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This blog aims to make "evidence-based medicine" understandable to the lay person
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Tuesday, April 30, 2013

What are kidney stones? What are the symptoms of kidney stones?

Stones in the kidneys are a common clinical problem. You might see this medically referred to as "nephrolithiasis" or "urolithiasis".  For reasons not fully understood, the prevalence of kidney stones seems to be increasing. This could be related to the increase in obesity rates, dietary changes (availability of cheap, high sugar, high salt fast foods), or maybe, even changes in the climate (global warming!). Warmer weather is a known risk factor for kidney stones; which is probably why their prevalence in southeastern U.S. is 31% higher than the northwestern region!

So what are kidney stones made of?
Most stones are composed of calcium (up to 80%) . This calcium is usually found in combination with oxalate or phosphate. There are other non-calcium stones as well (for instance, those made of uric acid, cystine, drugs, etc) which are not encountered as often. Frequently, the stones can actually be a "mixed", having a bit of everything. If you have, or if you passed kidney stones, it is important to know what are they made of, since the treatment could be different depending on the type of stones present. The worst treatment approach to treating kidney stones is to assume that a stone is a stone is a stone! I will talk about this in my following posts.


Symptoms of kidney stones:

Usual symptoms of kidney stones can range from "no-symptoms" (wherein they might be discovered incidentally), to the impressive. This would also depend on the location of the stone along the urinary tract, the stones' size, and whether the stones are causing any kind of obstruction to the flow of urine. Small stones that  sit tight in the kidney might not cause any symptoms. Bigger ones could cause back or flank pain. When stones start to move and obstruct the flow or urine, the pain could start to radiate towards the groin as the stone makes it way down the ureter (the tube that carries urine from the kidney to the bladder). This pain could "come and go" in spasms (called "renal colic"), and be excruciating. Anecdotal claims suggest that it could be one of the most painful things known to man (and rank a close second for women, with childbirth!). The pain could be bad enough to make patients throw up. It could also be confused with other medical entities like appendicitis, ectopic pregnancy, or diverticulitis. Imaging studies like CT scans or ultrasound can help in differentiating between these. However, tiny stones are known to pass without causing any pain, until patients hear that "plonk" in their toilet! Sometimes patient might not pass a discrete stone, but continue to pass smaller pieces of debris, often referred to as "sand in the urine".

Pictorial representation of the urinary tract, with possible sites for the stone (in grey) to get stuck in. Symptoms depend on the stone size and location

Since stones do cause physical destruction of the superficial layers of the urinary tract, it is not unusual to see blood in the urine. The worst case scenario however is when a stone gets stuck in the urinary tract leading to obstruction to the outflow of urine and urinary stasis. Bacteria love static urine since it is an excellent medium for them to breed and grow, thus leading to an infection! Any kind of obstruction in the urinary tract in conjunction with infection is a medical emergency requiring immediate intervention.

Other less common symptoms include vague abdominal pain, urinary urgency or frequency, difficulty urinating, testicular pain, nausea, etc.

The above paragraphs describe the acute, short term symptoms of kidney stones. But what about the long term consequences? The most common long term consequence is, well, another kidney stone. People who have had one kidney stone are much more likely to develop another one (depending on their risk factors). There are data to suggest that the likelihood of forming another stone could be as high as 40% in five years, and 50% in 10 years! Needless to say, treatment of a kidney stone does not end with its removal/passage, but needs to actively focus on the preventive aspect of minimizing the risk of recurrence.

The other question that needs to be addressed over the long term is whether kidney stones can cause kidney disease or kidney failure? For the answer to that question, read on....!

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