Main points

• Many patients with ileocolic Crohn’s disease require one or more surgical interventions during their lifetime. In these patients, the indication for surgery is based on various criteria, such as the presence of stricturing or perforating disease, risk of postoperative recurrence, grade of inflammatory activity, and length of the intestinal loops involved.

• If the bowel resection is too extensive and residual small intestine is less than 75 cm, the patient may suffer from short bowel syndrome.

• The preoperative assessment of intestinal length is useful for predicting and quickly treating postoperative nutritional disorders.

• We recommend that vessel analysis software be employed for measuring the small bowel loops using computed tomography and magnetic resonance enterography.

Many patients with ileocolic Crohn’s disease (CD) require one or more surgical interventions during their lifetime. In these patients, the indication for surgery is based on various criteria, such as the presence of stricturing or perforating disease, risk for postoperative recurrence, grade of inflammatory activity, and length of the intestinal loops involved. If the bowel resection is too extensive and residual small intestine is less than 75 cm, the patient may suffer from short bowel syndrome.¹

The exact length of the small intestine remains controversial in the literature, and its measurement depends on the techniques used. In addition, some studies have reported that the length of the small bowel appears to be variable, depending on the age, sex, weight, and height of the patient.^2,3 A study by Regan et al.⁴ found that stenosis in patients with CD can occur because of the increased contractile activity of fibroblasts at the level of the extracellular matrix, appreciable both in healthy areas and in macroscopically inflamed regions. For this reason, patients with CD have a shorter bowel than that of the normal population.^2,3

In this paper, we describe a method for measuring intestinal loops through computed tomography enterography (CTE) or magnetic resonance enterography (MRE) using vessel analysis software. The method enables two-dimensional (2D) and three-dimensional (3D) curved multiplanar reconstructions (MPRs) and allows each loop to be stretched. Subsequently, the software creates a virtual image through which intestinal length can be measured linearly. This method has been used successfully in the evaluation of patients with acute diverticulitis, revealing a correlation between the lengths of colon involved, considered as a percentage of the entire colon, and the need for a patient to be hospitalized.⁵ The same method can be used to measure the intestinal length in patients with CD in many clinical situations, particularly when it is necessary to plan a surgical intervention in patients who have already undergone intestinal resection to avoid short bowel syndrome.¹

Technique

In our hospital, MRE and CTE are performed after the oral administration of a polyethylene glycol solution (PEG). We administer 1.5–2.0 L of PEG in doses of 100 mL starting 35 min before the MR and CT examinations.

When a patient has a known diagnosis of CD, we perform CTE only after the injection of an iodinated contrast medium. The CT technical parameters are presented in Table 1.

In MRE, the sequences are performed before and after the intravenous administration of a paramagnetic contrast medium: a single-shot T2-weighted and balanced steady-state-free precession sequence, T2-weighted fat-suppressed sequence, multiphase 3D T1-weighted fat-suppressed postcontrast image sequence, and diffusion-weighted imaging (values usually 0–800 or 0–600 s/mm²) sequence. The MR parameters are set out in Table 2.

The imaging criteria for CD diagnosis are summarized in Table 3.

The CT and MR examinations are revised using postprocessing technologies such as MPR, and a specific postprocessing 2D and 3D software (Vue PACS Carestream) is applied to these images. We select the series of images for the reconstruction using the “view as” button and then select “vessel analysis”. In this way, we obtain 3D and 2D reconstructions in axial, coronal, and sagittal planes. Using the manual protocol, we create a virtual image that makes the intestine tubular through the point-by-point identification of the intestinal lumen distended through PEG. On the image thus obtained, we can perform the necessary measurements to evaluate the patient using a linear measurement.

The time needed to perform the measurements is variable. Based on our calculations, between 20 and 30 min is required for each measurement, to which the time necessary to view the images and draft the report must be added.

Indications for surgical resection or the modification/confirmation of medical therapy are discussed in a multidisciplinary team meeting (MDT), held in our department once a week, in which radiologists, gastroenterologists, surgeons, and pathologists participate.

