What's happening: Shares of Nxstage Medical (NASDAQ:NXTM), a medical device maker focused on kidneys, soared as much as 13% in early session trading after the company reported better-than-expected second quarter results and provided guidance that was either above or at the high-end of what the Street was expecting. As of 2:30pm ET shares had settled into gains of nearly 7%.

Why it's happening: For the quarter, Nxstage Medical reported revenue of $80.3 million, an 8% increase from Q2 2014. The primary drivers of Nxstage's business growth were its critical care segment, which saw an 18% increase in sales to $14.6 million, and home health revenue which grew 16% to $44.8 million from the year-ago quarter. The one red mark was the company's in-center segment, which sells blood tubing sets and needles for hemodialysis patients, which saw sales decline by 11% to $18.6 million.

Net loss for the quarter shrank to $5.3 million from $7.1 million in the year-ago period, and it surpassed management's previous guidance that had called for a loss of $5.5 million to $7 million. All told, Nxstage Medical's Q2 loss of $0.08 per share was $0.02 narrower than expected, and its revenue was just a hair higher than expected.

Looking ahead, Nxstage Medical sees Q3 revenue in a range of $82 million to $83 million with a net loss in the range of $4.5 million to $5.5 million. For the full-year it maintained its sales guidance of $324 million to $328 million, but now expects to hit the high end of that estimate. The company also lowered its expected full-year loss to a range of $18 million to $20 million from a previous forecast that called for a full-year loss of $20 million to $24 million.