Procalcitonin kinetics following abdominal aortic surgery and its value for postoperative intestinal ischaemia detection

Abstract

Objective

The purpose of our study was to describe perioperative kinetics of procalcitonin (PCT) in patients undergoing aortic surgery, to compare the kinetics in the open abdominal aortic aneurysm (AAA) repair and aortobifemoral bypass for aortoiliac occlusive disease (AIOD), and to evaluate the ability of PCT to detect intestinal ischaemia.

Methods

A prospective non-randomized observational cohort study in 80 patients (62 men and 18 women) undergoing elective aortic surgery was performed. Serum PCT was measured at baseline and defined intraoperative and postoperative timepoints up to postoperative day 7. MRI contrast-enhanced imaging was used to detect intestinal ischaemia.

Results

The comparison of the AAA and AIOD cohort did not show any significant difference in PCT levels. Patients with intestinal ischaemia had higher serum PCT at multiple timepoints postoperatively. The most accurate timepoints for early diagnosis were postoperative day 3, followed by 24 h after declamping of the vascular reconstruction, and postoperative day 7. The sensitivity and negative predictive values were 100% in all mentioned timepoints. However, event at the best timepoint the specificity was 89% and the positive predictive value 43%.

Conclusions

Procalcitonin levels in the postoperative period at proper timepoints might help to detect postoperative intestinal ischaemia. The limitation of this marker is its low specificity for intestinal ischaemia and low positive predictive value. The highest value of this marker is that it can rule out this complication because normal PCT levels mean that intestinal ischaemia is very unlikely.

Keywords

Procalcitonin abdominal aortic aneurysm aortoiliac occlusive disease intestinal ischaemia complications

Introduction

Intestinal ischaemia is a well-known complication of abdominal aortic vascular surgery. The reported incidence of intestinal ischaemia in elective open abdominal aortic procedures ranges between 1% and 7% and rises to 5% to 9% if routine postoperative colonoscopy is performed.^1,2 The mortality of this condition exceeds 50%.³ The left colon is usually affected, but any part of the intestine might be involved. At present, we have no specific laboratory marker for the early detection of postoperative intestinal ischaemia.

Many new markers have been discussed lately, one of them being procalcitonin.⁴ Procalcitonin (PCT) is a 116-amino acid precursor of calcitonin normally released by the C cells of the thyroid gland. In sepsis or other pathological conditions, multiple organs and tissues are involved in PCT production, and in a broader sense, the entire body becomes a calcitonin precursor producing endocrine gland.⁵ Currently available data from experimental and clinical studies focussing on PCT as a marker of intestinal ischaemia show sensitivity, specificity and positive and negative values ranging between 72% and 100%; 68% and 91%; 27% and 90%; and 81% and 100%, respectively.⁶ The majority of studies evaluate PCT levels in one or multiple timepoints without a precise relation to primary insult. Only a couple of studies used defined timepoints in animals or humans.^7–11 Our knowledge of the perioperative kinetics of PCT is limited. The physiological value of PCT should be lower than 0.5 mg/L but the cut-off value indicative of intestinal ischaemia is unknown.¹²

The purpose of our study was to describe intraoperative and postoperative kinetics of PCT in patients undergoing aortic surgery, to compare the kinetics of PCT in the open abdominal aortic aneurysm (AAA) repair and aortobifemoral bypass for aortoiliac occlusive disease (AIOD) and to evaluate the ability of PCT to detect intestinal ischaemia in the postoperative period. We hypothesized that PCT kinetics might differ in AAA and AIOD cohorts, PCT levels will be higher in cases of intestinal ischaemia, and the time relation to surgery will lead to differences in marker accuracy. This study was a part of a grant project focussing on multiple markers of mesenteric ischaemia.

