According to the data of the World Health Organization (WHO), the mean frequency of tobacco smoking in Turkey was 31,2% (49,4% males & 17,6% females) in 2003 [6]. With such high smoking rates it is obvious that smoking is a major health problem in Turkey which requires attention. However, this epidemiologic information is valuable in assessing its possible effects on various systems. In our study we evaluated the possible effects of smoking on spontaneous passage rates of distal ureteral stones. Previous animal studies results have shown that nicotine increases ureteral contraction frequency [5, 7].
Ureteral stones are most often encountered in the distal portion. The treatment options for stones at this location differ between interventional management and watchful waiting according to the stone dimension. For stones left for spontaneous passage medical expulsive therapy option should be kept in mind. When initiating such a treatment the consequences of obstruction on kidney functions should be known and the period of watchful waiting should be limited with 4 weeks [1].
In the guideline published by EAU in 2013, spontaneous passage rates of stones was 68% and 95% consecutively for stones below 5 mm and 4 mm independent of location [1]. However the same guideline states that these rates significantly differ according to the stone location within the ureter. Spontaneous passage rates of stones below 4 mm in the proximal, mid and distal portions of the ureter were 25%, 45% and 70% respectively. A 5 mm cut-off value was used in the joint guideline of EAU and American Urological Association (AUA) published in 2007 [8]. According to these guidelines spontaneous passage rates were 68% for stones smaller than 5 mm and interventional treatment is advised in stones greater than 5 mm independent of the location the within the ureter. However location specific spontaneous passage rates are not stated in this guideline. Location of the stone within the ureter has been evaluated by some studies and all confirm that stone passage rates are higher in the distal portion [9, 10]. However, detailed evaluations and solid date with respect to stone site and stone size evaluations are scarce.
The subject of medical expulsive treatment has been analyzed in a recently published meta analysis [11]. According to this meta analysis the additional benefit of medical expulsive treatment decreased as stone diameter decreased. The fact that spontaneous expulsion rates increased as stone diameter decreased was the reason why medical expulsive treatment did not have a significant effect in smaller stones. Alpha-blocker studies have shown that stone sizes ≥5 mm demonstrated a significant benefit from medical expulsive treatment [11]. In our study the spontaneous expulsion rates of stones ≥4 mm were lower in patients with smoking habits. The rate of spontaneous expulsion was 46% in smokers and 67% in non-smokers with stones ≥4 mm. However the spontaneous expulsion rate of stones <4 mm was similar in both groups. The data from our study implies that smoking may decrease spontaneous expulsion rates of stones larger than 4 mm.
Anti-edema drugs, spasmolitics, alpha-blockers, calcium channel blockers, prostaglandin inhibitors, glycerin trinitrate and steroids have been researched as an option for medical expulsive therapy [11]. The role of the adrenergic system has been emphasized in many of these studies. The main adrenergic agonist noradrenalin has a dose dependent relationship. Noradrenalin increases the frequency of peristalsis with it s positive chronotropic effect and creates ureteral obstruction with its inotropic effect that causes contraction in the smooth muscle cells of the ureter. Due to these reasons alpha adrenergic stimulus decreases the amount of urine passed through the ureter [12]. Although, the role of the adrenergic system and ureter have extensively been evaluated similar studies about the ach receptor activity is far more less. Especially as nicotine has an effect on the ureteral ach receptors similar studies about its effect may also be carried out.
Boyarsky et al. have shown that nicotine increases the peristaltic activity of the ureter in dogs. In their study they administered nicotine by intravenous, inhaled or topical route and shown that both intravenous and inhaled nicotine, although effective at different dosages, do alter the peristalsis of the ureter [5]. Nicotine most probably exhibits this effect on the ureter over the cholinergic receptors proven to be present in the ureter also [13]. Further studies have shown that in each breath of a cigarette smoked there is 120 μg nicotine and about 50% of this is absorbed to the circulation in humans. After a single breath of a cigarette the concentration of nicotine reaches 0,15-0,25 μg/ml in the arterial blood [14]. Subsequently a person consuming one cigarette within 1 hour will have 18,3 ng/ml of nicotine in their blood. The study of Boyarsky has stroked our attention and lately the increasing attention to medical expulsive treatments has led us to evaluate the effect of smoking on spontaneous expulsion of ureteral stones.
Our study has shown that spontaneous expulsion of stones is not affected from smoking in patients with stones <4 mm. However in the group of patients with stone diameter ≥4 mm the rate of spontaneous expulsion was lower in patients with smoking habits. These results should be further confirmed with studies including larger numbers of patients.
