THE MYSTERY OF THE ANGLE OF HISS

The internist Wilhelm Hiss (1863–1934) was born as one of six children of the renowned anatomist and physiologist of the same name. Numerous discoveries—many of them still relevant today, particularly regarding the cardiac conduction system—are associated with his name.

However, he also turned his attention to the question of reflux. He observed that, when viewed from the front and with an intact diaphragm, the stomach consistently forms an acute angle with the esophagus. This is because the esophagus enters the stomach from the side rather than centrally at its apex. This resulting angle varies individually and typically ranges between 30 and 70 degrees.

During autopsies, His observed that in patients with reflux, the stomach had consistently shifted upward through the diaphragm. At the same time, this angle changed significantly: the higher the stomach moved, the flatter the angle became.

This led to an important question:

Does this angle play a role in reflux control? Was its flattening merely a consequence of organ displacement—or did it have a functional significance?

This hypothesis fascinated the medical community of the time. Then as now, microscopic examinations revealed no signs of disease or muscular weakness in either the esophagus or the stomach. Nor could a clearly defined closing sphincter be identified. The organs themselves appeared healthy—only their position was altered. But how, then, was closure achieved?

The only identifiable anatomical change remained this altered angle, which from then on became known as the “angle of Hiss.”

As is often the case in medicine, intense debate followed. Early surgical approaches aimed to reconstruct this angle. Expectations were high—but the results were disappointing: reflux persisted unchanged after surgery.

It was Allison and colleagues who later emphasized a crucial factor: the role of the diaphragm. They described the diaphragmatic crura as stable pillars essential for maintaining the proper position and alignment of the organs. When this structure weakens or is disrupted, this support is lost—and the organs shift.

This fundamental insight can now be confirmed by the research of Dr. med. Eckhard Löhde. In retrospect, it becomes clear how close these early researchers came to our current understanding. What they lacked, however, were modern imaging techniques such as cardiac MRI, which allow visualization of the complex interaction between the beating heart, diaphragm, and esophagus.

Today, we know the answer: the angle of Hiss—as already suspected at the time—has no independent function in reflux control. Rather, it serves as an indicator that the anatomical arrangement of the organs has been disturbed.

The key task, therefore, is to understand and restore this interaction in three dimensions. When the organs are returned to their natural position, their function also normalizes. The angle of Hiss then returns to its typical configuration—not as a cause, but as a consequence of correctly restored anatomy.

Yours,

PD Dr.med. Eckhard Löhde