Methods

Patients

We performed a prospective non-randomized observational cohort study on 80 patients being operated on between November 2017 and September 2020 in our department. The mean age of patients was 68.0 ± 8.4 years; 62 patients were men and 18 were women. The study was consecutively offered to all patients scheduled for elective aortic surgery for AAA or AIOD fulfilling the inclusion criteria to enrol 50 AAA patients and 30 AIOD patients. In the AAA group, we offered the study to patients where aneurysmatic or atherosclerotic disease affecting iliac arteries implied the need to construct at least one distal anastomosis on the femoral artery in the groin. The reason was to achieve a similar extent of operative trauma. In the AIOD group, we offered the study to patients with lifestyle-limiting intermittent claudication only (Rutherford classification 1–3) to exclude the potential influence of critical limb-threatening ischaemia on marker levels. The exclusion criterion was a contraindication for magnetic resonance imaging (MRI). The study protocol was approved by the Ethical Committee of St. Anne’s University Hospital Brno, ref. number 3 G/2017 and all patients were enrolled after they signed informed consent. The overall acceptance rate was 37% (80 of 216 patients offered to participate). Thirty-three percent of patients refused to participate in the study because they already felt the stress of an extensive aortic procedure and didn’t agree with any additional lab tests or imaging. Eight percent gave the fear of MRI imaging as a reason for refusal, three percent claimed that they had claustrophobia and nineteen percent didn’t want to participate in any research study.

Surgical technique

Both, open AAA repair and aortobifemoral bypass in AIOD patients were performed without any specific study modification. Procedures were conducted under general anaesthesia and the aorta was exposed using a transperitoneal approach through a midline laparotomy. The aneurysm was replaced using Dacron graft (Ra bv K graft, VUP Medical, Czech Republic) with the proximal anastomosis in an end-to-end fashion. We perform inferior mesenteric artery reimplantation in case of intraoperative colonic ischaemia, presence of large dominant inferior mesenteric artery, bilateral internal iliac occlusion and prior colon surgery. The decision was on the operating surgeon. The inferior mesenteric artery in the AAA group was ligated in all cases. Distal anastomoses were performed in end-to-end fashion to the iliac artery and end-to-side fashion to the common femoral artery (26%) or in an end-to-side fashion to both common femoral arteries (74%). We used the same Dacron graft for aortobifemoral bypasses. In aortoiliac occlusive disease, we prefer the end-to-side proximal anastomosis (93%) but in two cases we performed end-to-end anastomosis (7%). The inferior mesenteric artery was ligated just in one case where the proximal end-to-end anastomosis was performed. In all other AIOD cases, we preserved the artery. Distal anastomoses to femoral arteries were in all cases performed in an end-to-side fashion.

Sample collection and PCT measurement

We have collected eight venous blood samples from the central venous line per patient. The timing of sample collection was as follows. One hour before surgery, we collected sample S-BL (timepoint BL, BaseLine). Two samples were collected during the procedure. Sample S-CL1H was taken 1 hour after aortic cross-clamping or just immediately before the complete declamping of vascular reconstruction, which came sooner (timepoint CL1H, CLamping 1 Hour). Sample S-DC10M was collected 10 min after complete declamping of vascular reconstruction (timepoint DC10M, DeClamping 10 Minutes). The postoperative samples S-DC3H, S-DC6H and S-DC24H were taken 3 h, 6 h and 24 h after complete declamping (timepoints DC3H, DeClamping 3 Hours; DC6H, DeClamping 6 Hours; and DC24H, DeClamping 24 Hours), respectively. Samples S-POD3 and S-POD7 were collected on postoperative days 3 and 7 at 7 a.m. (timepoints POD3, PostOperative Day 3; and POD7, PostOperative Day 7). The samples were immediately processed and PCT levels were analysed using electrochemiluminescence immunoassay (Elecsys BRAHMS PCT, Roche).

MRI imaging

Starting on postoperative day 3, we performed MR enterocolography in enrolled patients. The imaging was postponed up to postoperative day 7 according to the patient’s status and ability to cooperate during imaging. The majority of examinations were performed between postoperative days 3 and 5 (86%). We have used a 1.5 T MRI scanner (Philips Ingenia, Philips Health Systems). We administered gadoteric acid (Dotarem, Guerbet) as an intravenous contrast for imaging. All patients received intravenous butylscopolamine (Buscopan, Boehringer Ingelheim) before imaging to reduce bowel motion artefacts and we have used breath hold or breath triggering to reduce breathing motion artifacts. We have used similar sequences for imaging as published by Mazzei et al.¹³ with the addition of T1 sequences (Table 1). The imaging took between 20 and 30 min to complete given the patient’s ability to cooperate. We assessed: wall thickening with heterogeneous enhancement (hypoperfusion/reperfusion) and zones of low attenuation compatible with severe colonic oedema, a shaggy contour bowel wall, a loss of colonic haustra, with varying degrees of pericolic streakiness, gas in vessel wall or mesenteric veins. MR images were independently evaluated by two radiologists experienced in gastrointestinal imaging, reaching a consensus agreement. The result was binary: no MRI signs of intestinal ischaemia/MRI signs of intestinal ischaemia.

