IMAGING

Precaval right renal arteries: prevalence and morphologic associations at spiral CT
Yeh BM, Coakley FV, Meng MV, Breiman RS, Stoller ML
Department of Radiology, University of California San Francisco, 505 Parnassus Ave, Box 0628, C-324C, San Francisco, CA, USA
Radiology 2004; 230: 429-433

• Purpose: To determine the prevalence and morphologic associations of precaval right renal arteries at spiral computed tomography (CT).
• Materials and Methods: The authors retrospectively reviewed 186 arterial phase contrast material-enhanced spiral CT scans of the abdomen (5.0-mm section thickness in 97 scans, 2.5 mm in 89 scans) obtained during a 2-year period to identify patients with precaval right renal arteries. During routine interpretation of CT scans at daily readout, the authors prospectively identified 39 additional patients with precaval right renal arteries. All cases were evaluated for anatomic variants and associated clinical findings. Fisher exact analysis and chi2 analysis were performed to compare the frequency of anatomic variants between patients with and those without precaval renal arteries.
• Results: Nine of 186 patients had precaval right renal arteries, for a prevalence of 5%. In the 48 patients with precaval renal arteries, 52 precaval arteries were found, of which 48 were accessory and four were dominant. Fourteen patients had right pelviectasis to the level of the precaval artery, and three of these had a clinical diagnosis of right ureteropelvic junction obstruction. Eighteen (35%) of the 52 precaval renal arteries arose from the anterior aspect of the aorta (within 30 degrees of the midline). The lower pole of the right kidney was rotated anteriorly in two (22%) of nine and 13 (33%) of 39 patients with precaval renal arteries in the retrospective and prospective groups, respectively, compared with four (2%) of 177 patients without precaval arteries (P < 0.05 and P < 0.001, respectively).
• Conclusion: On the basis of these results, precaval right renal arteries appear to be more common than previously reported. Anterior rotation of the lower pole of the right kidney should prompt a search for precaval renal arteries.
  
  
• Editorial Comment
  Recently multidetector row CT(MDCT), using fast data acquisition and narrow collimation, has been shown a valuable method for angiographic applications. MDCT angiography provides additional anatomic data, notably regarding the angle of origin of the renal arteries, that is potentially useful for planning interventional procedures.This method is highly accurate an thus particularly useful for the detection of accessory renal arteries, early branching, and renal vein anomalies with an overall accuracy rate ranging from 89–100%. With the crescent use of the conservative and laparascopic renal surgery the importance of previous knowledgment of these anatomic variants and their associations is essential for the safety and success of these procedures.
  In this manuscript the authors detected 9 of 186 patients with precaval right renal arteries, with a prevalence of 5%. These anomalous vessels were more frequently found in patients with an anteriorly rotated lower pole of the right kidney.For this reason they suggest that the finding of renal anomalies, especially an anteriorly rotated lower pole of the right kidney, should prompt a search for precaval renal arteries. We have seen sporadic cases of precaval right renal arteries only in patients with horseshoe kidneys.
  In the 48 patients with precaval renal arteries, 52 precaval arteries were found, of which 48 were accessory and four were dominant. Fourteen patients had right pelviectasis to the level of the precaval artery, and three of these had a clinical diagnosis of right ureteropelvic junction obstruction. Since the anatomic position of the right renal artery is behind the inferior vena cava(IVC) and only the right gonadal vein is expected to pass anterior to IVC, an anomalous right renal artery passing anterior to the IVC can be injured inadvertently, especially during the retroperitoneal approach. Another important information is regarding the ventral origin of these precaval right renal arteries found in 37% of patients.This anterioir origin may result in misidentification at laparoscopy of such vessels as the inferior or superior mesenteric or hepatic arteries. Additional important feature is related to frequency of patients with precaval right renal arteries(up to 6%) which may develop symptomatic ureteropelvic junction obstruction. This information requires adequate preoperative protocol for the MDCT examination in order to demonstrate this anatomic variation which will allow usefull information for conservative renal surgery and endopyelotomy.

Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil