Identification of risk factors and clinical model construction of abdominal distension after radical cystectomy
Original Article

Identification of risk factors and clinical model construction of abdominal distension after radical cystectomy

Yuanjiong Qi#, Yang Liu#, Xun Liu#, Jingxian Li, Shiyong Qi, Zhihong Zhang

Tianjin Institute of Urology, The Second Hospital of Tianjin Medical University, Tianjin, China

Contributions: (I) Conception and design: Y Qi, Y Liu, X Liu; (II) Administrative support: S Qi, Z Zhang; (III) Provision of study materials or patients: Y Qi, Y Liu, J Li; (IV) Collection and assembly of data: J Li; (V) Data analysis and interpretation: Y Qi, X Liu; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

#These authors contributed equally to this work.

Correspondence to: Shiyong Qi; Zhihong Zhang. Department of Urology, Tianjin Institute of Urology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China. Email: yongshiqi@126.com; zhangzhihongtianj@163.com.

Background: The occurrence of abdominal distention after radical cystectomy (RC) is common. We sought to determine risk factors of abdominal distention after RC, and to establish a simple and reliable nomogram for clinical risk assessment.

Methods: Clinical information on 139 patients who underwent RC from January 2020 to August 2021 was collected. The chi-square test, hypergeometric test, and univariate/multivariate logistic regression were utilized to explore the relationship between variables and abdominal distention after RC. A nomogram was then used to predict the probability of abdominal distension for the patients who underwent RC. Calibration and receiver operating characteristic (ROC) curves were used to evaluate the accuracy of the model.

Results: We found that 35 patients (25%) occurred in abdominal distention after RC. Among the patients, 7 of them developed intestinal obstruction. Postoperative water fasting time and abdominal surgery history were independent risk factors for abdominal distension after surgery. Finally, we constructed a risk model to predict the probability of abdominal distension after surgery. This model showed good fitting and calibration and excellent diagnostic performance with an area under the curve (AUC) of 0.804.

Conclusions: Postoperative water fasting time and abdominal surgery history were independent risk factors for abdominal distension after surgery. There was no significant difference in the incidence of postoperative abdominal distention between robot-assisted cystectomy and laparoscopic cystectomy.

Keywords: Risk factors; radical cystectomy (RC); abdominal distention; robot-assisted radical cystectomy (RARC)

Submitted Jul 01, 2022. Accepted for publication Nov 12, 2022.

doi: 10.21037/tau-22-455

Introduction

Bladder cancer (BCa) is one of the ten most common cancers worldwide. It is one of the tumors with the greatest impact on postoperative quality of life, most notably muscle-invasive bladder cancer (MIBC) (1). Treatments for MIBC include neoadjuvant therapy followed by radical cystectomy (RC), pelvic lymph node dissection, urinary diversion, or a bladder-sparing protocol in selected patients (2). The common methods of urinary diversion are an ileal conduit, an orthotopic neobladder, or a cutaneous diversion (3). Postoperative ileus (POI) is one of the most common complications following RC, leading to prolonged length of hospital stay (LOS) and increased costs (4). A previous study revealed that factors for ileus post-cystectomy include obesity and older age (5). Increased intravenous fluids is associated with prolonged POI and longer LOS in patients who underwent robot-assisted radical cystectomy (RARC) (6). Xue et al. reported that factors for ileus post-cystectomy include chronic constipation and increased dosage of laxatives (7). POI is the most common cause of prolonged LOS after RC (8). It usually appears three to five days after surgery, and is often accompanied by abdominal distention of varying degrees (9). Therefore, it is necessary to pay attention to abdominal distension after surgery and take corresponding measures.

Very few studies have investigated the factors leading to abdominal distension after RC thoroughly. Moreover, no studies have combined laparoscopic radical cystectomy (LRC) with RARC. Therefore, we retrospectively analyzed the clinical data of 139 patients who underwent RC in our hospital. We then developed a nomogram to predict abdominal distension in patients with RC and its accuracy was encouraging. Our study provides a theoretical basis for the prevention and nursing of abdominal distension after RC. We present the following article in accordance with the TRIPOD reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-22-455/rc).

Methods

Data collection and inclusion/exclusion criteria

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Medical Ethics Committee of the Second Hospital of Tianjin Medical University (No. KY2022K080) and informed consent was taken from all the patients. The clinical information of 139 BCa patients who underwent RC in the second hospital of Tianjin Medical University from January 2020 to August 2021 was collected, including gender, age, the stomach tube insertion before the operation, postoperative water fasting time, body mass index (BMI), as well as the history of smoking, hypertension, diabetes, cardiovascular disease, abdominal surgery history, and operation method.

Study inclusion criteria included: (I) patients who underwent RC could articulate their true feelings; (II) obtain informed consent. Exclusion criteria: there were intestinal lesions before surgery or insanity.

Abdominal distension was defined as a subjective sensation of gassiness, trapped gas, or a feeling of pressure or being distended without obviously visible distension (10).

Statistical analysis

In this study, R x64 4.1.2 statistical software was used to process the data. Chi-square and Hypergeometric tests were used to describe the distribution of categorical variables, respectively. Univariate or multivariable logistic regression was used to analyze risk factors associated with abdominal distention after RC by utilizing rms R package. A nomogram was established based on logistic regression and stepwise regression and verified by calibration curves. The specificity and sensitivity of its prediction were assessed using receiver operating characteristic (ROC) curves by using ROCR R package. For all analyses, P<0.05 was considered statistically significant.

Results

A total of 139 patients conformed to our inclusion criteria. Firstly, we summarize the baseline characteristics of the patients (Table 1). Postoperative abdominal distension occurred in 35 patients. No significant differences were found between the two groups in terms of demographics such as age and gender. To explore the distribution of different clinical information, we calculated the percentage of variables between abdominal distension and the non-distension group. We found the distribution of the variables (including the stomach tube insertion before the operation, diversion mode of urinary flow, lymphadenectomy, postoperative water fasting time, and abdominal surgery history group) showed a statistically significant difference between the abdominal distension and non-distension groups (Figure 1A). We found the odds of patients with the stomach tube insertion before the operation, postoperative water fasting time, and abdominal surgery history were higher than those who did not undergo these treatments.

Table 1

Baseline characteristics of patient

Characteristics Abdominal distension/non-distension
n No Yes χ2 P
Gender
   Female 21 17 4 0.185 0.667
   Male 118 87 31
Age (years)
   <65 46 32 14 0.634 0.426
   ≥65 93 72 21
Completed high school
   No 42 33 9 0.210 0.647
   Yes 97 71 26
The stomach tube insertion
   No 101 84 17 12.094 0.001
   Yes 38 20 18
Postoperative water fasting time (days)
   <4 83 76 7 28.500 0.000
   ≥4 56 28 28
BMI (kg/m2)
   <24 54 37 17 0.843 0.359
   ≥24 79 61 18
Smoking
   No 48 38 10 0.425 0.514
   Yes 91 66 25
Hypertension
   No 74 58 16 0.698 0.404
   Yes 65 46 19
Diabetes
   No 111 82 29 0.072 0.789
   Yes 28 22 6
Cardiovascular disease
   No 107 81 26 0.042 0.837
   Yes 32 23 9
Abdominal surgery history
   No 110 87 23 4.076 0.044
   Yes 29 17 12
Lymphadenectomy
   No 35 22 13 2.756 0.097
   Yes 104 82 22
Operation method
   Laparoscopic 78 54 24 3.492 0.175
   Open 3 3 0
   Robot-assisted 58 47 11
Diversion mode of urinary flow
   Ileal conduit 86 62 24 1.231 0.540
   Neobladder 8 7 1
   Ureterocutaneostomy 45 35 10

BMI, body mass index.

Figure 1 Clinical features of patients. (A) The distribution of the variables of patients. *, P<0.05; **, P<0.01; ****, P<0.0001. (B) Hypergeometric test of risk factors associated with abdominal distention after RC. The numbers in the purple circle add up to patients who developed postoperative abdominal distention; the numbers in the blue circle add up to patients who fit the variable below the circle. RC, radical cystectomy.

Among these, 28 of 56 patients who underwent postoperative water fasting time longer than or equal to 4 days experienced abdominal distension (P value =3.310E-09), 18 of 38 patients who underwent the stomach tube insertion before operation had abdominal distension (P value =7.55E-05), 12 of 29 patients who experienced abdominal surgery before occurred abdominal distension (P value =0.008), and 24 of 78 patients who underwent a laparoscopic operation developed abdominal distension (P value =0.027), the hypergeometric test indicated the occurrence of these outcomes were not random events (Figure 1B).

