Hospital Medicine Explained: Internal Medicine, Kidneys and Lungs

By vaayaa Editorial Team · Subject panel: Dr. Priya Sharma (MD, Internal Medicine), Dr. Sarah Johnson (MD, Public Health)

Internal medicine, nephrology, and pulmonology are three interconnected pillars of hospital care, each addressing a distinct but overlapping set of conditions across the full patient journey. Understanding how they function as systems, what roles exist within them, and where the workforce is heading helps students and professionals make informed decisions about where to build their careers.

Three specialties sit at the core of most hospital inpatient services: internal medicine, which manages the broadest range of adult conditions; nephrology, which focuses on kidney function and its systemic consequences; and pulmonology, which covers the lungs, airways, and the sleep disorders that intersect with respiratory health. Together they account for a large share of hospital admissions, outpatient clinic visits, and chronic disease management programmes worldwide. A working knowledge of all three helps anyone involved in healthcare delivery, from ward coordinators to health administrators, understand why patients move through the system the way they do.

This discourse covers what each field is, who works in it, what skills and tools matter, and where the workforce is heading. The data come from the US Bureau of Labor Statistics, the International Society of Nephrology Global Kidney Health Atlas, the Global Burden of Disease Study, the USRDS Annual Data Report, and peer-reviewed journals. Every figure is sourced and dated. Readers considering a structured learning pathway can start with the Internal and Hospital Medicine programme, which covers how internal and hospital medicine departments function as systems from admission to discharge.

Internal Medicine and Hospital Medicine: The Generalist Engine of Inpatient Care

Internal medicine is the branch of medicine concerned with the prevention, diagnosis, and non-surgical treatment of diseases in adults. Hospital medicine is a practice model within internal medicine where physicians, called hospitalists, work exclusively in the inpatient setting rather than splitting time between a clinic and a ward. The two terms are often used together because hospitalists now manage the majority of general medical admissions in US hospitals, and similar models are spreading across the UK, Australia, and parts of Asia. ^[1]

The BLS Occupational Outlook Handbook reports 73,100 general internal medicine physician jobs in the US in 2025, with 4% growth projected from 2025 to 2035 and roughly 22,100 physician and surgeon openings per year across all specialties over that period. ^[1] The HRSA National Center for Health Workforce Analysis, published in December 2025, projects a shortage of 20,660 full-time-equivalent general internal medicine physicians by 2038, a figure that underscores the structural pressure on the specialty. ^[1] The Society of Hospital Medicine's 2025 State of Hospital Medicine Report found that 64% of hospital medicine groups expected full-time-equivalent growth in the coming year. ^[1]

Fact BLS OEWS May 2025 counted 67,150 wage-and-salary general internal medicine physicians (SOC 29-1216) in the US, excluding the self-employed. The OOH figure of 73,100 includes self-employed physicians. Both are published by the US Bureau of Labor Statistics.

Typical Roles and Day-to-Day Work

The hospitalist physician is the most visible role, but the department runs on a wider team. Hospitalists conduct daily ward rounds, review test results, coordinate specialist consultations, manage medication reconciliation, and lead discharge planning. Supporting them are case managers, utilisation review nurses, clinical documentation improvement specialists, and ward administrators who track bed capacity and compliance with payer requirements. ^[2] The BLS OEWS May 2025 reports a US annual mean wage of $267,200 and a median of $256,560 for general internal medicine physicians, reflecting a profession where compensation has risen alongside demand. ^[3]

Non-clinical roles in hospital medicine have grown as health systems have adopted electronic health records, value-based payment models, and quality reporting requirements. A clinical documentation improvement specialist, for example, reviews physician notes to ensure that the coded diagnoses accurately reflect patient complexity, which directly affects hospital reimbursement. A bed management coordinator tracks real-time occupancy and facilitates transfers between units. These roles require an understanding of how the department functions as a system, not just how individual patients are treated.

