Renal and peri-renal abscesses in children: proposed physio-pathologic mechanisms and treatment algorithm.

Renal and perinephric abscess in children are uncommon. Three basic pathophysiologic mechanisms are involved, namely, hematogenous spread, ascending infection and contamination by proximity to an infected area. Six pediatric patients diagnosed with renal abscess were treated at our institution from 1990-2000. Five patients were females; ages ranged from 3-17 years (mean 11.8 years). Diagnosis, as expected, was not readily apparent at presentation. Computerized tomography and renal sonograms were the most useful imaging modalities. Gram-negative bacteria were commonly isolated; only one patient grew Staphylococcus aureus. All patients received broad-spectrum intravenous antibiotics. Additional treatments consisted of percutaneous drainage (4 patients), exploratory laparotomy (1 patient, for presumed Wilm's tumor) and nephrectomy (2 patients). A new classification of the etiologic mechanisms of this condition is proposed along with a simple and practical treatment algorithm.

Perinephric pseudocysts in the cat: a retrospective study and review of the literature.

Perinephric pseudocysts (PNPs) are fluid-filled fibrous sacs that surround the kidney and are not lined by an epithelium. In cats, PNPs are idiopathic, but they usually occur in association with chronic renal failure (CRF). Thirteen cats with PNPs were examined. PNPs occurred in mixed breed cats of either sex with a median age of 16 years. The PNP was palpable on physical examination and usually was interpreted as renomegaly. Clinicopathologic findings reflected CRF, and urinary tract infection was common. Rarely, a primary renal disease was diagnosed concurrent with PNPs and CRF. Diagnosis of PNPs was made by ultrasound examination and fine-needle aspiration, and treatment was by surgical removal of the PNP or ultrasound-guided drainage. Compared to previous reports of PNPs, this series of cats tended to be older and no sex predilection was found, but other findings were similar to those in the literature. Cats with PNPs may have a favorable prognosis if CRF is not severe and no other concurrent diseases are present.

Effects of endothelin upon blood pressure in normotensive rabbits and in perinephritis hypertension.

AIMS: The effects of endothelin upon blood pressure were investigated in normotensive and hypertensive rabbits. METHODS: Endothelin was injected intravenously into conscious animals and blood pressure was monitored. Groups were pretreated with vehicle, calcium antagonists, indomethacin to block prostaglandin release, or NG-nitro-L-arginine methyl ester (L-NAME) to block endothelium-derived relaxing factor (EDRF) production in order to study the mechanisms of action of endothelin in normotensive and hypertensive animals. RESULTS: Intravenous endothelin caused a rapid depressor response lasting less than 1 min followed by a prolonged pressor response. Calcium antagonists attenuated this pressor response. Hypertensive animals showed a greater sensitivity to calcium antagonists than normotensives. High concentrations of calcium antagonists abolished the pressor response, revealing a more prolonged depressor response lasting up to 5 min. Indomethacin pretreatment caused an apparent dose-related increase in pressor responses in all animals. L-NAME pretreatment enhanced responses in normotensives but caused no change or a decrease in these responses in hypertensive animals. Neither calcium antagonists, indomethacin or L-NAME modified the initial depressor response to endothelin. However when given together with nifedipine infusion, which abolished the pressor response, indomethacin and L-NAME decreased the duration of the depressor response. CONCLUSIONS: In conscious rabbits extracellular calcium influx is important in mediating pressor responses to endothelin. In normotensive rabbits endothelin apparently causes release of prostaglandin and EDRF modifying responses. In hypertensive rabbits, a role for prostaglandins but not EDRF was observed in modulating responses to endothelin. Thus, the measured response to endothelin is the sum of a number of effects, the relative importance of which may be altered in pathological conditions.

Changes in diastolic cardiac function in developing and stable perinephritic hypertension in conscious dogs.

