Retroperitoneal cysts with congential, ipsilateral renal agenesis of left kidney: a case report

Unilateral renal agenesis is defined as the congenital absence of renal tissue of one side that results from a lack of induction of the metanephric blastema by the ureteral bud. Primary retroperitoneal cysts lying in the retroperitoneal fatty tissue have no apparent connections with any anatomical structure except by loose areolar tissue and are rare. They remain asymptomatic and are diagnosed incidentally.

A 28-year female presented with complain of epigastric pain for 2 years. On examination, abdomen was soft and non-tender without any palpable masses. Abdominal ultrasonography revealed enlarged right kidney with left retroperitoneal cyst and absent left kidney. This finding was later confirmed by CT abdomen. The patient underwent ultrasound guided drainage of the lesion and a total of 300 ml of clear fluid was obtained. The fluid was examined to perform microbiological analysis and to exclude the presence of neoplastic cells. All tests were found to be negative.

Unilateral renal agenesis is associated with other congenital anomalies of the kidney, urinary tract. Retroperitoneal cysts are rare intra-abdominal tumors. The urogenital cysts arise from the vestiges of the embryonic urogenital apparatus and can be classified into pronephric, mesonephric, metanephric, and mullerian. In view of the anatomical location of these embryonal organs, the position of the retroperitoneal cysts can determine from which of the 3 divisions of the primitive urinary apparatus it arose. CT is ideal for assessing retroperitoneal cysts.

The occurrence of retroperitoneal cyst with congenital absence of ipsilateral kidney is a rare clinical phenomenon.