Fresenius Medical Care AG & Co. KGaA (FMS) shares tumbled 6.60% in pre-market trading on Tuesday, as investors grappled with persistent growth challenges despite the company's better-than-expected third-quarter revenue. The German dialysis provider's stock decline reflects growing concerns about its ability to maintain sustainable growth in its key U.S. market.

According to Citi analysts, Fresenius Medical Care surpassed consensus revenue expectations for the third quarter. However, this positive result was overshadowed by ongoing issues in the company's U.S. operations. The analysts highlighted "persistent lackluster same-market treatment growth in the U.S." as a key challenge for the company, casting doubt on Fresenius Medical Care's path to achieving sustainable 2% volume growth in this crucial market.

Adding to investor worries, the analysts noted concerns about sluggish flu vaccine uptake, although they acknowledged it's still early in the flu season. Furthermore, the company faces potential risks from a slowdown in treatments exposed to Medicare and the impact of inflation on wages and disposable costs. These factors collectively paint a challenging picture for Fresenius Medical Care's near-term prospects, leading to the significant pre-market sell-off despite the company's revenue beat.