It is Tuesday, 2:15 in the afternoon, and a solo internist in a town of eleven thousand people is looking at a patient whose labs do not quite fit anything clean.
Nothing here is an emergency. The patient is stable, sitting in the next room, waiting for a plan. But the picture is ambiguous enough that she wants a second set of eyes, the kind of five-minute conversation that happens forty times a day in a hospital-based practice: lean into the next office, describe the case, hear "yeah, I'd think about X too" or "have you considered Y," and move on with more confidence than you had ten minutes ago.
She does not have a next office. Her practice is her, a nurse, and a receptionist. The nearest internist she knows well enough to call without an appointment practices ninety minutes away and is not reachable until evening. She could message a former co-resident, if the timing works. She could post in a Facebook group for rural physicians and hope someone with more experience answers before the patient's ride home arrives. She could search UpToDate again, though she has already read the relevant section twice.
She makes the call she thinks is right, alone, the same way she has made several hundred calls like it this year, because there is no one down the hall and there never will be.
This is not the dramatic case, the complication or the crisis. It is the ordinary Tuesday afternoon question that institutional medicine answers in five minutes and independent medicine does not answer at all.
The hallway is nearly universal, and nearly all of it belongs to people with a hallway
Start with how routine informal peer consultation is inside institutions, because the contrast is the entire point.
87.5 percent of subspecialists reported fielding a curbside consult in the prior week, averaging 3.6 curbsides weekly, according to research published in Obstetric Medicine. In hospital settings generally, 82 percent of physicians report being asked for "hallway medicine" and 91 percent agree to provide it, per a 2021 study in BMC Primary Care. This is not a fringe behavior tolerated by a few generous colleagues. It is the dominant mode by which ambiguous clinical questions get a second opinion in institutional medicine, happening dozens of times a day across any hospital or large group practice.
None of that infrastructure exists for a physician who has no colleagues in the building. And a large share of American physicians fit exactly that description. 11.9 percent of physicians practice solo, and 47 percent practice in groups of ten or fewer, according to the AMA's 2024 Physician Practice Benchmark Survey. Add roughly 57,000 physicians currently working locum tenens, arriving at unfamiliar hospitals without the relationships that make hallway medicine possible, and the population without a functioning hallway is not a marginal edge case. It is a substantial fraction of practicing American physicians.
This is a coordination failure, not a shortage
It would be easy to read this as simply a physician-supply problem, and it is worth being precise about why that framing is wrong.
The peer these physicians need typically exists. There is very often another internist, another family physician, another general surgeon within professional reach who would happily answer a five-minute question. What does not exist is any mechanism connecting the two of them at the moment the question arises. This is the same category of failure this series has documented in curbside consultation generally: the trust and willingness are real, but there is no router, no record, and no way for a solo physician to know who among the thousands of physicians in her specialty is both reachable right now and willing to take the question of a stranger.
Rural professional isolation research names this explicitly. The National Rural Health Association's 2025 workforce policy brief identifies professional isolation as a compounding factor in rural physician retention, distinct from and additive to compensation, workload, and lifestyle factors that dominate most recruitment conversations. Isolation is not simply an unpleasant side effect of rural practice; it is a measured driver of why physicians leave.
The backup that does exist is thin, gated, and expensive
It is not that solo and rural physicians have zero options. It is that every option that exists is thinner, slower, or more restrictive than the hallway consult it is trying to replace.
Formal e-consult platforms like RubiconMD and AristaMD provide a genuine, liability-conscious channel to specialist opinion, and they represent real progress over having nothing. But they are purchased by health plans and health systems, not by individual physicians, and the pricing, reportedly somewhere in the range of $30 to $70 per e-consult though unverified in this session, reflects a business built to sell into an institutional buyer. A solo internist with no employer purchasing this benefit on her behalf typically has no access to it at all.