Table 1.

MRI sequences used in the study.

Sequence name	T2W TSE	T2W TSE	T1W TSE	T2W TSE	T2W TSE	T1W TSE	T1W TSE	T1W TSE
Orientation	Coronal	Coronal	Coronal	Transversal	Transversal	Transversal	Transversal	Coronal
TR (ms)	380	380	412	380	380	412	412	412
TE (ms)	80	80	5	80	80	5	5	5
FOV (mm)	450 x 330	450 x 330	450 x 330	250 x 360	250 x 360	350 x 350	350 x 350	450 x 350
Slice thickness (mm)	6	6	5	6	6	5	5	5
Acquisition voxel (mm)	1.4 x 1.65	1.8 x 1.93	1.8 x 2.21	1.8 x 1.93	1.4 x 1.65	1.6 x 1.97	1.6 x 1.97	1.8 x 2.21
Gap (mm)	0	0	1	0	0	1	1	1
SENSE	4	3.5	2	3.5	4	2	2	2
Fat saturation	NO	SPAIR	SPIR	SPAIR	NO	SPIR	SPIR	SPIR
Respiratory compensation	Triggered	Triggered	Triggered	Triggered	Triggered	Breath hold	Breath hold	Triggered
Contrast	Native						Contrast enhanced

TR: Repetition time, TE: Echo time, FOV: Field of view, SENSE: Sensitivity encoding, TSE: Turbo spin echo, SPAIR: Spectral adiabatic inversion recovery, SPIR: Spectral presaturation with inversion recovery.

Intestinal ischaemia detection

The intestinal ischaemia was primarily diagnosed by MRI imaging (performed according to study protocol). The diagnosis might have been established before MRI by other methods (CT imaging, surgical procedure) if they had been performed sooner in the postoperative course based on the clinician’s decision. This happened twice in the study. In one case the complication was detected by the computed-tomography imaging performed before the planned MRI, and in one case by the surgical exploration (transmural ischaemia leading to peritonitis).

Data analysis

All data analyzes were performed in R.¹⁴ Univariate analyses were performed using the Fisher exact test for qualitative variables and logistic regression models for continuous predictors. Spearman correlation coefficient was applied for pairs of continuous variables. ROC (receiver operating characteristic) curves were applied for threshold identification. Statistical significance was set at level alpha = 0.05.

Results

The descriptive data of patients are given in Table 2. There were two significant differences between AAA and AIOD groups. The AAA patients were on average 10 years older and there were 18% of patients with chronic kidney disease (CKD) in the AAA group. There was not any patient with this condition in the AIOD group. We completed successfully all 80 aortic procedures.

Table 2.

Cohort description and comparison of AIOD and AAA group.

	All patients	AIOD	AAA	p-value
Number of patients	80	30	50	—
Age (years)	68.0 ± 8.4	62.6 ± 8.5	71.3 ± 6.3	.000*
Male gender (%)	77.5	70	82	.271
High blood pressure (%)	85	83.3	86	.756
Diabetes mellitus (%)	26.3	33.3	22	.301
Hyperlipidaemia (%)	63.7	66.7	62	.811
Coronary artery disease (%)	30	26.7	32	.802
Atrial fibrillation (%)	7.5	0	12	.079
Cerebrovascular disease (%)	16.3	20	14	.539
Chronic lung disease (%)	17.5	16.7	18	1.000
Thyroid disease (%)	10	10	10	1.000
Chronic kidney disease (%)	11.3	0	18	.023*
Smoking (%)	52.5	56.7	50	.646
BMI (kg/m²)	27.5 ± 4.2	27.4 ± 4.3	27.6 ± 4.1	.803

Data are presented as counts, mean ± standard deviation, percents. AIOD: aortoiliac occlusive disease, AAA: abdominal aortic aneurysm, ^* statistically significant difference.

The MRI imaging was performed in 79 patients (excluding the patient with transmural necrosis). The imaging was fully completed in 71 cases, the remaining eight MRI investigations were of lower quality or incomplete due to patients’ inability to cooperate in the postoperative period. All poor-quality or incomplete MRI examinations did not show any signs of intestinal ischaemia. We have decided to add up intestinal ultrasound in these patients, which was originally not a part of the study protocol. The results were normal in all cases. In one patient we performed postoperative computed tomography based on clinical suspicion of peripheral arterial embolism. This was not a part of the protocol and there were no signs of intestinal ischaemia. In the 30-day postoperative follow, no clinical signs of intestinal ischaemia developed in these eight patients.

