Nephrolithiasis

Question 1

Describe symptoms of nephrolithiasis

Answer 1

Acute flank pain that is colicky with radiation

Question 2

What is the etiology of nephrolithiasis

Answer 2

Impaction of stone in calyx, UPJ, pelvic brim, posterior pelvis, or UPJ. Impaction is unlikely if < 2mm.

Question 3

What is the epidemiology of nephrolithiasis?

Answer 3

Upper tract stones most common in western countries (1-5% incidence). Male: female is 2:1; white: black is 3:1

Question 4

Risk factors for nephrolithiasis?

Answer 4

Genetics, environment (warm environment = dehydration, sun = increased vitamin D activity), occupation (sedentary are at greater risk, medical conditions (gout, hyperparathyroidism, hyperthyroidism, short gut syndrome, chemotherapy, glucocorticoids.

Question 5

Presentation of nephrolithiasis?

Answer 5

Nausea/vomiting, irritative voiding symptoms, gross hematuria, fever/chills ( due to blockage of toxins), microhematuria, chronic UTI, renal failure

Question 6

Evaluation of nephrolithiasis

Answer 6

1. Urinalysis: particularly for microhematuria, pyuria (rare without hematuria; if heavy, rule out UTI), crystalluria (helpful if struvite, uric acid, and cysteine), pH (< 5.5 is uric acid; >7 is struvite)
2. US and abdominal x-ray and CT scan (US good for pregnancy; CT better but carries lot’s of radiation that can’t be used for pregnancy)
3. urine culture
4. serum electrolytes
5. CBC if febrile
6. HCG in female
7. IVP

Question 7

management of nephrolithiasis

Answer 7

1. give fluids
2. pain meds
3. See if it passes (75% 5mm or less will pass)
4. analgesics (such as opiates like morphine sulfate or Percocet or non-steroidals like toradol)
5. 10% may require admission for fever solitary kidney or failure to control symptoms
6. medical expulsive therapy such as hydration or alpha blockers (these stop constricting ureters), anti-inflammatory, pain control with narcotics, steroids

Question 8

What do you do for emergency treatment?

Answer 8

1. Create a stent to divert the urine from the stone.
2. Drain it with percutaneous nephrostomy
3. endourology (stone surgery)
4. extracorporeal shock wave lithotripsy (break it up with sound waves)

Question 9

Describe calcium stones

Answer 9

1. calcium phosphate stones precipitate at a higher pH than calcium oxalate
2. most common type of stone (80%)
3. promoted by hypercalciuria (idiopathic or secondary to conditions of hypercalcemia such as cancer and increased PTH. Oxalate crystals can result from ethylene glycol, vitamin C, or Crohn disease. Treatments for recurrent stones include thiazides and citrate.
4. These stones are radiopaque on x-ray. 5. These crystals appear as an envelope or coffin lid.

Question 10

Describe ammonium magnesium phosphate stones

Answer 10

1. These stones precipitate at a higher than normal pH.
2. Also known as struvite, these are caused by infection with urease positive bugs (proteus mirabilis, staphylococcus, klebsiella) that hydrolyze urea to ammonia and cause urine alkylation and stone formation.
3. Second most common type of stone (15%).
4. Results in staghorn calculi in renal calyces which act as a nidus for UTI.
5. Treatment involves surgical removal (due to size) and eradication of pathogen ( to prevent recurrence).
6. Radioopaque
7. Crystal appears as a coffin lid.

Question 11

Describe uric acid stones

Answer 11

1. Risk factors are hot, arid climates, low urine volume, and acidic pH.
2. This is the most common stone seen in patients with gout; hyperuricemia (e.g. in leukemia or myeloproliferative disorders)
3. Visible on CT and US, but not x-ray
4. third most common type of stone at 5%
5. treatment is hydration and alkalinization of urine (potassium bicarbonate)
6. Radiolucent and appears as rhomboids or rosettes on CT.

Question 12

Cystine stones

Answer 12

1. Mostly seen in children secondary to cystinuria (a genetic defect of tubules that results in decreased absorption of cysteine). 2. Can form staghorn calculi.
2. Sodium nitroprusside test positive.
3. radiopaque and appear as hexagonal crystals
4. treatment involves alkalinization of urine and hydration.

Question 13

Cystinuria

Answer 13

cysteine and basic amino acids are defective in both intestine and kidney. Cysteine can not be resorbed from the glomerular filtrate and concentrates in urine. In this urine, cysteine is oxidized to cysteine which crystallizes into kidney stones.

Question 14

Overactive PRPP synthetase (enzyme used in purine and pyrimidine synthesis)

Answer 14

X linked disorder resulting in overproduction of nucleotides. The condition leads to increased degradation resulting in hyperuricemia, gout, and kidney stones.

Question 15

Hyperparathyroidism

Answer 15

Result of tumor of parathyroid gland (primary hyperparathyroidism) or renal failure (secondary hyperparathyroidism). Patients can present with fractures of long bones, renal stones, GI disturbance, lethargy, and wekness.