Construction and validation of a nomogram model for predicting infectious kidney stones before surgery

doi:10.3877/cma.j.issn.1674-1358.2023.05.003

Abstract

Abstract:

Objective

To establish a nomogram model for preoperative prediction of infectious kidney stones.

Methods

Total of 350 patients with kidney stones diagnosed in Wujin Hospital Affiliated to Jiangsu University (Wujin Clinical College of Xuzhou Medical University) from February 2020 to February 2023 were summarized, retrospectively, and were randomly divided into a modeling set (245 cases) and a validation set (105 cases) according to 7︰3. The modeling focused on 91 cases with infectious kidney stones and 154 cases with non-infectious kidney stones, and verified 39 cases of concentrated infectious kidney stones and 66 cases of non-infectious kidney stones. The clinical data of patients in infective kidney stone group and non-infective kidney stone group were compared in the modeling set. The minimum absolute convergence and selection operator regression (Lasso) model and multi-factor Logistic regression model were used to screen the risk factors of infective kidney stone. The nomographic model was established and verified by 1 000 self-repeated samples through R software.

Results

Univariate comparison showed that female, recurrent kidney stones and staghorn stones in the infectious kidney stones group were more, the stone area was larger, while the Hounsfield unit (HU) of stones was significantly fewer; positive preoperative bladder urine culture (PBUC), urine white blood cell count (WBC) and bacterial count, urine protein positive, urine nitrite positive, positive urine leukocyte esterase (ULE), urine pH value, and urine turbidity positive were significantly higher, while urine specific gravity was significantly lower; blood uric acid was lower, while blood phosphorus and magnesium were higher (all P < 0.05). Lasso screened 8 most differential indicators, namely female, recurrent kidney stones, stone area ≥ 601 mm², HU value < 1 000, positive PBUC, positive ULE, urine pH and urine turbidity positive. Logistic regression showed that female (OR = 1.568, 95%CI: 1.231-1.902, P < 0.001), recurrent kidney stones (OR = 3.023, 95%CI: 2.568-3.467, P < 0.001), stone area ≥ 601 mm² (OR = 2.123, 95%CI: 1.756-2.569, P < 0.001), HU value < 1 000 (OR = 3.856, 95%CI: 3.456-4.325, P < 0.001), positive PBUC (OR = 1.895, 95%CI: 1.623-2.325, P < 0.001), positive ULE (OR = 1.754, 95%CI: 1.326-2.124, P < 0.001), urinary pH > 6.5 (OR = 1.323, 95%CI: 1.102-1.889, P < 0.001) and positive urine turbidity (OR = 1.602, 95%CI: 1.314-1.956, P < 0.001) were the risk factors to infectious kidney stones. R software was used to establishe a nomogram model, with a total score of 220 points. The receiver operating curve (ROC) showed that the area under the curve (AUC) of the nematic model was 0.856 (95%CI: 0.810-0.912, P < 0.001), the sensitivity and specificity were 79.8% and 83.2%, respectively, indicating that the diagnostic areas of the model were better. The calibration curve and decision curve also showed that the model had a good fit and clinical net benefit ratio.

Conclusions

Female, recurrent kidney stones, stone area ≥ 601 mm², HU value < 1 000, positive PBUC, positive ULE, urine pH and positive urine turbidity could assist in assessing the risk of infectious kidney stones. A nomogram model that has good application potential to guide clinical practice was established.

Key words: Infectious kidney stones, Nomogram model, Preoperative bladder urine culture, Urinary leukocyte esterase

Peng Zheng, Saiping Wu, Xiuzhang Xie, Qingfeng Shi. Construction and validation of a nomogram model for predicting infectious kidney stones before surgery[J]. Chinese Journal of Experimental and Clinical Infectious Diseases(Electronic Edition), 2023, 17(05): 299-306.

