Faculty Bibliography

Plasma atrial natriuretic peptide (ANP) levels are elevated in patients with bilateral ureteral obstruction (BUO). To further evaluate the role of ANP in postobstructive diuresis, natriuresis and recovery of renal function, 3 groups of dogs were studied: Group 1, 6 dogs that underwent 48 hours of unilateral ureteral obstruction (UUO); Group 2, 6 dogs that underwent 48 hours of BUO; and Group 3, 6 dogs volume replete with normal saline during 48 hours of BUO. All 3 groups underwent hourly hemodynamic and clearance studies for 15 hours after the release of obstruction. Group 1 experienced no increase in either urine output or sodium excretion from the ipsilateral or contralateral kidney after release of obstruction. Groups 2 and 3 both experienced an initial diuresis and natriuresis after BUO (p < 0.01). However, in Group 2 diuresis and natriuresis after BUO ceased at 5 and 2 hours, respectively, while in Group 3 both persisted for 10 and 9 hours, respectively. Before obstruction the GFR was similar in all three groups. In Group 1 the GFR decreased significantly in the ipsilateral kidney (34.5 +/- 1.4 to 14.48 +/- 1.5 ml. per minute, (p < 0.01)) and increased significantly in the contralateral kidney (32.4 +/- 2.8 to 44.4 +/- 2.0 ml. per minute, (p < 0.05)) and remained so throughout the postobstruction period. The GFR in Groups 2 and 3 decreased to a similar level 1 hour after release (13.3 +/- 1.7 and 17.5 +/- 3.4 ml. per minute, respectively); however, Group 2 remained decreased during the period after release while group 3 increased to 23.4 +/- 3.4 ml. per minute (p < 0.01) at 11 hours after release of obstruction. In Group 2 the control plasma ANP level was 17.9 +/- 3.7 pg./ml. and was not altered by BUO, whereas ANP increased significantly after 48 hour BUO in Group 3, from 30.6 +/- 6.7 to 63.7 +/- 11.7 pg./ml. (p < 0.01). Before and after 48 hours of BUO, the pulmonary capillary wedge pressure was 5.0 +/- 2.0 mm. Hg and 7.0 +/- 1.0 mm. Hg (NS) in Group 2, while it increased from 7.18 +/- 1.5 mm. Hg to 11.6 +/- 1.9 mm. Hg (p < 0.01) in Group 3. We conclude that volume expansion during BUO enhances postobstructive diuresis and natriuresis and allows a greater recovery of GFR after release of the obstruction. This effect may be mediated through elevated plasma levels of ANP as measured in this study.

Acquired cystic kidney disease occurs in over 74% of patients with ESRD on hemodialysis for more than 4 yr. A variety of complications have been associated with these cysts including bleeding, lithiasis, infection, obstruction, and malignant transformation. An ESRD patient who developed accelerating hypertension secondary to an acute perinephric hematoma due to a bleeding-acquired renal cyst is described. The hypertension, which was refractory to aggressive drug therapy, was controlled only after the involved kidney was removed, after the demonstration of an elevated ipsilateral renal vein renin level. This is the first case reported in which worsening hypertension, apparently due to the "Page Kidney," developed as a complication of perinephric bleeding in an ESRD patient with acquired cystic kidney disease.

This study was undertaken to review our operative experience in the management of pediatric renal trauma. Over a 2-year period (August 1988 to August 1990) 25 of 60 children undergoing celiotomy sustained renal injuries. There were 22 boys and three girls ranging in age from 5 to 18 years. Eighty-four per cent were victims of gunshot wounds, 12 per cent were stabbed, and 4 per cent sustained blunt trauma. The 25 injured children sustained a total of 45 individual organ injuries. Only 16 per cent required a nephrectomy, while the great majority (84%) were managed with renal sparing procedures. When we compared survivors to nonsurvivors, there was more thoracic and vascular injury along with more blood transfusion requirements in nonsurvivors. There was no statistical difference in Pediatric Trauma Score (PTS) between survivors and nonsurvivors (9.8 +/- 0.26 vs 9.5 +/- 1.5). Preoperative intravenous pyelographies (IVPs) performed in 52 per cent of all patients demonstrated the site of injury, presence of contralateral function as well as the anatomic position of the kidneys. We conclude that renal injury is common following penetrating abdominal trauma in childhood, however, these injuries can be managed by early operation with renal sparing procedures. There is a high incidence of associated intra-abdominal injury in those who have sustained penetrating renal trauma, but mortality is more common in patients sustaining associated thoracic and vascular injuries. An IVP should be performed, even in the absence of hematuria, when trauma trajectory strongly suggests urologic injury. This study also illustrates the sharp rise in drug-related urban violence with an associated increase in pediatric renal trauma.

