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The Lesser Circulation of the Kidney
239
THE LANCET LONDON:SATURDAY, AUGUST 17, 1946
The Lesser Circulation of the
Kidney
light is shed on our conception of renal by current work at Oxford, summarised in a preliminary communication from TRUETA, BARCLAY, FRESH
function
FRANKLIN, DANIEL, and PRICHARD circulated at
on
p.
237, and
of the
meeting Physiological Society.! Their investigations began in attempts to explain the mechanism of crush syndrome ; and, having demonstrated that a nervous reflex profoundly alters the renal blood-flow, they proceeded by a series of experiments, which need not be recounted here, to disclose the existence of a delicately balanced alternative circulation through the cortex and the medulla respectively. The vascular architecture of the cortex is sufficiently complicated to be still the subject of anatomical investigation, although it has been intensively studied for many years. The arrangea
recent
ment and functions of the
vasa
recta,
on
the other
hand, have been relatively neglected ; though, diswisdom after the event, it may now be admitted that the peculiar lea,sh-like disposition of these wide vascular loops in the medulla is not one that appears primarily related to the nutrient requirements of the tubules of that part. Their most important function seems to lie in the provision of an alternative route for the blood flowing through the
playing
the important cortical circulation variable degree, be shut down. This functional conception has important physiological and pathological implications. Thus it becomes understandable how physiological diminutions in urinary output may be adjusted-for example, when large amounts of fluid are being eliminated from the body by other routes—without greatly diminishing the It provides an blood-flow through the kidney. the sudden cessation of diuresis in for explanation stress 2 since the medulto an emotional dogs subjected is nervous This inhibition control. under lary bypass of diuresis was not demonstrated when the splanchnic nerves had previously been cut, and the kidneys denervated. The only obvious alternative explanation of these observations would be to suppose that the sole change lay in constriction of the cortical vessels, with resulting ischsemia. But this would mean that the vascular bed, through which a quarter of the bloodoutput of the heart flows, is suddenly cut out of the circulation. From this a sudden and dramatic rise in blood-pressure might be expected, unless a bypass were provided to take this extra volume of blood. There is no record of such a rise in blood-pressure. It is therefore reasonable to suppose that, during active diuresis, the cortical circulation is fully open,
kidney, whereby may, to
a
1. J. Physiol. (in the press). 2. O’Connor, W. J., Verney, E. B.
33, 77.
Quart. J. exp. Physiol. 1945,
while in anuria the medullary circulation is in action and the cortical circulation is thus bypassed. For pathologists this may well be the key to many conundrums. A certain type of renal lesion common to a variety of conditions, such as the crush syndrome, incompatible blood-transfusion, blackwater fever, and renal failure complicating abortion-to name the best known of them-is now generally recognised, and has been frequently described of late years. In these kidneys there are variable degrees of tubular degeneration and necrosis in the cortex ; the cortex as a whole is relatively ansemic, though the interlobular veins may be engorged, while the vasa recta are conspicuously engorged ; the presence of large numbers of pigmented casts within the tubules, especially the collecting tubules in the medulla, completes the main features of the picture. It is of interest to recall that SnAW DUNN and MONTGOMERY3 observed, in a heterogeneous group of cases showing renal cortical necrosis, that the arrest of circulation was incomplete in the proximal parts of the interlobular arteries " owing to easier escape of blood through deep glomeruli whose efferents pass by short routes direct to the medulla and not to the cortical rete." Evidence has been collected pointing to an anoxic mechanism in the production of this picture, and the term " renal anoxia " has been coined for it by B. G. MAEGRAITH. In the letter by MAEGRAITII and R. E. HAVARD published in our last issue the belief is clearly expressed that, in this syndrome, there is some redistribution of the blood-flow within the kidney ... it is unlikely that the dynamics of the renal circulation will be elucidated until better techniques enable us to study the living functioning organ." This prophecy has been speedily fulfilled : the anoxia results from the shunting of blood from the cortex to the medulla. Supporting evidence from the angle of treatment is provided in the recent report by O’SULLIVAN and SPITZER4 of a series of cases of acute renal failure complicating abortion. Two of the most serious of these were cured by a bilateral posterior splanchnic block, according to the method of KAPPIS. In both the response was dramatic, though in one the operation was at first ineffective and had to be repeated after six days, when the patient appeared moribund. This method of treatment, which according to O’SULLIVAN and SPITZER was first introduced by NEUWIRTH in 1922, is manifestly deserving of further trial in these cases of anuria. Much remains to be learnt concerning the stimuli that deflect the renal blood from the cortex to the medulla, and the transitions that turn a physiological into a pathological process. The incidence of anoxic cortical changes, of the kind that have been mentioned, in such diverse conditions as sulphonamide therapy, Clostridium welchii infections, and burns suggests that certain toxins can initiate the reflex, which serves to protect the cortical elements from damage. We know nothing as yet of those minor adjustments of the renal circulation that are unattended by pathological sequelse, but we may be justified in regarding the "
pathological examples mechanism
has
been
as
cases
called
where too
protective drastically into a
operation. 3. Dunn, J. S., Montgomery, G. L. J. Path. Bact. 1941, 52, 1. 4. O’Sullivan, J. V., Spitzer, W. J. Obstet. Gynœc. 1946, 53, 158.