Case 1

Patient 1 is a 74-year-old man with known CD treated through medical therapy. He was hospitalized for persistent abdominal pain and serotonin fever (>38°C), but his symptoms did not respond to medical therapy. His bowel movements were regular, and there was only one incident of vomiting. At admission, his blood tests were normal except for C-reactive protein (CRP) values (19.8 mg/L; normal values <5.0). The patient underwent CTE (Figure 1), and the results were discussed in the MDT. The MDT decision was to perform intestinal resection, with the intestine measured during ileocolonic resection using a radiological measurement.

Case 2

Patient 2 is a 43-year-old woman with known stenosing CD treated through medical therapy. She was hospitalized for worsening abdominal pain with constipation. Blood tests: normocytic anemia (hemoglobin: 10.4 g/dL; normal values 12.0–15.0), erythrocyte sedimentation rate (ESR): 43 mm (normal values 0–20), CRP: 6 mg/L (normal values <5.0). During hospitalization, the treatments were effective, and her condition continued to improve.

Subsequently, MRE was performed (Figure 2), and the results were discussed in the MDT. The MDT decision was to continue medical therapy.

Case 3

Patient 3 is a 36-year-old man with known CD treated through medical therapy. He was experiencing severe pain following diarrhea (about 2–4 discharges per day). He had also experienced weight loss of approximately 5–6 kg in the previous 2 months.

In the endoscopic examination, the ileocecal valve appeared substenotic and was covered by edematous and bleeding mucosa, and a single ulcer was detected. The mucosa of the ileum also appeared edematous and sensitive to bleeding with ulcers.

Blood tests on admission to the hospital were normal except for CRP (20.3 mg/L; normal values <5.0) and ESR (30 mm; normal values 0–20).

The patient underwent CTE to determine the appropriate treatment (Figure 3), and the results were discussed in the MDT. The MDT decision was to not perform surgical therapy because of the high risk of short bowel syndrome and to continue medical therapy.

Discussion

Previously, the measurement of the length of the small intestine was performed using a barium X-ray.³ Currently, the calculation of the length of the intestine is conducted through MRE or CTE, using vascular imaging software,⁶ 2D MPR,⁷ or an automatic calculation method.⁸

In our hospital, two gastrointestinal radiologists use the method described here to measure intestinal length (both small bowel and colon) in all patients with CD, especially in patients with extensive alteration of the small bowel who must undergo surgery. Coronal and sagittal MPR using CTE or coronal and axial images from MRE do not allow the small bowel to be visualized in its longitudinal extension if a long section of intestine is affected by the pathology. In this paper, we have described a method to measure intestinal length and presented three patients with CD.

Patient 1 had a diseased intestine less than a meter long and no response to medical therapy; he therefore underwent ileal resection surgery. After ileocolonic resection, the intestine measurement was consistent with the radiological measurement, and no complications in the postsurgical course were identified. Patient 2 exhibited signs of disease activity, and the CT showed small bowel alteration affecting the last 40 cm of the ileum. He responded to medical therapy, and therefore, in the MDT, it was decided to continue with this course of treatment. Patient 3 had extensive bowel involvement with the consequent high risk of short bowel syndrome; it was therefore decided to continue medical therapy.

The technique described in this paper is used to calculate the length of both the small intestine and colon. The measurement was performed on the colon for diverticular disease.⁵ In CD, it has greater practical utility for measuring the healthy or pathological small intestine to avoid performing an extensive resection that would lead to short bowel syndrome. Breathing artifacts do not hinder the measurement either in CT or MR.

If patients have fistulas, they are a candidate for bowel resection surgery, and the radiological support consists of measuring the length of the pathological small bowel loops, residual normal bowel, and distance of the fistula from the ileocecal valve or from the Treitz. In the case of stenosis, using this method enables the length of the stenosis to be measured. In addition, for stenosis or skip lesions, their distance from the ileocecal valve can be calculated, providing information that could be useful in cases of stricturoplastic therapy or the endoscopic dilation of the stenosis.

In conclusion, the vessel analysis method is easy to perform to measure the extent of the disease, and it is usually available in radiological departments. The measurements performed by us have always proved useful during MTDs for both clinicians and surgeons to make the correct therapeutic (medical or surgical) decision.

Conflict of interest disclosure

The authors declared no conflicts of interest.