Tutorial 41 - Acute Kidney Injury

Question 1

An AKI is defined as a reduction in kidney function that has developed within hours to days. What parameters are commonly used to determine if a patient has an AKI?

Answer 1

• Rise in serum creatinine concentration
• Decline in urine output

Question 2

What is the commonly accepted criteria for an AKI for the following:
- serum creatinine concentration
- urine output

Answer 2

Serum creatinine concentration:
- increase ≥0.3 mg/dL (27 micromol/L) within 48 hours OR
- increase to ≥1.5 times the baseline value (either known or presumed to have within prior 7 days)

Urine output:
- decrease in urine volume to <0.5 mL/kg/hour for more than six hours

Question 3

What are signs and symptoms of an AKI?

Answer 3

• Decreased urine output
• Hypertension
• Edema

NOTES:
- Symptoms result directly from decreased kidney function.
- Some patients may be asymptomatic!

Question 4

What are the general causes of pre-renal AKIs? (x3)

Dr. Yusuf: please review (from UpToDate article) - how would you test this information? -CZ

Also - how do you want to test information in the notes - see following question.

Answer 4

1. Decreased renal artery perfusion.
2. Renal venous congestion
3. Drugs affecting glomerular hemodynamics

NOTES:
- Can occur with total body volume depletion (diarrhea, vomiting, acute bleeding, unreplenished insensible losses, excessive diuretic therapy, third-space sequestration (eg, crush injury or acute pancreatitis)
- Can occur in euvolemic patients due to low arterial blood pressure (occurs different types of distributive shock (eg, sepsis or anaphylaxis), or any loss of arteriolar vasomotor tone (eg, overtreatment with antihypertensive medication).
- Can occur in patients with total body volume overload who have reduced kidney perfusion due to a low effective circulating volume (severe heart failure with reduced ejection fraction or decompensated liver disease with portal hypertension and ascites (ie, hepatorenal syndrome)).

- Prerenal: hypovolemia, hemorrhage, distributive shock, congestive hear

Question 5

What conditions can lead to an AKI in a hypervolemic (volume overloaded) patient?

Answer 5

Low effective circulating blood volume.

• Severe heart failure
• Hepatorenal syndrome (Decompensated liver disease with portal hypertension and ascites)

Question 6

What are renal (intrinsic) causes of AKI?

Answer 6

**1. Renal vascular disease **
* Small vessel disease (atheroembolic disease, and thrombotic microangiopathies, such as thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP/HUS), scleroderma, and malignant hypertension)
* Large vessel diseaes (renal infarction from aortic dissection, systemic thromboembolism, renal artery abnormality (such as aneurysm), and acute renal vein thrombosis)

2. Glomerular Disease

3. Tubular and interstitial disease (acute tubular necrosis, acute interstitial nephritis)

Acute tubular necrosis - typically from ischemia (cardiac surgery, sepsis, and/or shock) or nephrotoxic exposure.
- May occur in conjunction with use of NSAIDs or radiocontrast (esp in patients with decreased kidney perfusion)
- May occur after exposure to nephrotoxic medications (amphotericin, cisplatin)

Acute interstitial nephritis - often drug-induced (NSAIDs, various antibiotics, and checkpoint inhibitors for cancer immunotherapy)

Question 7

What is the most common etiology of a post-renal cause of AKI?

Answer 7

Obstruction along the urinary tract.

Commonly:
- prostatic disease (hyperplasia or cancer)
- urothelial carcinoma
- gynecologic/metastatic cancer

Question 8

What is the most common cause of an obstruction along the urinary tract causing AKI?

Answer 8

Prostatic disease (hyperplasia or cancer).

Question 9

For hospitalized patients who develop AKIs, what are the indications that a patient should be assessed for urgent dialysis?

Dr. Yusuf - should this be included? From UpToDate article.

Answer 9

• refractory pulmonary edema
• life-threatening hyperkalemia or metabolic acidosis,
• encephalopathy
• pericardial rub

Question 10

You are seeing a hospitalized patient who was admitted two days ago due to septic shock. They have now developed an AKI since being in the hospital. What is the most likely classification (pre-renal, renal, or post-renal) and cause of their AKI?

Dr. Yusuf - please reword/rephrase. Also - should their be more questions about the approach to AKI outlined in the UpToDate article?

Answer 10

Renal.