Use of the immunosuppressive agent cyclosporine A (CyA) is limited by its associated nephrotoxicity, characterized by an increase in renal vascular resistance (RVR) and reductions in renal blood flow (RBF) and glomerular filtration rate (GFR). The vascular endothelium produces vasoactive substances including endothelium derived relaxation factor (EDRF) and endothelin (ET), which modulate vascular tone. Since CyA has been shown to damage the endothelium, we examined the renal hemodynamic response to intrarenal ET infusion (4 micrograms./kg./minute) in chronic cyclosporine-treated dogs. Prior to ET infusion, CyA-treated dogs had a lower RBF and a greater RVR than normal dogs. In normal dogs, after ET infusion RVR increased from 30.24 +/- 0.64 to 44.60 +/- 1.66 mmHg./ml./minute (p < 0.001), RBF decreased from 4.26 +/- 0.28 to 2.90 +/- 0.30 ml./min./g. (p < 0.001) and GFR decreased from 50.20 +/- 5.90 to 36.50 +/- 7.90 ml. per minute (p < 0.001). In contrast, there was no change in RBF, GFR and RVR after intrarenal ET infusion in CyA-treated dogs. Prior to ET infusion, arterial plasma ET concentration was 5.0 +/- 1.1 pg./ml. in CyA-treated dogs, similar to 7.5 +/- 1.4 pg./ml. in normal dogs, and was not significantly altered in either group after intrarenal ET infusion. We conclude that ET may not contribute to the increased RVR in chronic cyclosporine nephrotoxicity, and suggest a vascular toxicity of CyA, rendering renal vessels unresponsive to the vasoconstrictive effect of ET.

Plasma prorenin is normally higher than renin and usually changes in response to the same stimuli. In dogs, plasma prorenin and renin disappear after bilateral nephrectomy, indicating that both are of renal origin. It has been proposed that prorenin may mediate tissue renin systems via its reversible intrinsic renin-like activity. The renin-angiotensin system has been implicated in the changes in renal function that occur with bilateral ureteral obstruction, but plasma prorenin has not been investigated. We therefore studied the effect of 48-hour bilateral obstruction on plasma prorenin in two groups of dogs: one was volume expanded (N = 5), while the other group (N = 6) was euvolemic. Plasma prorenin concentration increased fourfold in both groups, angiotensinogen increased twofold, while plasma renin activity was unchanged. Following release of obstruction, plasma renin fell slightly while prorenin and angiotensinogen remained elevated. There was a positive relationship between plasma prorenin and renin before (r = 0.63, P less than 0.05) and after (r = 0.76, P less than 0.01) obstruction. Post-obstruction, ERPF and GFR were subnormal but filtration fraction was maintained; the higher the ERPF and GFR the higher the plasma prorenin post-obstruction (r = 0.83, P less than 0.01 and r = 0.77, P less respectively; N = 11). These results show that impairment of renal function during bilateral obstruction is associated with an increase in plasma prorenin but not renin. Nonetheless, there is a positive relationship between plasma prorenin and renin both pre- and post-obstruction. Thus, preferential impairment of clearance of prorenin relative to renin may occur during bilateral obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal response to release of bilateral ureteral obstruction resembles that to intravenous administration of atrial natriuretic peptide. In a prospective study we measured plasma atrial natriuretic peptide levels before and serially after relief of obstruction in 9 patients (mean age 65 +/- 2 years old) with bilateral ureteral obstruction and azotemia. Obstruction was documented by renal ultrasonography. Before relief of obstruction blood urea nitrogen and serum creatinine levels were 85 +/- 18 (mean +/- standard error) and 8.2 +/- 1.3 mg. per dl., respectively, accompanied by metabolic acidosis but not hyperkalemia. Mean plasma atrial natriuretic peptide (measured by radioimmunoassay) was 129 +/- 28, which was markedly elevated compared to 46 +/- 7 pg. per ml. in 7 age-matched control subjects (p less than 0.01). After relief of obstruction, prominent post-obstructive diuresis and natriuresis ensued; the plasma atrial natriuretic peptide level progressively decreased to that noted in the control group, accompanied by improvement in renal function, and diminishing diuresis and natriuresis. These findings were associated with a significant weight loss and an increase in plasma renin activity (from a mean of 1.57 +/- 0.68 to 5.27 +/- 1.82 ng. per ml. per hour, p less than 0.01). These results suggest that atrial natriuretic peptide release is augmented in patients with bilateral ureteral obstruction and azotemia, probably due to hypervolemia, and may contribute to post-obstructive diuresis and natriuresis.

Primary localized amyloidosis of the ureter is very rare, and only 22 cases have been reported in the world literature. We report the twenty-third case along with a review of the relevant literature. Due to its radiologic resemblance to malignancy, many cases were treated by nephroureterectomy in the past. The case being reported here was successfully treated by local excision and ureteroneocystostomy.