The captopril renogram: a new tool for diagnosing and predicting obstruction in childhood hydronephrosis

Plasma renin activity for monitoring vesicoureteric reflux therapy: mid-term observations

OBJECTIVE

To study plasma renin activity (PRA) as an early marker for monitoring treatment of vesicoureteric reflux (VUR).

PATIENTS AND METHODS

Fifty-nine children (35 males and 24 females), mean age 43.3+/-26.5 (range 4.5-89) months, with various grades (I-V) of primary VUR were enrolled. PRA, renal scars, split renal function (SRF), glomerular filtration rate (GFR), serum creatinine, blood pressure and episodes of breakthrough urinary tract infection were monitored at regular intervals. Surgery was performed as per currently accepted criteria. PRA values were used for post-hoc analysis of results.

RESULTS

Thirty-eight children (64.4%) underwent anti-reflux surgery during the mean follow up of 17.1+/-3.1 months; 21 (35.6%) continued on non-operative follow up. Rise in PRA up to the time of surgery was seen in all patients. It normalized after surgery in 86%, and reduced but plateaued at a higher level than normal in 13.8% in the surgical group. While improvement in SRF and GFR was seen only in 2/38 (5.2%) and 12/38 (31.6%), respectively, blood pressure stabilized in 30.7% and serum creatinine showed inconsistencies. In non-operatively managed cases, improvement in SRF was seen in only one case and GFR in 14.2% of cases. However, 80.9% children showed a progressive rise in PRA throughout the period of non-operative follow up.

CONCLUSION

Current end points of non-operative management already cause irreversible renal damage by the time surgery is indicated. Our results suggest that serial measurement of plasma renin activity may help in better stratification of patients with moderate to high grade (III-V) VUR with respect to management and prognosis.

Contribution of the renin-angiotensin system to the intrarenal resistive index in chronic unilateral partial ureteral obstruction in dogs

PURPOSE

We investigated the role of the renin-angiotensin system on intrarenal hemodynamics in chronic unilateral partial ureteral obstruction (UPUO) using Doppler ultrasound (US).

METHODS

In 11 dogs with chronic UPUO, we determined the renal resistive index (RI) before and 1 h after the intravenous infusion of an angiotensin-converting enzyme (ACE) inhibitor (captopril), an angiotensin II receptor type 1 (ART1) antagonist (L-158,809), and the combination of these two drugs. Change in resistive index (ΔRI) was calculated as RI after the administration of each tested material minus baseline RI.

RESULTS

At the baseline measurement, significant differences in RI were seen between obstructed and nonobstructed kidneys. ACE inhibitor, ART1 antagonist, or the combination of these drugs did not result in any significant changes in RI in either obstructed or nonobstructed kidneys. However, in obstructed kidneys, ΔRI in the combination of ACE inhibitor and ART1 antagonist were significantly greater than those in ACE inhibitor or ART1 antagonist alone, whereas there were no significant differences in those values in nonobstructed kidneys.

CONCLUSION

These observations suggest that the renin-angiotensin system in dogs with chronic UPUO may not contribute significantly to the differences in intrarenal RI between obstructed and nonobstructed kidneys. However, the angiotensin-producing pathways and angiotensin II receptor subtypes other than ACE and ART1 may have some different effects between obstructed and nonobstructed kidneys.

Congenital unilateral hydronephrosis: a review of the impact of diuretic renography on clinical treatment

PURPOSE

The natural history of and optimal treatment for asymptomatic congenital hydronephrosis is unknown, mainly because most published series are nonrandomized or retrospective with nonstandardized followup regimens. In this survey we provide an overview of the different strategies used for the treatment of congenital unilateral hydronephrosis.

MATERIALS AND METHODS

A comprehensive literature review of clinical studies of asymptomatic congenital unilateral hydronephrosis is presented.

RESULTS

Different criteria for surgical intervention and different followup regimens have been used. Identification of the population at risk has been attempted but results are ambiguous. Surgery is done in approximately 25% of cases when using deteriorating differential function, symptoms and/or increasing hydronephrosis as criteria for operation. A nonstandardized renographic assessment does not compromise evaluation of the ideal followup but it may compromise the functional outcome.

CONCLUSIONS

More studies of kidneys with decreased function, severe hydronephrosis or poor drainage investigated with a standardized protocol are needed to clarify the natural history and establish optimal guidelines for treatment and followup.

