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Urology

Question
93 out of 129
 

Which of the following type of Renal calculi are commonly seen with proteus infection?



A Cysteine
B Ca oxalate

C Uric acid
D Triple PO4

Ans. D Triple PO4 Ref: Love & Bailey, 25th ed

a. Struvite stones are also known as infection stones, urease or triple-phosphate stones.

b. About 10–15% of urinary calculi consist of struvite stone

c. The formation of struvite stones is associated with the presence of urea-splitting bacteria, most commonly Proteus mirabilis (but also Klebsiella, Serratia, Providencia species).

d. These organisms are capable of splitting urea into ammonia, decreasing the acidity of the urine and resulting in favorable conditions for the formation of struvite stones.

e. Struvite stones are always associated with urinary tract infections. pH is typically >7

Other types of renal stones

1. Calcium oxalate stones

a. The most common type of kidney stone is composed of calcium oxalate crystals, occurring in about 80% of cases, and the factors that promote the precipitation of crystals in the urine are associated with the development of these stones.

b. This is perhaps related to the role of calcium in binding ingested oxalate in the gastrointestinal tract.

c. As the amount of calcium intake decreases, the amount of oxalate available for absorption into the bloodstream increases; this oxalate is then excreted in greater amounts into the urine by the kidneys.

d. In the urine, oxalate is a very strong promoter of calcium oxalate precipitation, about 15 times stronger than calcium.

2. Uric acid (urate)

a. About 5–10% of all stones are formed from uric acid.

b. Uric acid stones form in association with conditions that cause hyperuricosuria with or without high blood serum uric acid levels (hyperuricemia); and with acid/base metabolism disorders where the urine is excessively acidic (low pH) resulting in uric acid precipitation.

c. A diagnosis of uric acid nephrolithiasis is supported if there is a radiolucent stone, a persistent undue urine acidity, and uric acid crystals in fresh urine samples.

d. Associated with high purine intake (meat, legumes, fish) malignancy.

3. Cystine stones:

Cystine stones(2%)

a. Intrinsic metabolic defect resulting in of renal tubular reabsorbtion of cystine , ornithine, lysine and arginine

b. Can be treated with low methionine diet, increasing urine output or alkalinizing agents.

i. Drug induced stone disease-the medication or their metabolites can precipitate in urine causing stone formation. They are indinavir, guafenesin, tiamterene, silicate(overuse of antaacidscontaining magnesium silicate) and sulfa drugs-sulfadiazine, sulfasalazine, acetyl sulfamethoxazole.

4. Table of Cystine stone

Ca urate are associated with the following disorders:

a. Hyperparathyroidism b. Increased gut absorbtion of calcium

c. Renal calcium leak d. Renal phosphate leak

e. Hperuricosuria f. Hyperoxaluria

g. Hypercitraturia h. Hypomagnesuria

Urology Flashcard List

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