The effects of developing perinephritic hypertension (2-3 weeks) and a more stable period of perinephritic hypertension (approximately 14 weeks) were examined on indexes of left ventricular (LV) diastolic function in conscious, chronically instrumented dogs. The complete period of diastole was studied using indexes of isovolumic relaxation (tau), early filling (LV +dD/dt), and stiffness (myocardial stiffness and chamber stress/diameter ratio). During developing hypertension, increased LV end-diastolic pressure, LV end-diastolic stress, peak filling rate, myocardial stiffness, and the stress/diameter ratio increased (p less than 0.05); the time constant tau was not changed. These changes were associated with preserved baseline levels of coronary blood flow (radioactive microspheres) but an impaired coronary vasodilator response to adenosine. Acute administration of phenylephrine in the normotensive dogs caused increases in systolic and diastolic stress and resulted in increases in myocardial stiffness and in the stress/diameter ratio similar to values observed in developing hypertension. During stable hypertension, LV end-diastolic stress, peak filling rate, and both parameters of late-diastolic function (myocardial stiffness and stress/diameter ratio) returned toward control values, but the isovolumic relaxation time constant was increased. Quantitative histological evaluation revealed no increase in stainable connective tissue in dogs with stable hypertension compared with control dogs, and hydroxyproline concentration was not increased in the subendomyocardium, midmyocardium, or subepimyocardium of the dogs with chronic perinephritic hypertension. Thus, in developing hypertension, major alterations in diastolic function were observed that were not structurally related, since these changes 1) could be induced in normal dogs by increasing preload and afterload acutely with phenylephrine and 2) were improved during the ensuing stable period of hypertension.

Inotropic response to norepinephrine is augmented early and maintained late in conscious dogs with perinephritic hypertension.

We studied the inotropic responses to intravenous infusions of norepinephrine in nine conscious chronically instrumented dogs before and early (2-4 weeks) in the development of perinephritic hypertension; seven conscious dogs were studied later (approximately 14 weeks), during a more stable phase of hypertension. perinephritic hypertension was associated with a 24% increase in left ventricular (LV) mass during developing hypertension; no further increase was seen during the stable hypertension phase. LV end-systolic stress was increased early (p less than 0.01) but was normalized later. The LV end-systolic stress-volume relation demonstrated an enhanced contractile response to norepinephrine during developing hypertension, which returned toward control later in the course of stable hypertension. The LV dP/dt responses to norepinephrine (0.4 microgram/kg/min) were significantly greater during developing hypertension (7,509 +/- 337 mm Hg/sec, p less than 0.05) compared with the control period (4,737 +/- 286 mm Hg/sec) and returned toward the control value during stable hypertension (5,168 +/- 465 mm Hg/sec). The enhanced inotropic responses to norepinephrine in developing hypertension were preserved in the presence of ganglionic blockade, suggesting that the augmentation was not mediated via reflex mechanisms. These physiological responses were associated with an increase in beta-adrenergic receptor density, but no significant change in basal or maximal adenylate cyclase stimulation occurred during developing hypertension. Thus, in contrast to prior studies in anesthetized animals, the inotropic response to beta-adrenergic stimulation is not depressed in conscious dogs but is enhanced selectively during the development of hypertension and maintained during stable hypertension.

Left ventricular end-systolic wall stress--dimension relationship in unanesthetized dogs with perinephritic hypertension.

To study myocardial contractility in hypertensive hearts with normal wall motion, we examined left ventricular end-systolic wall stress-dimension relationships (ESWDR) during a baseline period (CS: control stage) and in the eighth week after induction of systemic hypertension by Page's method (HS: hypertensive stage) in unanesthetized dogs. The mean aortic blood pressure increased from 94 +/- 11 to 142 +/- 26 mmHg (p less than 0.01). The end-diastolic left ventricular posterior wall thickness increased significantly during the HS (9.4 +/- 1.3 vs 7.3 +/- 1.3 mm; HS vs CS), and its dimension was significantly (p less than 0.05) smaller than it was during the CS (37.0 +/- 4.2 vs 39.9 +/- 4.6 mm; HS vs CS). There were no significant differences between the 2 stages in left ventricular fractional shortening (31.9 +/- 5.0 vs 32.6 +/- 2.8; HS vs CS), in end-systolic meridional left ventricular wall stress (75.3 +/- 10.8 vs 68.3 +/- 15.6 10(3) dynes/cm2; HS vs CS), or in the ESWDR slopes (98.6 +/- 17.7 vs 94.0 +/- 19.7; HS vs CS). The ESWDR dimension intercepts significantly decreased from 2.0 +/- 0.3 to 1.8 +/- 0.3 cm during the HS; that is, the relationship shifted to the left with no significant change in the slope. At autopsy, the ratio of left ventricular weight to body weight of the hypertensive dogs was significantly (p less than 0.01) greater than that of sham-operated control dogs (6.0 +/- 0.9 vs 4.3 +/- 0.5 g/kg).(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased intraocular pressure in dogs with one-kidney, one wrapped hypertension.

