Renal, Urinary Systems and Electrolytes II

Question 1

What acid-base disorders are associated with aspirin (salicylate) toxicity?

[…] (early) and […] (late)

Answer 1

What acid-base disorders are associated with aspirin (salicylate) toxicity?

respiratory alkalosis (early) and metabolic acidosis (late)

respiratory alkalosis due to increased respiratory drive; metabolic acidosis due to increased production/decreased elimination of organic acids

Question 2

What acid-base disturbance is associated with primary adrenal insufficiency (Addison disease)?

Answer 2

Normal anion gap metabolic acidosis

decreased aldosterone results in retention of H+

Question 3

What antibiotic is associated with hyperkalemia and elevated serum creatinine?

Answer 3

Trimethoprim

due to blockade of epithelial Na+ channels (ENaC) in the collecting tubule; elevated creatinine is an artificial increase due to inhibition of renal creatinine secretion (GFR remains the same)

Question 4

What are the most common renal pathologies (2) seen with analgesic nephropathy?

Answer 4

papillary necrosis and chronic tubulointerstitial nephritis

may have sterile pyuria, WBC casts, microscopic hematuria, and/or mild proteinuria on urinalysis

Question 5

What BUN:creatinine ratio is suggestive of prerenal acute kidney injury?

Answer 5

> 20:1 BUN:creatinine

Question 6

What class of anti-depressants is commonly associated with SIADH?

Answer 6

SSRIs

especially in elderly patients

Question 7

What class of antibiotics used to treat severe gram-negative infections is potentially nephrotoxic?

Answer 7

Aminoglycosides

Question 8

What class of drugs are useful for patients with urge incontinence?

Answer 8

Anti-muscarinics (e.g. oxybutynin)

first-line treatments include bladder training and pelvic floor muscle exercises; medical therapy is reserved for those who don’t respond

Question 9

What classes of medications (2) are used for pain management in patients with kidney stones?

Answer 9

narcotics and NSAIDs (preferred with normal renal function)

e.g. morphine (narcotic) and ketolorac (NSAID)

Question 10

What complication may result from correcting hypernatremia too quickly?

Answer 10

Cerebral edema

“high to low, your brain will blow”

Question 11

What complication may result from correcting hyponatremia too quickly?

Answer 11

Osmotic demyelination syndrome (central pontine myelinolysis)

“low to high, your pons will die”

Question 12

What does a positive leukocyte esterase on urine dipstick indicate?

Answer 12

Significant pyuria

Question 13

What does positive nitrites on urine dipstick indicate?

Answer 13

Gram negative bacteria

Question 14

What drug class is useful for the management of recurrent nephrolithiasis secondary to idiopathic hypercalciuria?

Answer 14

Thiazide diuretics

other preventive measures include increased fluid intake and a low Na+/protein diet

Question 15

What drug should be discontinued in an acutely ill patient with sepsis and acute renal failure taking low-dose aspirin, atorvastatin, metformin, and sitagliptin?

Answer 15

Metformin

nephrotoxins, such as NSAIDs and metformin, should NOT be given to patients with acute renal failure or sepsis; low-dose aspirin has not been shown to precipitate or worsen renal failure

Question 16

What effect does intracellular magnesium have on renal K+ secretion?

Answer 16

Decreased K+ secretion

via inhibition of renal outer medullary potassium (ROMK) channels

Question 17

What formula is used to calculate the anion gap in patients with metabolic acidosis?

Answer 17

AG = (Na+) - (HCO3- + Cl-)

should be calculated in all patients with metabolic acidosis to narrow the differential

Question 18

What formula is used to calculate the osmolal gap?

Answer 18

measured serum osmolality - calculated serum osmolality

Question 19

What formula is used to calculate the serum osmolality?

Answer 19

the normal osmolal gap (measured - calculated) is < 10

Question 20

What hematologic laboratory values are consistent with abnormal hemostasis due to chronic renal failure?

PT: […]

PTT: […]

Platelet count: […]

Bleeding time: […]

Answer 20

What hematologic laboratory values are consistent with abnormal hemostasis due to chronic renal failure?