Then, we conducted the univariate logistic regression to excavate effective factors for the clinical outcome (Table 2). The results revealed a statistically significant association between the stomach tube insertion before surgery [yes vs. no: odds ratio (OR) 4.447; P<0.001], postoperative water fasting time (≥4 vs. <4 days: OR 10.857; P<0.001), and abdominal surgery history (yes vs. no: OR 2.670; P<0.05) for abdominal distension. In contrast, other variables showed no significant association with clinical outcomes.

Table 2

Univariate/multivariable logistic regression analysis for abdominal distension after radical cystectomy

Variable Univariate logistic regression Multivariate logistic regression
OR 95% CI P value OR 95% CI P value
Gender (male vs. female) 1.514 0.513−5.569 0.485 − − −
Age (years), (≥65 vs. <65) 0.667 0.302−1.494 0.317 − − −
The stomach tube insertion (yes vs. no) 4.447 1.964−10.268 0.000379 1.023 0.342−3.011 0.968
Postoperative water fasting time (days), (≥4 vs. <4) 10.857 4.472−29.621 5.72E−07 11.401 3.71−38.846 4.11E-05
BMI (kg/m2), (≥24 vs. <24) 0.642 0.294−1.104 0.265 − − −
Smoking (yes vs. no) 1.439 0.638−3.438 0.393 − − −
Hypertension (yes vs. no) 1.497 0.695−3.263 0.304 − − −
Diabetes (yes vs. no) 0.771 0.263−1.993 0.609 − − −
Cardiovascular disease (yes vs. no) 1.219 0.483−2.902 0.662 − − −
Abdominal surgery history (yes vs. no) 2.67 1.105−6.376 0.027 3.14 1.123−9.099 0.0304
Lymphadenectomy (yes vs. no) 0.454 0.198−1.056 0.0628 − − −
Robot-assisted vs. laparoscopic 0.527 0.226−1.167 0.122 − − −
Ureterocutaneostomy vs. others 0.789 0.329−1.786 0.579 − − −

OR, odds ratio; CI, confidence interval; BMI, body mass index; others, Ileal Conduit and Neobladder.

In multivariate logistic regression (Table 2), we took the variables with statistical significance in the univariate logistic regression into the analysis and explore the relationship between them and abdominal distension. Forward and backward stepwise logistic regression algorithms and the Akaike information criterion (AIC) were systematically applied to screen the factors. Two factors were identified as effective predictors of abdominal distension after RC, including postoperative water fasting time (≥4 vs. <4 days: OR 11.401; P=4.11E-05) and abdominal surgery history (yes vs. no: OR 3.14; P=0.0304).

To provide the clinician with a quantitative method to predict a patient’s probability of abdominal distension after RC, we constructed a nomogram that integrated the risk factors from the multiple logistic regression (Figure 2A). Calibration plots showed that the nomogram did well compared to an ideal model. The predictive accuracy of the nomograms is shown in Figure 2B,2C with the area under the curve (AUC) of 0.804.

Figure 2 Clinical model construction of abdominal distention. (A) Nomogram predicting the probability of abdominal distention in patients undergoing RC. Instructions: locate the patient’s actual situation (postoperative water fasting time or abdominal surgery history) on the corresponding axis. Draw a line straight upward to the point axis to determine the points toward the probability of abdominal distention the patient receives for the variable value. Perform this process for the other variable and sum the points for each predictor. Locate the final sum on the total point axis. Draw a line straight down to find the patient’s probability of abdominal distention after surgery. (B) Calibration curves of our nomogram in predicting abdominal distention after RC. (C) ROC curves in predicting abdominal distention after RC with the AUC of 0.804. RC, radical cystectomy; ROC, receiver operating characteristic; AUC, area under the curve.

Finally, we collected other data (including data on postoperative hospital stay and intestinal obstruction) for these 139 patients. We found that majority of abdominal distension patients (77%) had a postoperative hospital stay of longer than or equal to 10 days (P=0.002, Chi-square). Moreover, among the abdominal cohort, seven patients (20%) developed intestinal obstruction, whereas non-distension cohort, no patients developed intestinal obstruction (P=2.303E-05, Chi-square) (Table 3). Among all patients, 7 patients developed POI, all of them had mechanical intestinal obstruction, and the average time of appearance was 10 days after operation. One patient died due to aspiration without gastrointestinal decompression, one patient underwent intestinal adhesion release, and the remaining five patients were discharged with gastrointestinal decompression combined with traditional Chinese medicine. The mean number of postoperative hospital days was longer in the patient with intestinal obstruction than in the other patients (16.71 vs. 10.42; P=0.095); we considered the difference was not statistically significant because the number of patients was small.