Role of plasma renin activity in the management of primary vesicoureteric reflux: A preliminary report

BACKGROUND

Nonoperative management is the choice of therapy in most patients with primary vesicoureteric reflux (VUR). Such patients are regularly monitored for breakthrough urinary tract infection, deterioration of renal function, and progression/ appearance of new scars as the indicators for switching over to surgical intervention. In this descriptive study, we report our additional observations on serial measurement of plasma renin activity (PRA) in a group of such children followed prospectively.

METHODS

Twenty-six children (16 males and 10 females) with various grades (grades I to V) of primary VUR were enrolled. Besides the conventional investigations, we also monitored PRA. Ureteric reimplantation was performed based on established international criteria. PRA levels were correlated with the need for surgical intervention retrospectively.

RESULTS

Mean age at presentation was 39.3 months (range, 12 to 120 months). Nineteen children (73%) were subjected to ureteric reimplantation. The mean PRA in this group (N = 19) was 6.97 ng/mL/hour versus 3.28 ng/mL/hour in patients who were continued on nonoperative management (N = 7). Postoperatively, the PRA reduced and stabilized in all 18 patients at a mean value of 5.4 ng/mL/hour.

CONCLUSION

The currently accepted end points of medical management are inconsistent. On the other hand, 94.7% of children in the surgical group had shown an activation and a progressive increase in PRA. Postoperatively, the PRA was reduced and stabilized in all these patients. Our preliminary observations suggest that high PRA is a more sensitive indicator for surgical intervention as compared to the existing criteria.

Prognostic significance of captopril renography for managing congenital unilateral hydronephrosis

PURPOSE

In this prospective study we evaluated the results of captopril enhanced diuretic renography in patients with congenital unilateral ureteropelvic junction type hydronephrosis. Captopril renography helps to distinguish patients who have renin-angiotensin system activation from those in whom it is not yet activated. Renin-angiotensin system activation heralds the beginning of compensatory vasoactive response in the kidney. Identifying grades of such activation may help in determine the end points of nonoperative management.

MATERIALS AND METHODS

We prospectively studied 25 patients with suspected unilateral ureteropelvic junction obstruction treated at our department. A prenatal diagnosis was made in 60% of cases. Patient age was 1 to 144 months (mean 40) and the male-to-female ratio was 4:1. Followup was 6 to 72 months (mean 30). Patient evaluation and analysis included sonography, standard diuretic and captopril renography, glomerular filtration rate, serum creatinine and blood pressure. The indications for surgery were symptoms, differential function below 35%, or a documented decrease of 10% or more during followup. Activation of the renin-angiotensin system was considered positive when split renal function decreased significantly by 5% or more in an obstructed system on a post-captopril study. The results of captopril renography were examined retrospectively in patients who required surgery according to preexisting criteria.

RESULTS

Society for Fetal Urology hydronephrosis grade was II to IV in 8, 10 and 7 renal units, respectively. The renin-angiotensin system was activated in 8 of the 25 cases (32%) of unilateral ureteropelvic junction obstruction. In 15 patients there was no change on pre-captopril and post-captopril studies and in 2 split renal function on the obstructed side marginally increased on the post-captopril study. Surgical correction was required in only 6 of the 8 patients with renin-angiotensin system activation. Of those who required surgery hydronephrosis was grades II to IV in 3, 1 and in 2 patients, respectively.

CONCLUSIONS

In the current study renin-angiotensin system activation correlated with the need for surgery in 75% of the cases of congenital unilateral ureteropelvic type hydronephrosis. Since captopril serves to identify patients who have renin-angiotensin system activation, it may also be possible to grade this activation. Our preliminary results show that there may be a role for captopril renography for identifying the risk group for surgical intervention.

Angiotensin converting enzyme inhibition worsens the excretory phase of diuretic renography for obstructive hydronephrosis

PURPOSE

A growing body of evidence identifies the renin-angiotensin system as a key factor in the onset and progression of renal damage in chronic partial obstruction, which often represents a complex diagnostic challenge. A prospective study was undertaken to evaluate the role of captopril mercaptoacetyltriglycine-3 (MAG-3) renography as an early diagnostic test of obstruction. We report the results in a subgroup of children who underwent surgical correction for pyeloureteral obstruction.