Project ECHO, the tele-mentoring model built at the University of New Mexico, is a genuinely effective mechanism for building rural clinician capacity around specific conditions, delivered by academic hubs on a fixed schedule to enrolled clinics. It is not built for the ad hoc, "I have a question right now about this specific patient" need that drives the vast majority of hallway consults inside an institution. A physician outside an ECHO cohort, or with a question outside its scheduled topic, gets nothing from it.
Ethics backup is even thinner. Only 59 percent of rural physicians report having access to an ethics committee at all, and of those, only 43 percent operate 24/7, according to research in the Journal of Regional Medical Campuses. For the roughly 40 percent with no ethics committee access whatsoever, an ambiguous ethical question carries the same isolation as an ambiguous clinical one, with even less of a workaround.
Informal channels fill the remaining gap, unevenly. A text to a former co-resident works when the timing lines up and fails when it does not. A specialty Facebook or WhatsApp group offers volume but no verification of who is answering or whether they are actually qualified to. Doximity's "Ask" feature has shifted toward AI-generated answers rather than routed human response, closing off what had been one of the few semi-formal channels for this exact need.
Locums physicians experience the sharpest version of this
It is worth separating out locum tenens physicians specifically, because their version of this problem compounds isolation with genuine unfamiliarity.
Roughly 56 percent of locum tenens physicians start within their first ten years of practice, per a 2025 CHG report, meaning a meaningful share of the locums workforce is relatively early-career, arriving at unfamiliar hospitals under two-week or six-week contracts with no time to build the relationships that make hallway medicine possible even where a hallway physically exists. Locums usage itself has been rising, with a reported 25 percent increase in 2025, which means more physicians, not fewer, are entering this exact isolation pattern every year, even as the industry narrative describes locums as filling access gaps for patients rather than creating a peer-support gap for the physicians filling them.
Why nobody serves this physician
This is the structural diagnosis. Every party positioned to build a fix for the department of one has a reason not to.
Health systems buy e-consult access for their own employed clinicians, because the purchasing decision is made by an institution with a budget line for it, and a solo independent physician outside that institution is simply not the customer being served.
Academic medical centers give ECHO time on their own schedule and their own terms, built around specific conditions and specific enrolled clinics, not around the general, unpredictable flow of everyday clinical questions a solo physician actually has.
Specialty societies run listservs with no routing mechanism. A question posted to a society listserv may or may not reach someone both qualified and available, and there is no accountability structure ensuring that it does.
Doximity moved its human "Ask" feature toward AI-generated response, removing what had been one of the closest things to a routed human answer available to any physician regardless of practice setting, at exactly the moment its scale could have made it valuable for this population.
No party currently serves the physician who is not inside a buyer's institutional contract. That is not an oversight; it is the predictable result of a market where every existing solution is designed around an institutional purchaser, and the department of one, by definition, has no institution to do the purchasing.
AI has changed what kind of question is left over
It is worth being honest about what large language models have already absorbed from this problem, because overstating the remaining gap would be dishonest in the other direction.
A meaningful share of what used to require a hallway consult, a drug interaction check, a dosing question, a differential for a straightforward presentation, can now be answered adequately by an AI assistant, and solo and rural physicians have almost certainly benefited from this more than institutionally embedded physicians, because it partially closes a gap that used to have no substitute at all.
What AI does not replace is the specific, judgment-dependent question that depends on someone having actually seen a similar patient: not "what is the differential for this presentation" but "does this specific, slightly atypical picture in this specific patient worry you the way it worries me." That is precisely the question a hallway curbside answers and an AI answer, however competent generically, cannot, because it requires a second clinician's pattern-matched intuition against a case they can actually picture, not a synthesis of published literature. The residual demand for human peer review has not shrunk to zero; it has concentrated on exactly the cases where informal consultation always mattered most.
The liability question that keeps this informal
Any serious attempt to build routed peer consultation for the department of one runs into the same liability question that governs curbside consultation generally, and it deserves to be named rather than assumed away.
