Intestinal ultrasound for monitoring postoperative Crohn’s disease: A systematic review and clinical implications

Table 1 Summary of key studies evaluating bowel wall thickness on intestinal ultrasound as a predictor of postoperative recurrence in Crohn’s disease

Ref.	Year	Design	Number	Site assessed	Timing	BWT threshold	Outcome predicted	Sensitivity	Specificity	Statistic
Andreoli et al[6]	1998	Prospective	41	NTI	Within 2 weeks of colonoscopy	> 5 mm	Endoscopic recurrence	81%	86%	Accuracy = 83%
Parente et al[1]	2004	Prospective	127	NTI	12 months post-operative	≥ 6 mm or < 40% reduction	Clinical recurrence	NR	NR	HR = 8.9
Rispo et al[7]	2006	Prospective	45	NTI	12 months	> 5 mm	Endoscopic recurrence (Rutgeerts ≥ i3)	94%	100%	NR
Pallotta et al[10]	2010	Prospective	58 (111 evaluations)	Anastomosis + NTI	6-24 months post- operative	> 3.5 mm (ICA) + > 3 mm (NTI)	Endoscopic recurrence	100% (for ICA > 3.5 mm)	NR	AUROC = 0.95 (combined)
Cammarota et al[8]	2013	Retrospective	196	Anastomosis	6-15 months post- operative	> 3 mm	Surgical recurrence	NR	NR	RR = 2.1

NTI: Neo-terminal ileum; ICA: Ileocolonic anastomosis; BWT: Bowel wall thickness; NR: Not reported; HR: Hazard ratio; AUROC: Area under the receiver operating characteristic curve; RR: Relative risk.

Table 2 Diagnostic performance of individual and combined intestinal ultrasound parameters and fecal calprotectin for detecting postoperative recurrence in Crohn’s disease, %

Ref.	Year	Parameter	Sensitivity	Specificity	PPV	NPV	Diagnostic accuracy	Comment
Furfaro et al[5]	2023	BWT ≥ 3 mm	77	65	81	59	73	Independent predictor of POR; OR = 2.43
		Mesenteric lymph nodes	35	97	95	43	56	Strong predictor; OR = 15.63
		FCP ≥ 50 μg/g	83	64	81	67	76	Independent predictor; OR = 8.58
		BWT ≥ 3 mm + FCP ≥ 50 μg/g	65	93	94	59	75	Best combined predictor
		BWT ≥ 3 mm + FCP ≥ 50 μg/g + LN+	33	100	100	59	66	Highest specificity; no false positives
Yebra Carmona et al[11]	2022	BWT > 3 mm + hyperemia	81	87	85	84	83	Strong correlation with endoscopy and FCP
		Hyperemia alone (grade ≥ 2)	67	74	70	72	71	Associated with endoscopic recurrence and FCP

BWT: Bowel wall thickness; FCP: Fecal calprotectin; LN+: Mesenteric lymph node enlargement; PPV: Positive predictive value; NPV: Negative predictive value; POR: Postoperative recurrence; OR: Odds ratio.

Table 3 Summary of selected studies evaluating small intestine contrast ultrasonography in detecting postoperative recurrence in Crohn’s disease

Ref.	Year	Design	Number	Timing of SICUS	BWT threshold	Sensitivity	Specificity	Accuracy/comments	Specificity	Statistic
Castiglione et al[14]	2008	Prospective	40	Within 7 days post-operative	> 3 mm	82%-94%	> 90%	Early detection with high sensitivity	NR	HR = 8.9
Calabrese et al[13]	2009	Prospective	40	Within 14 days post-operative	> 3 mm	92.5%	NR	Accurate grading of severity	NR	RR = 2.1
Onali et al[12]	2010	Prospective	58	12 months post-operative	> 3 mm	100%	NR	SICUS detected all cases of POR	100%	NR
Onali et al[15]	2016	Retrospective	58	3-year follow-up	> 3 mm	100%	NR	Useful long-term monitoring tool	86%	Accuracy = 83%
Biancone et al[3]	2007	Prospective	72	6-12 months post-operative	> 3 mm	NR	NR	Correlation with capsule endoscopy	NR	AUROC = 0.95 (combined)
Pallotta et al[10]	2010	Prospective	58	6-24 months post-operative	> 3.5 mm (ICA) + > 3 mm (NTI)	100%	NR	AUROC = 0.95 (combined ICA + NTI)	NR	NR

SICUS: Small intestine contrast ultrasonography; BWT: Bowel wall thickness; ICA: Ileocolonic anastomosis; NTI: Neo-terminal ileum; NR: Not reported; POR: Postoperative recurrence; AUROC: Area under the receiver operating characteristic curve; HR: Hazard ratio; RR: Relative risk.

Table 4 Key studies evaluating the role of contrast enhanced ultrasound in the detection and characterization of postoperative recurrence in Crohn’s disease

Ref.	Year	Technique	Sample size	Thresholds	Key findings
Paredes et al[16]	2013	CEUS	60	BWT > 3 mm; CEUS > 34.5%, CEUS > 46%, CEUS > 70%	CEUS improved diagnostic accuracy for endoscopic recurrence to 98.3% with score 2 (BWT > 5 mm or enhancement > 46%). Score 3 (BWT > 5 mm, enhancement > 70%, or fistula) detected 94% of severe recurrence. AUC = 0.99 for recurrence
Martínez et al[4]	2019	CEUS	N/A	N/A	CEUS effectively differentiated inflammatory vs fibrotic lesions post-surgery. Reinforced role of CEUS in enhancing IUS precision and in early recurrence assessment

CEUS: Contrast enhanced ultrasound; BWT: Bowel wall thickness; AUC: Area under the curve; IUS: Intestinal ultrasound; N/A: Not applicable.

Table 5 Comparison of diagnostic performance of intestinal ultrasound parameters with endoscopic findings (Rutgeerts score) in postoperative Crohn’s disease

Ref.	Year	Sample size	IUS parameters	Reference standard	Agreement (κ)	AUROC	Sensitivity	Specificity	Key findings
Yebra Carmona et al[11]	2022	39	BWT > 3 mm + Limberg score > 1	Rutgeerts ≥ i2	0.5	0.75	81.0%	87.0%	IUS had higher diagnostic accuracy than clinical or lab parameters.
Macedo et al[18]	2022	39	BWT > 3 mm and/or Limberg score > 1	Rutgeerts ≥ i2	0.5	0.75	88.9%	61.9%	Loss of wall stratification and hyperemia were most predictive of recurrence.

IUS: Intestinal ultrasound; BWT: Bowel wall thickness; AUROC: Area under the receiver operating characteristic curve.

Table 6 Summary of studies comparing fecal calprotectin and intestinal ultrasound for detecting postoperative recurrence in Crohn’s disease

Ref.	Year	Sample size	Timepoint	FCP cut-off	IUS threshold	FCP sensitivity/specificity (%)	IUS sensitivity/specificity (%)	Key insight
Orlando et al[19]	2006	39	3 months (IUS, FCP), 12 months (endoscopy)	> 200 mg/L	BWT ≥ 5 mm	63/75	26/90	Calprotectin more sensitive; IUS more specific at 3 months. Combining both could guide early colonoscopy
Furfaro et al[5]	2023	> 100	3-6 months post-operative	≥ 50 μg/g	BWT ≥ 3 mm	83/64	77/65	FCP and IUS individually useful; combination improved specificity and PPV. FCP < 50 μg/g + BWT < 3 mm had NPV 95.5%

IUS: Intestinal ultrasound; FCP: Fecal calprotectin; BWT: Bowel wall thickness; NPV: Negative predictive value.