Stock market investing is easier than ever, even if you don't have heaps of cash lying around in your brokerage account. If you've got just $90, you could buy a piece of one of these high-growth healthcare stocks

Each of these companies is just scraping the surface of large and untapped addressable patient populations. Here's why adding them to your portfolio now could help it outperform in 2022 and beyond.

Smart investor looking for stocks to buy.

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CareDx

Carefully monitoring organ transplant recipients for initial signs of rejection can save healthcare plan sponsors a bundle. Until CareDx (NASDAQ:CDNA) came along, though, deciding how heavily to compromise a patient's immune system involved a lot of guesswork.

CareDx's diagnostic services look for fragments of DNA that enter the bloodstream when a transplanted organ gets attacked by the immune system. The company's also marketing new digital services to help manage all the data its transplant monitoring services generate. 

The company reported third-quarter revenue that soared 42% year over year to an annualized $302 million. This is a great start, but it's only the beginning. CareDx estimates its total addressable market at roughly $12 billion annually.

At the moment, you can own a piece of this fast-growing diagnostics company for around $40 per share. Without another diagnostics business to challenge CareDx in the transplant diagnostics niche, there's a pretty good chance it will keep growing by leaps and bounds in the years to come.

Medical professionals at work.

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Nevro

Nevro (NYSE:NVRO) is a medical device company that makes spinal cord stimulators that provide drug-free pain relief. The pandemic has pressured sales this year pushing the stock down by more than half.

A national health survey in 2019 found out that more than one-fifth of American adults experience chronic pain. For 7.4% of adults in the U.S., their pain frequently limited work and life activities.

In July, the FDA approved Nevro's spinal cord stimulation treatment for painful diabetic neuropathy. More than 2 million Americans with nerve pain due to diabetes can't manage their condition with conventional drugs and Nevro's device is the only one specifically approved for their condition.

Nevro thinks capturing just 1% of this available market would more than double topline revenue. With such a big space to grow into, patient investors who buy this stock at its recent price of around $87 could see some eye-popping returns down the road.

Doctor at work.

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Inari Medical

Inari Medical (NASDAQ:NARI) is another medical device company with a strong position in a specialized niche. The company markets devices that remove life-threatening blood clots.

Without another competitor in this niche, sales are climbing through the roof. Third-quarter revenue soared 88% year over year and 15% compared to the previous quarter.

At an annualized $292 million in the third quarter, topline revenue has a lot of space to grow. Inari Medical's devices, ClotTriever and FlowTriever are already cleared by the FDA to treat conditions representing a $3.8 billion annual market opportunity. 

Inari Medical stock has been trading for around $82 per share. With the venous clot removal space all to itself, it's worth it.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.