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Cystic malformations of the spleen
310
INTERNATIONAL
elective method is a one stage shunt operation. This technic of splenorenal shnnt is useful for the therapy of older children.--
Keiji~'d Suruga. CYSTIC
MALIZOR~IATIONS OF
THE
SPLEEN,
P. Schadku. Zbl. Chir. 90:2378, 1965. Cystic malformations of the spleen are rare. Usually they are complications of inflammation or cystic degenerative tumors. In a very few cases the cysts are congenital. The author presents 2 cases. In a 10 year old boy the cyst was ruptured because of abdominal trauma; in a 6 year old girl a tumor was palpated. In all patients with tumors in the left upper abdominal quadrant the possibility of a splenic cyst must be considered. Selective angiography of the splenic artery, and contrast-visualization of the adjacent organs can lead to an accurate diagnosis. For splenectomy the abdominal route is preferred.--E. A. Kole. GENITOURINARY TRACT
M. CIaridge. Brit. J. Urol. 37:620, 1965.
T H E PItYSIOLOGY OF MICTURIrION.
Physiology of urinary retention. The intravesical pressure is above atmospheric pressure and urine would leak but for the resistance in the urethra. The detrusor muscle exerts a tension on being stretched, producing the normal bladder tone which is independent of the nerve supply. The pressure in the bladder conforms to the law of Laplace for a sphere which states that the hydrostatic pressure in a hollow sphere is equal to twice the tension in its wall divided by the radius. Thus, if the wall tension and the radius increase equally the intravesical pressure remains constant. The urethral resistance is not due to any encircling muscular sphincter reciprocally innervated by the sympathetic nervous system. The intraurethral pressure at rest is always higher than the intravesical pressure and depends on the law of Laplace as applied to a hollow cylinder which states that the pressure is equal to the wall tension divided by the radius. As the urethra is closed and the radius therefore infinitesimally small, a low wall tension can produce a high intraluminal pressure. The tension results mainly from the
A B S T R A C T S O F P E D I A T R I C SURGERY
passive elasticity of the tissues surrounding the proximal urethra. The intravesical pressure depends not only on t h e tone of the bladder muscle but also on the intra-abdominal pressure. Since the proximal urethra also lies above the pelvic diaphragm it is similarly affected by intraabdominal pressure and the gradient between it and the bladder is maintained. The striated external sphincter acts as an accessory muscle of continence during short periods of extreme stress bnt does not play any part in control under normal conditions. Physiology of bladder emptying. When voiding occurs the intravesical pressure is raised by detrusor contraction under neural control. The manner by which the urethral resistance is reduced is disputed. Probably vesico-urethral muscular contraction opens and shortens the proximal urethra. This concept is supported by flow rate studies during mictnrition. In normal subjects, the flow rate of urine depends on the initial volume in the bladder; the greater the volume the greater the rate. The tension exerted by the detrusor fibres on stimulation depends upon their initial length; those ~bres acting on the bladder neck will therefore produce a wider aperture and greater urethral funnelling the greater the bladder volume. At the end of micturition the urethra is emptied by the voluntary muscles surrounding it. The proximal urethra is emptied back into the bladder and in the male the penile urethra is expressed by the bnlbo-eavernosus muscle.--/. H. Johnston. PYURIA AND BACTERIURIA IN INFANTS AND CHILDREN. T H E VALUE OF P Y U m A AS A DIAGNOSTIC CRITERION OF URINARY
TaACT INFECTIONS. Charles V. Pryles and Christopher R. Eliot. Amer. J. Dis. Child. 110:628-635, 1965. This is a detailed and well-controlled study" on 136 infants and children attending the Pediatric Renal Clinic at the Boston City Hospital. This study reaffirms the point that a "routine urine for analysis is an uncontrolled procedure that never should be done.'" Reports in the past have not been well-controlled, i.e., not on clean-voided ulidstream specimens and hence, the bacteriology and microscopic finding of pyuria has not been well-controlled. This study also strongly reaffirms the
INTERNATIONAL
elective method is a one stage shunt operation. This technic of splenorenal shnnt is useful for the therapy of older children.--
Keiji~'d Suruga. CYSTIC
MALIZOR~IATIONS OF
THE
SPLEEN,
P. Schadku. Zbl. Chir. 90:2378, 1965. Cystic malformations of the spleen are rare. Usually they are complications of inflammation or cystic degenerative tumors. In a very few cases the cysts are congenital. The author presents 2 cases. In a 10 year old boy the cyst was ruptured because of abdominal trauma; in a 6 year old girl a tumor was palpated. In all patients with tumors in the left upper abdominal quadrant the possibility of a splenic cyst must be considered. Selective angiography of the splenic artery, and contrast-visualization of the adjacent organs can lead to an accurate diagnosis. For splenectomy the abdominal route is preferred.--E. A. Kole. GENITOURINARY TRACT