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References 26

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临床资料	无感染性肾结石组（154例）	感染性肾结石组（91例）	统计量	P值
人口学信息
男/女（例）	98/56	36/55	χ² = 13.380	< 0.001
年龄（ ± s，岁）	55.6 ± 6.7	56.8 ± 7.2	t = 0.564	0.423
BMI（ ± s，kg/m²）	23.2 ± 1.4	23.4 ± 1.5	t = 0.236	0.687
高血压[例（%）]	62（40.3）	32（35.2）	χ² = 0.628	0.428
糖尿病[例（%）]	31（20.1）	11（12.1）	χ² = 2.604	0.107
结石特征
复发性肾结石[例（%）]	32（20.8）	36（39.6）	χ² = 10.062	0.002
鹿角形结石[例（%）]	33（21.4）	31（34.1）	χ² = 4.734	0.030
双侧结石[例（%）]	19（12.3）	12（13.2）	χ² = 0.037	0.847
结石面积（ ± s，mm²）	658.9 ± 123.4	1 023.5 ± 325.6	t = 32.526	< 0.001
HU值（ ± s）	989.7 ± 253.2	754.5 ± 102.2	t = 19.658	< 0.001
治疗方式[例（%）]			χ² = 1.131	0.568
mPCNL	62（40.3）	35（38.5）
RIRS	53（34.4）	37（40.7）
ESWL	39（25.3）	19（20.8）
留置输尿管支架[例（%）]	17（11.0）	13（14.3）	χ² = 0.561	0.454
经皮肾造口术[例（%）]	15（9.7）	10（11.0）	χ² = 0.097	0.755
尿液分析
阳性PBUC [例（%）]	38（24.7）	49（53.8）	χ² = 21.254	< 0.001
WBC（ ± s，× 10⁹/L）	326.5 ± 112.4	512.6 ± 102.4	t = 10.235	< 0.001
RBC（ ± s，× 10⁹/L）	135.6 ± 45.7	123.5 ± 42.3	t = 0.869	0.232
细菌量（ ± s，个/ml）	75.6 ± 12.3	125.4 ± 23.6	t = 9.635	< 0.001
蛋白阳性[例（%）]	36（23.4）	40（44.0）	χ² = 11.321	0.001
亚硝酸盐阳性[例（%）]	31（20.1）	35（38.5）	χ² = 9.766	0.002
ULE阳性[例（%）]	75（48.7）	74（81.3）	χ² = 25.537	< 0.001
pH（ ± s）	6.1 ± 0.3	6.5 ± 0.4	t = 5.003	< 0.001
浊度阳性[例（%）]	32（20.8）	33（36.3）	χ² = 7.036	0.008
比重（ ± s）	1.010 ± 0.003	1.008 ± 0.003	t = 3.968	0.003
血生化（ ± s）
肌酐（μmol/L）	116.9 ± 22.4	120.2 ± 23.6	t = 0.654	0.369
BUN（mmol/L）	6.2 ± 1.3	6.3 ± 1.2	t = 0.352	0.845
尿酸（μmol/L）	388.9 ± 52.3	356.5 ± 45.9	t = 4.124	0.001
PTH（pg/ml）	52.6 ± 13.4	50.2 ± 12.3	t = 0.458	0.723
钙（mmol/L）	2.28 ± 0.13	2.26 ± 0.12	t = 0.069	0.912
磷（mmol/L）	1.14 ± 0.03	1.18 ± 0.03	t = 3.996	0.002
镁（mmol/L）	0.83 ± 0.02	0.85 ± 0.03	t = 3.325	0.005

