IS Case 158: Duplicated renal collecting system
Imaging Sciences URMC 2008
Publication Date: 2009-05-21
Patient is an 84-year-old male with history of lymphoma and bilateral hydronephrosis. Bilateral nephrostomy tubes were removed after chemotherapy. Patient developed abdominal and flank pain later in the same day after bilateral nephrostomy tube removal. Patient also with drainage at the bilateral nephrostomy sites.
Non-contrast enhanced CT demonstrated hydronephrosis of the bilateral kidneys and continued need for nephrostomy tubes (Fig. 1). After unsuccessful attempt at recannulizing the old tract, a fresh tract was created and a nephrostomy placed in the right kidney (Fig. 2). After creation of a tract into the left kidney, contrast injection did not reveal adequate filling of the entire renal collecting system and the ureter. A second tract was created more superiorly and contrast injection demonstrated what appeared to be two separate collecting systems (Fig. 3). Two nephrostomy tubes were placed into the left kidney. A follow-up nephrostomy tube check study, performed one month later, demonstrated two ureters, one from each renal moiety (Figs. 4 & 5).
Duplicated renal collecting system
One of the primary indications for external drainage of the collecting system is a pyeloureteral obstructive process. A nephrostomy tube can be placed to alleviate symptoms from the hydronephrosis and prevent damage to the kidney. The nephrostomy can also be used for direct access into the collecting system to administer antibiotics, chemotherapeutic drugs, or agents for dissolving stones.
Percutaneous placement of a nephrostomy tube has several potential complications including bleeding with up to 3.6% of patient requiring blood transfusion and up to 2% requiring surgery. Other major complications include hydrothorax, pneumothorax and life-threatening sepsis. Minor complications include microscopic hematuria, pain and urine extravasation.
A special situation exists when there is a duplicated collecting system. One school of thought is to initially place only one nephrostomy tube as in a normal kidney. Then the patient is evaluated at a later time to determine if there is adequate decompression of the renal collecting system and then placement of a second nephrostomy tube if needed. This way the risk of potential complications is decreased. The other school of thought is to place two nephrostomy tubes at the onset thereby avoiding the need to bring the patient back.
Duplicated collecting system or duplex collecting system is a kidney containing two pyelocaliceal systems that is associated with one or two ureters. Duplication occurs as a broad spectrum ranging from a bifid pelvis to complete duplication of the ureters. Complete duplication of the ureters occur in 0.2% of live births. Partial duplication occurs in 0.6%. There is no ethnic or gender predilection for ureteric duplication.
When there is complete duplication of the ureters, the ureter draining the lower pole moiety inserts in its normal trigonal position and is prone to reflux. The ureter draining the upper pole moiety inserts in an ectopic location in the bladder, medially and inferiorly. The upper pole moiety is often obstructed and associated with a ureterocele. These findings are referred to as the Weigert-Meyer rule.
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