Development of clinical prediction models for dyssynergic defecation and rectal sensitivity in patients with functional constipation using patient-reported outcomes

For millions of people, the simple act of having a bowel movement is a source of daily struggle. This condition, known as functional constipation, is not merely about infrequent trips to the bathroom; it is a complex disorder where the body's natural signals and muscle movements fail to coordinate. Sometimes the problem lies in how the colon moves waste, but often the issue is deeper, rooted in the rectum and the muscles that control the exit. In some cases, the muscles that should relax to let stool pass instead tighten or push against it, creating a blockage. In others, the nerves in the rectum become overly sensitive, making normal sensations feel like pain, or conversely, they become dull, failing to signal that a bowel movement is needed. Doctors have long relied on a specialized test called high-resolution anorectal manometry to see exactly what is happening inside. This procedure involves inserting a thin, sensitive tube to measure pressure and sensation, providing a clear picture of the internal mechanics. However, the equipment is expensive, the test is invasive, and it requires a specialist, meaning many patients cannot easily access this crucial information.

A team of researchers at Lu'an Hospital of Anhui Medical University set out to find a simpler way to identify these specific problems before a patient ever steps into a specialized testing room. They wondered if the answers could be found in the patient's own story and the details they could report themselves. By listening carefully to how patients described their symptoms, the quality of their stools, and their emotional state, the researchers aimed to build a set of tools that could predict whether a person was likely to have these specific muscle or nerve issues. Their goal was not to replace the specialized test, but to create a preliminary filter—a way to sort patients and decide who truly needs the more complex investigation.

To do this, the researchers followed 130 adults who had been diagnosed with functional constipation. Before any specialized testing took place, these individuals filled out a series of detailed questionnaires. These forms asked about the shape and consistency of their stool, the severity of their abdominal pain, how much their constipation affected their daily life, and whether they felt anxious or depressed. They also recorded basic facts like their age and medical history. Only after completing these forms did the patients undergo the high-resolution anorectal manometry test. This test served as the ground truth, allowing the researchers to compare the patients' self-reported answers against the actual physical findings inside their bodies. The test revealed that nearly 75 percent of the participants had a specific coordination problem where the muscles worked against each other, while others showed signs of either overly sensitive or under-sensitive nerves in the rectum.

The researchers then used this data to build three separate prediction models, each designed to spot a different type of problem. For the muscle coordination issue, they found that a combination of four factors provided a strong clue: the patient's age, the hardness of their stool, the severity of their stool-related symptoms, and whether they screened positive for anxiety. Older patients with harder stools, more severe stool symptoms, and anxiety were more likely to have the muscle coordination problem. The model they built from these factors was quite accurate, correctly identifying the issue in the majority of cases when tested against the actual results.

For the issue of overly sensitive nerves, the researchers discovered a different set of clues. Here, the strongest predictors were the patient's level of anxiety, the degree to which constipation had lowered their quality of life, and the severity of their abdominal pain and stool symptoms. People who reported significant abdominal discomfort and a high burden of anxiety were more likely to have nerves that were too sensitive. The model for this condition also performed well, successfully distinguishing those with hypersensitive nerves from those with normal sensation.

Finally, for the problem of under-sensitive nerves, where the rectum fails to feel the urge to go, the model pointed again to age and stool characteristics. Older adults with harder stools and a high burden of stool-related symptoms were the most likely to have this blunted sensation. The researchers noted that while the model for this specific condition was also effective, the pattern of symptoms was distinct from the other two groups. In all three cases, the tools they created were able to separate the patients into the correct categories with a high degree of reliability, suggesting that a doctor could use a simple conversation and a few standard questionnaires to get a very good idea of what might be wrong.

The study concludes that these prediction models offer a practical way to screen patients before they undergo invasive testing. By using information that is already available during a routine visit, doctors can better identify who is at risk for specific physiological abnormalities. This approach does not eliminate the need for the specialized test, which remains the gold standard for diagnosis, but it provides a valuable first step. It allows medical teams to prioritize resources and offer more targeted care, ensuring that patients receive the right investigation at the right time. The researchers acknowledge that their work was done with a single group of patients and that these tools will need to be tested on larger, more diverse groups to confirm their usefulness everywhere. However, the findings suggest a promising path forward, turning the patient's own experience into a powerful diagnostic guide.