The comparison of postoperative kinetics of PCT in AAA and AIOD groups gave no significant results. Therefore, we considered the whole cohort of all aortic surgery patients uniform for other analyses.

As already mentioned, there were two statistical differences in demographics between AIOD and AAA groups. We performed posthoc subanalyses to evaluate the influence of age and CKD on PCT levels in studied cohorts. Spearman correlation analysis for age gave a significant result for sample S-POD7 (p = .002). The older patients had higher PCT levels at this timepoint, but the absolute differences were negligible. The influence of CKD on PCT levels was significant in S-CL1H (p = .025). The absolute difference between averages was smaller than 0.02 ng/L.

In the postoperative period, we have recorded 6 cases of acute postoperative intestinal ischaemia (7.5%); two cases in the AIOD group and four in the AAA group. The details are given in Table 3. In four patients, the left colon was affected with non-transmural ischaemia, which was detected using MRI. The inferior mesenteric artery was patent in three patients before and two after the procedure. Both internal iliac arteries were patent in four patients before and three after the surgery. In one patient, we had to ligate the left internal iliac artery. The right internal iliac artery remained patent. The treatment was conservative and all patients survived. In two patients, the right portion of the colon and terminal ileum was affected. In one patient MRI confirmed the diagnosis already established by contrast-enhanced computed tomography and the patient underwent exploratory laparotomy on postoperative day 3 to rule out transmural intestinal necrosis based on clinical indication. The patient had a patent inferior mesenteric artery and both iliac before the procedure, the inferior mesenteric artery was ligated and both iliac arteries remained patent after surgery. The patient died on the 14th postoperative day. Repeated ultrasound examinations performed during the postoperative course have never visualized a progression to transmural necrosis and no peritonitis developed in the postoperative course. In the other patient, there was transmural ischaemia with colon necrosis and peritonitis development within 48 h. Before the procedure, the patient had a patent inferior mesenteric artery and right internal iliac artery, after the procedure just the right internal iliac remained patent. We performed re-laparotomy, confirmed gangrene of the right-hand portion of the colon and performed a right hemicolectomy. The patient died due to septic shock on the third postoperative day.

Table 3.

Vessel patency, imaging, intraoperative findings and PCT positive timepoints in patients with intestinal ischaemia.

	Preoperative vessel patency			Postoperative vessel patency
Patient no.	IMA	Right IIA	Left IIA	IMA	Right IIA	Left IIA	Imaging or intraoperative finding	PCT positive timepoints
13	No	Yes	Yes	No	Yes	No	MRI: Ischaemia of descending colon, sigmoid colon and proximal rectum	DC3H, DC24H to POD7
25	Yes	Yes	Yes	Yes	Yes	Yes	MRI: Ischaemia of sigmoid colon	DC3H to POD7
35 (died on postoperative day 3)	Yes	Yes	No	No	Yes	No	Intraoperative findings: Ischaemia of terminal ileum, cecum, and ascending colon MRI: Not performed	CL1H to POD3, POD7 not available
43	Yes	Yes	Yes	Yes	Yes	Yes	MRI: Ischaemia of descending colon	CL1H, DC3H to POD7
54	Yes	Yes	Yes	No	Yes	Yes	MRI: Ischaemia of sigmoid colon	CL1H to DC3H, DC24H to POD7
77 (died on postoperative day 14)	Yes	Yes	Yes	No	Yes	Yes	CT and MRI: Ischaemia of terminal ileum, cecum and ascending colon Intraoperative findings: No transmural ischaemia	CL1H to POD7

IMA: inferior mesenteric artery, IIA: internal iliac artery.

The differences in artery patency between patients with or without mesenteric ischaemia were not statistically significant. The celiac trunk was patent in all patients in both groups, there were three ostial stenoses, all in the non-ischaemic group. Similarly, the superior mesenteric artery was patent in all patients in both groups with three cases of ostial stenosis in the non-ischaemic group. No patient had both stenoses in our cohort. The inferior mesenteric artery was patent in 75.7% preoperatively and 31.1% postoperatively in the non-ischaemic group. In the ischaemic group, the preoperative and postoperative patencies were 83.3% and 33.3%, respectively. The internal iliac arteries were both patent in 85.1%, one occluded in 5.4% and both occluded in 9.5% preoperatively and both patent in 74.3%, one occluded in 9.5%, and both occluded in 16.2% postoperatively in the non-ischaemic group. The patients with mesenteric ischaemia had both internal iliac patent in 83.3% and one occluded in 16.7% preoperatively and both patent in 66.7% and one occluded in 33.3% postoperatively.