THE LANCET LONDON:SATURDAY, AUGUST 17, 1946
The Lesser Circulation of the
Kidney
light is shed on our conception of renal by current work at Oxford, summarised in a preliminary communication from TRUETA, BARCLAY, FRESH
function
FRANKLIN, DANIEL, and PRICHARD circulated at
on
p.
237, and
of the
meeting Physiological Society.! Their investigations began in attempts to explain the mechanism of crush syndrome ; and, having demonstrated that a nervous reflex profoundly alters the renal blood-flow, they proceeded by a series of experiments, which need not be recounted here, to disclose the existence of a delicately balanced alternative circulation through the cortex and the medulla respectively. The vascular architecture of the cortex is sufficiently complicated to be still the subject of anatomical investigation, although it has been intensively studied for many years. The arrangea
recent
ment and functions of the
vasa
recta,
on
the other
hand, have been relatively neglected ; though, diswisdom after the event, it may now be admitted that the peculiar lea,sh-like disposition of these wide vascular loops in the medulla is not one that appears primarily related to the nutrient requirements of the tubules of that part. Their most important function seems to lie in the provision of an alternative route for the blood flowing through the
playing
the important cortical circulation variable degree, be shut down. This functional conception has important physiological and pathological implications. Thus it becomes understandable how physiological diminutions in urinary output may be adjusted-for example, when large amounts of fluid are being eliminated from the body by other routes—without greatly diminishing the It provides an blood-flow through the kidney. the sudden cessation of diuresis in for explanation stress 2 since the medulto an emotional dogs subjected is nervous This inhibition control. under lary bypass of diuresis was not demonstrated when the splanchnic nerves had previously been cut, and the kidneys denervated. The only obvious alternative explanation of these observations would be to suppose that the sole change lay in constriction of the cortical vessels, with resulting ischsemia. But this would mean that the vascular bed, through which a quarter of the bloodoutput of the heart flows, is suddenly cut out of the circulation. From this a sudden and dramatic rise in blood-pressure might be expected, unless a bypass were provided to take this extra volume of blood. There is no record of such a rise in blood-pressure. It is therefore reasonable to suppose that, during active diuresis, the cortical circulation is fully open,
kidney, whereby may, to
a
1. J. Physiol. (in the press). 2. O’Connor, W. J., Verney, E. B.
33, 77.
Quart. J. exp. Physiol. 1945,
while in anuria the medullary circulation is in action and the cortical circulation is thus bypassed. For pathologists this may well be the key to many conundrums. A certain type of renal lesion common to a variety of conditions, such as the crush syndrome, incompatible blood-transfusion, blackwater fever, and renal failure complicating abortion-to name the best known of them-is now generally recognised, and has been frequently described of late years. In these kidneys there are variable degrees of tubular degeneration and necrosis in the cortex ; the cortex as a whole is relatively ansemic, though the interlobular veins may be engorged, while the vasa recta are conspicuously engorged ; the presence of large numbers of pigmented casts within the tubules, especially the collecting tubules in the medulla, completes the main features of the picture. It is of interest to recall that SnAW DUNN and MONTGOMERY3 observed, in a heterogeneous group of cases showing renal cortical necrosis, that the arrest of circulation was incomplete in the proximal parts of the interlobular arteries " owing to easier escape of blood through deep glomeruli whose efferents pass by short routes direct to the medulla and not to the cortical rete." Evidence has been collected pointing to an anoxic mechanism in the production of this picture, and the term " renal anoxia " has been coined for it by B. G. MAEGRAITH. In the letter by MAEGRAITII and R. E. HAVARD published in our last issue the belief is clearly expressed that, in this syndrome, there is some redistribution of the blood-flow within the kidney ... it is unlikely that the dynamics of the renal circulation will be elucidated until better techniques enable us to study the living functioning organ." This prophecy has been speedily fulfilled : the anoxia results from the shunting of blood from the cortex to the medulla. Supporting evidence from the angle of treatment is provided in the recent report by O’SULLIVAN and SPITZER4 of a series of cases of acute renal failure complicating abortion. Two of the most serious of these were cured by a bilateral posterior splanchnic block, according to the method of KAPPIS. In both the response was dramatic, though in one the operation was at first ineffective and had to be repeated after six days, when the patient appeared moribund. This method of treatment, which according to O’SULLIVAN and SPITZER was first introduced by NEUWIRTH in 1922, is manifestly deserving of further trial in these cases of anuria. Much remains to be learnt concerning the stimuli that deflect the renal blood from the cortex to the medulla, and the transitions that turn a physiological into a pathological process. The incidence of anoxic cortical changes, of the kind that have been mentioned, in such diverse conditions as sulphonamide therapy, Clostridium welchii infections, and burns suggests that certain toxins can initiate the reflex, which serves to protect the cortical elements from damage. We know nothing as yet of those minor adjustments of the renal circulation that are unattended by pathological sequelse, but we may be justified in regarding the "
pathological examples mechanism
has
been
as
cases
called
where too
protective drastically into a
operation. 3. Dunn, J. S., Montgomery, G. L. J. Path. Bact. 1941, 52, 1. 4. O’Sullivan, J. V., Spitzer, W. J. Obstet. Gynœc. 1946, 53, 158.