PT: Normal

PTT: Normal

Platelet count: Normal

Bleeding time: Prolonged

underlying cause is platelet dysfunction

Question 21

What imaging modalities (2) are preferred for detecting kidney stones?

Answer 21

CT scan of the abdomen without contrast (preferred) or ultrasound

high sensitivity and specificity; also can detect radiolucent stones, which are missed on abdominal X-ray

Question 22

What imaging modality is preferred for diagnosis of renal cell carcinoma?

Answer 22

CT scan of the abdomen

Question 23

What is recommended treatment for an acute rejection of a renal transplant?

Answer 23

IV steroids

Question 24

What is the best test to screen for the initial stages of diabetic nephropathy?

Answer 24

Urine test for microalbumin:creatinine ratio

either spot or timed urine collection; dipsticks only detect excess urinary protein when > 300mg/24hr (macroalbuminuria) and thus are not useful for screening

Question 25

What is the current recommended screening regimen for bladder cancer?

Answer 25

Not recommended, even in patients with significant smoking and family histories

Question 26

What is the earliest renal abnormality seen in diabetic nephropathy?

Answer 26

Glomerular hyperfiltration hyperfiltration is also the major pathophysiologic mechanism of glomerular injury; GBM thickening is the first change that can be quantitated

Question 27

What is the immediate treatment for severe hypercalcemia (\> 14mg/dL or symptomatic)?

Answer 27

saline hydration + calcitonin hypercalcemia may induce nephrogenic diabetes insipidus leading to polyuria and fluid loss; other symptoms include weakness, GI distress, and neuropsychiatric symptoms

Question 28

What is the initial step in management for a post-operative patient with acute renal failure and oliguria (\< 250 mL urine in 12 hours)?

Answer 28

Bedside bladder scan to assess for urinary retention

Question 29

What is the initial therapy for patients with hypertension and renal artery stenosis?

Answer 29

ACE inhibitors or ARBs an acceptable rise in serum creatinine is \< 30%; renal artery stenting or surgical revascularization is reserved for patients who fail to achieve adequate BP control with medical therapy

Question 30

What is the initial treatment for acute hyponatremic encephalopathy (e.g. headache, nausea/vomiting, AMS)?

Answer 30

Hypertonic (3%) saline may occur as a complication of hypotonic fluid administration (iatrogenic hyponatremia)

Question 31

What is the initial treatment for prerenal acute kidney injury?

Answer 31

IV normal saline need to restore renal perfusion and prevent development of acute tubular necrosis

Question 32

What is the likely cause of acute kidney injury in patients receiving IV acyclovir?

Answer 32

Renal tubular obstruction (crystal-induced AKI) most patients develop AKI within 24 - 48 hours after drug exposure

Question 33

What is the likely cause of acute renal failure in a patient with high anion and osmolal gap metabolic acidosis and calcium oxalate crystals on urinalysis?

Answer 33

Ethylene glycol poisoning calcium oxalate crystals are described as envelope-shaped

Question 34

What is the likely cause of anion gap metabolic acidosis in a patient with a recent generalized tonic-clonic seizure?

Answer 34

Post-ictal lactic acidosis transient and typically resolves without treatment within 90 minutes following resolution of seizure activity

Question 35

What is the likely cause of metabolic alkalosis in a young woman with low urine Cl-?

Answer 35

Self-induced vomiting other etiologies include nasogastric suctioning and prior diuretic use

Question 36

What is the likely diagnosis in a cirrhotic patient with decreasing GFR, normal urinalysis, lack of improvement with IV fluids, and no other renal dysfunction?

Answer 36

Hepatorenal syndrome common inciting factors include spontaneous bacterial peritonitis and GI bleeding

Question 37

What is the likely diagnosis in a euvolemic patient with high serum osmolality and low urine osmolality?