临床资料	无感染性肾结石组（154例）	感染性肾结石组（91例）	统计量	P值
人口学信息
男/女（例）	98/56	36/55	χ² = 13.380	< 0.001
年龄（ ± s，岁）	55.6 ± 6.7	56.8 ± 7.2	t = 0.564	0.423
BMI（ ± s，kg/m²）	23.2 ± 1.4	23.4 ± 1.5	t = 0.236	0.687
高血压[例（%）]	62（40.3）	32（35.2）	χ² = 0.628	0.428
糖尿病[例（%）]	31（20.1）	11（12.1）	χ² = 2.604	0.107
结石特征
复发性肾结石[例（%）]	32（20.8）	36（39.6）	χ² = 10.062	0.002
鹿角形结石[例（%）]	33（21.4）	31（34.1）	χ² = 4.734	0.030
双侧结石[例（%）]	19（12.3）	12（13.2）	χ² = 0.037	0.847
结石面积（ ± s，mm²）	658.9 ± 123.4	1 023.5 ± 325.6	t = 32.526	< 0.001
HU值（ ± s）	989.7 ± 253.2	754.5 ± 102.2	t = 19.658	< 0.001
治疗方式[例（%）]			χ² = 1.131	0.568
mPCNL	62（40.3）	35（38.5）
RIRS	53（34.4）	37（40.7）
ESWL	39（25.3）	19（20.8）
留置输尿管支架[例（%）]	17（11.0）	13（14.3）	χ² = 0.561	0.454
经皮肾造口术[例（%）]	15（9.7）	10（11.0）	χ² = 0.097	0.755
尿液分析
阳性PBUC [例（%）]	38（24.7）	49（53.8）	χ² = 21.254	< 0.001
WBC（ ± s，× 10⁹/L）	326.5 ± 112.4	512.6 ± 102.4	t = 10.235	< 0.001
RBC（ ± s，× 10⁹/L）	135.6 ± 45.7	123.5 ± 42.3	t = 0.869	0.232
细菌量（ ± s，个/ml）	75.6 ± 12.3	125.4 ± 23.6	t = 9.635	< 0.001
蛋白阳性[例（%）]	36（23.4）	40（44.0）	χ² = 11.321	0.001
亚硝酸盐阳性[例（%）]	31（20.1）	35（38.5）	χ² = 9.766	0.002
ULE阳性[例（%）]	75（48.7）	74（81.3）	χ² = 25.537	< 0.001
pH（ ± s）	6.1 ± 0.3	6.5 ± 0.4	t = 5.003	< 0.001
浊度阳性[例（%）]	32（20.8）	33（36.3）	χ² = 7.036	0.008
比重（ ± s）	1.010 ± 0.003	1.008 ± 0.003	t = 3.968	0.003
血生化（ ± s）
肌酐（μmol/L）	116.9 ± 22.4	120.2 ± 23.6	t = 0.654	0.369
BUN（mmol/L）	6.2 ± 1.3	6.3 ± 1.2	t = 0.352	0.845
尿酸（μmol/L）	388.9 ± 52.3	356.5 ± 45.9	t = 4.124	0.001
PTH（pg/ml）	52.6 ± 13.4	50.2 ± 12.3	t = 0.458	0.723
钙（mmol/L）	2.28 ± 0.13	2.26 ± 0.12	t = 0.069	0.912
磷（mmol/L）	1.14 ± 0.03	1.18 ± 0.03	t = 3.996	0.002
镁（mmol/L）	0.83 ± 0.02	0.85 ± 0.03	t = 3.325	0.005

影响因素	β值	Wald χ²值	OR值	95%CI	P值
女性	0.602	6.897	1.568	1.231~1.902	< 0.001
复发性肾结石	1.235	32.321	3.023	2.568~3.467	< 0.001
结石面积≥ 601 mm²	0.963	15.587	2.123	1.756~2.569	< 0.001
HU值< 1 000	1.528	52.634	3.856	3.456~4.325	< 0.001
阳性PBUC	0.898	13.325	1.895	1.623~2.325	< 0.001
阳性ULE	0.756	9.032	1.754	1.326~2.124	< 0.001
尿pH > 6.5	0.456	5.265	1.323	1.102~1.889	< 0.001
尿液浊度阳性	0.668	8.124	1.602	1.314~1.956	< 0.001

影响因素	β值	Wald χ²值	OR值	95%CI	P值
女性	0.602	6.897	1.568	1.231~1.902	< 0.001
复发性肾结石	1.235	32.321	3.023	2.568~3.467	< 0.001
结石面积≥ 601 mm²	0.963	15.587	2.123	1.756~2.569	< 0.001
HU值< 1 000	1.528	52.634	3.856	3.456~4.325	< 0.001
阳性PBUC	0.898	13.325	1.895	1.623~2.325	< 0.001
阳性ULE	0.756	9.032	1.754	1.326~2.124	< 0.001
尿pH > 6.5	0.456	5.265	1.323	1.102~1.889	< 0.001
尿液浊度阳性	0.668	8.124	1.602	1.314~1.956	< 0.001

组别	敏感度（%）	特异度（%）	阳性预测值（%）	阴性预测值（%）	AUC	95%CI	P值
建模集	85.2	90.3	84.3	95.2	0.899	0.831~0.945	< 0.001
验证集	79.8	83.2	79.8	86.5	0.856	0.810~0.912	< 0.001

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