelial “spike and dome,” associated with solid tumors, HBV, HCV, and SLE.
- Biopsy shows diffuse capillary wall thickening and “spike and dome” appearance due to subepithelial immune deposits.
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30. A 27-year-old woman with dysuria, urinary frequency, and suprapubic pain for the past 3 days. She is afebrile. Urinalysis shows positive leukocyte esterase and nitrites. What is the best initial treatment?
➔ Oral nitrofurantoin or TMP-SMX
- Note: Acute cystitis is an infection of the urinary bladder, typically presenting with dysuria, suprapubic pain, urinary frequency, and urgency, but without systemic symptoms like fever or chills.
- Risk factors include female sex (short urethra), sexual activity, indwelling catheters, diabetes mellitus, and impaired bladder emptying.
- For prevention of acute cystitis:
○ In case of urinary catheter: 1) don’t use it if unnecessary; 2) take it out as soon as possible; 3) for long term use, use intermittent catheterization instead; 4) if you have to use a foley catheter for long term, change it every two weeks; 5) never give antibiotic for UTI prevention
In case of a sexually active woman with recurrent cystitis: 1) ask them to urinate after intercourse; 2) give postcoital nitrofurantoin or TMP-SMX; 3) if doesn’t get better, give daily nitrofurantoin or TMP-SMX
○ In case of a recurrent UTI without any known risk factor: Think of Diabetes Mellitus - Common pathogens:
○ Escherichia coli (most common), Staphylococcus saprophyticus (especially in sexually active women), Klebsiella, Proteus mirabilis (urine may smell like ammonia). - Urinalysis: Positive leukocyte esterase (WBCs) and nitrites (Enterobacteriaceae).
- Treatment: Empirical antibiotics such as trimethoprim-sulfamethoxazole (TMP-SMX) or nitrofurantoin.
31. An old diabetic woman has fever, chills, flank pain, and nausea. On examination, she has costovertebral angle tenderness. Urinalysis shows white blood cell casts, pyuria, and bacteriuria. What is the most likely diagnosis?
➔ Acute pyelonephritis
- Note: Acute pyelonephritis is an infection of the renal parenchyma, characterized by neutrophilic infiltration of the interstitium and cortex.
- Risk factors: Urinary tract obstruction, Indwelling catheter, Diabetes mellitus, and Pregnancy (progesterone-mediated ureteral tone reduction).
- Urinalysis: Pyuria (WBCs in urine), white blood cell casts.
- Treatment: IV antibiotics (ceftriaxone or fluoroquinolones for most empiric treatments)
- Note: in case of no initial treatment, think of abscess (ultrasound or CT for diagnosis) or emphysematous pyelonephritis (gas in kidney, diagnosis with imaging, mainly in diabetic patients).
32. A menopause woman with urgency and incontinence episodes. Has to rush to the bathroom, but has incontinence on the way to the bathroom. What pharmacologic action is the best treatment?
➔ Oxybutynin
- Urge incontinence: Due to detrusor muscle overactivity (Upper motor neuron sign); presents as sudden strong urge to urinate.
○ Treated with antimuscarinic drugs (e.g., oxybutynin) to block M3 receptors or by stimulating beta-3 adrenergic receptors (eg, mirabegron). - Note: in all urinary incontinence cases, first rule out reversible causes of incontinence like: delirium, UTI, atrophic vaginitis, polyuria (diabetes), constipation, and … .
33. A 45-year-old man with a history of poorly controlled type 1 diabetes reports frequent episodes of involuntary urine leakage and difficulty starting urination. What would most likely be found on further evaluation?
➔ Increased postvoid residual volume
- Note: Overflow incontinence: Due to impaired bladder emptying, causes constant dribbling and feeling of incomplete voiding.
- Common risk factors: long-standing Diabetes and Benign prostatic hyperplasia
○ Treat with intermittent catheterization.
34. A 50-year-old woman with a urinary leakage while coughing or laughing. What is the most likely underlying cause of her condition?
➔ Urethral sphincter dysfunction (or pelvic floor muscle weakness)
- Stress incontinence: Due to weak sphincter or hypermobile urethra (due to weak Levator ani muscle complex). Triggered by increased intra-abdominal pressure (eg, coughing).
- Risk factor: vaginal delivery and post menopausal state.
Treat with Kegel exercises or a sling supporting the pelvic floor.
35. A 53-year-old man presents with bilateral flank discomfort and a history of nocturia. Exam reveals a palpable abdominal mass and hepatomegaly. Labs show elevated creatinine and BUN. What is the most likely diagnosis?
➔ Autosomal dominant polycystic kidney disease (ADPKD)
- Note: ADPKD is due to mutations in PKD1 or PKD2 and manifests with renal cysts, hypertension, and hematuria. Patients often remain asymptomatic until adulthood, when cyst growth causes renal impairment.
- A common USMLE tip: HTN+ bilateral flank masses.
- Extra-renal features include liver cysts and cerebral aneurysms.
- ACE inhibitors decrease the speed of progression.
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36. An elderly patient with sudden shortness of breath, high blood pressure, crackles in both lungs, and elevated creatinine. She feels better after diuretics. What’s the next best test?
➔ Renal duplex ultrasound.
- Note: Renal artery stenosis ➔ secondary hypertension. It’s diagnosed with renal duplex ultrasound or MR angiography to assess the degree of narrowing.
- Results in activation of RAAS ➔ Hypokalemia + ↑ Creatinine + Hypertension
- Patient > 40 or has HTN/DM ➔ think of atherosclerosis. If <40 ➔ think of fibromuscular dysplasia.
