Kidney stones: Pathology review

In the Emergency Department, two people with similar symptoms came in.

One of them is 35 year old Conrad who has a terrible left flank pain, along with nausea and vomiting and the other one is 40 year old Sam who has left flank pain, but also has dysuria.

An electrolyte panel and urinalysis was done in both individuals.

Results showed that Conrad had normal levels of calcium in the blood, but urinalysis showed hypercalciuria and hematuria.

Sam’s urinalysis showed positive leukocyte esterase, as well as positive nitrites and hematuria. Abdominal CT showed radiopaque masses in their ureters.

Now, the suspicion is that both individuals have kidney stones, but there are actually several types of kidney stones and we need to know what we’re dealing with in order to give the right treatment.

Okay, let’s first talk about how kidney stones form.

Urine’s a combination of water, which acts as a solvent, and all sorts of particles, or solutes.

In general, when certain solutes become too concentrated in the solvent, they become supersaturated.

Urinary supersaturation of certain solutes results in precipitation out of the solution and formation of crystals.

Those crystals then act as a nidus, or place where more solutes can deposit and over time it builds up a crystalline structure.

This can happen if there’s an increase in the solute, or a decrease in the solvent, as would be the case with dehydration.

This means that dehydration leads to a low urine volume which can further put a person at risk for kidney stones.

Okay, let’s now talk about the different types of stones.

There are four main types of stones.

Calcium stones are present in about 80 percent of the cases, while struvite stones are present in about 15 percent of the cases and uric acid stones are present in about 5 percent of the cases.

Finally, a super rare type of stone is a cysteine stone.

Let’s start with calcium stones.

With calcium stones, in most cases, the inorganic precipitate is calcium oxalate, formed by a positively charged calcium ion binding to a negatively charged oxalate ion, which results in a black or dark brown colored stone that’s shaped like an envelope or a dumbbell.

Calcium oxalate stones appear radiopaque on X-ray, as well as on a CT-scan.