In Germany, the patient receives a letter of referral (Überweisungsschein) for admission to a clinic or referral to a specialist, which is also sent to the clinic as well. The same applies when the patient is discharged from hospital or is referred to a specialist or general practitioner for further treatment.

lettre de liaison | der Überweisungsschein Pl.: die Überweisungsscheine
https://dict.leo.org/englisch-deutsch/doctor's report

La lettre de liaison/prescription doit faire état du diagnostic et de l'objectif du traitement.
The referral/prescription should state the diagnosis and goal of therapy.
https://fr.techdico.com/traduction/francais-anglais/lettre d...

C’est pourquoi la lettre de liaison est rendue obligatoire depuis 2016 par un décret concernant son contenu minimum et ses modalités de transmissions (15). Ce décret a appuyé l’article 63 du code de déontologie médicale qui encadrait les rapports entre le médecin traitant d’un patient et un praticien hospitalier l’ayant pris en charge (17,18).
Le décret de 2016 a affirmé l’obligation de la présence de la lettre de liaison pour tout patient adressé à un établissement de santé. Elle devait synthétiser les informations nécessaires à la prise en charge du patient. Le même décret ajoutait des obligations concernant la lettre de liaison à la sortie d’hospitalisation (15).
:
Abstract
The referral letter was made mandatory in 2016 in France. Its aim is to guarantee continuity
of optimal patient care between general practitioners (GPs) and the hospital.
https://dumas.ccsd.cnrs.fr/dumas-03800981/document

A referral is a letter from your doctor or health professional to another health professional or health service. Referrals are made to get expert help with the diagnosis or treatment of your health problem.
Most referral letters are written by your family doctor (general practitioner, or GP). Referrals can be made to:
• a specialist doctor
• an allied health professional, such as a psychologist or physiotherapist
• radiology, for x-rays or other imaging services
• pathology services (for blood tests)
https://www.healthdirect.gov.au/what-is-a-referral

A referral letter is a vital form of communication between primary and secondary care, and can play an important role in the early pathway of patient care. A poorly written referral letter could cause the patient’s treatment to be delayed, which can result in a worse prognosis.
To ensure a seamless transition of care, the patient’s initial complaint and medical history need to be provided to the new therapist or clinician.
It is often the only means of passing on knowledge, so it’s important to include all relevant facts.
Referral letters are crucial for good record-keeping, too.
A copy of referral letter, the date it was emailed or posted, and copies of any responses should all be saved in the patient’s record in your practice management system.
https://www.writeupp.com/blog/write-successful-gp-letter-ref...