- Another scenario:
○ 1. ↑ Creatinine after starting ACEi/ARBs
○ 2. HTN + abdominal bruit. - Note: In severe renal artery stenosis → Treat with angioplasty (put stents in renal arteries). But in milder forms → Treat with ACEi/ARB (Check potassium and Creatinine routinely because ACEi/ARB can cause hyperkalemia and AKI in these patients)
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37. A healthy young athlete has mild proteinuria in the afternoon. No other symptoms. What’s the next step?
➔ Check urine protein once before sleep and once after waking up
- Note: Orthostatic proteinuria: Higher urine protein is present when upright but at normal levels when lying down.
- Benign and doesn’t need further testing if there are no other symptoms. They might say foamy urine in the afternoon; it means proteinuria.
38. A 2-month-old boy has signs of UTI. Ultrasound shows a distended bladder. What’s the likely cause?
➔ Posterior urethral valves
- Note: A congenital bladder outlet obstruction. Only in male infants. Often spotted on prenatal ultrasound, showing bladder distension or hydronephrosis (bilateral).
- Severe obstruction can lead to oligohydramnios and the POTTER sequence.
In an infant, suspect if: UTI + bladder distention +/- hydronephrosis. - Another USMLE scenario: neonate who have not urinated yet+ lower abdominal mass.
39.A 6-month-old girl has signs of febrile UTI. An antibiotic is started. What’s the best next step?
➔ Renal and Bladder Ultrasound (RBUS)
- Note: First febrile UTI (<2 years): Do RBUS; add voiding cystourethrogram (VCUG) only if RBUS is abnormal.
- First febrile UTI (≥2 years): No imaging, observe.
- Recurrent febrile UTIs (all ages): Do both RBUS and VCUG.
- Note: Vesicoureteral reflux (VUR) allows retrograde flow of urine from the bladder into the ureters and kidneys, leading to recurrent pyelonephritis, renal scarring, and potentially secondary hypertension if untreated.
40. A young man with sudden, severe left-sided flank pain radiating to the groin. He has gross hematuria but no fever. Imaging reveals a small stone in the mid-ureter. What laboratory finding is most likely?
➔ Normocalcemia, hypercalciuria
- Note: Flank pain radiating to the groin w/o hematuria suggests kidney stones.
- Calcium stones (calcium oxalate/phosphate) are the most common kidney stones. Most patients have idiopathic hypercalciuria but normal serum calcium levels
- Envelope-shaped casts.
41. A patient with renal colic is found to have a calcium-oxalate stone. Which drug can lower the risk of stone formation?
➔ Hydrochlorothiazide (Thiazide diuretics lower the calcium in urine)
- Note: Risk factors for calcium stones:
- Hypercalciuria → Hyperparathyroidism, idiopathic Hypercalciuria
- Hyperoxaluria → fat malabsorption (crohn’s disease): calcium binds fat → ↑ free oxalate absorption in gut→ calcium-oxalate stones in the kidney
- Loop diuretics (↑ calcium in urine)
Preventive: - ↓ sodium, protein, and oxalate intake
- Thiazide diuretics (↓ calcium in urine)
- ↑Fluid intake reduces the risk of kidney stones regardless of stone type.
42. A 55-year-old woman with a history of recurrent urinary tract infections has fever, dysuria, and right flank pain. Imaging reveals a large staghorn calculus. What infection is most likely involved?
➔ Klebsiella infection
- Note: Causes of Staghorn calculi:
- Struvite (Ammonium magnesium phosphate) → radiopaque, coffin-lid shape.
Caused by urease + bacteria (Proteus and Klebsiella). Treatment: eradicate infection, surgery. - Cystine → faintly radiopaque, hexagonal shape. Defect in COLA transporter (cysteine, ornithine, lysine, and arginine).
Treatment: low-sodium diet, alkalinization, chelators.
43. A heavy smoker with painless hematuria. Urinalysis confirms blood, and urine cytology shows malignant cells. Cystoscopy reveals a bladder mass. What histologic finding is most associated with poor prognosis in this patient?
➔ Involvement of the muscularis propria
- Note: Diagnosis of bladder cancer:
Painless hematuria (especially in patients with risk factors) → U/A (confirm hematuria) → Urine cytology → Cystoscopy - Penetration into the muscularis propria (muscle layer) indicates a higher stage (T2 or greater) and is associated with a poor prognosis in bladder cancer.
- Risk factor: Smoking and cyclophosphamide.
44. A 59-year-old man presents with hematuria and left-sided varicocele that fails to decompress when lying down. Labs show erythrocytosis. What is the best initial diagnostic step?
➔ Abdominal CT scan
- Note: Renal cell carcinoma (RCC): flank pain, hematuria, and sometimes a palpable mass. A left-sided varicocele that does not decompress when supine suggests obstruction of the left renal vein. RCC is associated with paraneoplastic syndromes such as polycythemia and thrombocytosis. The best initial test is an abdominal CT scan.
45. A 54-year-old man undergoes a CT scan of the abdomen after mild self-limited abdominal pain. Imaging shows a thin-walled, homogenous, unilocular kidney lesion with no enhancement. What is the next best step?
➔ Reassurance only
- Note: Simple vs. complex cystic mass:
- Simple: Thin wall, no septa, homogenous, no contrast enhancement → No follow-up needed
- Complex: Thick, irregular wall. Multilocular, septa, heterogenous, contrast enhancement → Biopsy or follow-up imaging.
🏁 Final Thoughts
You made it to the end—well done! These high-yield notes are designed to save you time and keep you focused on what actually matters for Step 2 CK. Review these vignettes regularly—steady practice beats cramming.
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Disclaimer
Version 1.0 August 2025. No part of this document may be reproduced or distributed without written permission. For personal study only. Medical information herein is for educational purposes and does not constitute clinical advice. Always confirm with current guidelines and your institution’s policies.
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