Core Skills and Tools

• Clinical knowledge of common inpatient conditions: pneumonia, heart failure, sepsis, venous thromboembolism, and decompensated chronic disease.
• Familiarity with electronic health record platforms such as Epic, Cerner, and Meditech for documentation, order entry, and care coordination.
• Understanding of DRG-based reimbursement, length-of-stay benchmarks, and readmission reduction programmes.
• Communication skills for handoffs between shifts, family meetings, and multidisciplinary rounds.
• Knowledge of accreditation standards from bodies such as The Joint Commission and CMS Conditions of Participation.

The Internal and Hospital Medicine programme covers this in depth, building the non-clinical expertise needed to coordinate safe, efficient, and compliant inpatient care. You can explore the free first section of Internal and Hospital Medicine before committing to the full programme.

Nephrology and Dialysis Care: Managing Kidney Disease Across the Continuum

Nephrology is the medical specialty concerned with the diagnosis and treatment of kidney diseases, including chronic kidney disease (CKD), acute kidney injury (AKI), electrolyte disorders, hypertension related to kidney dysfunction, and kidney replacement therapy. The specialty sits at the intersection of internal medicine, cardiology, and endocrinology because the kidneys regulate fluid balance, blood pressure, acid-base chemistry, and the clearance of metabolic waste, meaning kidney dysfunction ripples across almost every organ system.

The global burden of kidney disease is substantial and growing. The ISN Global Kidney Health Atlas, published in The Lancet Global Health in 2024, reports a global median CKD prevalence of 9.5% (IQR 5.9 to 11.7), with the highest prevalence in Eastern and Central Europe at 12.8%. ^[4] The 2024 Global Burden of Disease Study estimates that 9.1% of the world's population is affected by CKD. ^[5] When acute kidney injury and end-stage renal disease are added, the number of individuals with some form of kidney disease rises to approximately 850 million, according to the USRDS 2024 Annual Data Report. ^[6] In the United States alone, about 1 in 7 American adults, nearly 37 million people, have kidney disease, and approximately 558,000 Americans are currently on dialysis. ^[7]

Fact Global kidney failure prevalence has tripled since 1990, rising from 1.6 million to 4.6 million in 2023, according to data cited by the American Kidney Fund drawing on USRDS and GBD sources.

The Workforce Gap in Nephrology

Despite this enormous disease burden, the nephrology workforce is under serious strain. The ISN Global Kidney Health Atlas found that nephrologist shortages are reported in 107 out of 167 countries, representing 64% of surveyed nations. ^[8] The global median prevalence of nephrologists is just 11.75 per million population (pmp), with an 80-fold difference between low-income and high-income countries. ^[9] In Africa the figure falls to 1.12 pmp, and in South Asia to 1.81 pmp. ^[9] North America and the Caribbean report 19.68 pmp, and Western Europe 24.41 pmp, but even in Europe an overall 21.3% reduction in the nephrology workforce occurred between 2015 and 2024. ^[10]

The ISN-GKHA survey also found that more than half of countries reported shortages of dialysis nurses (58%), vascular access coordinators (59%), and transplant surgeons (65%), in addition to nephrologists (64%). ^[8] This means the workforce gap is not limited to physicians: it extends to the entire care team that supports patients on kidney replacement therapy. Global expert groups predict further reductions in the nephrology workforce over the next decade, with declining interest in nephrology careers compounding the problem. ^[11]

Typical Roles and Day-to-Day Work

A nephrology department in a large hospital typically includes nephrologist physicians, nephrology nurses, dialysis technicians, dietitians specialising in renal nutrition, social workers, and care coordinators. The nephrologist manages the medical aspects of CKD progression, prescribes dialysis parameters, oversees transplant evaluation, and handles acute consultations from other wards for AKI or electrolyte emergencies. Dialysis technicians set up and monitor haemodialysis machines, check water quality, and troubleshoot alarms during sessions that typically last three to four hours, three times per week per patient.

Peritoneal dialysis coordinators train patients to perform dialysis at home, a modality that has grown significantly: the 2024 USRDS Annual Data Report shows that incident patients on peritoneal dialysis increased by 69%, from 8.3% to 14.0% of new dialysis starts, over the reporting period. ^[12] This shift toward home-based care creates demand for nurses and coordinators who can teach, troubleshoot remotely, and manage supply chains for dialysis consumables.