Answer 37

Diabetes insipidus (central or nephrogenic) common cause of euvolemic hypernatremia

Question 38

What is the likely diagnosis in a euvolemic patient with low serum osmolality (\< 275 mOsm/kg) and normal/high urine osmolality (\> 100 mOsm/kg)?

Answer 38

SIADH also typically have elevated urine sodium concentration (\> 40 mEq/L)

Question 39

What is the likely diagnosis in a female with bladder pain that is relieved with voiding, as well as dyspareunia, urinary frequency/urgency, and normal urinalysis?

Answer 39

Interstitial cystitis (painful bladder syndrome) treatment is palliative and includes trigger avoidance, amitriptyline, and analgesics

Question 40

What is the likely diagnosis in a hepatitis C patient with palpable purpura, hematuria, proteinuria, and low serum complement?

Answer 40

Mixed cryoglobulinemia other symptoms include arthralgias, hepatosplenomegaly, peripheral neuropathy, and non-specific systemic symptoms

Question 41

What is the likely diagnosis in a middle-aged patient with chronic renal failure, a palpable right flank mass, and an enlarged liver?

Answer 41

Autosomal dominant polycystic kidney disease (ADPKD) the right kidney, which is lower and easier to palpate than the left; other symptoms of ADPKD include intermittent flank pain, hematuria, UTIs, and nephrolithiasis

Question 42

What is the likely diagnosis in a patient on RIPE therapy for tuberculosis who presents with painless "red" urine?

Answer 42

Drug reaction rifampin may result in red to orange discoloration of bodily fluids (e.g. urine, saliva, sweat, tears)

Question 43

What is the likely diagnosis in a patient started on nitroprusside who presents with flushing, confusion, and metabolic acidosis?

Answer 43

Cyanide toxicity risk factors for cyanide toxicity due to nitroprusside include prolonged infusion (\> 24 hours) and high rates (5-10 μg/kg/min), as well as chronic kidney disease

Question 44

What is the likely diagnosis in a patient who develops a spike in creatinine a day after having a CT with IV contrast?

Answer 44

Contrast-induced nephropathy transient increase that normalizes within 5-7 days; higher risk in patients with elevated baseline creatinine and diabetes

Question 45

What is the likely diagnosis in a patient who overdosed on cocaine and presents with elevated K+ and creatine phosphokinase (CPK)?

Answer 45

Rhabdomyolysis another key clinical feature is a positive urine dipstick for blood, but no RBCs seen on microscopy (due to myoglobin in the urine)

Question 46

What is the likely diagnosis in a patient who presents with periorbital swelling and hematuria three weeks after a skin infection?

Answer 46

Post-streptococcal glomerulonephritis urinalysis may show hematuria with RBC casts and mild proteinuria; additionally, C3 complement levels are low

Question 47

What is the likely diagnosis in a patient with a recent infection who presents with fever and rash with WBC casts and eosinophiluria on urinalysis?

Answer 47

Drug-induced interstitial nephritis the patient's infection is likely being treated with an antibiotic that precipitated the nephritis; treatment is to discontinue the offending agent

Question 48

What is the likely diagnosis in a patient with a recent seizure who has a large amount of blood on urinalysis with few RBCs on microscopy?

Answer 48

Myoglobinuria (secondary to rhabdomyolysis) urinalysis cannot detect the difference between hemoglobin and myoglobin but microscopic exam for RBCs can add clarity

Question 49

What is the likely diagnosis in a patient with a renal transplant for 3 days who presents with oliguria, elevated creatinine/BUN, lymphocytic infiltration on biopsy, and normal serum cyclosporine levels?

Answer 49

Acute transplant rejection

Question 50

What is the likely diagnosis in a patient with a unilateral varicocele that fails to empty when the patient is recumbent, as well as hematuria, fever, and thrombocytosis?

Answer 50

Renal cell carcinoma unilateral varicoceles that fail to empty when a patient is recumbent should raise suspicion for an underlying mass that obstructs venous flow

Question 51

What is the likely diagnosis in a patient with an elevated serum Ca2+ and low urine Ca2+/Cr clearance ratio (\< 0.01)?

