Extrarenal pelvis is the presence of the renal pelvis outside the renal hilum. Extrarenal pelvis is caused by an elongation of the urine-forming ducts of the kidney. It affects about 10 percent of the population, explains Radiopaedia.org.
The renal pelvis is a chamber where all urine-forming ducts meet, according to Dr. Rajesh Ahlawat for DoctorNDTV.com. It routes all urine to the urinary bladder. Any portion of the renal pelvis located outside the kidney is considered extrarenal pelvis. Extrarenal pelvis may appear to be an obstruction when viewed via an ultrasound. A person should undergo tests to determine whether he has an extrarenal pelvis or a blockage.