Core Skills and Tools

• Understanding of kidney physiology: glomerular filtration rate (GFR), creatinine clearance, fluid and electrolyte balance, and acid-base regulation.
• Familiarity with haemodialysis and peritoneal dialysis equipment, including machine setup, membrane selection, and access management.
• Knowledge of KDIGO (Kidney Disease: Improving Global Outcomes) clinical practice guidelines, which set international standards for CKD staging and management.
• Patient education skills for dietary compliance, fluid restriction, medication adherence, and home dialysis training.
• Data management for dialysis adequacy measures (Kt/V), vascular access surveillance, and quality reporting to CMS for ESRD facilities in the US.

The Nephrology and Dialysis Care programme builds practical knowledge for supporting patients and healthcare teams across nephrology settings, from kidney function basics to dialysis care coordination. The free first section of Nephrology and Dialysis Care gives a clear sense of the programme's scope and approach.

Estimate The 2024 GBD Study estimates that CKD death rates are forecast to increase by over 30% from 2022, and in western Europe CKD is projected to become the third cause of death by 2050, according to analysis published in Nephrology Dialysis Transplantation in October 2026.

Pulmonology, Respiratory Therapy, and Sleep Medicine: Breathing, Lungs, and Rest

Pulmonology is the medical specialty focused on the respiratory system, covering the lungs, airways, pleura, and the muscles and structures that drive breathing. It overlaps substantially with critical care medicine, since many pulmonologists also manage patients in intensive care units, and with sleep medicine, since disordered breathing during sleep is one of the most common respiratory presentations. The specialty addresses conditions including COPD, asthma, pneumonia, interstitial lung disease, pulmonary hypertension, lung cancer, and obstructive sleep apnoea.

COPD alone affects more than 400 million people globally and remains the third leading cause of death worldwide, according to The Lancet Respiratory Medicine. ^[13] The Global Burden of Disease Study 2021 estimated 213.4 million prevalent COPD cases globally, with the disease causing 3.7 million deaths and 79.8 million disability-adjusted life years (DALYs) in that year. ^[14] Models published in JAMA Network Open project that the number of COPD cases globally will increase by 23% from 2020 to 2050, approaching 600 million patients. ^[15] Obstructive sleep apnoea affects approximately 14% of the global population, according to research cited in a systematic review published in ScienceDirect. ^[16]

The Respiratory Therapy Workforce

Respiratory therapists (RTs) are the clinical backbone of pulmonology departments and ICUs. The BLS Occupational Outlook Handbook reports that respiratory therapists held about 142,000 jobs in the US in 2025, with a 2025 median annual wage of $82,280. ^[17] Employment is projected to grow 9% from 2025 to 2035, much faster than the average for all occupations, generating about 8,600 openings per year. ^[17] Using the BLS 2024 projection series, employment growth for respiratory therapists is estimated at 12.1% from 2024 to 2034, adding approximately 16,800 jobs over the decade. ^[18] US News and World Report ranked respiratory therapist as the 12th best job overall and 4th in healthcare careers for 2026. ^[19]

Pulmonologist physicians numbered approximately 17,570 in the US according to Zippia analysis of occupational data, with an average salary of $290,288 in 2024. ^[20] The RT workforce is considerably larger and more accessible by entry-level credential: the BLS notes that an associate's degree is the typical entry-level education for respiratory therapists, making it one of the more accessible pathways into a well-paid clinical role. ^[17]

Fact The BLS reported a 2025 median annual wage of $82,280 for respiratory therapists, with the lowest 10% earning less than $63,660 and the highest 10% earning more than $118,050. Source: BLS Occupational Outlook Handbook, 2025 edition.

Typical Roles and Day-to-Day Work

Respiratory therapists work in emergency rooms, ICUs, general wards, pulmonary rehabilitation centres, sleep laboratories, and increasingly in home healthcare settings. ^[17] In the ICU, an RT manages mechanical ventilators, adjusts ventilation parameters, performs airway suctioning, and assists with intubation. On the general ward, RTs administer inhaled medications, conduct pulmonary function tests, and educate patients on inhaler technique and breathing exercises. In a sleep laboratory, a polysomnographic technologist monitors patients overnight, scoring sleep stages and respiratory events to diagnose conditions such as obstructive sleep apnoea, central sleep apnoea, and hypoventilation syndromes.

