British Journol (I/Urology ( 1976). 48, 7- 1 I
0
Urinary Citrate Excretion in Stone-Formers and Normal Controls s.
(i.
WELSHMAN
and M. G .
MCGEOWN
Departments of Clinical Chemistry and Nepplrrology, Belfast City Hospital, Belfast
Citrate is a normal constituent of human urine and is known to form a soluble complex with calcium. The physiological implications of this complex formation have been studied by Hastings c't al. (1934) and by Greenwald (1938). The possibility that a reduction in the urinary excretion of citrate might result in the precipitation of calcium oxalate and the formation of renal calculi has been considered by a number of workers. A reduction in the daily citrate excretions of stone-formers has been reported by Boothby and Adams (1934), Kissin and Locks (1941) and Scott, Huggins and Selman (1943). According to Conway, Maitland and Rennie (1949) only stone-formers with infected urine had a reduced excretion of citrate and they concluded that post-renal destruction of citrate was the probable reason for differences between stone-formers and controls. Hodgkinson (1962) investigated urinary citrate excretion in stone-formers and controls, and concluded that reduced citrate excretion by stone-formers appeared to be the result of impaired renal function. Shorr, Bernheim and Taussky (1942) found that, in women, the excretion of citrate rises during ovulation and that administration of oestrogens increases urinary citrate excretion. In the present study, the 24-hour urinary citrate levels of normal males and females were estimated and compared with those of male and female stone-formers. The results for citrate excretions were also related to urinary calcium excretions.
Material and Methods 24-hour urine collections were obtained from 117 male and 47 female patients with calcium containing stone in whom no aetiological factor had been discovered. These patients were admitted to the Belfast City Hospital over a 3-year period. The diagnosis was established either by the radiological evidence of a stone in the renal tract, or by the passage of a stone or its removal at operation. All patients had normal renal function and were free of urinary tract infection at the time of collection. Stone-formers with such known aetiological factors as hyperparathyroidism, renal tubular acidosis, sarcoidosis and vitamin D intoxication were excluded. Patients with a blood urea over 40 mg/100 ml were excluded from the study. Patients with frank idiopathic hypercalciuria were included. There were 2 control groups, patient and non-patient. 24-hour urine collections were obtained from the individuals in each group. 73 male and 85 female patients with various non-renal diseases were used as patient controls and 108 young adults (aged 17-30 years), consisting of army personnel, nurses and laboratory workers, served as non-patient controls. All the female control cases were single; it is not known how many were using an oral contraceptive. All subjects were on a free diet except that stone-formers were encouraged to maintain a high fluid intake. It was assumed that the effect of individual variations in diet would be insignificant in an investigation involving a relatively large number of persons drawn from a homogeneous population. The difference in diet at home and in homital ought not to be significant as every attempt is made by this hospital to provide a diet similar to that consumed by the patients at home. 7
8
t11117 ISH JOURNAL OF
UKOLOLY
Table I The 24-hour Urinary Excretion of Citrate (mg/24 hours) of Stone-Formers, Patient Controls and Young Adult Controls Group
No.
Mean
S.E.M. ~
~~
S.D.
Actual range 12-848 12-1232 76-792
I 9-865 16-1328 191-1521
~~~~
~~
236 328 370
16.6 30.3
Young adult controls
117 73 59
21.2
I79 256 I72
S tone-formers Females[ Patient controls Young adult controls
47 85 49
22 1 344 552
33.1 29.8 37.7
20 1 275 272
St one-formers
Table I1 Correlation Coefficients and Linear Regression Equations for Citrate on Calcium in mg/24 hours for Stone-Formers, Patient Controls and Young Adult Controls Group
No.