MATERIALS AND METHODS

Pyeloplasty was performed in 12 patients, including 10 males, 2 to 72 months old (median age 7) with unilateral hydronephrosis, including normal renal function and blood pressure. Basal and captopril enhanced diuretic renography with 99mtechnetium MAG-3 was performed within 24 hours using the same hydration and diuretic stimulus (0.75 mg./kg. furosemide), and 0.75 mg./kg. captopril was administered orally 60 to 90 minutes before scintigraphy.

RESULTS

No adverse effects or modifications of the blood pressure were observed after captopril administration. The diuretic response was deeply worsened by angiotensin converting enzyme inhibition in each hydronephrotic kidney even when the basal study was only slightly abnormal (15-minute washout basal -27 +/- 16%, after captopril -9 +/- 13, p <0.005). After surgical correction the diuretic washout during angiotensin inhibition appeared normal in all patients (15-minute washout -56 +/- 14%). Separate renal function and parenchymal transit of MAG-3 were not modified by angiotensin converting enzyme inhibition, preoperatively or postoperatively.

CONCLUSIONS

Our data confirm the influence of angiotensin on the kidney excretory system in human hydronephrosis and suggest a role for captopril enhanced diuretic renography in the early diagnosis of pyeloureteral obstruction. Further work is needed to evaluate angiotensin converting enzyme inhibition as a protective agent in obstructive nephropathy.

Angiotensin converting enzyme inhibition worsens the excretory phase of diuretic renography for obstructive hydronephrosis

PURPOSE

A growing body of evidence identifies the renin-angiotensin system as a key factor in the onset and progression of renal damage in chronic partial obstruction, which often represents a complex diagnostic challenge. A prospective study was undertaken to evaluate the role of captopril mercaptoacetyltriglycine-3 (MAG-3) renography as an early diagnostic test of obstruction. We report the results in a subgroup of children who underwent surgical correction for pyeloureteral obstruction.

MATERIALS AND METHODS

Pyeloplasty was performed in 12 patients, including 10 males, 2 to 72 months old (median age 7) with unilateral hydronephrosis, including normal renal function and blood pressure. Basal and captopril enhanced diuretic renography with 99mtechnetium MAG-3 was performed within 24 hours using the same hydration and diuretic stimulus (0.75 mg./kg. furosemide), and 0.75 mg./kg. captopril was administered orally 60 to 90 minutes before scintigraphy.

RESULTS

No adverse effects or modifications of the blood pressure were observed after captopril administration. The diuretic response was deeply worsened by angiotensin converting enzyme inhibition in each hydronephrotic kidney even when the basal study was only slightly abnormal (15-minute washout basal -27 +/- 16%, after captopril -9 +/- 13, p <0.005). After surgical correction the diuretic washout during angiotensin inhibition appeared normal in all patients (15-minute washout -56 +/- 14%). Separate renal function and parenchymal transit of MAG-3 were not modified by angiotensin converting enzyme inhibition, preoperatively or postoperatively.

CONCLUSIONS

Our data confirm the influence of angiotensin on the kidney excretory system in human hydronephrosis and suggest a role for captopril enhanced diuretic renography in the early diagnosis of pyeloureteral obstruction. Further work is needed to evaluate angiotensin converting enzyme inhibition as a protective agent in obstructive nephropathy.

Tc-99m DTPA renography in patients with collagen disease

PURPOSE

This study evaluated the use of Tc-99m DTPA renography in patients with collagen disease.

MATERIALS AND METHODS

Tc-99m DTPA renal scintigraphy was performed in 28 patients with clinically diagnosed collagen disease. Twenty-two other patients who underwent renal scintigraphy and were subsequently shown to have no kidney abnormalities served as the control group.

RESULTS

One quarter of the patients with collagen disease had abnormal findings of renography, despite the absence of abnormal laboratory data. Renograms were 100% sensitive for the detection of renal disease in patients with collagen disease, and their specificity was 53% when serum blood urea nitrogen, serum creatinine concentration, and proteinuria were the only measures of renal impairment considered. The glomerular filtration rate was not significantly different between the groups, but the bilateral time to peak was significantly greater in the patients with collagen disease. Hydronephrosis was present in 7% of patients with collagen disease.

CONCLUSION

Renography is useful for detecting early changes of renal involvement when the clinical state of collagen disease is evaluated.