Answer 51

Familial hypocalciuric hypercalcemia due to abnormal calcium-sensing receptors (CaSR); differentiated from primary hyperparathyroidism by low urine Ca2+ excretion (\< 0.01)

Question 52

What is the likely diagnosis in a patient with an elevated serum PTH/Ca2+ and normal urine Ca2+/Cr clearance ratio (\> 0.02)? ## Footnote [...]

Answer 52

Primary hyperparathyroidism differentiated from familial hypocalciuric hypercalcemia by increased urine Ca2+ excretion (\> 0.02)

Question 53

What is the likely diagnosis in a patient with anasarca, pulmonary edema, hematuria, and proteinuria (1+)?

Answer 53

Acute nephritic syndrome the presence of hematuria and pulmonary edema helps distinguish nephritic syndrome from other causes of edema (e.g. hypoalbuminemia, cirrhosis, heart failure)

Question 54

What is the likely diagnosis in a patient with colicky flank pain that radiates to the groin?

Answer 54

Nephrolithiasis

Question 55

What is the likely diagnosis in a patient with cor pulmonale treated with loop diuretics that develops elevated creatinine and BUN?

Answer 55

Prerenal acute kidney injury suggested by BUN:creatinine ratio \> 20

Question 56

What is the likely diagnosis in a patient with elevated BUN and creatinine (\< 20:1 ratio) after an episode of hypovolemic shock?

Answer 56

Acute tubular necrosis characterized by muddy brown casts; distinguishing features from pre-renal AKI include BUN:creatinine ratio \< 20:1, urine Na+ \> 20 mEq/L, and FeNA \> 2%

Question 57

What is the likely diagnosis in a patient with hematuria a few days after an upper respiratory infection with normal complement levels?

Answer 57

IgA nephropathy (synpharyngitic glomerulonephritis) quicker onset (within 5 days) and normal complement levels help differentiate IgA nephropathy from PSGN

Question 58

What is the likely diagnosis in a patient with intermittent flank pain, low-volume voids, and occasional episodes of high-volume voids?

Answer 58

Obstructive uropathy e.g. due to renal calculi; high-volume voids occur due to large volume of retained urine overcoming the obstruction (post-obstructive diuresis)

Question 59

What is the likely diagnosis in a patient with lethargy and asterixis, and the laboratory findings below? ## Footnote BUN: 78 mg/dL Albumin: 3.8 g/dL AST: 38 U/L ALT: 44 U/L Creatine kinase: 32,000 U/L

Answer 59

What is the likely diagnosis in a patient with lethargy and asterixis, and the laboratory findings below? BUN: 78 mg/dL Albumin: 3.8 g/dL AST: 38 U/L ALT: 44 U/L Creatine kinase: 32,000 U/L Uremic encephalopathy

Question 60

What is the likely diagnosis in a patient with lower extremity edema, 4+ proteinuria, and a kidney biopsy demonstrating dense deposits within the GBM?

Answer 60

Membranoproliferative glomerulonephritis (MPGN) type II also known as "dense deposit disease"

Question 61

What is the likely diagnosis in a patient with poorly controlled diabetes that presents with overflow incontinence with a high post-void residual volume (\> 50 mL)?

Answer 61

Diabetic autonomic neuropathy symptoms include dribbling and poor urinary stream

Question 62

What is the likely diagnosis in a patient with QRS widening and peaked T waves on ECG?

Answer 62

Hyperkalemia other EKG changes include loss of the P wave and prolonged PR and/or shortened QT interval

Question 63

What is the likely diagnosis in a patient with tuberculosis who presents with hyponatremia, hyperkalemia, and eosinophilia?

Answer 63

Primary adrenal insufficiency

Question 64

What is the likely diagnosis in a young female with hypokalemia, metabolic alkalosis, normotension, and low urine Cl-?

Answer 64

Surreptitious vomiting low urine Cl- helps distinguish vomiting from other causes of hypokalemia, alkalosis, and normotension (e.g. diuretic abuse, Bartter syndrome, and Gitelman's syndrome)