M. CIaridge. Brit. J. Urol. 37:620, 1965.
T H E PItYSIOLOGY OF MICTURIrION.
Physiology of urinary retention. The intravesical pressure is above atmospheric pressure and urine would leak but for the resistance in the urethra. The detrusor muscle exerts a tension on being stretched, producing the normal bladder tone which is independent of the nerve supply. The pressure in the bladder conforms to the law of Laplace for a sphere which states that the hydrostatic pressure in a hollow sphere is equal to twice the tension in its wall divided by the radius. Thus, if the wall tension and the radius increase equally the intravesical pressure remains constant. The urethral resistance is not due to any encircling muscular sphincter reciprocally innervated by the sympathetic nervous system. The intraurethral pressure at rest is always higher than the intravesical pressure and depends on the law of Laplace as applied to a hollow cylinder which states that the pressure is equal to the wall tension divided by the radius. As the urethra is closed and the radius therefore infinitesimally small, a low wall tension can produce a high intraluminal pressure. The tension results mainly from the
A B S T R A C T S O F P E D I A T R I C SURGERY
passive elasticity of the tissues surrounding the proximal urethra. The intravesical pressure depends not only on t h e tone of the bladder muscle but also on the intra-abdominal pressure. Since the proximal urethra also lies above the pelvic diaphragm it is similarly affected by intraabdominal pressure and the gradient between it and the bladder is maintained. The striated external sphincter acts as an accessory muscle of continence during short periods of extreme stress bnt does not play any part in control under normal conditions. Physiology of bladder emptying. When voiding occurs the intravesical pressure is raised by detrusor contraction under neural control. The manner by which the urethral resistance is reduced is disputed. Probably vesico-urethral muscular contraction opens and shortens the proximal urethra. This concept is supported by flow rate studies during mictnrition. In normal subjects, the flow rate of urine depends on the initial volume in the bladder; the greater the volume the greater the rate. The tension exerted by the detrusor fibres on stimulation depends upon their initial length; those ~bres acting on the bladder neck will therefore produce a wider aperture and greater urethral funnelling the greater the bladder volume. At the end of micturition the urethra is emptied by the voluntary muscles surrounding it. The proximal urethra is emptied back into the bladder and in the male the penile urethra is expressed by the bnlbo-eavernosus muscle.--/. H. Johnston. PYURIA AND BACTERIURIA IN INFANTS AND CHILDREN. T H E VALUE OF P Y U m A AS A DIAGNOSTIC CRITERION OF URINARY
TaACT INFECTIONS. Charles V. Pryles and Christopher R. Eliot. Amer. J. Dis. Child. 110:628-635, 1965. This is a detailed and well-controlled study" on 136 infants and children attending the Pediatric Renal Clinic at the Boston City Hospital. This study reaffirms the point that a "routine urine for analysis is an uncontrolled procedure that never should be done.'" Reports in the past have not been well-controlled, i.e., not on clean-voided ulidstream specimens and hence, the bacteriology and microscopic finding of pyuria has not been well-controlled. This study also strongly reaffirms the