We examined the relationship of intraocular pressure and the development of one-kidney, one wrapped (perinephritic) hypertension in the dog. Conscious femoral arterial pressure (direct arterial puncture) and intraocular pressure (Schiotz tonometer) were measured weekly before and after the surgical induction of hypertension in 11 healthy male mongrel dogs and before and after unilateral nephrectomy in 15 normotensive control dogs. Preoperative mean arterial pressure (102 +/- 5 vs 99 +/- 8 [SD] mm Hg, hypertensive vs control dogs) and intraocular pressure (18.1 +/- 2.5 vs 17.7 +/- 2.1 mm Hg, hypertensive vs control dogs) were similar in both groups. In normotensive control dogs, mean arterial pressure and intraocular pressure averaged over the postoperative period (4-8 weeks) did not differ significantly from preoperative values. In contrast, during the same period arterial pressure significantly increased and intraocular pressure significantly decreased in hypertensive dogs (arterial pressure, 163 +/- 8 mm Hg; intraocular pressure, 11.9 +/- 4.0 mm Hg; p less than 0.001 for both values compared with corresponding values in control dogs). Intraocular pressure was inversely related to arterial pressure in hypertensive dogs (r = 0.56, p less than 0.01). These observations indicate that intraocular pressure decreases with the development of canine one-kidney, one wrapped hypertension. The mechanism of this decrease may be related to abnormalities in Na+,K+-adenosine triphosphatase activity found in this form of hypertension.

Systemic and regional hemodynamic characteristics of bilateral cellophane perinephritis hypertension in conscious rabbits.

Using the radioactive microsphere technique, systemic and regional hemodynamic variables were measured in normotensive rabbits and in rabbits with bilateral cellophane perinephritis hypertension. An average decrease in cardiac output of 18 percent was measured in the hypertensive rabbits as a result of a reduction in stroke volume; heart rate remained unchanged. Thus, in the established phase, hypertension was maintained by the elevated total peripheral resistance. A redistribution of cardiac output was observed in the hypertensive rabbits; a significantly higher fraction was received by the brain, small intestine and heart. The weight normalized blood flow to the kidneys, spleen, skeletal muscles, bones and fat was significantly decreased while an increase in vascular resistance was observed in the hypertensive rabbits in all the organs investigated. A negative correlation existed between the weight of the left ventricle and the blood flow to the left ventricle in hypertensive rabbits, suggesting inadequate coronary perfusion as myocardial hypertrophy becomes more pronounced.

Effects of angiotensin antagonists in various forms of experimental arterial hypertension.

The dependence of renal hypertension on increased levels of angiotensin II was investigated in conscious dogs at various stages of hypertension of four different types. Two of the most potent angiotensin inhibitors, Sar1-Ile8- and Sar1-Thr8-angiotensin II, were infused separately in various doses and at different times throughout the evolution of renal hypertension. The results of these experiments are consistent with the view that the renin-angiotensin system may participate in the acute and malignant phases of renal hypertension; they do not provide evidence for its participation when hypertension enters the chronic phase.

Perinephritis hypertension in monkeys. I. An increase of plasma renin activity associated with increased permeability of retinal vessels and angionecrosis.

The renal parenchyma of 5 crub-eating monkeys (Macaca irus) was wrapped by cellophane, and plasma renin activity, blood pressure and vascular permeability of ocular ground were measured in comparison with 5 unoperated control monkeys. The results demonstrated that increases of systolic arterial pressure, plasma renin activity, and permeability of the retinal vessels were found in 4 operated monkeys. There was no such abnormal finding in the unoperated control monkeys. Generally there was a rough parallelism among levels of plasma renin activity and systolic blood pressure, an increase of permeability of retinal vessels and fibrinoid angionecrosis and/or necrotizing angitis similar to polyarteritis nodosa.