Captopril-enhanced 99Tcm-MAG3 renal scintigraphy in subjects with suspected renovascular hypertension

Efficacy of Antihypertensive Therapy in a Child with Unilateral Focal Fibromuscular Dysplasia of the Renal Artery: A Case Study and Review of Literature

Background: Fibromuscular dysplasia (FMD) is one of the important etiologies of renovascular hypertension in children. It is usually resistant to multiple antihypertensive agents and can cause extreme elevation in blood pressures, which can lead to end organ damage if not promptly diagnosed and treated. Treatment options include medical management with antihypertensive agents, balloon or stent angioplasties, surgical revascularization, and nephrectomy. The aim of the study was to review the efficacy of antihypertensive therapy only in the management of FMD in a very young child. Methods: This is a retrospective chart study with review of literature. Results: Here, we report a 22-month-old toddler who presented with severe resistant hypertension and cardiomyopathy who was found to have focal FMD of the right renal artery. She also presented with proteinuria, hyponatremia that was probably secondary to pressure natriuresis, hypokalemia, hyperaldosteronism, and elevated plasma renin activity. The stabilization of blood pressures was done medically with the usage of antihypertensive medications only, without the need for angioplasty or surgical revascularization. Conclusions: We demonstrate that surgical intervention may not always be necessary in the treatment of all cases of FMD, especially in a small child where such intervention may be technically challenging and lead to potential complications. Hence, medical management alone may be sufficient, at least for the short-term, in small children with controlled hypertension and normal renal function, with surgical intervention reserved for FMD with medication-refractory hypertension and/or compromised renal function.

Radionuclides in nephrourology, Part 2: pitfalls and diagnostic applications

Radionuclide renal scintigraphy provides important functional data to assist in the diagnosis and management of patients with a variety of suspected genitourinary tract problems, but the procedures are underutilized. Maximizing the utility of the available studies (as well as the perception of utility by referring physicians) requires a clear understanding of the clinical question, attention to quality control, acquisition of the essential elements necessary to produce an informed interpretation, and production of a report that presents a coherent impression based on data contained in the report and that specifically addresses the clinical question. To help achieve these goals, part 1 of this review addressed the available radiopharmaceuticals, quality control, and quantitative indices, including the measurement of absolute and relative renal function. Part 2 assumes familiarity with part 1 and focuses on the common clinical indications of suspected obstruction and renovascular hypertension; part 2 also summarizes the status of radionuclide renal imaging in the evaluation of the transplanted kidney and the detection of infection, discusses potential pitfalls, and concludes with suggestions for future research. The series of SAM questions accompanying parts 1 and 2 has been designed to reinforce and extend points made in the review. Although the primary focus is the adult patient, aspects of the review also apply to the pediatric population.

Clinical Use of Laboratory Tests for the Identification of Secondary Forms of Arterial Hypertension

The prevalence of secondary hypertension can be underestimated if appropriate tests are not performed. The importance of selecting patients with a high pre-test probability of secondary forms of hypertension is first discussed. The laboratory tests currently used for seeking a cause of hypertension are critically reviewed, with emphasis on their operative features and limitations. Strategies to identify primary aldosteronism, the most frequent form of secondary hypertension, and to determine its unilateral or bilateral causes are described. Treatment entails adrenalectomy in unilateral forms, and mineralocorticoid receptor blockade in bilateral forms. Renovascular hypertension is also a common, curable form of hypertension, that should be identified as early as possible to avoid the onset of cardiovascular target organ damage. The tests for its confirmation or exclusion are discussed. The various tests available for the diagnosis of pheochromocytoma, which is much rarer than the above but extremely important to identify, are also described, with emphasis on recent developments in genetic testing. Finally, the tests for diagnosing some rarer monogenic forms and other renal and endocrine causes of arterial hypertension are explored.

Renovascular disease

The gold standard for the diagnosis of renal artery stenosis is angiography, with response to treatment the proof of its significance. Non-invasive methods of investigation are required and are now available including functional imaging, ultrasound, CT and MR angiography and the merits and limitations of these tests are discussed.

Radionuclide renography: a personal approach

Recent advances have increased the value of radionuclide renography in evaluating the patient with suspected disease of the genitourinary tract. The use of the consensus process to help standardize procedures and recommend interpretative criteria provides guidance for the nuclear medicine practitioner, serves as a basis to improve the standard of practice, and facilitates pooling of data from different centers. This review draws on the consensus criteria to present a personal approach to radionuclide renography with a particular emphasis on diuresis renography and the detection of renovascular hypertension. Patients are encouraged to come well hydrated and void immediately prior to the study. Our standard radiopharmaceutical is 99mTc mercaptoacetyltriglycine (MAG3). Routine quantitative indices include a MAG3 clearance, whole kidney and cortical (parenchymal) regions of interest, measurements of relative uptake, time to peak height (Tmax), 20 min/max count ratio, residual urine volume and a T(1/2) in patients undergoing diuresis renography. A 1-minute image of the injection site is obtained at the conclusion of the study to check for infiltration because infiltration can invalidate a plasma sample clearance and alter the renogram curve. A postvoid image of the kidneys and bladder is obtained to calculate residual urine volume and to better evaluate drainage from the collecting system. In patients undergoing diuresis renography, the T(1/2) is calculated using a region of interest around the activity in the dilated collecting system. A prolonged T(1/2), however, should never be the sole criterion for diagnosing the presence of obstruction; the T(1/2) must be interpreted in the context of the sequential images, total and individual kidney function, other quantitative indices and available diagnostic studies. The goal of ACE inhibitor renography is to detect renovascular hypertension, not renal artery stenosis. Patients with a positive study have a high probability of cure or amelioration of the hypertension following revascularization. In patients with azotemia or in patients with a small, poorly functioning kidney, the test result is often indeterminate (intermediate probability) with an abnormal baseline study that does not change following ACE inhibition. In patients with normal renal function, the test is highly accurate. To avoid unrealistic expectations on the part of the referring physician, it is often helpful to explain the likely differences in test results in these two-patient populations prior to the study.

Differences between 99mTc-DTPA and 99mTc-MAG3 captopril renographies in renovascular hypertension

Captopril renography (CRS) with 99mTc-DTPA and 99mTc-MAG3 was performed on a 21-year-old woman with renovascular hypertension due to right renal artery stenosis caused by fibromuscular dysplasia. In the affected kidney, the renogram pattern was substantially changed with 99mTc-DTPA and 99mTc-MAG3 following the administration of captopril, and the quantitated renal uptake indicating individual renal function was significantly decreased in 99mTc-DTPA and slightly decreased in 99mTc-MAG3. In the contralateral normal kidney, the renogram showed some minor changes with both radioagents, while the quantitated renal uptake was significantly decreased with 99mTc-DTPA and substantially increased with 99mTc-MAG3. The combined use of physiologically different renal agents 99mTc-DTPA and 99mTc-MAG3 is helpful in investigating hemodynamic and functional changes in the stenosed kidney as well as the normal kidney in RVH.