241: Urinary Obstruction and Urinary Stones

Question 1

At which 3 points in the ureter is a stone most likely to get stuck?

Answer 1

Ureteral pelvic junction (UPJ)

Iliac vessels

Ureteral vesical juction (UVJ)

Question 2

What is the most serious complication of post-obstructvie diuresis?

Answer 2

Hyponatremia

This can be fatal

Question 3

How would you manage a septic patient with hydronephrosis and an obstructing stone in the proximal ureter?

Answer 3

Place a stent or percutaneous nephrostomy tube

Let everything drain and treat infection. Can go back and get the stone later. Operating during infection is likely to do more harm than good.

Question 4

List the top 3 most common kinds of kidney stones

Answer 4

Calcium oxalate

Uric acid

Calcium phosphate

Question 5

What are the classifications of hypercalcuria?

Answer 5

Absorptive (from GI)

Renal leak (not reabsorbing enough Ca)

Primary hyperparathyroidism (releasing too much Ca from bones)

Question 6

What is the difference between hydronephrosis and obstructive nephropathy?

Answer 6

Hydronephrosis = descriptive term, any dilation in renal pelvis and calyces

Obstructive nephropathy = damage to renal parenchyma due to obstruction

Question 7

What are the 3 phases of acute obstruction

Answer 7

• Phase 1: Renal blood flow and ureteral pressure increase (1-1.5 hours)
  
  • Vasodilation of afferent arterioles
• Phase 2: Decreased RBP, increased ureteral pressure (1.5-5 hours)
  
  • Still trying to squeeze out the obstruction
  • Vasoconstriction
• Phase 3: both decrease (>5 hours)
  
  • Give up
  • Because of increase in afferent arteriole resistance
  • Lack of perfusion to glomeruli

Question 8

What is post-obstructive diuresis?

Answer 8

Excretion of salt and water in excess of that retained during obstruction

Kidney’s can’t reabsorb Na or concentrate urine like normal. Need to monitor for possible hyponatremia

Question 9

What is the prevalence of kidney stones?

Answer 9

10% of Americans

50% recurrence rate within 5 years

Question 10

What are causes of hyperoxaluria (too much oxalate)?

Answer 10

• Dietary (high oxalate food, vit C supplementation)
• Genetic disorders (very rare)
• Enteric (intestinal malabsorption, less fat to bind with oxalate in intestine)

Question 11

What are causes of hyperuricosuria?

too much uric acid

Answer 11

• Gout (too much purines from animal protein)
• Chronic diarrhea
• Increased turnover of nucleic acids
• Increased synthesis (alcohol)
• Inborn errors of metabolism
• Meds (losartan)

Question 12

What kind of stones are DM patients more likely to ahve?

Answer 12

Uric acid stones

Have more acidic urine due to impaired renal ammonium excretion

Question 13

How can you treat struvite/infection stones?

Answer 13

Antibiotics to treat the urease-producing bacteria

Must be stone free

Question 14

Why is it important to relieve obstruction of the kidney?

Answer 14

• Urine backing through the collecting system impairs GFR
• Causes acute and/or chronic kidney disease