Citrate Calcium (nig/24 hr) (mg/24 hr)
Linear regression equation
~~~
Females
~
~
( Stone-formers Patient controls Young adult controls
117 73 59
236 328 3 70
203 I83 213
Cit
Stone-formers Patient controls Young adult controls
47 85 49
22 1 344 552
149 174 148
Cit = 67+ 1.07 Ca Cit = 2 3 9 + 0 6 2 Ca Cit = 3 1 2 f I . 6 3 Ca
{
=
I I'
ie\t P
~-
101 +0.66 Ca
Cit = I20+ 1 14 Ca
Ci t = 250+ 0.56 Ca
Citrate in urine was estimated by a specific method using citrate lyase (Welshman and McCanibridge. 1973). Calcium was determined by an autoanalyser technique (Technicon Methodology N-3B), involving the reaction of cresolphthalein complexone with calcium in the presence of diethylamine. Creatinine was determined hy the alkaline picrate reaction, using an autoanalyser (Technicon Methodology N-l 1b).
Results The mean 24-hour citrate excretion, expressed as mg per 24 hours, of stone-formers, young adult controls and patient controls, are given in Table I. The mean citrate excretion of the male stoneformers was significantly lower (P 0.05) in citrate excretion between the male and female patient controls. In the young adult control group, females exhibited a highly significant increa\e ( P < 0.001) in citrate excretion relative to the males. The urinary citrate excretions of stone-formers and controls were compared with their 24-hour urinary calcium. These values and the linear correlation equations for citrate on calciuni lire shown in Table 11. A significant correlation was observed for citrate on calcium i n all groups. Citrate excretion was found t o rise with increasing calcium excretion. Using analysis of covariance i t was found that the linear regression lines for the male stone-formers and both male control
URINARY CITRATE EXCRETION IN STONE-FORMERS A N D NORMAL CONTROLS
9
Young female controls
Young inale comrols L
0
IUU
?I10 70Il Cdlcium (in& 24hr)
4011
5011
Fig. 1. Linear regression lines of urinary citrate on calcium for young male controls and young female controls.
groups did not differ significantly in either slope or position (P>0.05). The linear regression lines for female stone-formers and both female control groups were not significantly different in slope (P>O.O5). However the positions of the lines for the young adult females and the female stoneformers are significantly different (P ~ 0 . 0 5 showing ) that the mean citrate excretion relative to calcium is greater in the young female controls compared with the female stone-formers. The linear regression equations of citrate on calcium for the young adult male and female controls given in Figure 1, are significantly different in slope (P
0
Urinary Citrate Excretion in Stone-Formers and Normal Controls s.
(i.
WELSHMAN
and M. G .
MCGEOWN
Departments of Clinical Chemistry and Nepplrrology, Belfast City Hospital, Belfast
Citrate is a normal constituent of human urine and is known to form a soluble complex with calcium. The physiological implications of this complex formation have been studied by Hastings c't al. (1934) and by Greenwald (1938). The possibility that a reduction in the urinary excretion of citrate might result in the precipitation of calcium oxalate and the formation of renal calculi has been considered by a number of workers. A reduction in the daily citrate excretions of stone-formers has been reported by Boothby and Adams (1934), Kissin and Locks (1941) and Scott, Huggins and Selman (1943). According to Conway, Maitland and Rennie (1949) only stone-formers with infected urine had a reduced excretion of citrate and they concluded that post-renal destruction of citrate was the probable reason for differences between stone-formers and controls. Hodgkinson (1962) investigated urinary citrate excretion in stone-formers and controls, and concluded that reduced citrate excretion by stone-formers appeared to be the result of impaired renal function. Shorr, Bernheim and Taussky (1942) found that, in women, the excretion of citrate rises during ovulation and that administration of oestrogens increases urinary citrate excretion. In the present study, the 24-hour urinary citrate levels of normal males and females were estimated and compared with those of male and female stone-formers. The results for citrate excretions were also related to urinary calcium excretions.
