In other countries, when patients recover from a terrifying brain bleed — or, for that matter, when they battle cancer, or heal from a serious accident, or face down any other life-threatening health condition — they are allowed to spend their days focusing on getting better. Only in America do medical treatment and recovery coexist with a peculiar national dread: the struggle to figure out from the mounting pile of bills what portion of the fantastical charges you actually must pay. It is the sickness that eventually afflicts most every American.

What’s less understood is the extent to which our current medical-billing system itself is responsible for the high prices patients are charged. There are, of course, many factors that have led to the United States’ record-breaking $3 trillion health care bill: runaway drug prices, excessive testing and sky-high charges for even the most basic medical interventions. But all of those individual price increases have been enabled — indeed, aided and abetted — by the complex system of billing and coding that underlies bills like those sent to Wickizer. That system, with its lines of alphanumeric codes and arcane medical abbreviations, has given birth to a gigantic new industry of consultants, armies of back-room experts whom medical providers and insurance companies deploy against each other in an endless war over which medical procedures were undertaken and how much to pay for them. Caught in the crossfire are Americans like Wanda Wickizer, left with huge bills and indecipherable explanations in languages they cannot possibly understand.

Disease-classification systems originated during an outbreak of the bubonic plague in 17th-century London — epidemiologic constructs to classify and track causes of death and prevent the spread of infections among populations that spoke different languages. In the 1890s, the French physician and statistician Jacques Bertillon further systematized death reporting by introducing the Bertillon Classification of Causes of Death, the first medical-coding system, which was adopted and modified in many countries. It became an official global effort, which was periodically revised by an international commission. During the first half of the 20th century, the number of entries naturally increased with improved understanding of science, and many countries began tabulating not just causes of deaths but also the incidence of diseases.

In the 1940s, the World Health Organization took over stewardship of Bertillon’s system and renamed it to reflect a new, broader focus: the International Statistical Classification of Diseases, Injuries and Causes of Death (ICD). The codes became an invaluable tool, a common language for epidemiologists and statisticians to track the world’s afflictions. But over the last several decades in the United States, codes gradually took on a bedrock financial function as the basis for medical billing. In 1979, the government decided to use what by then were called ICD-9 codes — which specify the patient’s diagnosis — in adjudicating Medicare and Medicaid claims, with some modifications added specifically for that purpose; the United States version was called ICD-9-CM. (The country has recently moved to a new iteration, ICD-10-CM.) For its beneficiaries, Medicare pays a fixed fee for inpatient hospitalization based primarily on the ICD-CM code, which is translated into a DRG (diagnosis-related group) code — which is the immediate basis for reimbursement.

Other insurers followed in making codes the basis for billing. Coding systems begot new coding systems, because few hospitals wanted to be paid according to Medicare’s relatively low DRG standards. And because strategic coding meant increased payment, that begot coding specialists and coding courses and coding degrees. There are now different increasingly complex coding languages that define payment for different kinds of services: CPT codes, for office visits delivered by doctors, as well as HCPCS, ICD-PCS-CM and DRG, for charges that are incurred in the hospital. There are tens of thousands of codes in each lexicon that have become increasingly specific. For example, there are different codes for in-office earwax removal depending on the method used (irrigation or instruments), different codes for delivering different vaccinations and a code for each injection delivered in the hospital. Different insurers also use different coding systems. While Medicare would have most likely considered Wickizer’s brain bleed as DRG 021, if billed to a commercial insurer, it could result in more than a dozen ICD codes and hundreds of HCPCS entries.