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Ask Dr. Schwartz: Treating extrinsic compression

We sat down with Dr. Bradley Schwartz, Chairman of Urology, Southern Illinois University, to discuss his experience with the Resonance® Metallic Ureteral Stent. In the first installment of this three-part series, Dr. Schwartz talks about his approach to treating extrinsic ureteral compression.

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What is extrinsic compression?
One of the biggest questions I get is on external compression. Remember that the ureter is a tube. It’s like a garden hose. When it has obstruction, or when there is obstruction of the ureter, it can be coming from things outside the ureter—so things pushing or compressing on it—or it can be coming from something inside the ureter. Inside the ureter is very simple. You can think of that as a stone. If a stone—or a golf ball in the garden hose, a stone in the ureter—is obstructing, that’s going to be intrinsic obstruction. And if you have something on the outside—let’s say you have pliers squeezing the garden hose—that’s extrinsic compression. So where do we see it? When do we see it? What’s the most common thing that we typically see? The most common type of extrinsic compression typically is from some type of malignancy or treatment from a malignancy. So, a lot of pelvic—all the pelvic organs—have lymph nodes and some direct extensions. So, if you have a prostate cancer, a uterine cancer, a cervical cancer, a colon cancer, these all are prone to having lymph node enlargement or organ enlargement that are going to encroach and start to compress the ureter.

The ureter is a retroperitoneal organ. So, it lies behind the big bag that encompasses a lot of the intestine, spleen, liver, etc. So, behind that bag, lie the ureters, and the ureters really pretty much lie on musculoskeletal structures. And so when something compresses it, there’s nowhere for it to really go and it basically compresses then against the ureter. The ureter doesn’t really live in a very good neighborhood. It’s surrounded by a lot of the gynecologic organs, the GI tract, and obviously the urinary tract is intimately involved. So, take for instance just a lymphoma, which is not even a cancer of an organ; it’s a cancer of the lymph system. When those lymph nodes enlarge and get bigger, they will start to compress and grow and then impinge on the ureter, causing external compression. And that is what we mean by external compression.

The thing that kind of separates or distinguishes, a lot of times, is that when you start passing wires and catheters up into a ureter that has extrinsic compression, the mucosa is really usually normal. And what you’re trying to do is really just kind of separate mechanically whatever forces are pushing the ureter. You compare that to something intrinsic, where you have a cancer of the ureter that involves the mucosa, you now have a lot of tissue that’s really very heterogeneous, very rough, very brittle, and it can be extremely difficult to even pass a wire or a catheter. So, the subtleties are different. And they can be very important when trying to determine what type of stent to use, when to use it, and then how am I going to actually get a wire and a catheter up into the kidney and let it drain properly?

How do you treat extrinsic compression?
When one identifies extrinsic compression, again, you obviously want to figure out why. If it’s something that’s treatable, let’s say it’s adenopathy from a cancer, you can potentially give chemotherapy, radiation, and hopefully shrink that, and you might actually alleviate that obstruction over time. The important thing, though, is acutely, you still need some type of drainage of that kidney. So, you want to preserve kidney function. You want to preserve renal function. The only ways to really do that are something retrograde—so you can place a stent retrograde—or you can put a nephrostomy tube in antegrade. Those are pretty much the only two temporary forms of drainage that we have.

What is your algorithm for treating extrinsic compression?
Again, I think when you’re talking about any type of ureteral obstruction, extrinsic compression included, when we’re presented with these patients, we’re usually dealt a patient who has hydronephrosis, flank pain, renal insufficiency, something along those lines that then lead to a radiologic investigation. That would be a CT scan, MRI, renal ultrasound. When we diagnose hydronephrosis and ureteral obstruction, we are typically called upon to relieve that obstruction by the routes I just mentioned. Either stenting or percutaneous approach.

My algorithm is pretty clear. And I think it makes logical sense in how to manage a patient. First of all, these patients need to be acutely unobstructed. So, the first thing we do is we will go in, do a cystoscopy, make sure the bladder is okay, pass a wire up under fluoroscopy, and then put a stent in that is appropriately sized. Whether it be 6 Fr, 7 Fr, 8 Fr, probably doesn’t matter a great deal. We’d like to make it the correct size, so we can measure the kidney to the bladder, we can measure the length of the patient. We would typically use a 24 cm stent, but clearly it can go up or down from there, depending upon a lot of other factors. But I think acute drainage is very, very important. And then we can get the patient back in and discuss with them how long do they need the stent? Is this going to be a chronic thing? Is their overall condition treatable? So, if they have a terminal malignancy that is going to eventually take their life, then we may not have any further discussions, quite frankly. If their life expectancy is a year, two years, three years, or unknown, but the length  of time that the obstruction will be in place, then we need to have a discussion about how we’re going to manage the obstruction. And at that time, I will then let them know that we have a stent that’s FDA approved for 12 months. It has been time-tested; we use it all the time. And we would try to inform them, at least, that there’s a metal stent [Resonance] available.

Once they decide that, sure, a metal stent is for them, we then have this: the algorithm again kind of goes down a pretty simplistic path. I never say “never,” and I never say “always.” But I never put a metal stent in up front, to be the first stent the patient has ever received. Why? I have to make sure they tolerate a stent well, and I have to make sure it’s going to drain, or at least have some effect on the obstruction that we’re trying to treat. So, once I’m convinced they can tolerate the stent, and it at least works to some degree, only then I’ll change that stent in probably three or four months. If we put the metal stent in, I then put the stent in with the assumption that it’s going to be in for one year, twelve calendar months. I will then set them up for a repeat stent change in 12 months. I will periodically, through that time, order serum creatinines, which quite frankly is oftentimes done by their oncologists, because they’re undergoing cancer treatments and therapies anyway, and I will not infrequently, maybe three or four, maybe every four or five months, get a renal ultrasound just to make sure that the hydronephrosis is not worsening. I think one of the misconceptions is that if the hydronephrosis is not completely gone, that this metal stent is failing and that’s not necessarily true. Once these kidneys become hydronephrotic, they will frequently not ever rebound to their completely normal, decompressed state. So that, right there, is not a failure, if the hydronephrosis is not worsening. If it’s stable, then I’m okay with that.

Dr. Schwartz is a paid consultant of Cook Medical.