Acute tubular necrosis (ischemic damage to the proximal and distal tubule due secondary to decreased perfusion from septic shock).

Question 11

What serum potassium level is used to define hyperkalemia?

Answer 11

Serum [K+] of > 5.5 mmol/L

Question 12

What are the symptoms of hyperkalemia, and at what serum potassium level do these symptoms usually begin to develop?

Answer 12

arrhythmias, muscle weakness and paralysis, (and even death)

Symptoms start to develop when serum [K+] of > 6.5 mmol/L**

** Not a hard and fast rule.

Question 13

What are the two major mechanisms of hyperkalemia?

Answer 13

Impaired potassium excretion
* common in acute or chronic kidney disease when glomeruli can’t dispose of serum potassium)
* can occur with decreased aldosterone secretion/response

Increased potassium release from cells (intracellular potassium shift).

Question 14

What are causes of intracellular potassium shift?

Answer 14

• Cellular injury leading to potassium leak from cells (rhabdomyalysis, excessive exercise, other hemolytic processes)
• Metabolic acidosis (DKA, increased EtOH consumption, sepsis)
• Insulin deficiency
• Tumour lysis syndrome
• Medications (e.g., digoxin, succinylcholine, beta blockers, calcium channel blockers, tacrolimus, mannitol)

Question 15

What is the occurence of hyperkalemia in hospitalized patients?

Answer 15

1-10%

Question 16

What is the typical order of progression of the following EKG changes associated with hyperkalmia?

• Lengthening of the PR interval and QRS duration.
• QRS “sine wave” pattern
• Loss of P waves
• Tall, peaked T-waves

Dr. Yusuf - can you confirm this order? This is the order that you had in the text of the background reading, but the hyperkalemia table from uptodate that you included in the illness script describes: tall peaked T waves; shrinking then loss of P waves; widening of QRS interval then “sine wave”, ventricular arrhythmia, and asystole.

Answer 16

1. Tall, peaked T-waves
2. Progressive lengthening of the PR interval and QRS duration
3. Loss of P waves
4. QRS “sine wave” pattern

Question 18

How do you manage a patient with a hyperkalemic emergency?

Answer 18

1. Calcium gluconate: 1000 mg (10 mL of 10% solution) IV over two to three minutes.
2. Insulin and glucose: bolus injection of 10 units of regular insulin, followed immediately by 50 mL of 50% dextrose (25 g of glucose).*
3. Therapy to remove potassium from the body

*NOTE: only give glucose if serum glucose is <13.9mmol/L

Question 19

What are the methods of potassium removal from the body?

Answer 19

• Hemodialysis
• Diuretics
• Gastrointestinal cation exchanger (eg, patiromer).

Question 20

What are the general classifications of AKIs, and what are some causes for each?

Answer 20

• Prerenal: hypovolemia, hemorrhage, distributive shock, congestive heart failure, decompensated cirrhosis, drugs (NSAIDs, ACEI, ARBs – cause intrarenal vasoconstriction)
• Renal: acute tubular necrosis (ATN), acute interstitial nephritis (AIN), vasculitis, hemolytic anemia, scleroderma, renal artery obstruction/infarction, infection, drugs (via interstitial or tubular damage).
• Postrenal: prostatic obstruction most common, malignancy, nephrolithiasis.

Question 21

You are reviewing the urinalysis of a hospitalized patient who has developed acute kidney injury (AKI). The report shows significant hematuria with dysmorphic red blood cells, RBC casts, and albuminuria.

Which type of kidney disease is most likely responsible for these findings?

Answer 21

Proliferative glomerulonephritis (eg. IgA nephropathy, ANCA- associated vasculitis, lupus nephritis)

Question 22

You are reviewing the urinalysis of a hospitalized patient who has developed acute kidney injury (AKI). The report describes multiple granular and epithelial cell casts with free epithelial cells

Which type of kidney disease is most likely responsible for these findings?

Answer 22

Acute tubular necrosis in a patient with underlying acute kidney injury

Question 23

A 72-year-old man presents to the emergency department with acute diarrhea that began three days ago. He reports passing 7-8 loose, watery stools per day and has noticed some blood mixed with the stool. He also has a history of coronary artery disease and was hospitalized two weeks ago for a mild heart attack, during which he received antibiotics. He currently feels weak and lightheaded.