Curbside consults are legally treated, in most jurisdictions and under most analyses, as informal peer opinion rather than a formal consultation creating a doctor-patient relationship with the answering physician, provided the exchange is de-identified and the treating physician retains clinical responsibility. This is precisely why e-consult vendors like RubiconMD built structured documentation and a defined scope of engagement into their product: it converts an informal exchange into something with a clearer liability boundary, at the cost of speed and spontaneity. Any product serving the department of one has to walk the same line: fast enough to replace a hallway conversation, but structured enough that neither the asking nor the answering physician is exposed to liability neither intended to take on.
What would actually work
Route on same-day willingness, not just specialty match. The physicians who could answer a rural internist's Tuesday-afternoon question are not scarce; they are simply unidentifiable at the moment she needs them. A system that surfaces who is both in the right specialty and currently willing to take a quick question solves the actual bottleneck.
De-identify by default. Every exchange should proceed without patient identifiers, both to protect the patient and to keep the interaction squarely inside the informal peer-opinion frame that keeps liability manageable for both physicians.
Make the peer opinion explicitly non-binding, with responsibility unchanged. The answering physician offers professional experience, not a clinical order, and the treating physician retains full responsibility for the decision. This needs to be structural, not a line in a terms-of-service document nobody reads.
Build reciprocity into the design, not payment alone. A pure pay-per-question model recreates the RubiconMD and AristaMD pattern of an institutional buyer standing between a physician and access. A model where physicians earn standing by answering others' questions creates a sustainable norm that does not depend on a health system's budget cycle.
Give locums physicians a portable peer network that travels with the contract, not the hospital. A locums physician's isolation is structural to the job; a peer-access layer tied to the physician rather than to whichever hospital she is currently contracted at is the only version that actually follows her need.
Create a defined escalation path to formal referral. When the honest answer is "this needs a real specialist visit, not a curbside opinion," the system should make that clear and help initiate it, rather than letting an informal channel substitute for care that genuinely requires more.
Track ethics questions as a distinct category with equivalent access. With 41 percent of rural physicians having no ethics committee at all, an ambiguous ethical question deserves the same same-day peer-access mechanism as a clinical one, not a lower priority because it is harder to route.
What you can do now
If you practice solo, in a small group, rural, or as a locum
Name three physicians you could reach today with an ambiguous case, and if you cannot, treat that as the finding it is. The absence of a hallway is not a permanent condition; it is a relationship gap that deliberate outreach can close faster than most physicians assume.
Reconnect with your training cohort specifically for this purpose. Co-residents and co-fellows are, by a wide margin, the peers most likely to answer quickly and honestly, precisely because the relationship already exists; the barrier is usually that neither side has made explicit that this kind of question is welcome.
Use AI for what it is actually good at, and notice where it stops being enough. A dosing question or a standard differential is a reasonable AI query. The moment you find yourself wanting someone to say "does this worry you as much as it worries me," that is the signal you need a human peer, not a better prompt.
If you lead a rural hospital, CAH, or locums agency
Treat peer-access isolation as a retention lever, not a wellness add-on. The National Rural Health Association names professional isolation as a compounding retention factor; addressing it directly is cheaper than the roughly $250,000-plus cost of recruiting a replacement physician.
Ask whether your ethics-committee gap is actually being felt. With under 60 percent of rural physicians reporting ethics committee access, and less than half of those 24/7, this is a specific, nameable gap worth surfacing rather than assuming is adequately covered.
Build onboarding for locums that includes peer contacts, not just facility orientation. A locum physician who arrives with two or three names she can call with a case question is meaningfully less isolated than one who arrives with a badge and an EHR login.
If you build clinical software or a physician network
Design for the physician who has no institutional buyer, not just the one whose employer will pay per consult. Every existing e-consult product sells to a system or a payer; the market for a physician-purchased or reciprocity-based version of the same access has gone almost entirely unaddressed.
Solve for willingness and speed, not just directory accuracy. A correct specialty listing that does not indicate who is actually reachable right now recreates the ghost-network problem this series has documented elsewhere. Same-day willingness is the scarce signal, not the credential itself.
