A HH is a common, chronic disease of the digestive tract with complex etiology and high incidence. The condition is also associated with severe complications such as bleeding, ulceration and erosion caused by reflux, which may lead to esophageal stenosis, and malignant transformation leading to esophageal adenocarcinoma [6, 7]. Long-term reflux has a serious negative impact on a patient’s life, and many patients worry about the effect of surgical treatment, so they often suffer from insomnia and anxiety [8]. Laparoscopic hernia repair combined with fundoplication has become the gold standard treatment for a HH, and has the advantages of a large field of vision, minimal surgical trauma, a remarkable anti-reflux effect, and fast recovery [9]. Postoperative symptom improvement is the primary concern of patients. Of the patients included in this study, 33 patients had poor improvement of symptoms after surgery. Thus, we developed a model to predict factors associated with a poor improvement of symptoms and the result of the model can be used to determine whether patients need surgical treatment.
Nomograms are widely used to illustrate the outcomes of predictive models, and to identify a patient’s prognosis or outcome based on clinical variables [10]. Nomograms can be highly accurate, and can help clinicians to make better plans to manage individual patients [11]. The prediction model established in this study was shown to have good accuracy by ROC curve analysis and other methods.
In this study, the highest score nomogram score was for DCI; the greater the DCI, the higher the probability of poor improvement of symptoms. HRM is a common method for evaluating esophageal motility, and the anti-reflux barrier, and it is widely used in the detection and assessment of esophageal motility disorders [12, 13]. DCI is an important parameter in HRM, and refers to the pressure × duration × length of contraction in the smooth muscle of esophagus, and the measure is used to judge the intensity of esophageal contractions. The higher the DCI, the higher the intensity of esophageal contraction and the stronger anti-reflux activity [14]. Savarino et al. [15] found that the lower the contractile ability of the esophagus body, the weaker the clearance ability of the esophagus after reflux, thus making reflux symptoms more serious. Our results showed that a higher DCI was associated with a higher probability of poor improvement of symptoms. One of the probable reasons is that DCI indicates the intensity of esophageal contraction. As mentioned above, the larger the value, the greater the ability to clear the reflux. This suggests that some of the symptoms of a patient, such as acid reflux and heartburn, which may be caused by the weakening of esophageal dynamic, are not obvious before surgery. However, the operation itself does not change the intensity of esophageal contraction, which leads to poor improvement in postoperative symptoms.
Our results also showed that no smoking history was also an independent risk factor for poor improvement in symptoms. Study has shown that smoking is an independent risk factor for gastroesophageal reflux [16.] Moreover, gastroesophageal reflux symptoms are more obvious in long-term smokers than in short-term smokers. Smoking also reduces the pressure of the lower esophageal sphincter [17], and the frequency of gastroesophageal reflux increases significantly. This leads to the reflux of stomach contents to the lower esophagus, resulting in the destruction of the barrier between the esophagus and the stomach, and further causes reflux, heartburn, and other symptoms. Compared with smokers, patients without a history of smoking had less reflux and heartburn before surgery, and less overall symptoms after surgery, but the improvement in symptoms was less significant than in smokers.
Based on an AUC = 0.878, and the good alignment of the calibration curve with the actual curve, we can see that the accuracy of the model developed in this study is high. However, this study still has some limitations. The sample size is small, and the study was done at a single center. A multi-center study is needed to verify the accuracy of the results. There were no objective indicators of improvement. Improvement of symptoms was based on the subjective responses of patients during a telephone interview, which can be subject to inaccuracies.
In summary, this study established a clinical prediction model for postoperative symptom improvement in HH patients. Patients can decide whether surgery is necessary or not based on the predicted results of this model. ROC curve, calibration curve and DCA all show that this model has good predictive efficacy, and can also provide evidence for clinicians to make decisions in clinical practice.