Renovascular disease: Doppler ultrasound

Abnormal renal resistive index in patients with mild-to-moderate chronic obstructive pulmonary disease

BACKGROUND

Arterial rigidity and endothelial dysfunction are systemic manifestations of chronic obstructive pulmonary disease (COPD). The decrease in renal vascular resistance in order to adapt the increase in glomerular filtration rate after oral protein loading is known as normal renal functional reserve. We tested the hypothesis that COPD patients, even in those with mild-to-moderate airflow obstruction, are affected by systemic inflammation associated with abnormal renal functional reserve.

MATERIALS AND METHODS

The study enrolled 24 current smokers with a cigarette smoking history ≥ 25 pack-years and 8 nonsmokers with normal spirometry as control. Doppler sonography detected the renal resistive index (RRI) before and after oral protein loading to determine the renal functional reserve. Pulmonary function and serum tumor necrosis factor α (TNF-α) levels were analyzed to compare with the renal functional reserve.

RESULTS

The smokers were stratified into 3 groups (Group 1: smokers with normal spirometry, Group 2: mild COPD, Group 3: moderate COPD); nonsmokers as Group 4. The baseline RRI levels were similar in Group 1 and Group 4. After protein loading, the RRI elevated in all smoking groups; moreover, Group 3 had the highest RRI and with longer duration than other groups. The smokers with higher serum TNF-α levels had a longer RRI elevation. Multiple linear regression revealed forced expiratory volume in one second (FEV1), serum TNF-α levels and aging were independently predictive factors of impaired renal functional reserve.

CONCLUSIONS

A greater impairment in renal functional reserve of COPD patients was correlated with more severe airway obstruction and inflammation.

[Doppler US of the urinary system and renal vessels in normal and pathologic conditions]

The interest of Doppler ultrasound (US) in urinary tract investigation has dramatically increased during the past 10 years. It can provide useful diagnostic informations in pedicular and intrarenal vascular disorders, some medical nephropathies, in the assessment of renal tumors and urinary tract disorders including urolithiasis, acute obstruction and ureteral reflux. Recent technical improvements including the development of US contrast agents (microbubbles) have contributed to increase the diagnostic accuracy of the technique.

Renal infarction secondary to a subcapsular haematoma following percutaneous renal biopsy

We present the case of post-biopsy subcapsular haematoma leading to infarction of the kidney. This is a very uncommon complication of percutaneous renal biopsy. The radiological findings in this case are shown, highlighting the sonographic finding of the renal interlobar arteries having reversed flow in diastole in connection with very high resistance because of compression by a subcapsular haematoma. Although reversed diastolic flow has been well described in renal vein thrombosis, we know of no case report of this finding in association with severe ischaemia of the kidney due to tamponade.

[Diagnostic imaging of peripheral renal vascular disorders]

Peripheral vascular disorders of the kidney involve the intrarenal branches of the renal vascular tree. It include occlusive (infarction and cortical necrosis) and non-occlusive vascular lesions (acquired arteriovenous fistulas, arteriovenous malformation, false aneurysms and microaneurysms). Initial diagnosis relies on color Doppler US and CT angiography. Angiography plays a therapeutic role. MR imaging provides useful diagnostic information on perfusion disorders especially in patients with renal insufficiency.

Emergency Doppler evaluation of the liver and kidneys

Doppler ultrasound is useful in the emergent evaluation of the liver and kidney transplant patient. Arterial stenosis, pseudoaneurysm, and venous thrombosis are treatable causes of allograft failure that can be detected easily with color and spectral Doppler. Doppler has a limited but important role in the emergent evaluation of the native liver and kidneys, usually involving prior biopsy or instrumentation.

Sonography of the kidney and urinary tract

Sonography has become integral to the evaluation and management of patients with renal disease. Although many of the procedures discussed in this issue are not feasible for all nephrologists, sonography clearly is. It is convenient and saves time, both for the physician and the patient, and the equipment is not expensive. It is not a difficult skill to learn, as evidenced by the growing number of nephrologists who have learned it, and it greatly enhances the practice of nephrology. Even nephrologists who do not plan to acquire this skill should be familiar with it to understand the indications and limitations, and to participate in its interpretation. Sonography, both the performance and interpretation, is an acquired skill that requires hands-on training, supervision, and practice, and thus cannot be learned solely by reading. Therefore, the goal here is not to teach sonography but rather to provide a basic overview of sonography, discuss its role in nephrology, and present information relevant to incorporating sonography into a nephrology practice.

Intrarenal color duplex examination of aortic endograft patients with suprarenal stents

PURPOSE

To report an experience using intrarenal color duplex ultrasonography (ICDU) to detect high-grade renal artery stenosis in patients who had endovascular repair of abdominal aortic aneurysm (AAA) with suprarenal stent fixation.

METHODS

Twenty-eight patients (25 men; mean age 71 years, range 58-83) who had endovascular AAA repair with suprarenal stenting at least 3 months prior to commencement of this study were screened with ICDU. Acceleration time (AT), peak systolic velocity (PSV), end diastolic velocity (EDV), and resistive index (RI) were measured. The Doppler waveform was quantitatively scored on a scale from 0 to 4. AT >0.07 seconds, RI <0.45, or a Doppler waveform score of 0 or 1 (indicating loss of early systolic peak) were indicative of high-grade renal artery stenosis.

RESULTS

Median follow-up was 15.5 months (range 3-34). ICDU was successful in 54 (98%) of 55 kidneys scanned. No AT values exceeded 0.07 seconds, all RIs were >0.45, and no waveforms had loss of early systolic peak, indicating that no patient had evidence of high-grade renal artery stenosis.

CONCLUSIONS

ICDU is a simple and affordable method that seems well suited to periodic screening in patients with suprarenal stents. Longer follow-up with a larger number of patients is needed before definite conclusions can be drawn about the effect of suprarenal stenting on renal circulation.

Sonographic evaluation of renal failure

Sonography is a critical component of the evaluation of both acute and chronic renal failure; however, most nephrologists have a limited knowledge of this procedure. The acoustic properties, limited spectrum of pathological changes, and ease of visualization of the kidneys, coupled with the safety, simplicity, and low cost of sonography, make it the modality of choice for renal imaging. This review discusses the basics of sonography as they apply to the kidney and describes the findings encountered in the more common causes of renal failure. Although many sonographic findings are nonspecific, their diagnostic use is greatly enhanced by a familiarity with the clinical presentation and a thorough understanding of renal pathophysiological characteristics. Therefore, nephrologists should be knowledgeable about renal sonography and participate in its interpretation.

Huge renal arteriovenous malformation mimicking simple parapelvic cyst

The presenting symptoms of renal arteriovenous malformations are usually gross hematuria and hypertension. Herein we present an unusual case of huge renal arteriovenous malformation without these signs, but with ultrasound picture mimicking simple parapelvic cyst. Other imaging test, including Duplex ultrasound, computerized tomography and aortography, demonstrated that vascular lesion. We suggest that Duplex ultrasound should accompany the routine renal ultrasound in order not to miss such cases, especially when the physical examination suggests intra-abdominal vascular lesion or bleeding.