Frequently asked questions
Where can a solo physician get a quick specialist opinion without a formal referral? Options today are limited and mostly informal: a former co-resident, a specialty Facebook or WhatsApp group, or a purchased e-consult service like RubiconMD or AristaMD if an employer or payer provides access. There is currently no general, member-owned channel serving physicians outside an institutional buyer's contract.
Are curbside consults legally risky for the physician giving the opinion? Generally low risk when the exchange is de-identified and understood as informal peer opinion rather than a formal consultation, with the treating physician retaining clinical responsibility. This is the legal logic e-consult vendors have built structured documentation around to make the boundary explicit rather than relying on informal custom alone.
How common is curbside consultation in hospital-based medicine? Extremely common. 87.5 percent of subspecialists reported fielding a curbside consult in the past week, averaging 3.6 per week, per research in Obstetric Medicine. In a broader hospital sample, 82 percent of physicians report being asked for informal "hallway medicine" and 91 percent agree to provide it, per a 2021 BMC Primary Care study.
What percentage of physicians practice solo or in very small groups? 11.9 percent of US physicians practice solo, and 47 percent practice in groups of ten physicians or fewer, according to the AMA's 2024 Physician Practice Benchmark Survey, meaning nearly half of practicing physicians lack the built-in colleague density that makes institutional hallway medicine possible.
Do rural physicians have reliable access to an ethics consultation service? Not consistently. Only 59 percent of rural physicians report having access to an ethics committee at all, and of those, only 43 percent operate 24/7, according to research published in the Journal of Regional Medical Campuses, leaving a substantial share of rural physicians without same-day ethics backup for ambiguous cases.
Do locum tenens physicians experience professional isolation differently than employed physicians? Yes, in a compounded way. Roughly 56 percent of locum physicians are within their first ten years of practice, arriving at unfamiliar hospitals under short-term contracts with no time to build the relationships that make informal peer consultation possible, on top of the roughly 57,000 physicians currently working locums nationally, a population that grew an estimated 25 percent in 2025.
The bottom line
Inside a hospital or a large group practice, an ambiguous case gets a second opinion in about five minutes, dozens of times a day, from a colleague standing in the next office. Nearly 88 percent of subspecialists field one every week without thinking twice about it.
Outside that building, for the 11.9 percent of physicians in solo practice and the 47 percent in groups of ten or fewer, that five-minute conversation simply does not exist. Not because the willing colleague is unavailable somewhere in the profession, but because nothing connects a solo internist in a town of eleven thousand people to the internist ninety minutes away who would happily answer her question, if either of them knew the other was reachable right now.
Every formal substitute that has been built, e-consult platforms, ECHO, society listservs, is purchased by or built around an institution, which means the physician with no institution gets none of it. AI has absorbed a real share of the routine question, the dosing check, the standard differential, but it has not touched the specific, judgment-dependent question that only another clinician who has seen something like it can actually answer.
That solo internist is going to make her Tuesday afternoon call alone, the way she makes several hundred calls a year, because the department she needs was never built for her, and nobody currently owns the job of building it.
Part of a series on the missing professional infrastructure of healthcare. Previously: The Protocol Reinvention Tax
Evidence note: the curbside-consult frequency figures are from Obstetric Medicine (2017) and BMC Primary Care (2021). Solo and small-practice figures are from the AMA Physician Practice Benchmark Survey (2024). Rural ethics-committee access figures are from the Journal of Regional Medical Campuses. Locum tenens figures (roughly 57,000 current locums, 56 percent within their first ten years, a 25 percent rise in 2025 usage) are from CHG's 2025 locum tenens reporting. Professional isolation as a rural retention factor is from a 2025 National Rural Health Association policy brief. E-consult pricing figures ($30 to $70 per consult) are noted in the source material as unverified in this session and should be treated as approximate. The opening scenario is a composite illustration built from the patterns documented in this evidence, not a specific reported case.