Which of the following features in this patient’s presentation are considered red flags that warrant further workup?

A. Age
B. History of recent hospitalization
C. Blood in the stool
D. Duration of diarrhea
E. Profuse watery diarrhea
F. History of recent antibiotic use

(Select all that apply.)

Answer 23

Correct answers: A, B, C, E, F.

These red flags include advanced age, recent hospitalization, recent antibiotic use, presence of blood in the stool, and profuse watery diarrhea, all of which warrant further investigation and possibly sending a stool sample for culture, C. difficile testing, and other relevant studies.

Question 24

Question:

A 55-year-old male presents to his primary care physician with a complaint of blood in his urine, which he noticed for the first time this morning. He reports no pain, but he is currently on anticoagulation therapy for atrial fibrillation. He denies recent exercise, trauma, or any signs of infection. A urinalysis confirms the presence of gross hematuria.

Which of the following steps is most appropriate in managing this patient’s hematuria?

A. Reassure the patient that this is likely benign and no further testing is needed.
B. Stop anticoagulation therapy and monitor the patient for 1-2 weeks.
C. Order imaging studies, such as ultrasound or CT, to evaluate for structural causes of hematuria.
D. Perform a cystoscopy immediately to rule out malignancy.
E. Prescribe antibiotics empirically to treat a possible urinary tract infection.

Answer 24

Correct answer: C

NOTES:
* Anticoagulation and antiplatelet agents can also make any of the more benign causes more worrisome, particularly in cases of constant gross hematuria and obstruction with clots.
* If a cause is not obvious for the hematuria, and remains persistent, imaging such as ultrasound or CT can be helpful to such out structural causes of hematuria.
* Cystoscopy can be helpful with direct visualization when malignancy is a strong consideration, or in unexplained gross hematuria.

Question 25

Question:

A 72-year-old woman is brought to the emergency department after feeling lightheaded and weak. She reports having severe diarrhea for the past three days. On examination, she appears dehydrated with dry mucous membranes and a rapid pulse. Her blood pressure is 85/55 mmHg, and her heart rate is 110 beats per minute. Laboratory tests show an elevated blood urea nitrogen (BUN) to creatinine ratio.

Which of the following is the most likely cause of this patient’s acute kidney injury (AKI)?

A. Prostatic obstruction
B. Acute interstitial nephritis (AIN)
C. Vasculitis
D. Hypovolemia
E. Nephrolithiasis

Answer 25

Correct answer: D

The patient’s history of severe diarrhea, signs of dehydration, and an elevated BUN-to-creatinine ratio are indicative of a prerenal etiology, with hypovolemia being the most likely cause.

Question 26

A 65-year-old man with a history of cirrhosis presents to the clinic with increasing abdominal distension and swelling in his legs over the past week. He reports feeling fatigued and notes that he has not been urinating as much as usual. On examination, he has tense ascites and peripheral edema. His blood pressure is 90/60 mmHg, and laboratory tests reveal an elevated blood urea nitrogen (BUN) to creatinine ratio.

Which of the following is the most likely cause of this patient’s acute kidney injury (AKI)?

A. Prostatic obstruction
B. Nephrolithiasis
C. Decompensated cirrhosis
D. Acute tubular necrosis (ATN)
E. Scleroderma

Answer 26

Correct answer: C

The presence of ascites, peripheral edema, hypotension, and an elevated BUN-to-creatinine ratio suggest that decreased renal perfusion due to cirrhosis (low effective circulating volume) is the most likely cause of this patient’s AKI.

Question 27

A 45-year-old woman presents to the hospital with a two-day history of fever, rash, and decreased urine output. She recently completed a course of antibiotics for a sinus infection. On examination, she has a diffuse maculopapular rash, and laboratory tests reveal elevated serum creatinine and eosinophilia. A urinalysis shows white blood cell casts and mild proteinuria.

Which of the following is the most likely cause of this patient’s acute kidney injury (AKI)?

A. Hypovolemia
B. Acute interstitial nephritis (AIN)
C. Prostatic obstruction
D. Nephrolithiasis
E. Congestive heart failure

Answer 27

Correct answer: B

The patient’s recent antibiotic use, presence of fever, rash, eosinophilia, and findings on urinalysis (white blood cell casts and mild proteinuria) are classic signs of AIN, making it the most likely cause of her AKI.