Published: December 1, 2021 | 4 mins read
Smoking’s Impact on Kidney Stone Passage Rate
Among the many repercussions of smoking, the adverse effects on the respiratory system and cardiovascular health have long been established. However, one observational study conducted in Turkey has sparked the idea that there’s also an association between smoking and passage rates of kidney stones.
In this article, we will explain in detail the study’s findings to shed light on the significant impact of smoking on kidney stone passage rates.
A previous study done in dogs showed that nicotine positively impacted peristalsis or the constant contraction and relaxation of muscles. This muscle activity can be found throughout the body, including the ureter, which affects stone passage.
Thus, this later study aimed to know if nicotine has the same effect on humans. In particular, they wanted to analyze the effect of smoking on passage rates for kidney stones located in the distal or the lower portion of the ureter.
This study included 88 patients with stones that are less than 10 millimeters in size. They are grouped by smokers (33 subjects) and non-smokers (50 subjects). These patients were observed for four weeks without any intervention (epidemiological). Another important note was that none of the patients were on alpha-blockers because alpha-blockers are known to help in spontaneous stone passage rates.
After the four-week observation period, the researchers were able to see striking results.
For stones between one and four millimeters, non-smokers and smokers almost have the same passage rates (92-100%). The only reason the number was slightly lower for non-smokers (92%) is that they had a bigger sample size. As the sample grows larger, the influence of individual cases decreases, so the estimate becomes more likely to reflect the proper population proportion.
Regarding stones that were four to eight millimeters in size, the results are also roughly the same, 60 to 65% passage rate.
But the really curious thing came in with stones between eight and 10 millimeters. None of the smokers in this study passed their kidney stones, while 80% of the non-smokers passed their stones.
Although, please take note that this is an epidemiological study. Meaning it is purely observational in nature, and no interventions were done. The researchers strictly looked at the data and drew results from their observations. And this is important to consider because we all know that correlation is not causation. More research is still needed to prove this matter.
From all the information above, we can assume that passage rates of stones less than five millimeters will be roughly 68% for both smokers and non-smokers. And this is pretty much on par with the American Urological Association’s data for stones under five millimeters. And around 80% of research out there agrees with this information.
In the US, five millimeters is usually the cutoff point for whether your doctor would suggest surgery or simply suggest you go home and take alpha-blockers, like Tamsulosin, to pass your stone.
When it comes to the passage rates of stones greater than four millimeters, smokers passed 46% of their stones, while non-smokers passed 67%. And again, for stones that are eight to 10 millimeters, no smokers passed, while 80% of non-smokers ended up passing their stones.
The possible reason behind this large gap on passage rates can be connected with nicotine’s impact on a hormone called vasopressin. This hormone is also referred to as “anti-diuretic hormone” (ADH). And from the name itself, it promotes lesser urine output because it signals the kidneys to reabsorb water back to the bloodstream.
Since nicotine triggers the release of ADH in our brain, it causes lesser urination. And the direct result is a slower stone passage. We will dig deeper on this topic in a future blog.
Though this study is observational, we hope this article helped you understand how smoking negatively impacts stone passage rates.