Sonographic and laboratory findings in hypertensive patients suspected to have renal artery stenosis at Moi Teaching and Referral Hospital, Eldoret, Kenya

Abstract

Background: Renal artery stenosis is the leading cause of secondary hypertension. Global prevalence of hypertension is 22% and across the WHO regions it is highest in Africa (30%). Up to 5% (3.5 to 4 million) of all occurrences of hypertension in the United States are caused by renal artery stenosis. The prevalence varies according to the population examined. This prevalence in our region is unknown and the diagnosis is probably missed in many patients. Timely diagnosis is important since renal artery stenosis is a correctable cause of hypertension. Objectives: To describe sonographic findings and determine the prevalence of renal artery stenosis and its association with age, gender, renal functions, lipid profile and Body Mass Index in adult hypertensive patients suspected to have renal artery stenosis at Moi Teaching and Referral Hospital. Methods: This was a cross sectional study done at the ultrasound room in the Department of Radiology and Imaging, Moi Teaching and Referral Hospital, Eldoret between October 2015 and October 2016. Consecutive sampling technique was used on consenting adult hypertensive patients with clinical features suggestive of renal artery stenosis as per the American Heart association Guidelines of 2005 who underwent renal Duplex Doppler ultrasonography. A 3.5- 7 MHz curvilinear phase array transducer of a Philips HD11 XE machine model 2006 was used. All the images were reviewed by two consultant radiologists. Descriptive statistics were summarized for patient socio-demographics. Frequency tables were generated for categorical variables. Inferential statistics were done using Chi-square and Fishers exact tests. Results were presented using tables and charts. Results: The study included 169 participants with a median age of 46 (IQR 30). One hundred and five (62.1%) of them were females. In the findings; Sonographic prevalence of renal artery stenosis was 33.7%. Areas of aliasing was present in 62.5% of those with renal artery stenosis, post stenotic turbulence in 75.4% and thickening and calcification of arterial wall in 3.6%. Tardus- Parvus waveform pattern was seen in 66.1% (on the right) and 64.9% (on the left) in patients with renal artery stenosis. Echogenic kidneys were seen in 25 (43.9%) and loss of corticomedullary differentiation in 15 (26.3%) of the patients with renal artery stenosis. More females (63.2%) had renal artery stenosis than males, and majority, (43.8%) of those with renal artery stenosis were above 55 years. There was a significant association (p < 0.05) between elevated creatinine (above 80mmol/l) elevated urea ( above 8.3mmol/l), elevated potassium( above 5.1mmol/l)and presence of renal artery stenosis. Conclusion The sonographic prevalence of renal artery stenosis in adult hypertensive patients with specific clinical clues at MTRH was 33.7%. Parvus- Tardus was the commonest waveform pattern seen and there was an association between presence of renal artery stenosis and elevated levels of urea, creatinine, potassium,total cholesterol and triglyceride levels. Recommendation: We need to have a high index of suspicion for renal artery stenosis whenever parvus- tardus waveform pattern is encountered during renal Duplex Doppler ultrasonography.