In 1979, Panna joined JIPMER, Pondicherry in a teaching post, and also managed their newsletter. Later he joined the Government of the National Capital Territory of Delhi as a Specialist in 1981. As a part of technical co-operation program of Government of India and British Government he travelled to Liverpool and did a course on Instruction in Maternal, Perinatal and Child Healthcare at Liverpool School of Tropical Medicine from April to July 1984. In 1986 he joined back his alma mater Lok Nayak Hospital &Maulana; Azad Medical College, Delhi as Consultant Pediatrician. He remained with them till he retired on 31 March 2009 with over 30 years of Clinical/Teaching Experience.
Both during his tenure and post his retirement, he had been part of many associations and projects. He has been an active part of the Indian Academy of Pediatrics (IAP) since the '80s. In 1993 he became Fellow, Indian Academy of Pediatrics. He was an accomplished academician and after serving the Editorial Board of the Journal of Indian Pediatrics in various capacities for two decades, he assumed charge as Editor-in-Chief (2002-2007). During his tenure, the Journal scaled greater heights including getting indexed in the Science Citation Index Expanded, which paved the way for obtaining its first Impact Factor. He was elected Secretary and President of IAP (Delhi) and subsequently became the National President of IAP in 2009. He retired the same year, and for many this would have been the pinnacle of their achievements. But for Dr. Choudhury, this was just a new launchpad into the stratosphere of Public Health.
Post retirement, he was much in demand with national and international agencies for his skills, his experience and his sincere work ethics and considered a Key Opinion Leader by all in this field. He never said no to any request, irrespective of how busy he might be. He continued to guide IAP in various positions including as Chairman of IAP Committee on Immunization (2008-2011), Chairperson of the National Newborn Resuscitation Program (NRP) under IAP (since 2009, aimed at improving child survival), and IAP National President's Representative. Other noteworthy assignments included National Convener of IAP 'Under 5 Child Survival Intervention Program'(2007), Chairperson and Secretary of the Nutrition Sub chapter of IAP, Editor of the bulletin of the Nutrition Sub chapter 'Nutrisearch', and Convener of IAP Task Force for framing Guidelines for Management of Diarrhoea and IAP Task Force for Hospital Management of Severely Malnourished Children.
Dr. Panna Choudhury was a founder member and Vice Chairman of the Child Health Foundation - an organization established for promotion of child survival, child health and child development. He served as an Advisor/Expert/ Investigator for many organizations including WHO, UNICEF, INCLEN, Asia Pacific Pediatric Association, Emory University, Bill and Melinda Gates Foundation and the Government of India. He was a certified Master Trainer for 'Helping Babies Breathe' course by the American Academy of Pediatrics. He was a Visiting Faculty at John Hopkins School of Public Health, Children's Hospital of Michigan and St. Mary's Hospital, London. He worked with the Indian Council of Medical Research on AYUSH and 'Reducing maternal and neonatal mortality' Project. He advocated child health on different media and tirelessly pursued the cause of Mother and Child Health through Government, National and International bodies. He was elected International Advisory Board Member of Journal of Pediatrics, for a period from 2012 to 2017 and travelled extensively in the US in this role. He also travelled across Asia, Africa and Europe advocating his various causes. He had recently been appointed as Special Advisor to Board Member, GAVI - The Vaccine Alliance from 2015 to 2017. He has written over a hundred papers, published in peer-reviewed indexed journals, authored books that are considered staple for medical students, written or edited or reviewed countless more articles, chapters and books. Some of his notable works are 'Principles of Pediatric and Neonatal Emergencies', 'Nutrition in Children: Developing Country Concerns', 'Frontiers in Pediatrics', Pediatric Drug Companion, IAP Textbook of Pediatrics and Guidebook of IAP Committee on Immunization. His last professional action, just two days before his death, was to review an article written for an IAP Guidebook for Parents. His felicitations and trophies fill entire rooms including an Award of Merit for Excellence in Contribution towards the Medical Profession by the Indian Medical Association, presented by the Health Minister of India in presence of the WHO India Chief. He had been conferred with fellowships of IAP, National Academy of Medical Sciences and Royal College of Tropical Medicine and Child Health. He was also Life Member of Hemato-Oncology, Adolescent, CANCL and the National Neonatology Forum, IMA.
Despite being such a legend in his profession, he was a man of very simple tastes and amazed people with his sincerity and gentleness. The first thing that struck anyone meeting him was his humility. He was an astute clinician and academician, and was able to bring people together despite their differences. He had a knack for settling disputes always keeping the national interest of survival and betterment of children in the forefront. He had expansive reach and influence, yet he was equally diligent and detail oriented. His combination of depth with breadth of experience, along with his clinical skills and success as a public health expert working through institutional complexities, made him revered in personal and professional circles.