PHILADELPHIA – Renal biopsies are a useful tool for optimizing outcomes in pregnant patients with active lupus nephritis, according to Dr. Derek M. Fine.
Although caution is advisable, a general aversion to biopsying pregnant patients is unwarranted, Dr. Fine of Johns Hopkins University, Baltimore, said at the meeting, sponsored by the American Society of Nephrology.
Dr. Derek M. Fine
An important question to ask yourself when deciding if a biopsy should be performed is whether without it you will really know what you are treating.
“For me, it’s very, very scary to take care of a lupus patient when I don’t know what’s going on,” said Dr. Fine, director of the Nephrology Fellowship Program at Johns Hopkins.
Other important questions include whether findings on biopsy will change your management, and whether prior histopathology can help you identify the current problem.
“I would say if it was in the previous few months, yes it’s going to be useful. But once you’re 6 months or a year out, you don’t know what’s going on,” he said, noting that while an educated guess can be made that something similar is going on, one can’t rely on prior histopathology in such cases.
“I’m not saying do it with reckless abandon, but think about doing a biopsy,” he said.
An important benefit of performing a biopsy is disease classification to guide management. Another is differential diagnosis, he said, noting that between 20% and 50% of lupus patients have antiphospholipid antibodies, and that a biopsy can also detect thrombi in the kidney, differentiate preeclampsia if there’s a question about that, and identify focal segmental glomerulosclerosis, which is not an uncommon diagnosis on biopsy in African American patients.
As for the risks of biopsying a pregnant patient, the data are sparse – the largest available study was conducted 27 years ago – but they suggest that complication rates with biopsy during pregnancy are low, and that fetal loss is extremely unusual.
Concerns about preterm labor are often cited as a reason to avoid biopsy, but kidney biopsies are not particularly stress inducing. Bleeding is a concern, but bleeding risk has declined over time, and the procedure has become safer with the use of real-time ultrasound and smaller-gauge needles.
“Doppler technology can tell me there is a bleed, often right away, and interventional radiology availability, compared with 1987, is significant. It was really in its infancy back then, but now to get an angiogram is pretty easy and I can get it done within an hour of doing a kidney biopsy,” he said.
Furthermore, pregnant patients tend to have improved coagulation, and thus reduced bleeding risk, although increased renal blood flow may counteract some of that benefit.
In one study, he and his colleagues found that the risk of bleeding was not much different in lupus and nonlupus patients, at about 2.7%, and the risk was reduced by 50% among those with platelet counts greater than 100,000/mm3, he said.
However, the complication rate seen in patients who undergo biopsy is not insignificant, and these patients should be monitored extremely closely after the procedure.
“It’s a low risk, but a real one,” he said.
The literature documents biopsies performed at up to 32 weeks’ gestation, but biopsy may not be worthwhile later in pregnancy when empiric therapy is more reasonable because of a shorter course, and because the fetus is more viable, he said.
Also, if a bleeding event requiring an angiogram occurs, it is easiest to shield the fetus with lead up to about 24 weeks’ gestation. After that point, it can be more difficult to shield the fetus because of positioning, and this should be taken into consideration.
“I get a little bit nervous doing a kidney biopsy beyond 24 weeks, mainly for this reason,” he said.
If necessary, however, a biopsy can be performed up to 28 weeks’ gestation, he added.
Keep in mind that histopathology cannot be predicted based on clinical features alone. “We really need to get tissue to know what we’re treating,” he said, describing patients with similar clinical features, but different histopathology as an example of why biopsy is important.
A one-size-fits-all approach to treatment doesn’t work under these circumstances; biopsy can help spare patients unnecessary or dangerous treatments, and can help optimize treatment to improve outcomes, he said.
He recommended doing a biopsy for proteinuria of 500 mg/dL or more, avoiding biopsy beyond 28 weeks’ gestation, minimizing bleeding risk, and – from a medicolegal standpoint – ensuring fetal well-being before biopsy to ensure that the biopsy is not blamed for fetal death.