Relationship between colon and kidney: a critical point for percutaneous procedures.

Objective: The aim of this study was to determine the frequency of anatomical variations of the colon associated with the kidney.

Material And Methods: A retrospective analysis was performed on 1000 consecutive abdominal computed tomography (CT) scans performed between July 2010 and September 2011. A line parallel to the horizontal plane was drawn through the posterior edge of each kidney at three renal levels: upper, middle and lower pole. The bowel between the psoas muscle and the kidney was determined as the interposition of the colon. The amount of perinephric fat was estimated and graded.

Results: The total number of patients undergoing CT scans was 1000 (male/female = 510/490). The mean age of patients was 42.2 years. Seventeen patients (1.7%) had retrorenal colon, of which 12 (1.2%) were on the left side, three (0.3%) on the right side and two (0.2%) were bilateral. Of these 17 cases, 11 were found at the lower, two at the middle and four at the upper pole of the kidney. There was grade I perirenal fat tissue in 13 and grade II in four cases. Interposition of the colon was detected in 32 (3.2%) patients, 30 (3%) on the right and two (0.2%) on the left. The grade of perirenal fat tissue in patients with colon interposition was as follows: 25 patients grade I, six patients grade II and one patient grade III.

Conclusions: In accessing the lower pole of the kidney, especially on the left side, the risk of colonic injury should be taken into consideration during percutaneous procedures, regardless of the patient's age and gender.