Finally, we have evaluated the ability of PCT to detect acute intestinal ischaemia. The univariate logistic regression comparing patients with and without intestinal ischaemia showed statistically significant differences between samples in multiple timepoints (Figure 1). Sample S-CL1H was the first statistically significant timepoint and S-DC10M was the most significant.

Figure 1.

Perioperative kinetics of procalcitonin in patients without (grey) and with (red) intestinal ischaemia. Statistically significant results marked with an asterisk.

We performed ROC analyses to assess in which timepoint is PCT the most accurate to detect acute intestinal ischaemia (Table 4). POD3 was the timepoint with the highest AUC, followed by DC24H, and POD7. The AUC was higher than 0.9 in all these timepoints and the sensitivity and negative predictive values were 100%. The specificity in POD3 was 89% and the positive predictive value was 43%. We have reviewed all eight false-positive results for S-POD3 and have found that in three cases the reason for PCT elevation was septic shock caused by respiratory infection, in one case cardiogenic shock in a patient with hypertrophic cardiomyopathy and intraoperative myocardial infarction. In the other four cases, we have not found any reason for PCT elevation. None of the false-positive patients in timepoints between DC3H and POD3 had liver dysfunction.

Table 4.

Receiver operating characteristic analysis of PCT levels for discrimination between groups with and without intestinal ischaemia in all.

Timepoint	Sensitivity	Specificity	tn	tp	fn	fp	AUC
BL	0.667	0.757	56	4	2	18	0.714
CL1H	0.667	0.767	56	4	2	17	0.776
DC10M	0.500	0.959	71	3	3	3	0.807
DC3H	1.000	0.608	45	6	0	29	0.849
DC6H	0.667	0.905	67	4	2	7	0.802
DC24H	1.000	0.797	59	6	0	15	0.923
POD3	1.000	0.892	66	6	0	8	0.947
POD7	1.000	0.865	64	5	0	10	0.923

tn: true negative, tp: true positive, fn: false negative, fp: false positive, AUC: area under the curve.

Discussion

Postoperative intestinal ischaemia in elective aortic surgery is a rare but serious complication with high mortality. Early diagnosis is crucial for treatment, but its establishment based on clinical symptomatology and standard laboratory tests is very unreliable. The recommended imaging for the diagnosis of intestinal ischaemia is an abdominal CT with contrast.¹⁵ In critically ill patients the imaging should be used judiciously because of possible adverse events during the transport and examination itself.¹⁶ Colonoscopy or sigmoidoscopy is recommended for the final confirmation of colon ischaemia.¹⁵ But they are not without the risk of complications. Therefore, there is an ongoing discussion on biomarkers and their potential to diagnose intestinal ischaemia.

Procalcitonin is one of the markers giving conflicting results in different types of studies focussing on intestinal ischaemia. This study evaluated postoperative kinetics of PCT at defined timepoints after aortic surgery. We have analysed two cohorts of aortic patients, where we might expect this complication.

The overall incidence of intestinal ischaemia was 7.5% and we were in the upper part of literally reported incidence. The incidence of intestinal ischaemia in the AIOD group seemed high as well. These numbers have led us to check the operative results of all aortic patients within the study timeframe. We have found that after the inclusion of patients who refused the study or did not fulfil inclusive criteria the incidence of intestinal ischaemia was lower. Considering the size of the cohort, the error on small numbers had at least a partial influence on the result. One of the two AIOD patients was asymptomatic and the diagnosis would be probably missed without imaging. The MRI imaging performed in study patients might have led to higher incidences similarly to routinely performed colonoscopy.³