Sleep medicine has grown into a distinct subspecialty with its own diagnostic and treatment infrastructure. A sleep clinic typically employs sleep physicians (often pulmonologists or neurologists with sleep fellowship training), polysomnographic technologists, and CPAP therapy coordinators who fit patients with positive airway pressure devices and follow up on adherence data transmitted remotely from the machines. The overlap between respiratory and sleep medicine means that professionals who understand both areas are particularly versatile.

Core Skills and Tools

• Respiratory physiology: lung volumes, spirometry interpretation, arterial blood gas analysis, and ventilation-perfusion relationships.
• Mechanical ventilation: modes (volume control, pressure control, CPAP, BiPAP), weaning protocols, and alarm management.
• Pulmonary function testing: spirometry, diffusion capacity (DLCO), bronchodilator response, and six-minute walk test.
• Sleep study interpretation: polysomnography scoring, apnoea-hypopnoea index (AHI), oxygen desaturation indices, and CPAP titration.
• Patient education for inhaler devices, smoking cessation, pulmonary rehabilitation, and home oxygen therapy.
• Familiarity with GOLD (Global Initiative for Chronic Obstructive Lung Disease) and GINA (Global Initiative for Asthma) guidelines.

The Pulmonology, Respiratory and Sleep Medicine programme provides a structured pathway for healthcare administrators and support professionals to understand respiratory physiology, diagnostic interpretation, and treatment coordination. The free first section of Pulmonology, Respiratory and Sleep Medicine is a good starting point for anyone assessing whether the field matches their background.

How the Three Fields Connect Inside a Hospital

Internal medicine, nephrology, and pulmonology are not siloed departments. A hospitalist admitting a patient with sepsis will almost certainly involve a nephrologist if acute kidney injury develops, and a pulmonologist or respiratory therapist if the patient requires mechanical ventilation. The three specialties share patients, share documentation systems, and share the same bed management pressures. Understanding the logic of each field makes cross-departmental communication faster and safer.

From a workforce perspective, all three fields are experiencing demand that outpaces supply. The HRSA projects a shortage of 20,660 full-time-equivalent general internal medicine physicians by 2038. ^[1] Nephrologist shortages are reported in 64% of countries globally. ^[8] Respiratory therapist demand is growing at more than three times the average rate for all US occupations. ^[17] This convergence of shortages means that non-clinical professionals who understand how these departments function, and who can coordinate care, manage data, and support compliance, are increasingly valuable across all three settings.

The career pathways in all three fields also share a common structure: entry through a clinical or administrative support role, progression through specialisation and credentialing, and advancement into leadership, education, or programme management. The skills built in one specialty transfer readily to the others, which is why a combined understanding of all three is a practical asset rather than an academic exercise.

Building a Career Across These Three Specialties

Career entry points vary by background. Clinical professionals typically enter through nursing, allied health, or medical education and then specialise. Non-clinical professionals, including health administrators, medical coders, care coordinators, and quality improvement analysts, enter through business, public health, or health information management programmes and build specialty knowledge on the job or through structured learning. Both routes lead to roles that are in high demand.

Credentialing matters in all three fields. Respiratory therapists in the US pursue the Registered Respiratory Therapist (RRT) credential from the National Board for Respiratory Care. Nephrology nurses can pursue the Certified Nephrology Nurse (CNN) credential from the Nephrology Nursing Certification Commission. Clinical documentation improvement specialists pursue the Certified Clinical Documentation Specialist (CCDS) credential from ACDIS. Each credential signals a level of verified competence that employers use to differentiate candidates in competitive hiring markets.

What Employers Look for Beyond Clinical Credentials

Health systems increasingly value professionals who understand the operational and regulatory context of specialty care, not just the clinical content. A dialysis unit manager needs to understand CMS ESRD quality measures, staffing ratios, and water treatment compliance, not just how to run a dialysis machine. A pulmonary function lab coordinator needs to understand accreditation standards from the American Association for Respiratory Care, equipment calibration schedules, and how to interpret spirometry reports well enough to flag quality issues. This operational layer of knowledge is what structured learning programmes in these fields are designed to build.

