Neural Network Analysis of Crystalluria Content to Predict Urinary Stone Type

Figures & data

Figure 1 Schematic diagram of the 4-node neural network model used to predict the stone type from several predictor variables including urinalysis results, crystal type, body mass index, red blood cell count, and white blood cell count.

Figure 2 Typical output from a neural network model, model statistics, including R-squared values and confusion matrices, are shown on the left side, and the equivalent summary for the validation tests are shown on the right side.

Abbreviation: RMSE, root mean square error.

Figure 3 Receiver-operating characteristic curves for training (left) and validation data (right).

Figure 4 Snapshot of the prediction profile curves generated from the neural network model. The curves show the relative effect of the various predictor variables on the probability of generating a particular stone type.

Table 1 Distribution of Different Stone Types

Stone Type	n	%
Calcium Oxalate	261	53.8
Carbonate Apatite	153	31.6
Uric Acid Dihydrate	35	7.2
Cystine	19	3.9
Ammonium Magnesium Phosphate	8	1.7
Ammonium Hydrogen Urate	4	0.8
Calcium Monohydrogen Phosphate Dihydrate (brushite)	1	0.2
Ammonium Dihydrogen Urate	1	0.2
Ammonium Magnesium Hexahydrate	1	0.2
Monohydrogen Phosphate	1	0.2
Uric Acid	1	0.2
Total	485	100

Table 2 Contingency Table Showing Crystal Type with Associated Stone Type

Urinalysis Crystals Grouped		Stone Type
		Ammonium Magnesium Hexahydrate	Calcium Oxalate	Carbonate Apatite	Cystine	Uric Acid Dihydrate	Total
AP4+/AU4+	Count	0	1	0	0	0	1
	Total %	0.00	2.13	0.00	0.00	0.00	2.13
	Cal %	0.00	5.88	0.00	0.00	0.00
	Raw %	0.00	100.00	0.00	0.00	0.00
AP4+/AU4+/CO+	Count	0	0	6	0	0	6
	Total %	0.00	0.00	12.77	0.00	0.00	12.77
	Cal %	0.00	0.00	35.29	0.00	0.00
	Raw %	0.00	0.00	100.00	0.00	0.00
Calcium Oxalate	Count	1	16	10	0	4	31
	Total %	2.13	34.04	21.28	0.00	8.51	65.96
	Cal %	100.00	94.12	58.82	0.00	40.00
	Raw %	3.23	51.61	32.26	0.00	12.90
Cystine	Count	0	0	0	1	0	1
	Total %	0.00	0.00	0.00	2.13	0.00	2.13
	Cal %	0.00	0.00	0.00	50.00	0.00
	Raw %	0.00	0.00	0.00	100.00	0.00
Uric Acid	Count	0	0	1	1	6	8
	Total %	0.00	0.00	2.13	2.13	12.77	17.02
	Cal %	0.00	0.00	5.88	50.00	60.00
	Raw %	0.00	0.00	12.50	12.50	75.00
Total	Count	1	17	17	2	10	47
	Total %	2.3	36.17	36.17	4.26	21.28

Abbreviations: AP4, amorphous phosphate; AU4, amorphous urate; CO+, calcium oxalate.

Table 3 Crystal Type and Associated Urinary pH

Crystal Type	pH (SD)
Calcium Oxalate	5.6 (0.59)
Uric Acid	5.2 (1.16)
Cystine	8.0 (0)
Amorphous Phosphate/Urate	7.2 (1.03)

Table 4 Stone Type and Associated pH

Stone Type	pH (N, SD)
Calcium Oxalate	5.4 (257, 0.79)
Carbonate Apatite	6.2 (147, 0.9)
Cystine	8.0 (19, 0.72)
Uric Acid Dihydrate	5.3 (35, 0.68)