Material and Methods 24-hour urine collections were obtained from 117 male and 47 female patients with calcium containing stone in whom no aetiological factor had been discovered. These patients were admitted to the Belfast City Hospital over a 3-year period. The diagnosis was established either by the radiological evidence of a stone in the renal tract, or by the passage of a stone or its removal at operation. All patients had normal renal function and were free of urinary tract infection at the time of collection. Stone-formers with such known aetiological factors as hyperparathyroidism, renal tubular acidosis, sarcoidosis and vitamin D intoxication were excluded. Patients with a blood urea over 40 mg/100 ml were excluded from the study. Patients with frank idiopathic hypercalciuria were included. There were 2 control groups, patient and non-patient. 24-hour urine collections were obtained from the individuals in each group. 73 male and 85 female patients with various non-renal diseases were used as patient controls and 108 young adults (aged 17-30 years), consisting of army personnel, nurses and laboratory workers, served as non-patient controls. All the female control cases were single; it is not known how many were using an oral contraceptive. All subjects were on a free diet except that stone-formers were encouraged to maintain a high fluid intake. It was assumed that the effect of individual variations in diet would be insignificant in an investigation involving a relatively large number of persons drawn from a homogeneous population. The difference in diet at home and in homital ought not to be significant as every attempt is made by this hospital to provide a diet similar to that consumed by the patients at home. 7
8
t11117 ISH JOURNAL OF
UKOLOLY
Table I The 24-hour Urinary Excretion of Citrate (mg/24 hours) of Stone-Formers, Patient Controls and Young Adult Controls Group
No.
Mean
S.E.M. ~
~~
S.D.
Actual range 12-848 12-1232 76-792
I 9-865 16-1328 191-1521
~~~~
~~
236 328 370
16.6 30.3
Young adult controls
117 73 59
21.2
I79 256 I72
S tone-formers Females[ Patient controls Young adult controls
47 85 49
22 1 344 552
33.1 29.8 37.7
20 1 275 272
St one-formers
Table I1 Correlation Coefficients and Linear Regression Equations for Citrate on Calcium in mg/24 hours for Stone-Formers, Patient Controls and Young Adult Controls Group
No.
Citrate Calcium (nig/24 hr) (mg/24 hr)
Linear regression equation
~~~
Females
~
~
( Stone-formers Patient controls Young adult controls
117 73 59
236 328 3 70
203 I83 213
Cit
Stone-formers Patient controls Young adult controls
47 85 49
22 1 344 552
149 174 148
Cit = 67+ 1.07 Ca Cit = 2 3 9 + 0 6 2 Ca Cit = 3 1 2 f I . 6 3 Ca
{
=
I I'
ie\t P
~-
101 +0.66 Ca
Cit = I20+ 1 14 Ca
Ci t = 250+ 0.56 Ca
Citrate in urine was estimated by a specific method using citrate lyase (Welshman and McCanibridge. 1973). Calcium was determined by an autoanalyser technique (Technicon Methodology N-3B), involving the reaction of cresolphthalein complexone with calcium in the presence of diethylamine. Creatinine was determined hy the alkaline picrate reaction, using an autoanalyser (Technicon Methodology N-l 1b).
Results The mean 24-hour citrate excretion, expressed as mg per 24 hours, of stone-formers, young adult controls and patient controls, are given in Table I. The mean citrate excretion of the male stoneformers was significantly lower (P 0.05) in citrate excretion between the male and female patient controls. In the young adult control group, females exhibited a highly significant increa\e ( P < 0.001) in citrate excretion relative to the males. The urinary citrate excretions of stone-formers and controls were compared with their 24-hour urinary calcium. These values and the linear correlation equations for citrate on calciuni lire shown in Table 11. A significant correlation was observed for citrate on calcium i n all groups. Citrate excretion was found t o rise with increasing calcium excretion. Using analysis of covariance i t was found that the linear regression lines for the male stone-formers and both male control
URINARY CITRATE EXCRETION IN STONE-FORMERS A N D NORMAL CONTROLS
9
Young female controls
Young inale comrols L
0
IUU
?I10 70Il Cdlcium (in& 24hr)
4011
5011
Fig. 1. Linear regression lines of urinary citrate on calcium for young male controls and young female controls.
groups did not differ significantly in either slope or position (P>0.05). The linear regression lines for female stone-formers and both female control groups were not significantly different in slope (P>O.O5). However the positions of the lines for the young adult females and the female stoneformers are significantly different (P ~ 0 . 0 5 showing ) that the mean citrate excretion relative to calcium is greater in the young female controls compared with the female stone-formers. The linear regression equations of citrate on calcium for the young adult male and female controls given in Figure 1, are significantly different in slope (P