• Regulatory literacy: understanding CMS, Joint Commission, and specialty-specific accreditation requirements.
• Data fluency: reading quality dashboards, interpreting length-of-stay reports, and contributing to performance improvement projects.
• Interdisciplinary communication: working effectively with physicians, nurses, therapists, and administrative staff.
• Patient-centred thinking: understanding the patient experience across a long-term condition such as CKD or COPD.
• Adaptability: as care models shift toward home-based and telehealth delivery, professionals who can support remote monitoring and virtual care coordination are increasingly sought.

Frequently asked questions

Conclusion

Internal medicine, nephrology, and pulmonology each address a distinct dimension of adult health, but they function as an integrated system inside any hospital. The hospitalist manages the breadth of inpatient care and coordinates the specialists. The nephrologist manages the kidneys and the systemic consequences of their failure. The pulmonologist and respiratory therapist manage the lungs, the airways, and the sleep disorders that compound respiratory disease. Understanding all three fields, their workflows, their workforce pressures, and their regulatory environments, gives any healthcare professional a more complete picture of how hospitals actually work.

The workforce data are consistent across all three fields: demand is rising faster than supply, and the gap is most acute in nephrology globally and in internal medicine in the United States. Respiratory therapy is the fastest-growing of the three by BLS projection, but all three fields are actively seeking professionals who combine clinical or operational knowledge with the ability to coordinate complex care. Whether the goal is a clinical role, an administrative one, or a leadership position, the investment in structured learning across these specialties is one of the more durable career decisions a healthcare professional can make.

This discourse describes education and careers in healthcare. It is general information, not medical advice.

References

1. careersource.im.org (citing BLS OOH 2025 and HRSA December 2025). How Many Hospitalists Are in the US? Workforce Size and Job Outlook for Employers (2026).
2. careersource.im.org. Physician Retention for Internal Medicine Teams (2026) (2026).
3. careersource.im.org (citing BLS OEWS May 2025). Hospitalist Salary by State (2026): Benchmarks to Build a Competitive Offer (2026).
4. The Lancet Global Health (Bello AK et al.). An update on the global disparities in kidney disease burden and care across world countries and regions (2024).
5. Tandfonline / Renal Failure (citing 2024 GBD Study). Public interest in chronic kidney disease and dialysis: a 20-year data analysis (2025).
6. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). USRDS 2024 Annual Data Report: International Comparisons (2024).
7. American Kidney Fund (citing USRDS and GBD). Quick kidney disease facts and stats (2026).
8. Oxford Academic / Nephrology Dialysis Transplantation (ISN-GKHA). A global assessment of kidney care workforce (2024).
9. PubMed / NCBI (ISN-GKHA survey). A global assessment of kidney care workforce (PubMed abstract) (2024).
10. Journal of Nephrology (Oxford Academic). Shortage of nephrologists: workforce decline on both sides of the Atlantic (2026).
11. PMC / NCBI. International Nephrology Masterclass in Chronic Kidney Disease: Rationale, Summary, and Future Perspectives (2024).
12. Home Dialysis Central (citing USRDS 2024). Home Dialysis Updates from the 2024 USRDS Annual Data Report (2024).
13. The Lancet Respiratory Medicine. The global burden of COPD: epidemiology and effect of prevention strategies (2024).
14. BMC Public Health / GBD 2021. Burden of chronic obstructive pulmonary disease and its attributable risk factors in 204 countries and territories, 1990-2021: results from the Global Burden of Disease Study 2021 (2025).
15. JAMA Network Open. Global Burden of COPD Through 2050 (2023).
16. ScienceDirect / Sleep Medicine. Prevalence and clinical characteristics of sleep disorders in chronic obstructive pulmonary disease: A systematic review and meta-analysis (2023).
17. U.S. Bureau of Labor Statistics. Respiratory Therapists: Occupational Outlook Handbook (2026).
18. respiratory-therapy.com (citing BLS and US News). Respiratory Therapist a 2026 Best Job (2026).
19. US News and World Report. Respiratory Therapist Career Rankings, Salary, Reviews and Advice (2025).
20. Zippia. Pulmonologist Job Outlook and Growth in the US (2025).