The use of MRI imaging for intestinal ischaemia detection performed in all but one patient of our cohort should be discussed as well. The most sensitive and specific method for the confirmation of colonic ischaemia is colonoscopy and it would be the most optimal method for the study. However, it is an invasive method with potential complications and during the study planning we performed a survey in our aortic patients and the majority of them were unwilling to participate if the colonoscopy would be a part of the study protocol. The study enrolment would be very slow and not feasible within the grant project timeframe. Therefore, we have decided to use noninvasive imaging. The recommended imaging for the diagnosis of colon ischaemia is CT with intravenous and oral contrast.¹⁵ The meta-analysis of CT imaging of mesenteric ischaemia showed a pooled sensitivity of 93.3% and a pooled specificity of 95.9%.¹⁷ The MRI imaging is not commonly used to diagnose intestinal ischaemia. Only a couple of studies compared MRI and CT imaging^13,17,18 but the results support the adequacy of these two methods. We do not expect MRI to become the diagnostic tool in an acute setting. The price is higher, availability lower, the time of the imaging is substantially longer (leading to lower tolerance of examination) and the patient’s cooperation is needed. The quality of MRI and CT imaging is very similar, so there is no reason to switch from CT to MRI except in specific cases. The main reason for the choice of this modality in our study was not to expose the study subjects to unnecessary radiation.

The comparison of the AAA and AIOD groups, in the beginning, was a logical step as we know that there might be differences in PCT kinetics after various types of surgery.^19,20 We did not find any significant differences between our study cohorts and the posthoc analyses focussing on age and CKD (the two factors significantly different in both cohorts) did not show any clinically relevant difference as well. The hypothesis of the difference of PCT kinetics between AAA and AIOD groups was rejected and so we consider the whole study uniform for further analyses.

The evaluation of the ability of PCT levels to help in the diagnosis of postoperative intestinal ischaemia was the main goal of our study. Two intraoperative timepoints were chosen based on animal studies as there are no data available on human subjects. The intraoperative PCT elevation is reported between 30 and 360 min after the onset of artificial ischaemia.^8,21 The analysis showed statistically significant differences in both intraoperative timepoints but the absolute differences were negligible. We doubt the potential value of intraoperative PCT levels for the diagnosis of intestinal ischaemia.

In the postoperative period, we have assessed two early timepoints at 3 and 6 h after complete reconstruction declamping and three later timepoints at 24 h after declamping, and postoperative days 3 and 7. The choice of timepoints was based on available data on humans. Zogheib and colleagues used 0, 3 and 6 h and postoperative days 1 and 2 for their proposed PALM score estimating the risk of intestinal ischaemia.²² Klingele and colleagues used baseline and postoperative day 1 samples, showing that PCT levels on a postoperative day 1 might help to diagnose non-occlusive mesenteric ischaemia.²³ Nagata and colleagues collected samples on postoperative days 1, 2 and 7, and found that the postoperative day 2 PCT levels were the most reliable for colonic ischaemia detection.¹⁰

Statistical analysis showed significant differences in sample S-DC3H and S-DC24H. Sample S-DC3H with ROC analysis giving AUC 0.85 might be interesting. However, there was still a lot of false-positive results and the average difference in PCT levels was 0.23 ng/mL. Considering the size of our cohort, a larger study to confirm the value of S-DC3H is needed.

The most accurate timepoints for postoperative intestinal ischaemia detection using PCT levels were postoperative day 3, followed by 24 h after declamping and postoperative day 7. We consider timepoints DC24H and POD3 as the clinically most important. With the AUC higher than 0.9, we conclude that PCT might help in postoperative intestinal ischaemia detection as a supportive test. The issue is the low specificity of this marker. It is questionable to perform a CT scan or colonoscopy based on PCT elevation in the postoperative period. The highest value of this marker is the exclusion of intestinal ischaemia because normal PCT levels below 0.5 ng/mL mean that the diagnosis of intestinal ischaemia is very unlikely. For the proper establishment of ideal cut-off value in clinically most relevant timepoints between POD1 and POD3 large-scale studies are needed.

Our study has of course some limitations. Only 80 patients were enrolled in the study and there were only 6 endpoints. Another limitation is the use of MRI imaging for the diagnosis of intestinal ischaemia and no confirmation by invasive measures like a colonoscopy. The strengths of the study are that this study was prospective with exactly defined timepoints for PCT sampling and only one sample missing (sample S-POD7 of patient no. 35 who died on postoperative day 3). The cohorts of patients were well defined, the procedures were elective and standardly performed, and all the patients except patient no. 35 (who was diagnosed by surgery) underwent medical imaging to detect intestinal ischaemia.

Conclusion

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by Ministry of Health of the Czech Republic, grant no. 17-29701A. All rights reserved.

ORCID iD

Peter Kruzliak

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