Acute Kidney Injury 5

Question 1

What is the primary cause of postrenal AKI?

Answer 1

Bilateral obstruction of the lower urinary tract or obstruction of a solitary kidney.

Question 2

What are common congenital causes of postrenal AKI?

Answer 2

Posterior urethral valves and ureteropelvic junction obstruction.

Question 3

What are common acquired causes of postrenal AKI?

Answer 3

Nephrolithiasis, blood clots, and tumors.

Question 4

What is the pathophysiological mechanism of postrenal AKI?

Answer 4

Obstruction increases intratubular and Bowman’s space hydrostatic pressure, reducing the pressure gradient across glomerular capillaries and GFR.

Question 5

How does unilateral obstruction differ from bilateral obstruction in postrenal AKI?

Answer 5

Unilateral obstruction is often asymptomatic due to compensatory function of the unaffected kidney, while bilateral obstruction causes significant renal dysfunction.

Question 6

What prenatal findings suggest postrenal obstruction?

Answer 6

Ultrasound showing obstruction and complications like oligohydramnios.

Question 7

What are complications of severe prenatal obstruction?

Answer 7

Pulmonary hypoplasia due to oligohydramnios.

Question 8

What are key urinary symptoms in children with postrenal AKI?

Answer 8

Difficulty urinating, weak stream, and anuria.

Question 9

What are additional clinical findings in postrenal AKI?

Answer 9

Abdominal or flank pain, gross hematuria, palpable bladder, or abdominal mass.

Question 10

What is the first-line imaging for postrenal AKI diagnosis?

Answer 10

Renal ultrasound.

Question 11

What is the role of voiding cystourethrogram in postrenal AKI?

Answer 11

To evaluate posterior urethral valves and ureteropelvic/ureterovesical junction obstruction.

Question 12

What lab findings are typical in postrenal AKI?

Answer 12

BUN-to-creatinine ratio <10, urine osmolality <350 mOsm/kg, and FENa >1%.

Question 13

What is the core treatment for postrenal AKI?

Answer 13

Relief of obstruction through catheter drainage or surgical intervention.

Question 14

What is post-obstructive diuresis?

Answer 14

Polyuria and electrolyte abnormalities occurring after relief of obstruction.

Question 15

Why does post-obstructive diuresis occur?

Answer 15

Altered sodium transporter expression, natriuretic factors, and impaired medullary gradient.

Question 16

What electrolytes are commonly lost during post-obstructive diuresis?

Answer 16

Sodium, potassium, calcium, bicarbonate, and chloride.

Question 17

How long does post-obstructive diuresis usually last?

Answer 17

Typically 24–36 hours but may persist for months in rare cases.

Question 18

What fluid is used for replacement during post-obstructive diuresis?

Answer 18

0.45% saline, given at a rate slower than the urine output rate.

Question 19

What are key monitoring parameters during post-obstructive diuresis?

Answer 19

Vital signs, volume status, urine output, and electrolytes.

Question 20

What complications can arise from poor monitoring of post-obstructive diuresis?

Answer 20

Severe volume depletion, hypokalemia, hyponatremia, hypernatremia, and hypomagnesemia.

Question 21

Why is renal ultrasound important in postrenal AKI?

Answer 21

It is the most sensitive and specific test for obstruction.

Question 22

What is a medical emergency in postrenal AKI?

Answer 22

Obstruction in a solitary kidney or bilateral obstruction.

Question 23

What are the main goals during the management of post-obstructive diuresis?

Answer 23

Avoiding severe volume depletion and correcting electrolyte imbalances.

Question 24

How does creatinine clearance change after obstruction relief?

Answer 24

It improves rapidly during post-obstructive diuresis.