Prevalence and Morphometric Characteristics of the Pyramidalis Muscle in a Sudanese Surgical Cohort: A Cross-Sectional Study at Al-Damazin Teaching Hospital

Inside the lower front wall of the human body, just above the genitals, lies a small, triangular piece of muscle that many people do not have. Called the pyramidalis, this tiny structure sits in front of the large vertical muscle that runs down the center of the abdomen. When it is present, it stretches from the pubic bone up to the midline seam of the abdominal wall. For centuries, anatomists have known that this muscle is a fickle companion; in some people, it appears on both sides, in others on just one, and in many, it is missing entirely. While it was once thought to help tighten the abdominal wall, modern understanding suggests its job is minor, as the surrounding muscles can easily take over its work. Yet, knowing whether this muscle exists in a specific patient remains important for surgeons. During operations in the lower belly, the muscle can serve as a helpful landmark, guiding the surgeon's hand, or it might offer a small piece of tissue for reconstruction if needed. Despite its potential utility, we know very little about how common it is among people in Africa, and specifically, no one had ever mapped its presence in the Sudanese population.

To fill this gap, a team of researchers in Sudan decided to look directly at the muscle during real surgeries. They worked at Al-Damazin Teaching Hospital in the Blue Nile region, observing fifty adults who were undergoing operations on their lower abdominal walls. Instead of relying on scans or studying bodies after death, the surgeons and their trainees simply opened the abdomen and looked. They checked carefully to see if the pyramidalis muscle was there, noting whether it appeared on the left, the right, or both sides. They also measured its size with a ruler and recorded the age, sex, and health history of each patient to see if these factors influenced whether the muscle was present. This direct approach allowed them to gather fresh, specific data on how this small muscle behaves in a group of people who had never been studied before.

The results revealed a landscape of variation. In this group of fifty patients, the muscle was found in thirty individuals, meaning it was present in sixty percent of the cases. In the remaining twenty people, the muscle was completely missing on both sides. When the muscle was present, it most often appeared on both the left and right sides together, a pattern seen in twenty-six of the patients. It was rare to find the muscle on only one side; just three people had it on the right alone, and only one person had it on the left alone. The researchers also discovered that the presence of this muscle was not random; it was linked to who the patient was. The muscle was significantly more common in women than in men. In the study, nearly ninety percent of the women had the muscle, while less than half of the men did. Age also played a role. The patients who had the muscle were, on average, about twenty years younger than those who did not. The average age for those with the muscle was roughly forty-four years, while those without it averaged sixty-four years. However, the study found no connection between the muscle and chronic health conditions like diabetes or high blood pressure; having these diseases did not make the muscle more or less likely to appear.

For the patients who had the muscle, the researchers took precise measurements to understand its physical scale. The average length of the muscle was about six and a half centimeters, though it varied from two centimeters to ten centimeters. Its thickness averaged just over one centimeter, ranging from one to three centimeters. These numbers give surgeons a concrete idea of what to expect when they encounter this structure. The study authors were careful to note that because they looked at patients at a single point in time, they could not say for sure if the muscle disappears as people get older or if it was simply never there in the first place. They also acknowledged that their group of fifty people was small and came from one specific hospital, so the findings might not represent every person in Sudan. Nevertheless, this work provides the first clear picture of the pyramidalis muscle in this region. It confirms that while the muscle is often present, it is far from guaranteed, and its existence is tied to sex and age. For surgeons operating in this part of the world, these findings serve as a practical reminder to look closely, as the anatomy they encounter may differ significantly from what is described in textbooks based on other populations.