Table 3

Partial effects of abdominal distention on patients

Variables Abdominal distension/non-distension, n [%]
n No Yes χ2 P value
Postoperative hospital stays (days)
   <10 65 [47] 57 [55] 8 [23] 9.49 0.002
   ≥10 74 [53] 47 [45] 27 [77]
Intestinal obstruction
   No 132 [95] 104 [100] 28 [80] 17.92 2.303E-05
   Yes 7 [5] 0 [0] 7 [20]

Discussion

RC is the surgical golden standard for MIBC (11). In most circumstances, laparoscopic surgery is an alternative to open surgery (12) because it reduces morbidity and speeds recovery (13). In addition, with the development of science and technology, a retrospective study recently showed that RARC is technically feasible and may reduce the incidence of blood loss, complications, and labor costs (14). POI is one of the most common complications after RC, with an incidence of 2% to 32% (15). Many factors could increase the incidence of POI, including male sex, infection, and increased intravenous fluids (6,16). For ileus, one of the most frequently reported problems after RC, follow-up control mainly depends on early recognition and subsequent treatment (15). Of note, abdominal distention is one of the main features of POI (17). However, evidence on the predictors of abdominal distention after RC is limited, and few retrospective studies were performed for LRC and RARC.

In our study, we retrospectively analyzed 139 patients who underwent the RC to determine the risk factors for postoperative abdominal distention and effective prevention strategies for managing abdominal distention complications. We did not find a significant difference between LRC and RARC in univariate/multivariate regression analysis, this may be caused by the small sample size. The univariate analysis represented that the stomach tube insertion before surgery was associated with abdominal distention after RC. The stomach tube insertion is used to prevent postoperative complications, such as nausea and vomiting, stomach content aspiration, and intestinal anastomotic leakage (18). However, it is reported that stomach tube might prolong gastrointestinal recovery and increase the duration of hospitalization (19). The stomach tube insertion was not statistically significant in the multivariate regression analysis. This could be the effect of postoperative water fasting time on it. Furthermore, abdominal surgery history was an independent risk factor in univariate/multivariate logistic regression analysis. Rybakov et al. show that previous abdominal surgery is a significant risk factor for POI (20), this may be caused by increased intraperitoneal adhesions in patients (21). Enhanced Recovery After Surgery (ERAS) was first introduced in colorectal surgery in the 1990s to reduce the perioperative burden and speed up patient recovery (22). It has recently been used in patients undergoing RC (23). In our study, patients whose postoperative water fasting time was longer than 4 days had a greater risk of abdominal distention than the others, this further illustrates the necessity to promote ERAS after surgery.

Finally, we used a nomogram to calculate the individual patient’s probability of abdominal distention after surgery, which is the first nomogram used to predict the probability of abdominal distention after RC. Our nomogram represents that the higher the score of a risk factor received, the greater its association with the occurrence of abdominal distention after surgery. As with other retrospective studies, the main limitation of our study is its ability to produce causality and control for all possible confounders. Furthermore, the expression ability of each patient also affects the outcome. Further validation is therefore required in a prospective randomized controlled trial.

Conclusions

Our study confirmed the risk factors for abdominal distention after RC. We recommend that the stomach tube should not be routinely used in the preoperative management of the patient undergoing RC. In addition, we provide a model to predict the probability of abdominal distention after RC so that physicians can take preventive measures in advance for high-risk patients. A stomach tube is feasible for high-risk patient and should be removed as soon as possible after the recovery of postoperative intestinal function. Meanwhile, we need to continue refining our model and perform more external validation to identify the patients.

Acknowledgments

Funding: This work was supported by The National Natural Science Foundation of China (No. 82070725).

Footnote

Reporting Checklist: The authors have completed the TRIPOD reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-22-455/rc

Data Sharing Statement: Available at https://tau.amegroups.com/article/view/10.21037/tau-22-455/dss

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-22-455/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-22-455/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Medical Ethics Committee of the Second Hospital of Tianjin Medical University (No. KY2022K080) and informed consent was taken from all the patients.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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Cite this article as: Qi Y, Liu Y, Liu X, Li J, Qi S, Zhang Z. Identification of risk factors and clinical model construction of abdominal distension after radical cystectomy. Transl Androl Urol 2022;11(12):1629-1636. doi: 10.21037/tau-22-455

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