Characteristics of the patients and the gallstones
The whole study group consisted of 46 consecutively cholecystectomized children (median age 13.5 years; range 0.2–18.9; median ISO-BMI 21.5 kg/m2; range 14.4–31.0), of whom 31 were female (Table 1, Fig. 1). All the patients had symptoms related to gallstone disease.
Table 1 Characteristics of the study patients in whole study group (n = 46)1 and in a subgroup, in which both serum and gallstones values were analysed (n = 28) BPS were more abundant in children than in adults (57 % versus 5 %, p < 0.001). The 26 patients with BPS (median age 11.9 years; range 0.2–18.9; median ISO-BMI 19.8 kg/m2; range 14.4–25.5; 15 girls) were on an average 3 years younger than the 20 CS ones (16 girls), and, respectively, the median of their ISO-BMI was 26 % lower (p < 0.05 for both) (Table 1). However, among those children, who participated in serum analysis (n = 28, 17 girls), gender distribution, age and ISO-BMI were equal between the stone subclasses and the controls (Table 1). Analysis of covariance showed that these confounding factors did not change the statistically significant differences in serum and gallstone values between the groups reported here. Two patients were Africans, the other BPS ones were Caucasians.
In the CS-group, most of the gallstones were idiopathic (70 %), whereas in the BPS-group the etiopathogenesis was more heterogeneous, and the most common clinical diagnosis were haemolytic diseases (38 %) and idiopathic (27 %) (Table 2). Only four PS patients had a history of parenteral nutrition. Preoperative serum values of haemoglobin, white and red blood cells, platelets, C-reactive protein and sedimentation rate were within normal limits in both subgroups of patients (not shown). Preoperative serum levels of γGT were elevated by 1.6- - 5-fold in 19 % of the patients with BPS and in 10 % among those with CS (p = 0.33) (Table 3). The median of total bilirubin level in serum was two times higher in BPS than in CS (p = 0.02) (Table 3). Respectively, serum levels of ALP were above the upper limit of normal by 1.1- - 1.3-fold in 8 % (BPS-group) and in 9 % (CS-group) (p = 1.00).
Table 2 Past or present clinical diagnosis in gallstone patients Table 3 Preoperative liver biochemistry of gallstone patients Of the BPS, 23 % were single, 8 % were multiple and 69 % were microlithiasis. Respective percent values for CS were 20 %, 25 % and 55 % (p = 0.267).
Of the five patients with bile duct stones, three had BPS and two had CS. These children had no specific characteristics in their serum sterol levels or in the composition of sterols in the gallstones.
One CS patient was African, one was American Indian, but the other CS ones were Caucasians.
Serum concentrations of enzymatic cholesterol, lipoprotein lipids and bile acids
The mean serum concentrations of lipoprotein lipids and bile acids were equal between the BPS and CS subclasses. The respective concentrations (±SEM) were for enzymatic cholesterol: 3.4 ± 0.3 mmol/l and 4.1 ± 0.3 mmol/l, for LDL-cholesterol 2.0 ± 0.2 mmol/l and 2.6 ± 0.3 mmol/l, for HDL-cholesterol 1.2 ± 0.1 mmol/l and 1.4 ± 0.1 mmol/l, for triglycerides 1.2 ± 0.2 mmol/l and 1.1 ± 0.2 mmol/l and for bile acids 10 ± 8 μmol/l and 21 ± 10 μmol/l.
Serum levels of squalene, cholesterol and non-cholesterol sterols
Compared to the control group, the BPS subclass was characterized by 20–106 % higher ratios to cholesterol of squalene, cholestenol, lathosterol and desmosterol (p < 0.05 for all) (Table 4). Respectively, that of cholestanol was ~11 % higher, but stigmasterol ~41 % lower than control values (p < 0.05 for both).
Table 4 Comparison of serum cholesterol, squalene and non-cholesterol sterols in patients with gallstones and controls Compared to the control group, the CS subclass also had high ratios to cholesterol of squalene and cholesterol precursor sterols excluding desmosterol (21–93 %, p < 0.05 for all), but low those of cholestanol and plant sterols (17–41 % below the control values, p < 0.05 for all) (Table 4).
The differences between the subclasses were 18 % lower cholesterol concentration, but 31–34 % higher ratios to cholesterol of cholestanol, campesterol and sitosterol in the BPS group than in the CS one (p < 0.05 for all) (Table 4). The ratio to campesterol of lathosterol in the CS subclass was 3.2-fold (p = 0.010) and 5.5-fold (p < 0.001) higher than in the BPS and the control groups, respectively (Table 4).
Gallstone sterols and squalene
Compared to the adult controls, the gallstones of the BPS-group were characterized by 2.0–3.1 –fold higher lanosterol and desmosterol values (in terms of mmol/mol of cholesterol) (Table 5). Parallel to that, also plant sterols and cholestanol values were 2.6–3.5 –fold above the controls (p < 0.001 for all) (Table 5).
Table 5 Comparison of gallstone composition of cholesterol, proportions of squalene and non-cholesterol sterols and total bile acids in black pigment stones (n = 26) and cholesterol stones (n = 20) between pediatric patients and adult controls (n = 187) The respective comparison in the CS-group revealed that lanosterol and desmosterol were 2.8–4.0 -fold above the controls (in terms of mmol/mol of cholesterol), and the relative markers of cholesterol absorption, i.e., cholestanol and campesterol, were 1.5–3.4 –fold higher than in controls (p < 0.001 for all) (Table 5).
The comparison of the two stone subclasses with each other showed that the cholesterol content in the BPS stones (mg/100 mg of stone) was, by definition, ~ 2 % of the CS-value (p < 0.001) (Table 5). Compared to the CS, in terms of mmol/mol of cholesterol, the BPS were rich in squalene and lanosterol, but lathosterol was only 46 % of the CS-value (p < 0.001 for both). Respectively, plant sterols sitosterol, stigmasterol and avenasterol, were 3–13 –fold higher in the BPS-subclass (p < 0.001 for all) (Table 5).
The total absolute amount of stone bile acids in BPS was double the controls and 4-times above that of CS (p < 0.05 for both) (Table 5).
Correlations
The age at the time of the cholecystectomy had practically no relation to the variables studied here. ISO-BMI was inversely related to the stone cholestanol proportion in the CS group only (n = 20, r = −0.586, p = 0.007).
In the patients with BPS, serum cholesterol and non-cholesterol sterols were poorly interrelated. However, squalene, the non-sterol precursor of cholesterol (surrogate marker of cholesterol synthesis), was inversely associated with campesterol and sitosterol in serum (as ratios to cholesterol) (r = −0.575 and r = −0.697, p = 0.025 and 0.004, respectively) (Fig. 2a). Furthermore, the stone cholestanol proportion was positively related to the concentration of serum bile acids (Fig. 2b).
In the patients with CS, the surrogate sterol markers of cholesterol absorption cholestanol, campesterol and sitosterol were almost consistently positively interrelated in serum and gallstones, being most evident between serum cholestanol/cholesterol –ratio and the stone proportions of the three surrogate markers of absorption (r-range: +0.673–+0.727, p < 0.03 for each) (Fig. 2c). Serum cholestanol/cholesterol ratio reflected also those of campesterol and sitosterol in serum. Lathosterol/cholesterol –ratio was inversely related to that of cholestanol in serum (r = −0.633, p = 0.036). Furthermore, ratios to cholesterol of serum and gallstone lathosterol were positively interrelated (r = +0.847, p = 0.001).